diff --git a/build/config.mk b/build/config.mk
index f2b48affa2e..ceb7f9764a3 100644
--- a/build/config.mk
+++ b/build/config.mk
@@ -5,6 +5,7 @@
 #
 #   - `make`
 #   - Backtraces
+#   - Syscall tracing
 #   - Function tracing
 #   - Reasonably small
 #   - Reasonably optimized
@@ -13,6 +14,7 @@ ifeq ($(MODE),)
 CONFIG_CCFLAGS +=		\
 	$(BACKTRACES)		\
 	$(FTRACE)		\
+	-DSYSDEBUG		\
 	-Og
 TARGET_ARCH ?=			\
 	-msse3
@@ -23,6 +25,8 @@ endif
 #   - `make MODE=opt`
 #   - Backtraces
 #   - More optimized
+#   - Syscall tracing
+#   - Function tracing
 #   - Reasonably small
 #   - No memory corruption detection
 #   - assert() / CHECK_xx() may leak code into binary for debuggability
@@ -35,6 +39,7 @@ CONFIG_CPPFLAGS +=		\
 CONFIG_CCFLAGS +=		\
 	$(BACKTRACES)		\
 	$(FTRACE)		\
+	-DSYSDEBUG		\
 	-O3
 TARGET_ARCH ?=			\
 	-march=native
@@ -122,6 +127,7 @@ CONFIG_CPPFLAGS +=		\
 CONFIG_CCFLAGS +=		\
 	$(BACKTRACES)		\
 	$(FTRACE)		\
+	-DSYSDEBUG		\
 	-O2			\
 	-fno-inline
 CONFIG_COPTS +=			\
@@ -287,7 +293,7 @@ endif
 # LLVM Mode
 ifeq ($(MODE), llvm)
 TARGET_ARCH ?= -msse3
-CONFIG_CCFLAGS += $(BACKTRACES) $(FTRACE) -O2
+CONFIG_CCFLAGS += $(BACKTRACES) $(FTRACE) -DSYSDEBUG -O2
 AS = clang
 CC = clang
 CXX = clang++
diff --git a/libc/calls/chdir.c b/libc/calls/chdir.c
index 101f6dfb811..07b57656d1f 100644
--- a/libc/calls/chdir.c
+++ b/libc/calls/chdir.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -30,10 +31,14 @@
  * @see fchdir()
  */
 int chdir(const char *path) {
-  if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
-  if (!IsWindows()) {
-    return sys_chdir(path);
+  int rc;
+  if (IsAsan() && !__asan_is_valid(path, 1)) {
+    rc = efault();
+  } else if (!IsWindows()) {
+    rc = sys_chdir(path);
   } else {
-    return sys_chdir_nt(path);
+    rc = sys_chdir_nt(path);
   }
+  STRACE("chdir(%#s) → %d% m", path, rc);
+  return rc;
 }
diff --git a/libc/calls/close.c b/libc/calls/close.c
index 68012071073..ae30694a12e 100644
--- a/libc/calls/close.c
+++ b/libc/calls/close.c
@@ -19,7 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/sock/internal.h"
 #include "libc/sysv/errfuns.h"
@@ -61,6 +61,6 @@ int close(int fd) {
     }
   }
   __releasefd(fd);
-  SYSDEBUG("close(%d) -> %d", fd, rc);
+  STRACE("%s(%d) → %d% m", "close", fd, rc);
   return rc;
 }
diff --git a/libc/calls/commandv.c b/libc/calls/commandv.c
index fde8e689aa7..be7b86d3074 100644
--- a/libc/calls/commandv.c
+++ b/libc/calls/commandv.c
@@ -19,7 +19,7 @@
 #include "libc/bits/bits.h"
 #include "libc/bits/safemacros.internal.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/log/libfatal.internal.h"
@@ -159,6 +159,6 @@ noasan char *commandv(const char *name, char pathbuf[hasatleast PATH_MAX]) {
       errno = f;
     }
   }
-  SYSDEBUG("commandv(%#s, %p) → %#s% m", name, pathbuf, res);
+  STRACE("commandv(%#s, %p) → %#s% m", name, pathbuf, res);
   return res;
 }
diff --git a/libc/runtime/describeframe.c b/libc/calls/describeframe.c
similarity index 89%
rename from libc/runtime/describeframe.c
rename to libc/calls/describeframe.c
index 6d1f04e096e..1dc78593f57 100644
--- a/libc/runtime/describeframe.c
+++ b/libc/calls/describeframe.c
@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/log/libfatal.internal.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"
 #include "libc/runtime/memtrack.internal.h"
 #include "libc/runtime/runtime.h"
@@ -28,21 +28,19 @@
 noasan const char *DescribeFrame(int x) {
   /* asan runtime depends on this function */
   char *p;
-  static char buf[128];
+  static char buf[32];
   if (IsShadowFrame(x)) {
-    p = buf;
-    p = __stpcpy(p, " shadow of ");
-    p = __fixcpy(p, UNSHADOW(ADDR(x)), 48);
+    ksnprintf(buf, sizeof(buf), " /*shadow:%.12p*/", UNSHADOW(ADDR(x)));
     return buf;
-    return " shadow ";
+    return " /*shadow*/ ";
   } else if (IsAutoFrame(x)) {
-    return " automap";
+    return " /*automap*/";
   } else if (IsFixedFrame(x)) {
-    return " fixed  ";
+    return " /*fixed*/  ";
   } else if (IsArenaFrame(x)) {
-    return " arena  ";
+    return " /*arena*/  ";
   } else if (IsStaticStackFrame(x)) {
-    return " stack  ";
+    return " /*stack*/  ";
   } else {
     return "";
   }
diff --git a/libc/runtime/describemapping.c b/libc/calls/describemapping.c
similarity index 88%
rename from libc/runtime/describemapping.c
rename to libc/calls/describemapping.c
index 3dffeab43f9..93e4f9d7417 100644
--- a/libc/runtime/describemapping.c
+++ b/libc/calls/describemapping.c
@@ -20,19 +20,26 @@
 #include "libc/sysv/consts/map.h"
 #include "libc/sysv/consts/prot.h"
 
+static noasan char DescribeMapType(int flags) {
+  switch (flags & MAP_TYPE) {
+    case MAP_FILE:
+      return 'f';
+    case MAP_PRIVATE:
+      return 'p';
+    case MAP_SHARED:
+      return 's';
+    default:
+      return '?';
+  }
+}
+
 noasan char *DescribeMapping(int prot, int flags, char p[hasatleast 8]) {
   /* asan runtime depends on this function */
   p[0] = (prot & PROT_READ) ? 'r' : '-';
   p[1] = (prot & PROT_WRITE) ? 'w' : '-';
   p[2] = (prot & PROT_EXEC) ? 'x' : '-';
-  if (flags & MAP_PRIVATE) {
-    p[3] = 'p';
-  } else if (flags & MAP_SHARED) {
-    p[3] = 's';
-  } else {
-    p[3] = '?';
-  }
-  p[4] = (flags & MAP_ANONYMOUS) ? 'a' : 'f';
+  p[3] = DescribeMapType(flags);
+  p[4] = (flags & MAP_ANONYMOUS) ? 'a' : '-';
   p[5] = (flags & MAP_GROWSDOWN) ? 'S' : '-';
   p[6] = (flags & MAP_FIXED) ? 'F' : '-';
   p[7] = 0;
diff --git a/libc/runtime/directmap-metal.c b/libc/calls/directmap-metal.c
similarity index 100%
rename from libc/runtime/directmap-metal.c
rename to libc/calls/directmap-metal.c
diff --git a/libc/runtime/directmap-nt.c b/libc/calls/directmap-nt.c
similarity index 87%
rename from libc/runtime/directmap-nt.c
rename to libc/calls/directmap-nt.c
index e50ce99d620..d083fe3717f 100644
--- a/libc/runtime/directmap-nt.c
+++ b/libc/calls/directmap-nt.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/enum/filemapflags.h"
 #include "libc/nt/enum/pageflags.h"
@@ -46,14 +46,14 @@ textwindows noasan struct DirectMap sys_mmap_nt(void *addr, size_t size,
     dm.maphandle = CreateFileMappingNuma(-1, &kNtIsInheritable,
                                          kNtPageExecuteReadwrite, upsize >> 32,
                                          upsize, NULL, kNtNumaNoPreferredNode);
-    SYSDEBUG("CreateFileMappingNuma(-1, kNtPageExecuteReadwrite, 0x%x/0x%x) -> "
-             "0x%x",
-             upsize, size, dm.maphandle);
+    STRACE(
+        "CreateFileMappingNuma(-1, kNtPageExecuteReadwrite, %'zu/%'zu) -> %p",
+        upsize, size, dm.maphandle);
     if (dm.maphandle) {
       dm.addr =
           MapViewOfFileExNuma(dm.maphandle, kNtFileMapWrite | kNtFileMapExecute,
                               0, 0, upsize, addr, kNtNumaNoPreferredNode);
-      SYSDEBUG("MapViewOfFileExNuma(WX, 0x%x) -> addr:0x%x", addr, dm.addr);
+      STRACE("MapViewOfFileExNuma(WX, %p) → addr:%p", addr, dm.addr);
       if (dm.addr) {
         for (i = 0; i < size; i += got) {
           got = 0;
@@ -78,20 +78,16 @@ textwindows noasan struct DirectMap sys_mmap_nt(void *addr, size_t size,
         (prot & PROT_WRITE) ? kNtPageExecuteReadwrite : kNtPageExecuteRead,
         handle != -1 ? 0 : size >> 32, handle != -1 ? 0 : size, NULL,
         kNtNumaNoPreferredNode);
-    SYSDEBUG("CreateFileMappingNuma(fhand:%d, prot:%s, size:0x%x) -> "
-             "handle:0x%x",
-             handle, (prot & PROT_WRITE) ? "XRW" : "XR",
-             handle != -1 ? 0 : size);
+    STRACE("CreateFileMappingNuma(fhand:%ld, prot:%s, size:%'zu) → %p", handle,
+           (prot & PROT_WRITE) ? "XRW" : "XR", handle != -1 ? 0 : size);
     if (dm.maphandle) {
       dm.addr = MapViewOfFileExNuma(
           dm.maphandle,
           (prot & PROT_WRITE) ? kNtFileMapWrite | kNtFileMapExecute
                               : kNtFileMapRead | kNtFileMapExecute,
           off >> 32, off, size, addr, kNtNumaNoPreferredNode);
-      SYSDEBUG(
-          "MapViewOfFileExNuma(prot:%s, off:0x%x, size:0x%x, addr:0x%x) -> "
-          "addr:0x%x",
-          (prot & PROT_WRITE) ? "WX" : "RX", off, size, addr, dm.addr);
+      STRACE("MapViewOfFileExNuma(prot:%s, off:%'ld, size:%'zu, addr:%p) → %p",
+             (prot & PROT_WRITE) ? "WX" : "RX", off, size, addr, dm.addr);
       if (dm.addr) {
         return dm;
       } else {
diff --git a/libc/runtime/directmap.c b/libc/calls/directmap.c
similarity index 80%
rename from libc/runtime/directmap.c
rename to libc/calls/directmap.c
index ab1a121b8e9..a07365028c6 100644
--- a/libc/runtime/directmap.c
+++ b/libc/calls/directmap.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/errno.h"
 #include "libc/nt/runtime.h"
 #include "libc/runtime/directmap.internal.h"
@@ -36,20 +36,18 @@ noasan struct DirectMap sys_mmap(void *addr, size_t size, int prot, int flags,
                                  int fd, int64_t off) {
   /* asan runtime depends on this function */
   char mode[8];
-  struct DirectMap dm;
+  struct DirectMap d;
   if (!IsWindows() && !IsMetal()) {
-    dm.addr = __sys_mmap(addr, size, prot, flags, fd, off, off);
-    SYSDEBUG("sys_mmap(0x%p%s, 0x%x, %s, %d, %d) -> 0x%p %s", addr,
-             DescribeFrame((intptr_t)addr >> 16), size,
-             DescribeMapping(prot, flags, mode), (long)fd, off, dm.addr,
-             dm.addr != MAP_FAILED ? "" : strerror(errno));
-    dm.maphandle = kNtInvalidHandleValue;
-    return dm;
+    d.addr = __sys_mmap(addr, size, prot, flags, fd, off, off);
+    d.maphandle = kNtInvalidHandleValue;
   } else if (IsMetal()) {
-    return sys_mmap_metal(addr, size, prot, flags, fd, off);
+    d = sys_mmap_metal(addr, size, prot, flags, fd, off);
   } else {
-    return sys_mmap_nt(addr, size, prot, flags,
-                       fd != -1 ? g_fds.p[fd].handle : kNtInvalidHandleValue,
-                       off);
+    d = sys_mmap_nt(addr, size, prot, flags,
+                    fd != -1 ? g_fds.p[fd].handle : kNtInvalidHandleValue, off);
   }
+  STRACE("sys_mmap(%.12p%s, %'zu, %s, %d, %'ld) → {%.12p, %p}% m", addr,
+         DescribeFrame((intptr_t)addr >> 16), size,
+         DescribeMapping(prot, flags, mode), fd, off, d.addr, d.maphandle);
+  return d;
 }
diff --git a/libc/calls/dup.c b/libc/calls/dup.c
index 13b9ee6e323..e8c01080148 100644
--- a/libc/calls/dup.c
+++ b/libc/calls/dup.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
@@ -36,6 +36,6 @@ int dup(int fd) {
   } else {
     fd2 = sys_dup_nt(fd, -1, 0);
   }
-  SYSDEBUG("dup(%d) -> %d", fd, fd2);
+  STRACE("%s(%d) → %d% m", "dup", fd, fd2);
   return fd2;
 }
diff --git a/libc/calls/dup2.c b/libc/calls/dup2.c
index 4ec133e97ef..108f739df36 100644
--- a/libc/calls/dup2.c
+++ b/libc/calls/dup2.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
@@ -32,11 +32,14 @@
  * @vforksafe
  */
 int dup2(int oldfd, int newfd) {
-  SYSDEBUG("dup2(%d, %d)", oldfd, newfd);
-  if (oldfd == newfd) return newfd;
-  if (!IsWindows()) {
-    return sys_dup3(oldfd, newfd, 0);
+  int rc;
+  if (oldfd == newfd) {
+    rc = newfd;
+  } else if (!IsWindows()) {
+    rc = sys_dup3(oldfd, newfd, 0);
   } else {
-    return sys_dup_nt(oldfd, newfd, 0);
+    rc = sys_dup_nt(oldfd, newfd, 0);
   }
+  STRACE("dup2(%d, %d) → %d% m", oldfd, newfd, rc);
+  return rc;
 }
diff --git a/libc/calls/dup3.c b/libc/calls/dup3.c
index fc6e1985839..717518fd78f 100644
--- a/libc/calls/dup3.c
+++ b/libc/calls/dup3.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/sysv/errfuns.h"
 
@@ -36,10 +36,12 @@
  * @see dup(), dup2()
  */
 int dup3(int oldfd, int newfd, int flags) {
-  SYSDEBUG("dup3(%d, %d, %d)", oldfd, newfd, flags);
+  int rc;
   if (!IsWindows()) {
-    return sys_dup3(oldfd, newfd, flags);
+    rc = sys_dup3(oldfd, newfd, flags);
   } else {
-    return sys_dup_nt(oldfd, newfd, flags);
+    rc = sys_dup_nt(oldfd, newfd, flags);
   }
+  STRACE("dup3(%d, %d, %d) → %d% m", oldfd, newfd, flags, rc);
+  return rc;
 }
diff --git a/libc/calls/execve.c b/libc/calls/execve.c
index 8e9fa67aeca..f7a278ecb27 100644
--- a/libc/calls/execve.c
+++ b/libc/calls/execve.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/kprintf.h"
@@ -39,35 +39,41 @@
  * @asyncsignalsafe
  * @vforksafe
  */
-int execve(const char *program, char *const argv[], char *const envp[]) {
+int execve(const char *prog, char *const argv[], char *const envp[]) {
+  int rc;
   size_t i;
-  if (!program || !argv || !envp) return efault();
-  if (IsAsan() &&
-      (!__asan_is_valid(program, 1) || !__asan_is_valid_strlist(argv) ||
-       !__asan_is_valid_strlist(envp))) {
-    return efault();
-  }
-  if (DEBUGSYS) {
-    kprintf("SYS: execve(%s, {", program);
-    for (i = 0; argv[i]; ++i) {
-      if (i) kprintf(", ");
-      kprintf("%s", argv[i]);
+  if (!prog || !argv || !envp ||
+      (IsAsan() &&
+       (!__asan_is_valid(prog, 1) || !__asan_is_valid_strlist(argv) ||
+        !__asan_is_valid_strlist(envp)))) {
+    rc = efault();
+  } else {
+#ifdef SYSDEBUG
+    if (__strace > 0) {
+      kprintf(STRACE_PROLOGUE "execve(%#s, {", prog);
+      for (i = 0; argv[i]; ++i) {
+        if (i) kprintf(", ");
+        kprintf("%#s", argv[i]);
+      }
+      kprintf("}, {");
+      for (i = 0; envp[i]; ++i) {
+        if (i) kprintf(", ");
+        kprintf("%#s", envp[i]);
+      }
+      kprintf("})%n");
     }
-    kprintf("}, {");
-    for (i = 0; envp[i]; ++i) {
-      if (i) kprintf(", ");
-      kprintf("%s", envp[i]);
+#endif
+    for (i = 3; i < g_fds.n; ++i) {
+      if (g_fds.p[i].kind != kFdEmpty && (g_fds.p[i].flags & O_CLOEXEC)) {
+        close(i);
+      }
     }
-    kprintf("})\n");
-  }
-  for (i = 3; i < g_fds.n; ++i) {
-    if (g_fds.p[i].kind != kFdEmpty && (g_fds.p[i].flags & O_CLOEXEC)) {
-      close(i);
+    if (!IsWindows()) {
+      rc = sys_execve(prog, argv, envp);
+    } else {
+      rc = sys_execve_nt(prog, argv, envp);
     }
   }
-  if (!IsWindows()) {
-    return sys_execve(program, argv, envp);
-  } else {
-    return sys_execve_nt(program, argv, envp);
-  }
+  STRACE("execve(%#s) failed %d% m", prog, rc);
+  return rc;
 }
diff --git a/libc/calls/fchmodat.c b/libc/calls/fchmodat.c
index d33db04cf2b..75db6c76189 100644
--- a/libc/calls/fchmodat.c
+++ b/libc/calls/fchmodat.c
@@ -19,7 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -42,14 +42,13 @@
 int fchmodat(int dirfd, const char *path, uint32_t mode, int flags) {
   int rc;
   if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
-  if (weaken(__zipos_notat) && weaken(__zipos_notat)(dirfd, path) == -1) {
-    rc = -1; /* TODO(jart): implement me */
+  if (weaken(__zipos_notat) && (rc = __zipos_notat(dirfd, path)) == -1) {
+    STRACE("zipos fchmodat not supported yet");
   } else if (!IsWindows()) {
     rc = sys_fchmodat(dirfd, path, mode, flags);
   } else {
     rc = sys_fchmodat_nt(dirfd, path, mode, flags);
   }
-  SYSDEBUG("fchmodat(%d, %s, %o, %d) -> %d %s", (long)dirfd, path, mode, flags,
-           rc != -1 ? "" : strerror(errno));
+  STRACE("fchmodat(%d, %#s, %#o, %d) → %d% m", dirfd, path, mode, flags, rc);
   return rc;
 }
diff --git a/libc/calls/fchownat.c b/libc/calls/fchownat.c
index 4b408dcf671..e4b55f6e8d5 100644
--- a/libc/calls/fchownat.c
+++ b/libc/calls/fchownat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -39,9 +40,15 @@
  */
 int fchownat(int dirfd, const char *path, uint32_t uid, uint32_t gid,
              int flags) {
-  if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
-  if (weaken(__zipos_notat) && weaken(__zipos_notat)(dirfd, path) == -1) {
-    return -1; /* TODO(jart): implement me */
+  int rc;
+  if (IsAsan() && !__asan_is_valid(path, 1)) {
+    rc = efault();
+  } else if (weaken(__zipos_notat) && (rc = __zipos_notat(dirfd, path)) == -1) {
+    STRACE("zipos fchownat not supported yet");
+  } else {
+    rc = sys_fchownat(dirfd, path, uid, gid, flags);
   }
-  return sys_fchownat(dirfd, path, uid, gid, flags);
+  STRACE("fchownat(%d, %#s, %d, %d, %#b) → %d% m", dirfd, path, uid, gid, flags,
+         rc);
+  return rc;
 }
diff --git a/libc/calls/fcntl.c b/libc/calls/fcntl.c
index 230fcb045d8..40ce8f3da00 100644
--- a/libc/calls/fcntl.c
+++ b/libc/calls/fcntl.c
@@ -28,6 +28,12 @@
  *
  *     CHECK_NE(-1, fcntl(fd, F_SETFD, FD_CLOEXEC));
  *
+ * This function lets you duplicate file descriptors without running
+ * into an edge case where they take over stdio handles:
+ *
+ *     CHECK_GE((newfd = fcntl(oldfd, F_DUPFD,         3)), 3);
+ *     CHECK_GE((newfd = fcntl(oldfd, F_DUPFD_CLOEXEC, 3)), 3);
+ *
  * This function implements POSIX Advisory Locks, e.g.
  *
  *     CHECK_NE(-1, fcntl(zfd, F_SETLKW, &(struct flock){F_WRLCK}));
diff --git a/libc/calls/fdatasync.c b/libc/calls/fdatasync.c
index 7da2a6f3042..2f63c428129 100644
--- a/libc/calls/fdatasync.c
+++ b/libc/calls/fdatasync.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
@@ -28,9 +29,12 @@
  * @asyncsignalsafe
  */
 int fdatasync(int fd) {
+  int rc;
   if (!IsWindows()) {
-    return sys_fdatasync(fd);
+    rc = sys_fdatasync(fd);
   } else {
-    return sys_fdatasync_nt(fd);
+    rc = sys_fdatasync_nt(fd);
   }
+  STRACE("%s(%d) → %d% m", "fdatasync", fd, rc);
+  return rc;
 }
diff --git a/libc/calls/fileexists.c b/libc/calls/fileexists.c
index ad6de423a98..164b0bee9b7 100644
--- a/libc/calls/fileexists.c
+++ b/libc/calls/fileexists.c
@@ -69,8 +69,7 @@ bool fileexists(const char *path) {
   } else {
     res = false;
   }
-  SYSDEBUG("fileexists(%s) -> %s %s", path, res ? "true" : "false",
-           res ? "" : strerror(errno));
+  STRACE("fileexists(%#s) → %hhhd% m", path, res);
   if (!res && (errno == ENOENT || errno == ENOTDIR)) {
     errno = e;
   }
diff --git a/libc/calls/flock.c b/libc/calls/flock.c
index c8f7af7f914..8d6a1a05886 100644
--- a/libc/calls/flock.c
+++ b/libc/calls/flock.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
@@ -30,9 +31,12 @@
  * @return 0 on success, or -1 w/ errno
  */
 int flock(int fd, int op) {
+  int rc;
   if (!IsWindows()) {
-    return sys_flock(fd, op);
+    rc = sys_flock(fd, op);
   } else {
-    return sys_flock_nt(fd, op);
+    rc = sys_flock_nt(fd, op);
   }
+  STRACE("flock(%d, %d) → %d% m", fd, op, rc);
+  return rc;
 }
diff --git a/libc/calls/fstat-nt.c b/libc/calls/fstat-nt.c
index fd4bce28645..c2909562a84 100644
--- a/libc/calls/fstat-nt.c
+++ b/libc/calls/fstat-nt.c
@@ -18,8 +18,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/stat.h"
-#include "libc/calls/sysdebug.internal.h"
 #include "libc/fmt/conv.h"
 #include "libc/macros.internal.h"
 #include "libc/nexgen32e/bsr.h"
@@ -64,7 +64,7 @@ static textwindows uint32_t GetSizeOfReparsePoint(int64_t fh) {
       z += x < 0200 ? 1 : bsrl(tpenc(x)) >> 3;
     }
   } else {
-    SYSDEBUG("GetSizeOfReparsePoint failed %d", GetLastError());
+    STRACE("%s failed %m", "GetSizeOfReparsePoint");
   }
   return z;
 }
@@ -122,7 +122,7 @@ textwindows int sys_fstat_nt(int64_t handle, struct stat *st) {
             st->st_blocks = ROUNDUP(actualsize, PAGESIZE) / 512;
           }
         } else {
-          SYSDEBUG("GetFileInformationByHandle failed %d", GetLastError());
+          STRACE("%s failed %m", "GetFileInformationByHandle");
         }
         break;
       default:
@@ -130,7 +130,7 @@ textwindows int sys_fstat_nt(int64_t handle, struct stat *st) {
     }
     return 0;
   } else {
-    SYSDEBUG("GetFileType failed %d", GetLastError());
+    STRACE("%s failed %m", "GetFileType");
     return __winerr();
   }
 }
diff --git a/libc/calls/fstat-sysv.c b/libc/calls/fstat-sysv.c
index f8ac0f05492..e05714552f9 100644
--- a/libc/calls/fstat-sysv.c
+++ b/libc/calls/fstat-sysv.c
@@ -17,7 +17,6 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -42,7 +41,6 @@ int32_t sys_fstat(int32_t fd, struct stat *st) {
     __stat2cosmo(st, &ms);
     return 0;
   } else {
-    SYSDEBUG("sys_fstat(%d) failed w/ %m", fd);
     return -1;
   }
 }
diff --git a/libc/calls/fstat.c b/libc/calls/fstat.c
index e41f50834c7..3ae6364b905 100644
--- a/libc/calls/fstat.c
+++ b/libc/calls/fstat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -29,15 +30,19 @@
  * @asyncsignalsafe
  */
 int fstat(int fd, struct stat *st) {
+  int rc;
   if (__isfdkind(fd, kFdZip)) {
-    return weaken(__zipos_fstat)(
+    rc = weaken(__zipos_fstat)(
         (struct ZiposHandle *)(intptr_t)g_fds.p[fd].handle, st);
   } else if (!IsWindows() && !IsMetal()) {
-    return sys_fstat(fd, st);
+    rc = sys_fstat(fd, st);
   } else if (IsMetal()) {
-    return sys_fstat_metal(fd, st);
+    rc = sys_fstat_metal(fd, st);
+  } else if (!__isfdkind(fd, kFdFile)) {
+    rc = ebadf();
   } else {
-    if (!__isfdkind(fd, kFdFile)) return ebadf();
-    return sys_fstat_nt(g_fds.p[fd].handle, st);
+    rc = sys_fstat_nt(g_fds.p[fd].handle, st);
   }
+  STRACE("fstat(%d, [%s]) → %d% m", fd, __strace_stat(rc, st), rc);
+  return rc;
 }
diff --git a/libc/calls/fstatat.c b/libc/calls/fstatat.c
index db489f107ff..1dc1357d35f 100644
--- a/libc/calls/fstatat.c
+++ b/libc/calls/fstatat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -38,15 +39,28 @@
  * @return 0 on success, or -1 w/ errno
  * @see S_ISDIR(st.st_mode), S_ISREG()
  * @asyncsignalsafe
+ * @vforksafe
  */
 int fstatat(int dirfd, const char *path, struct stat *st, int flags) {
+  /* execve() depends on this */
+  int rc;
   struct ZiposUri zipname;
-  if (__isfdkind(dirfd, kFdZip)) return einval(); /* TODO(jart): implement me */
-  if (weaken(__zipos_stat) && weaken(__zipos_parseuri)(path, &zipname) != -1) {
-    return weaken(__zipos_stat)(&zipname, st);
+  if (__isfdkind(dirfd, kFdZip)) {
+    STRACE("zipos dirfd not supported yet");
+    rc = einval();
+  } else if (weaken(__zipos_stat) &&
+             weaken(__zipos_parseuri)(path, &zipname) != -1) {
+    if (!__vforked) {
+      rc = weaken(__zipos_stat)(&zipname, st);
+    } else {
+      rc = enotsup();
+    }
   } else if (!IsWindows()) {
-    return sys_fstatat(dirfd, path, st, flags);
+    rc = sys_fstatat(dirfd, path, st, flags);
   } else {
-    return sys_fstatat_nt(dirfd, path, st, flags);
+    rc = sys_fstatat_nt(dirfd, path, st, flags);
   }
+  STRACE("fstatat(%d, %#s, [%s], %#b) → %d% m", dirfd, path,
+         __strace_stat(rc, st), flags, rc);
+  return rc;
 }
diff --git a/libc/calls/fsync.c b/libc/calls/fsync.c
index 39a8b447692..99b6286ec12 100644
--- a/libc/calls/fsync.c
+++ b/libc/calls/fsync.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
@@ -28,9 +29,12 @@
  * @asyncsignalsafe
  */
 int fsync(int fd) {
+  int rc;
   if (!IsWindows()) {
-    return sys_fsync(fd);
+    rc = sys_fsync(fd);
   } else {
-    return sys_fdatasync_nt(fd);
+    rc = sys_fdatasync_nt(fd);
   }
+  STRACE("%s(%d) → %d% m", "fsync", fd, rc);
+  return rc;
 }
diff --git a/libc/calls/ftruncate.c b/libc/calls/ftruncate.c
index a55b2fca4ad..5c17d57806a 100644
--- a/libc/calls/ftruncate.c
+++ b/libc/calls/ftruncate.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/sysv/errfuns.h"
 
@@ -32,11 +33,15 @@
  * @asyncsignalsafe
  */
 int ftruncate(int fd, int64_t length) {
-  if (fd < 0) return einval();
-  if (!IsWindows()) {
-    return sys_ftruncate(fd, length, length);
+  int rc;
+  if (fd < 0) {
+    rc = einval();
+  } else if (!IsWindows()) {
+    rc = sys_ftruncate(fd, length, length);
   } else {
-    if (fd >= g_fds.n) return ebadf();
-    return sys_ftruncate_nt(g_fds.p[fd].handle, length);
+    if (fd >= g_fds.n) rc = ebadf();
+    rc = sys_ftruncate_nt(g_fds.p[fd].handle, length);
   }
+  STRACE("ftruncate(%d, %'ld) → %d% m", fd, length, rc);
+  return rc;
 }
diff --git a/libc/calls/g_fds_init.S b/libc/calls/g_fds_init.S
index 4e7d3a9996b..b444acd8472 100644
--- a/libc/calls/g_fds_init.S
+++ b/libc/calls/g_fds_init.S
@@ -18,10 +18,10 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-	.init.start 302,_init_g_fds
+	.init.start 305,_init_g_fds
 	push	%rdi
 	push	%rsi
 	call	InitializeFileDescriptors
 	pop	%rsi
 	pop	%rdi
-	.init.end 302,_init_g_fds
+	.init.end 305,_init_g_fds
diff --git a/libc/calls/getcwd.c b/libc/calls/getcwd.c
index 536d8df798a..caa17091f8f 100644
--- a/libc/calls/getcwd.c
+++ b/libc/calls/getcwd.c
@@ -16,11 +16,13 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
+#include "libc/log/backtrace.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/str/str.h"
 #include "libc/sysv/errfuns.h"
@@ -43,19 +45,20 @@ char *getcwd(char *buf, size_t size) {
   if (buf) {
     p = buf;
     if (!size) {
-      SYSDEBUG("getcwd(%p, %x) EINVAL", buf, size);
       einval();
+      STRACE("getcwd(%p, %'zu) %m", buf, size);
       return 0;
     }
   } else if (weaken(malloc)) {
+    assert(!__vforked);
     if (!size) size = PATH_MAX + 1;
     if (!(p = weaken(malloc)(size))) {
-      SYSDEBUG("getcwd(%p, %x) ENOMEM", buf, size);
+      STRACE("getcwd(%p, %'zu) %m", buf, size);
       return 0;
     }
   } else {
-    SYSDEBUG("getcwd() EINVAL needs buf≠0 or STATIC_YOINK(\"malloc\")");
     einval();
+    STRACE("getcwd() needs buf≠0 or STATIC_YOINK(\"malloc\")");
     return 0;
   }
   *p = '\0';
@@ -85,6 +88,6 @@ char *getcwd(char *buf, size_t size) {
       }
     }
   }
-  SYSDEBUG("getcwd(%p, %x) -> %s", buf, size, r);
+  STRACE("getcwd(%p, %'zu) → %#s", buf, size, r);
   return r;
 }
diff --git a/libc/calls/getitimer.c b/libc/calls/getitimer.c
index 476df9bdaee..57b8937a994 100644
--- a/libc/calls/getitimer.c
+++ b/libc/calls/getitimer.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -29,13 +30,22 @@
  * @return 0 on success or -1 w/ errno
  */
 int getitimer(int which, struct itimerval *curvalue) {
+  int rc;
   if (IsAsan() && !__asan_is_valid(curvalue, sizeof(*curvalue))) {
-    return efault();
+    rc = efault();
+  } else if (!IsWindows()) {
+    rc = sys_getitimer(which, curvalue);
+  } else if (!curvalue) {
+    rc = efault();
+  } else {
+    rc = sys_setitimer_nt(which, 0, curvalue);
   }
-  if (!IsWindows()) {
-    return sys_getitimer(which, curvalue);
+  if (curvalue) {
+    STRACE("getitimer(%d, [{{%'ld, %'ld}, {%'ld, %'ld}}]) → %d% m", which,
+           curvalue->it_interval.tv_sec, curvalue->it_interval.tv_usec,
+           curvalue->it_value.tv_sec, curvalue->it_value.tv_usec, rc);
   } else {
-    if (!curvalue) return efault();
-    return sys_setitimer_nt(which, 0, curvalue);
+    STRACE("getitimer(%d, 0) → %d% m", which, rc);
   }
+  return rc;
 }
diff --git a/libc/calls/getpgid.c b/libc/calls/getpgid.c
index 8f8d0cac549..8ae485a7ee4 100644
--- a/libc/calls/getpgid.c
+++ b/libc/calls/getpgid.c
@@ -18,15 +18,19 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 
 /**
  * Returns process group id.
  */
 int getpgid(int pid) {
+  int rc;
   if (!IsWindows()) {
-    return sys_getpgid(pid);
+    rc = sys_getpgid(pid);
   } else {
-    return getpid();
+    rc = getpid();
   }
+  STRACE("%s(%d) → %d% m", "getpgid", pid, rc);
+  return rc;
 }
diff --git a/libc/calls/getrlimit.c b/libc/calls/getrlimit.c
index c651a3f707f..17f117bde02 100644
--- a/libc/calls/getrlimit.c
+++ b/libc/calls/getrlimit.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -31,7 +32,16 @@
  * @see libc/sysv/consts.sh
  */
 int getrlimit(int resource, struct rlimit *rlim) {
-  if (resource == 127) return einval();
-  if (IsAsan() && !__asan_is_valid(rlim, sizeof(*rlim))) return efault();
-  return sys_getrlimit(resource, rlim);
+  int rc;
+  char buf[64];
+  if (resource == 127) {
+    rc = einval();
+  } else if (IsAsan() && !__asan_is_valid(rlim, sizeof(*rlim))) {
+    rc = efault();
+  } else {
+    rc = sys_getrlimit(resource, rlim);
+  }
+  STRACE("getrlimit(%s, [%s]) → %d% m", __strace_rlimit_name(resource),
+         __strace_rlimit(buf, sizeof(buf), rc, rlim), rc);
+  return rc;
 }
diff --git a/libc/calls/getsid.c b/libc/calls/getsid.c
index a2f057528b5..4c29139f2df 100644
--- a/libc/calls/getsid.c
+++ b/libc/calls/getsid.c
@@ -18,10 +18,14 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 
 /**
  * Creates session and sets the process group id.
  */
 uint32_t getsid(int pid) {
-  return sys_getsid(pid);
+  int rc;
+  rc = sys_getsid(pid);
+  STRACE("%s(%d) → %d% m", "getsid", pid, rc);
+  return rc;
 }
diff --git a/libc/calls/getuid.c b/libc/calls/getuid.c
index f801a93f759..34eb2702f71 100644
--- a/libc/calls/getuid.c
+++ b/libc/calls/getuid.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/accounting.h"
@@ -51,11 +52,14 @@ static textwindows dontinline uint32_t GetUserNameHash(void) {
  * @vforksafe
  */
 uint32_t getuid(void) {
+  int rc;
   if (!IsWindows()) {
-    return sys_getuid();
+    rc = sys_getuid();
   } else {
-    return GetUserNameHash();
+    rc = GetUserNameHash();
   }
+  STRACE("%s() → %d% m", "getuid", rc);
+  return rc;
 }
 
 /**
@@ -68,9 +72,12 @@ uint32_t getuid(void) {
  * @vforksafe
  */
 uint32_t getgid(void) {
+  int rc;
   if (!IsWindows()) {
-    return sys_getgid();
+    rc = sys_getgid();
   } else {
-    return GetUserNameHash();
+    rc = GetUserNameHash();
   }
+  STRACE("%s() → %d% m", "getgid", rc);
+  return rc;
 }
diff --git a/libc/calls/ioctl_siocgifconf.c b/libc/calls/ioctl_siocgifconf.c
index debafc1b44f..a1b41bea4cb 100644
--- a/libc/calls/ioctl_siocgifconf.c
+++ b/libc/calls/ioctl_siocgifconf.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/bits/bits.h"
 #include "libc/bits/weaken.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/ioctl.h"
diff --git a/libc/calls/ioctl_tcgets.c b/libc/calls/ioctl_tcgets.c
index 564fcb7723c..5e9a7aa83c1 100644
--- a/libc/calls/ioctl_tcgets.c
+++ b/libc/calls/ioctl_tcgets.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
 #include "libc/calls/ioctl.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/metatermios.internal.h"
 #include "libc/calls/termios.internal.h"
 #include "libc/calls/ttydefaults.h"
@@ -65,23 +66,27 @@ static int ioctl_tcgets_sysv(int fd, struct termios *tio) {
  * @see ioctl(fd, TIOCGETA, tio) dispatches here
  */
 int ioctl_tcgets(int fd, ...) {
+  int rc;
   va_list va;
   struct termios *tio;
   va_start(va, fd);
   tio = va_arg(va, struct termios *);
   va_end(va);
   if (fd >= 0) {
-    if (!tio) return efault();
-    if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
-      return enotty();
+    if (!tio) {
+      rc = efault();
+    } else if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
+      rc = enotty();
     } else if (IsMetal()) {
-      return ioctl_tcgets_metal(fd, tio);
+      rc = ioctl_tcgets_metal(fd, tio);
     } else if (!IsWindows()) {
-      return ioctl_tcgets_sysv(fd, tio);
+      rc = ioctl_tcgets_sysv(fd, tio);
     } else {
-      return ioctl_tcgets_nt(fd, tio);
+      rc = ioctl_tcgets_nt(fd, tio);
     }
   } else {
-    return einval();
+    rc = einval();
   }
+  STRACE("ioctl_tcgets(%d, %p) → %d% m", fd, tio, rc);
+  return rc;
 }
diff --git a/libc/calls/ioctl_tcsets.c b/libc/calls/ioctl_tcsets.c
index a89abb0b806..4f665b2db46 100644
--- a/libc/calls/ioctl_tcsets.c
+++ b/libc/calls/ioctl_tcsets.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
 #include "libc/calls/ioctl.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/metatermios.internal.h"
 #include "libc/calls/termios.internal.h"
 #include "libc/dce.h"
@@ -86,5 +87,6 @@ int ioctl_tcsets(int fd, uint64_t request, ...) {
   if (rc != -1) {
     __nomultics = !(tio->c_oflag & OPOST);
   }
+  STRACE("ioctl_tcsets(%d, %p, %p) → %d% m", fd, request, tio, rc);
   return rc;
 }
diff --git a/libc/calls/isdirectory.c b/libc/calls/isdirectory.c
index c1c9278898f..2b92d311529 100644
--- a/libc/calls/isdirectory.c
+++ b/libc/calls/isdirectory.c
@@ -19,9 +19,9 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/metastat.internal.h"
 #include "libc/calls/struct/stat.h"
-#include "libc/calls/sysdebug.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -68,8 +68,7 @@ bool isdirectory(const char *path) {
   } else {
     res = isdirectory_nt(path);
   }
-  SYSDEBUG("isdirectory(%s) -> %s %s", path, res ? "true" : "false",
-           res ? "" : strerror(errno));
+  STRACE("isdirectory(%#s) → %hhhd% m", path, res);
   if (!res && (errno == ENOENT || errno == ENOTDIR)) {
     errno = e;
   }
diff --git a/libc/calls/isexecutable.c b/libc/calls/isexecutable.c
index f79f7ca6deb..f8de085a602 100644
--- a/libc/calls/isexecutable.c
+++ b/libc/calls/isexecutable.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/stat.h"
+#include "libc/sysv/consts/at.h"
 #include "libc/sysv/consts/s.h"
 
 /**
@@ -25,9 +26,11 @@
  *
  * @see access(exe, X_OK) which is more accurate on NT
  * @asyncsignalsafe
+ * @vforksafe
  */
 bool isexecutable(const char *path) {
+  /* execve() depends on this */
   struct stat st;
-  if (stat(path, &st)) return 0;
-  return st.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH);
+  if (fstatat(AT_FDCWD, path, &st, 0)) return 0;
+  return !!(st.st_mode & 0111);
 }
diff --git a/libc/calls/isregularfile.c b/libc/calls/isregularfile.c
index 66d0022d424..ca938c13043 100644
--- a/libc/calls/isregularfile.c
+++ b/libc/calls/isregularfile.c
@@ -40,7 +40,7 @@
  * @see isdirectory(), ischardev(), issymlink()
  */
 bool isregularfile(const char *path) {
-  int rc, e;
+  int e;
   union metastat st;
   struct ZiposUri zipname;
   if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
diff --git a/libc/calls/linkat.c b/libc/calls/linkat.c
index 2df6171c0b3..05ef16efbb6 100644
--- a/libc/calls/linkat.c
+++ b/libc/calls/linkat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -36,18 +37,20 @@
  */
 int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath,
            int flags) {
+  int rc;
   if (IsAsan() &&
       (!__asan_is_valid(oldpath, 1) || !__asan_is_valid(newpath, 1))) {
-    return efault();
-  }
-  if (weaken(__zipos_notat) &&
-      (weaken(__zipos_notat)(olddirfd, oldpath) == -1 ||
-       weaken(__zipos_notat)(newdirfd, newpath) == -1)) {
-    return -1; /* TODO(jart): implement me */
-  }
-  if (!IsWindows()) {
-    return sys_linkat(olddirfd, oldpath, newdirfd, newpath, flags);
+    rc = efault();
+  } else if (weaken(__zipos_notat) &&
+             ((rc = __zipos_notat(olddirfd, oldpath)) == -1 ||
+              (rc = __zipos_notat(newdirfd, newpath)) == -1)) {
+    STRACE("zipos fchownat not supported yet");
+  } else if (!IsWindows()) {
+    rc = sys_linkat(olddirfd, oldpath, newdirfd, newpath, flags);
   } else {
-    return sys_linkat_nt(olddirfd, oldpath, newdirfd, newpath);
+    rc = sys_linkat_nt(olddirfd, oldpath, newdirfd, newpath);
   }
+  STRACE("linkat(%d, %#s, %d, %#s, %#b) → %d% m", olddirfd, oldpath, newdirfd,
+         newpath, flags, rc);
+  return rc;
 }
diff --git a/libc/calls/lseek.c b/libc/calls/lseek.c
index e391f3bef39..07961309f1f 100644
--- a/libc/calls/lseek.c
+++ b/libc/calls/lseek.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/log/backtrace.internal.h"
 #include "libc/zipos/zipos.internal.h"
@@ -33,14 +34,17 @@
  * @asyncsignalsafe
  */
 int64_t lseek(int fd, int64_t offset, unsigned whence) {
+  int64_t rc;
   if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
-    return weaken(__zipos_lseek)(
+    rc = weaken(__zipos_lseek)(
         (struct ZiposHandle *)(intptr_t)g_fds.p[fd].handle, offset, whence);
   } else if (!IsWindows() && !IsOpenbsd() && !IsNetbsd()) {
-    return sys_lseek(fd, offset, whence, 0);
+    rc = sys_lseek(fd, offset, whence, 0);
   } else if (IsOpenbsd() || IsNetbsd()) {
-    return sys_lseek(fd, offset, offset, whence);
+    rc = sys_lseek(fd, offset, offset, whence);
   } else {
-    return sys_lseek_nt(fd, offset, whence);
+    rc = sys_lseek_nt(fd, offset, whence);
   }
+  STRACE("lseek(%d, %'ld, %d) → %'ld% m", fd, offset, whence, rc);
+  return rc;
 }
diff --git a/libc/calls/madvise-nt.c b/libc/calls/madvise-nt.c
index 6592ff700ee..ce50c000221 100644
--- a/libc/calls/madvise-nt.c
+++ b/libc/calls/madvise-nt.c
@@ -50,8 +50,7 @@ forceinline typeof(OfferVirtualMemory) *GetOfferVirtualMemory(void) {
 textwindows int sys_madvise_nt(void *addr, size_t length, int advice) {
   uint32_t rangecount;
   struct NtMemoryRangeEntry ranges[1];
-  if ((advice & (int)MADV_WILLNEED) == (int)MADV_WILLNEED ||
-      (advice & (int)MADV_SEQUENTIAL) == (int)MADV_SEQUENTIAL) {
+  if (advice == MADV_WILLNEED || advice == MADV_SEQUENTIAL) {
     typeof(PrefetchVirtualMemory) *fn = GetPrefetchVirtualMemory();
     if (fn) {
       ranges[0].VirtualAddress = addr;
@@ -65,7 +64,7 @@ textwindows int sys_madvise_nt(void *addr, size_t length, int advice) {
     } else {
       return enosys();
     }
-  } else if ((advice & (int)MADV_FREE) == (int)MADV_FREE) {
+  } else if (advice == MADV_FREE) {
     typeof(OfferVirtualMemory) *fn = GetOfferVirtualMemory();
     if (fn) {
       if (fn(addr, length, kNtVmOfferPriorityNormal)) {
diff --git a/libc/calls/madvise.c b/libc/calls/madvise.c
index d73571ae398..d4f2c7b516d 100644
--- a/libc/calls/madvise.c
+++ b/libc/calls/madvise.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -31,10 +32,18 @@
  * @see fadvise()
  */
 int madvise(void *addr, size_t length, int advice) {
-  if (IsAsan() && !__asan_is_valid(addr, length)) return efault();
-  if (!IsWindows()) {
-    return sys_madvise(addr, length, advice);
+  int rc;
+  if (advice != 127 /* see consts.sh */) {
+    if (IsAsan() && !__asan_is_valid(addr, length)) {
+      rc = efault();
+    } else if (!IsWindows()) {
+      rc = sys_madvise(addr, length, advice);
+    } else {
+      rc = sys_madvise_nt(addr, length, advice);
+    }
   } else {
-    return sys_madvise_nt(addr, length, advice);
+    rc = einval();
   }
+  STRACE("madvise(%p, %'zu, %d) → %d% m", addr, length, advice, rc);
+  return rc;
 }
diff --git a/libc/calls/mkdirat.c b/libc/calls/mkdirat.c
index 29ccaedb464..b34f8341880 100644
--- a/libc/calls/mkdirat.c
+++ b/libc/calls/mkdirat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/consts/at.h"
@@ -38,13 +39,16 @@
  * @see makedirs()
  */
 int mkdirat(int dirfd, const char *path, unsigned mode) {
-  if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
-  if (weaken(__zipos_notat) && weaken(__zipos_notat)(dirfd, path) == -1) {
-    return -1; /* TODO(jart): implement me */
-  }
-  if (!IsWindows()) {
-    return sys_mkdirat(dirfd, path, mode);
+  int rc;
+  if (IsAsan() && !__asan_is_valid(path, 1)) {
+    rc = efault();
+  } else if (weaken(__zipos_notat) && (rc = __zipos_notat(dirfd, path)) == -1) {
+    STRACE("zipos mkdirat not supported yet");
+  } else if (!IsWindows()) {
+    rc = sys_mkdirat(dirfd, path, mode);
   } else {
-    return sys_mkdirat_nt(dirfd, path, mode);
+    rc = sys_mkdirat_nt(dirfd, path, mode);
   }
+  STRACE("mkdirat(%d, %#s, %#o) → %d% m", dirfd, path, mode, rc);
+  return rc;
 }
diff --git a/libc/calls/mknod.c b/libc/calls/mknod.c
index 33b13d598c8..63d2b971569 100644
--- a/libc/calls/mknod.c
+++ b/libc/calls/mknod.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/consts/s.h"
@@ -38,14 +39,17 @@
  * @asyncsignalsafe
  */
 int mknod(const char *path, uint32_t mode, uint64_t dev) {
+  int rc;
   if (IsAsan() && !__asan_is_valid(path, 1)) return efault();
   if (mode & S_IFREG) return creat(path, mode & ~S_IFREG);
   if (mode & S_IFDIR) return mkdir(path, mode & ~S_IFDIR);
   if (mode & S_IFIFO) return mkfifo(path, mode & ~S_IFIFO);
   if (!IsWindows()) {
     /* TODO(jart): Whys there code out there w/ S_xxx passed via dev? */
-    return sys_mknod(path, mode, dev);
+    rc = sys_mknod(path, mode, dev);
   } else {
-    return enosys();
+    rc = enosys();
   }
+  STRACE("mknod(%#s, %#o, %#lx) → %d% m", path, mode, dev, rc);
+  return rc;
 }
diff --git a/libc/calls/mkntpath.c b/libc/calls/mkntpath.c
index 0f60e65ff52..85248baadd1 100644
--- a/libc/calls/mkntpath.c
+++ b/libc/calls/mkntpath.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
 #include "libc/calls/ntmagicpaths.internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/nt/systeminfo.h"
 #include "libc/str/oldutf16.internal.h"
 #include "libc/str/str.h"
@@ -76,8 +76,8 @@ textwindows int __mkntpath2(const char *path,
    * 4. Reserve ≥10 for CreateNamedPipe "\\.\pipe\" prefix requirement
    * 5. Reserve ≥13 for mkdir() i.e. 1+8+3+1, e.g. "\\ffffffff.xxx\0"
    */
-  char *q;
   char16_t *p;
+  const char *q;
   size_t i, n, m, z;
   if (!path) return efault();
   path = FixNtMagicPath(path, flags);
@@ -96,7 +96,7 @@ textwindows int __mkntpath2(const char *path,
   }
   n = tprecode8to16(p, z, q).ax;
   if (n == z - 1) {
-    SYSDEBUG("path too long for windows: %s", path);
+    STRACE("path too long for windows: %#s", path);
     return enametoolong();
   }
   for (i = 0; i < n; ++i) {
diff --git a/libc/calls/mkntpathat.c b/libc/calls/mkntpathat.c
index a2f4e2cef42..7dc8f49b70a 100644
--- a/libc/calls/mkntpathat.c
+++ b/libc/calls/mkntpathat.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/files.h"
 #include "libc/str/str.h"
@@ -35,7 +35,7 @@ int __mkntpathat(int dirfd, const char *path, int flags,
                                       kNtFileNameNormalized | kNtVolumeNameDos);
     if (!dirlen) return __winerr();
     if (dirlen + 1 + filelen + 1 > ARRAYLEN(dir)) {
-      SYSDEBUG("path too long: %.*hs\\%.*hs", dirlen, dir, filelen, file);
+      STRACE("path too long: %#.*hs\\%#.*hs", dirlen, dir, filelen, file);
       return enametoolong();
     }
     dir[dirlen] = u'\\';
diff --git a/libc/runtime/mman.greg.c b/libc/calls/mman.greg.c
similarity index 100%
rename from libc/runtime/mman.greg.c
rename to libc/calls/mman.greg.c
diff --git a/libc/runtime/mremap-sysv.c b/libc/calls/mremap-sysv.greg.c
similarity index 85%
rename from libc/runtime/mremap-sysv.c
rename to libc/calls/mremap-sysv.greg.c
index 76303f16143..83e5dd297c9 100644
--- a/libc/runtime/mremap-sysv.c
+++ b/libc/calls/mremap-sysv.greg.c
@@ -18,10 +18,19 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/bits/bits.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/sysv/consts/map.h"
 #include "libc/sysv/consts/mremap.h"
 #include "libc/sysv/errfuns.h"
 
+/**
+ * Relocates memory.
+ *
+ * This function lets you move to to different addresses witohut copying
+ * it. This system call is currently supported on Linux and NetBSD. Your
+ * C library runtime won't have any awareness of this memory, so certain
+ * features like ASAN memory safety and kprintf() won't work as well.
+ */
 privileged void *sys_mremap(void *p, size_t n, size_t m, int f, void *q) {
   bool cf;
   uintptr_t rax, rdi, rsi, rdx;
@@ -43,7 +52,7 @@ privileged void *sys_mremap(void *p, size_t n, size_t m, int f, void *q) {
       asm(CFLAG_ASM("syscall")
           : CFLAG_CONSTRAINT(cf), "+a"(rax)
           : "D"(p), "S"(n), "d"(q), "r"(r10), "r"(r8)
-          : "rcx", "r11", "memory", "cc");
+          : "rcx", "r9", "r11", "memory", "cc");
       if (cf) errno = rax, rax = -1;
     } else {
       rax = einval();
@@ -51,5 +60,6 @@ privileged void *sys_mremap(void *p, size_t n, size_t m, int f, void *q) {
   } else {
     rax = enosys();
   }
+  STRACE("sys_mremap(%p, %'zu, %'zu, %#b, %p) → %p% m", p, n, m, f, q, rax);
   return (void *)rax;
 }
diff --git a/libc/runtime/munmap-metal.c b/libc/calls/munmap-metal.c
similarity index 100%
rename from libc/runtime/munmap-metal.c
rename to libc/calls/munmap-metal.c
diff --git a/libc/runtime/munmap-sysv.c b/libc/calls/munmap-sysv.c
similarity index 93%
rename from libc/runtime/munmap-sysv.c
rename to libc/calls/munmap-sysv.c
index c4db57ac61f..2d93337dad0 100644
--- a/libc/runtime/munmap-sysv.c
+++ b/libc/calls/munmap-sysv.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/runtime/directmap.internal.h"
 #include "libc/runtime/memtrack.internal.h"
 
@@ -28,7 +28,7 @@ int sys_munmap(void *p, size_t n) {
   } else {
     rc = sys_munmap_metal(p, n);
   }
-  SYSDEBUG("sys_munmap(0x%p%s, 0x%x) -> %d", p,
-           DescribeFrame((intptr_t)p >> 16), n, (long)rc);
+  STRACE("sys_munmap(%p%s, %'zu) → %d", p, DescribeFrame((intptr_t)p >> 16), n,
+         rc);
   return rc;
 }
diff --git a/libc/calls/ntaccesscheck.c b/libc/calls/ntaccesscheck.c
index 79104c1c338..07f3a72a1a5 100644
--- a/libc/calls/ntaccesscheck.c
+++ b/libc/calls/ntaccesscheck.c
@@ -19,7 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/nt/enum/accessmask.h"
 #include "libc/nt/enum/securityimpersonationlevel.h"
@@ -87,24 +87,24 @@ textwindows int ntaccesscheck(const char16_t *pathname, uint32_t flags) {
           if (result || flags == F_OK) {
             rc = 0;
           } else {
-            SYSDEBUG("ntaccesscheck finale failed %d %d", result, flags);
+            STRACE("ntaccesscheck finale failed %d %d", result, flags);
             rc = eacces();
           }
         } else {
           rc = __winerr();
-          SYSDEBUG("AccessCheck failed: %m");
+          STRACE("%s failed: %m", "AccessCheck");
         }
       } else {
         rc = __winerr();
-        SYSDEBUG("DuplicateToken failed: %m");
+        STRACE("%s failed: %m", "DuplicateToken");
       }
     } else {
       rc = __winerr();
-      SYSDEBUG("OpenProcessToken failed: %m");
+      STRACE("%s failed: %m", "OpenProcessToken");
     }
   } else {
     e = GetLastError();
-    SYSDEBUG("GetFileSecurity failed: %d %d", e, secsize);
+    STRACE("GetFileSecurity failed: %d %u", e, secsize);
     if (!IsTiny() && e == kNtErrorInsufficientBuffer) {
       if (!freeme && weaken(malloc) && (freeme = weaken(malloc)(secsize))) {
         s = freeme;
diff --git a/libc/calls/ntspawn.c b/libc/calls/ntspawn.c
index a9f30a27ad0..6f53b38d156 100644
--- a/libc/calls/ntspawn.c
+++ b/libc/calls/ntspawn.c
@@ -19,7 +19,7 @@
 #include "libc/bits/pushpop.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/ntspawn.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/enum/filemapflags.h"
 #include "libc/nt/enum/pageflags.h"
@@ -95,7 +95,7 @@ textwindows int ntspawn(
       } else {
         __winerr();
       }
-      SYSDEBUG("CreateProcess(`%hs`, `%hs`) -> %d", prog16, block->cmdline, rc);
+      STRACE("CreateProcess(%#hs, %#hs) → %d% m", prog16, block->cmdline, rc);
     }
   } else {
     __winerr();
diff --git a/libc/calls/openat.c b/libc/calls/openat.c
index 501f54d0a2f..00f1ad72910 100644
--- a/libc/calls/openat.c
+++ b/libc/calls/openat.c
@@ -19,7 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/log/log.h"
@@ -73,8 +73,7 @@ int openat(int dirfd, const char *file, int flags, ...) {
   } else {
     rc = efault();
   }
-  SYSDEBUG("openat(%d, %s, %d, %d) -> %d %s", (long)dirfd, file, flags,
-           (flags & (O_CREAT | O_TMPFILE)) ? mode : 0, (long)rc,
-           rc == -1 ? strerror(errno) : "");
+  STRACE("openat(%d, %#s, %#x, %#o) → %d% m", dirfd, file, flags,
+         (flags & (O_CREAT | O_TMPFILE)) ? mode : 0, rc);
   return rc;
 }
diff --git a/libc/calls/pause.c b/libc/calls/pause.c
index 1ce657307f5..81ef62957e6 100644
--- a/libc/calls/pause.c
+++ b/libc/calls/pause.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/errno.h"
 #include "libc/sysv/consts/sig.h"
@@ -36,6 +37,7 @@ int pause(void) {
   int rc, olderr;
   sigset_t oldmask;
   olderr = errno;
+  STRACE("pause()");
   if ((rc = sys_pause()) == -1 && errno == ENOSYS) {
     errno = olderr;
     if (sigprocmask(SIG_BLOCK, NULL, &oldmask) == -1) return -1;
diff --git a/libc/calls/program_executable_name.c b/libc/calls/program_executable_name.c
index 38845cf9739..97ecf0468cb 100644
--- a/libc/calls/program_executable_name.c
+++ b/libc/calls/program_executable_name.c
@@ -20,7 +20,7 @@
 #include "libc/bits/bits.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/log/libfatal.internal.h"
@@ -125,7 +125,7 @@ textstartup void program_executable_name_init(int argc, char **argv,
   GetProgramExecutableName(executable, argv[0], auxv);
   errno = e;
   __stpcpy(program_executable_name, executable);
-  SYSDEBUG("program_executable_name → %#s", program_executable_name);
+  STRACE("program_executable_name → %#s", program_executable_name);
 }
 
 const void *const program_executable_name_init_ctor[] initarray = {
diff --git a/libc/calls/readlinkat-nt.c b/libc/calls/readlinkat-nt.c
index 13300dacaa5..ade68047171 100644
--- a/libc/calls/readlinkat-nt.c
+++ b/libc/calls/readlinkat-nt.c
@@ -20,7 +20,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/nexgen32e/bsr.h"
 #include "libc/nt/createfile.h"
@@ -39,7 +39,7 @@
 static textwindows ssize_t sys_readlinkat_nt_error(void) {
   uint32_t e;
   e = GetLastError();
-  SYSDEBUG("sys_readlinkat_nt() error %d", e);
+  STRACE("sys_readlinkat_nt() error %d", e);
   switch (e) {
     case kNtErrorNotAReparsePoint:
       return einval();
@@ -56,11 +56,11 @@ textwindows ssize_t sys_readlinkat_nt(int dirfd, const char *path, char *buf,
   uint64_t w;
   wint_t x, y;
   void *freeme;
-  uint32_t e, i, j, n, mem;
+  uint32_t i, j, n, mem;
   char16_t path16[PATH_MAX], *p;
   struct NtReparseDataBuffer *rdb;
   if (__mkntpathat(dirfd, path, 0, path16) == -1) {
-    SYSDEBUG("sys_readlinkat_nt() failed b/c __mkntpathat() failed");
+    STRACE("sys_readlinkat_nt() failed b/c __mkntpathat() failed");
     return -1;
   }
   if (weaken(malloc)) {
@@ -72,7 +72,7 @@ textwindows ssize_t sys_readlinkat_nt(int dirfd, const char *path, char *buf,
     rdb = (struct NtReparseDataBuffer *)buf;
     freeme = 0;
   } else {
-    SYSDEBUG("sys_readlinkat_nt() needs bigger buffer malloc() to be yoinked");
+    STRACE("sys_readlinkat_nt() needs bigger buffer malloc() to be yoinked");
     return enomem();
   }
   if ((h = CreateFile(path16, 0, 0, 0, kNtOpenExisting,
@@ -113,20 +113,20 @@ textwindows ssize_t sys_readlinkat_nt(int dirfd, const char *path, char *buf,
         if (freeme || (intptr_t)(buf + j) <= (intptr_t)(p + i)) {
           rc = j;
         } else {
-          SYSDEBUG("sys_readlinkat_nt() too many astral codepoints");
+          STRACE("sys_readlinkat_nt() too many astral codepoints");
           rc = enametoolong();
         }
       } else {
-        SYSDEBUG("sys_readlinkat_nt() should have kNtIoReparseTagSymlink");
+        STRACE("sys_readlinkat_nt() should have kNtIoReparseTagSymlink");
         rc = einval();
       }
     } else {
-      SYSDEBUG("DeviceIoControl(kNtFsctlGetReparsePoint) failed");
+      STRACE("%s failed %m", "DeviceIoControl(kNtFsctlGetReparsePoint)");
       rc = sys_readlinkat_nt_error();
     }
     CloseHandle(h);
   } else {
-    SYSDEBUG("CreateFile(kNtFileFlagOpenReparsePoint) failed");
+    STRACE("%s failed %m", "CreateFile(kNtFileFlagOpenReparsePoint)");
     rc = sys_readlinkat_nt_error();
   }
   if (freeme && weaken(free)) {
diff --git a/libc/calls/readlinkat.c b/libc/calls/readlinkat.c
index 93e4dcf811c..9b946c6a922 100644
--- a/libc/calls/readlinkat.c
+++ b/libc/calls/readlinkat.c
@@ -19,7 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -50,18 +50,17 @@
  */
 ssize_t readlinkat(int dirfd, const char *path, char *buf, size_t bufsiz) {
   ssize_t bytes;
-  struct ZiposUri zipname;
   if ((IsAsan() && !__asan_is_valid(buf, bufsiz)) || (bufsiz && !buf)) {
     bytes = efault();
-  } else if (weaken(__zipos_notat) && __zipos_notat(dirfd, path) == -1) {
-    SYSDEBUG("TOOD: zipos support for readlinkat");
-    bytes = enosys(); /* TODO(jart): code me */
+  } else if (weaken(__zipos_notat) &&
+             (bytes = __zipos_notat(dirfd, path)) == -1) {
+    STRACE("TOOD: zipos support for readlinkat");
   } else if (!IsWindows()) {
     bytes = sys_readlinkat(dirfd, path, buf, bufsiz);
   } else {
     bytes = sys_readlinkat_nt(dirfd, path, buf, bufsiz);
   }
-  SYSDEBUG("readlinkat(%d, %s, 0x%p, 0x%x) -> %d %s", (long)dirfd, path, buf,
-           bufsiz, bytes, bytes != -1 ? "" : strerror(errno));
+  STRACE("readlinkat(%d, %#s, [%#.*s]) → %d% m", dirfd, path, MAX(0, bytes),
+         buf, bytes);
   return bytes;
 }
diff --git a/libc/calls/releasefd.c b/libc/calls/releasefd.c
index 2708f696870..56316ec6e04 100644
--- a/libc/calls/releasefd.c
+++ b/libc/calls/releasefd.c
@@ -22,7 +22,7 @@
 void __releasefd(int fd) {
   int x;
   if (!__vforked && 0 <= fd && fd < g_fds.n) {
-    g_fds.p[fd].kind = kFdEmpty;
+    bzero(g_fds.p + fd, sizeof(*g_fds.p));
     do {
       x = g_fds.f;
       if (fd >= x) break;
diff --git a/libc/calls/renameat.c b/libc/calls/renameat.c
index f98061d8899..cf7eec9ced6 100644
--- a/libc/calls/renameat.c
+++ b/libc/calls/renameat.c
@@ -19,6 +19,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/consts/at.h"
@@ -36,18 +37,20 @@
  */
 int renameat(int olddirfd, const char *oldpath, int newdirfd,
              const char *newpath) {
+  int rc;
   if (IsAsan() &&
       (!__asan_is_valid(oldpath, 1) || !__asan_is_valid(newpath, 1))) {
-    return efault();
-  }
-  if (weaken(__zipos_notat) &&
-      (weaken(__zipos_notat)(olddirfd, oldpath) == -1 ||
-       weaken(__zipos_notat)(newdirfd, newpath) == -1)) {
-    return -1; /* TODO(jart): implement me */
-  }
-  if (!IsWindows()) {
-    return sys_renameat(olddirfd, oldpath, newdirfd, newpath);
+    rc = efault();
+  } else if (weaken(__zipos_notat) &&
+             ((rc = __zipos_notat(olddirfd, oldpath)) == -1 ||
+              (rc = __zipos_notat(newdirfd, newpath)) == -1)) {
+    STRACE("zipos renameat not supported yet");
+  } else if (!IsWindows()) {
+    rc = sys_renameat(olddirfd, oldpath, newdirfd, newpath);
   } else {
-    return sys_renameat_nt(olddirfd, oldpath, newdirfd, newpath);
+    rc = sys_renameat_nt(olddirfd, oldpath, newdirfd, newpath);
   }
+  STRACE("renameat(%d, %#s, %d, %#s) → %d% m", olddirfd, oldpath, newdirfd,
+         newpath, rc);
+  return rc;
 }
diff --git a/libc/calls/sched_yield.c b/libc/calls/sched_yield.c
index c268fa27949..04b744961aa 100644
--- a/libc/calls/sched_yield.c
+++ b/libc/calls/sched_yield.c
@@ -16,14 +16,15 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/dce.h"
-#include "libc/calls/internal.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/internal.h"
+#include "libc/dce.h"
 
 /**
  * Asks kernel to deschedule thread momentarily.
  */
 int sched_yield(void) {
+  /* TODO(jart): Add get_sched_yield() so we can STRACE() */
   if (!IsWindows()) {
     return sys_sched_yield();
   } else {
diff --git a/libc/calls/setrlimit.c b/libc/calls/setrlimit.c
index 332efffccfd..ae9e2b12185 100644
--- a/libc/calls/setrlimit.c
+++ b/libc/calls/setrlimit.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sysv/errfuns.h"
@@ -32,7 +33,16 @@
  * @vforksafe
  */
 int setrlimit(int resource, const struct rlimit *rlim) {
-  if (resource == 127) return einval();
-  if (IsAsan() && !__asan_is_valid(rlim, sizeof(*rlim))) return efault();
-  return sys_setrlimit(resource, rlim);
+  int rc;
+  char buf[64];
+  if (resource == 127) {
+    rc = einval();
+  } else if (IsAsan() && !__asan_is_valid(rlim, sizeof(*rlim))) {
+    rc = efault();
+  } else {
+    rc = sys_setrlimit(resource, rlim);
+  }
+  STRACE("setrlimit(%s, %s) → %d% m", __strace_rlimit_name(resource),
+         __strace_rlimit(buf, sizeof(buf), 0, rlim), rc);
+  return rc;
 }
diff --git a/libc/calls/sigaction.c b/libc/calls/sigaction.c
index a8dd0cd49e0..239c9022052 100644
--- a/libc/calls/sigaction.c
+++ b/libc/calls/sigaction.c
@@ -21,6 +21,7 @@
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/sigbits.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/sigaction-freebsd.internal.h"
 #include "libc/calls/struct/sigaction-linux.internal.h"
 #include "libc/calls/struct/sigaction-netbsd.h"
@@ -129,19 +130,8 @@ static void sigaction_native2cosmo(union metasigaction *sa) {
   }
 }
 
-/**
- * Installs handler for kernel interrupt, e.g.:
- *
- *     void GotCtrlC(int sig, siginfo_t *si, ucontext_t *ctx);
- *     struct sigaction sa = {.sa_sigaction = GotCtrlC,
- *                            .sa_flags = SA_RESETHAND|SA_RESTART|SA_SIGINFO};
- *     CHECK_NE(-1, sigaction(SIGINT, &sa, NULL));
- *
- * @see xsigaction() for a much better api
- * @asyncsignalsafe
- * @vforksafe
- */
-int(sigaction)(int sig, const struct sigaction *act, struct sigaction *oldact) {
+static int __sigaction(int sig, const struct sigaction *act,
+                       struct sigaction *oldact) {
   _Static_assert((sizeof(struct sigaction) > sizeof(struct sigaction_linux) &&
                   sizeof(struct sigaction) > sizeof(struct sigaction_xnu_in) &&
                   sizeof(struct sigaction) > sizeof(struct sigaction_xnu_out) &&
@@ -233,3 +223,25 @@ int(sigaction)(int sig, const struct sigaction *act, struct sigaction *oldact) {
   }
   return rc;
 }
+
+/**
+ * Installs handler for kernel interrupt, e.g.:
+ *
+ *     void GotCtrlC(int sig, siginfo_t *si, ucontext_t *ctx);
+ *     struct sigaction sa = {.sa_sigaction = GotCtrlC,
+ *                            .sa_flags = SA_RESETHAND|SA_RESTART|SA_SIGINFO};
+ *     CHECK_NE(-1, sigaction(SIGINT, &sa, NULL));
+ *
+ * @see xsigaction() for a much better api
+ * @asyncsignalsafe
+ * @vforksafe
+ */
+int(sigaction)(int sig, const struct sigaction *act, struct sigaction *oldact) {
+  int rc;
+  char buf[2][128];
+  rc = __sigaction(sig, act, oldact);
+  STRACE("sigaction(%s, %s, [%s]) → %d% m", strsignal(sig),
+         __strace_sigaction(buf[0], sizeof(buf[0]), 0, act),
+         __strace_sigaction(buf[1], sizeof(buf[1]), rc, oldact), rc);
+  return rc;
+}
diff --git a/libc/calls/sigaltstack.c b/libc/calls/sigaltstack.c
index 754fe4e9526..3f2a74eb02d 100644
--- a/libc/calls/sigaltstack.c
+++ b/libc/calls/sigaltstack.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/metasigaltstack.h"
 #include "libc/calls/struct/sigaltstack.h"
 #include "libc/dce.h"
@@ -70,37 +71,41 @@ static noasan void sigaltstack2linux(struct sigaltstack *linux,
  */
 noasan int sigaltstack(const struct sigaltstack *neu, struct sigaltstack *old) {
   int rc;
-  void *a, *b;
+  void *b;
+  const void *a;
   struct sigaltstack_bsd bsd;
   if (IsAsan() && ((old && __asan_check(old, sizeof(*old)).kind) ||
                    (neu && (__asan_check(neu, sizeof(*neu)).kind ||
                             __asan_check(neu->ss_sp, neu->ss_size).kind)))) {
-    return efault();
-  }
-  if (IsLinux()) {
-    a = neu;
-    b = old;
-  } else if (IsBsd()) {
-    if (neu) {
-      sigaltstack2bsd(&bsd, neu);
-      a = &bsd;
+    rc = efault();
+  } else if (IsLinux() || IsBsd()) {
+    if (IsLinux()) {
+      a = neu;
+      b = old;
     } else {
-      a = 0;
+      if (neu) {
+        sigaltstack2bsd(&bsd, neu);
+        a = &bsd;
+      } else {
+        a = 0;
+      }
+      if (old) {
+        b = &bsd;
+      } else {
+        b = 0;
+      }
     }
-    if (old) {
-      b = &bsd;
+    if ((rc = sys_sigaltstack(a, b)) != -1) {
+      if (IsBsd() && old) {
+        sigaltstack2linux(old, &bsd);
+      }
+      rc = 0;
     } else {
-      b = 0;
-    }
-  } else {
-    return enosys();
-  }
-  if ((rc = sys_sigaltstack(a, b)) != -1) {
-    if (IsBsd() && old) {
-      sigaltstack2linux(old, &bsd);
+      rc = -1;
     }
-    return 0;
   } else {
-    return -1;
+    rc = enosys();
   }
+  STRACE("sigaltstack() → %d% m", rc);
+  return rc;
 }
diff --git a/libc/calls/sigprocmask.c b/libc/calls/sigprocmask.c
index e9dd0202c5f..148a351c325 100644
--- a/libc/calls/sigprocmask.c
+++ b/libc/calls/sigprocmask.c
@@ -18,12 +18,23 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/dce.h"
+#include "libc/fmt/itoa.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/str/str.h"
+#include "libc/sysv/consts/sig.h"
 #include "libc/sysv/errfuns.h"
 
+static const char *DescribeHow(char buf[12], int how) {
+  if (how == SIG_BLOCK) return "SIG_BLOCK";
+  if (how == SIG_UNBLOCK) return "SIG_UNBLOCK";
+  if (how == SIG_SETMASK) return "SIG_SETMASK";
+  FormatInt32(buf, how);
+  return buf;
+}
+
 /**
  * Changes program signal blocking state, e.g.:
  *
@@ -40,25 +51,50 @@
  * @vforksafe
  */
 int sigprocmask(int how, const sigset_t *opt_set, sigset_t *opt_out_oldset) {
-  int32_t x;
-  if (IsAsan() &&
-      ((opt_set && !__asan_is_valid(opt_set, sizeof(*opt_set))) ||
-       (opt_out_oldset &&
-        !__asan_is_valid(opt_out_oldset, sizeof(*opt_out_oldset))))) {
-    return efault();
-  }
-  if (!IsWindows() && !IsOpenbsd()) {
-    return sys_sigprocmask(how, opt_set, opt_out_oldset, 8);
-  } else if (IsOpenbsd()) {
-    if (!opt_set) how = 1;
-    if (opt_set) opt_set = (sigset_t *)(uintptr_t)(*(uint32_t *)opt_set);
-    if ((x = sys_sigprocmask(how, opt_set, 0, 0)) != -1) {
-      if (opt_out_oldset) memcpy(opt_out_oldset, &x, sizeof(x));
-      return 0;
+  int x, rc;
+  char howbuf[12];
+  char buf[2][41];
+  sigset_t old, *oldp;
+  if (!(IsAsan() &&
+        ((opt_set && !__asan_is_valid(opt_set, sizeof(*opt_set))) ||
+         (opt_out_oldset &&
+          !__asan_is_valid(opt_out_oldset, sizeof(*opt_out_oldset)))))) {
+    if (!IsWindows() && !IsOpenbsd()) {
+      if (opt_out_oldset) {
+        bzero(&old, sizeof(old));
+        oldp = &old;
+      } else {
+        oldp = 0;
+      }
+      if (sys_sigprocmask(how, opt_set, oldp, 8) != -1) {
+        if (opt_out_oldset) {
+          memcpy(opt_out_oldset, &old, sizeof(old));
+        }
+        rc = 0;
+      } else {
+        rc = -1;
+      }
+    } else if (IsOpenbsd()) {
+      if (!opt_set) how = 1;
+      if (opt_set) opt_set = (sigset_t *)(uintptr_t)(*(uint32_t *)opt_set);
+      if ((x = sys_sigprocmask(how, opt_set, 0, 0)) != -1) {
+        if (opt_out_oldset) {
+          bzero(opt_out_oldset, sizeof(*opt_out_oldset));
+          memcpy(opt_out_oldset, &x, sizeof(x));
+        }
+        rc = 0;
+      } else {
+        rc = -1;
+      }
     } else {
-      return -1;
+      if (opt_out_oldset) bzero(opt_out_oldset, sizeof(*opt_out_oldset));
+      rc = 0; /* TODO(jart): Implement me! */
     }
   } else {
-    return 0; /* TODO(jart): Implement me! */
+    rc = efault();
   }
+  STRACE("sigprocmask(%s, %s, [%s]) → %d% m", DescribeHow(howbuf, how),
+         __strace_sigset(buf[0], sizeof(buf[0]), 0, opt_set),
+         __strace_sigset(buf[1], sizeof(buf[1]), rc, opt_out_oldset), rc);
+  return rc;
 }
diff --git a/libc/calls/sigsuspend.c b/libc/calls/sigsuspend.c
index d699b173dbf..c27c6a8e85f 100644
--- a/libc/calls/sigsuspend.c
+++ b/libc/calls/sigsuspend.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
@@ -31,12 +32,18 @@
  * @asyncsignalsafe
  */
 int sigsuspend(const sigset_t *ignore) {
-  unsigned x;
-  if (IsAsan() && !__asan_is_valid(ignore, sizeof(*ignore))) return efault();
-  if (!IsWindows()) {
+  int rc;
+  char buf[41];
+  if (!ignore || (IsAsan() && !__asan_is_valid(ignore, sizeof(*ignore)))) {
+    rc = efault();
+  } else if (!IsWindows()) {
+    STRACE("sigsuspend(%s)", __strace_sigset(buf, sizeof(buf), 0, ignore));
     if (IsOpenbsd()) ignore = (sigset_t *)(uintptr_t)(*(uint32_t *)ignore);
     return sys_sigsuspend(ignore, 8);
   } else {
-    return enosys(); /* TODO(jart): Implement me! */
+    rc = enosys(); /* TODO(jart): Implement me! */
   }
+  STRACE("sigsuspend(%s) → %d% m", __strace_sigset(buf, sizeof(buf), 0, ignore),
+         rc);
+  return rc;
 }
diff --git a/libc/calls/sigwinch-nt.c b/libc/calls/sigwinch-nt.c
index a9bb56e038d..b62ac6ef0cc 100644
--- a/libc/calls/sigwinch-nt.c
+++ b/libc/calls/sigwinch-nt.c
@@ -18,8 +18,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/winsize.h"
-#include "libc/calls/sysdebug.internal.h"
 #include "libc/errno.h"
 #include "libc/nt/struct/consolescreenbufferinfoex.h"
 #include "libc/str/str.h"
@@ -38,8 +38,8 @@ textwindows bool _check_sigwinch(struct Fd *fd) {
       if (old.ws_col != ws.ws_col || old.ws_row != ws.ws_row) {
         __ws = ws;
         if (old.ws_col | old.ws_row) {
-          SYSDEBUG("SIGWINCH %hhu×%hhu → %hhu×%hhu", old.ws_col, old.ws_row,
-                   ws.ws_col, ws.ws_row);
+          STRACE("SIGWINCH %hhu×%hhu → %hhu×%hhu", old.ws_col, old.ws_row,
+                 ws.ws_col, ws.ws_row);
           if (__sighandrvas[SIGWINCH] >= kSigactionMinRva) {
             bzero(&si, sizeof(si));
             ((sigaction_f)(_base + __sighandrvas[SIGWINCH]))(SIGWINCH, &si, 0);
diff --git a/libc/calls/strace.internal.h b/libc/calls/strace.internal.h
new file mode 100644
index 00000000000..1e2e9ecc1c1
--- /dev/null
+++ b/libc/calls/strace.internal.h
@@ -0,0 +1,34 @@
+#ifndef COSMOPOLITAN_LIBC_CALLS_STRACE_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_CALLS_STRACE_INTERNAL_H_
+#include "libc/calls/struct/rlimit.h"
+#include "libc/calls/struct/sigaction.h"
+#include "libc/calls/struct/stat.h"
+
+#define STRACE_PROLOGUE "%rSYS %5P %'18T "
+
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+#ifdef SYSDEBUG
+#define STRACE(FMT, ...)                                  \
+  do {                                                    \
+    if (__strace > 0) {                                   \
+      __stracef(STRACE_PROLOGUE FMT "%n", ##__VA_ARGS__); \
+    }                                                     \
+  } while (0)
+#else
+#define STRACE(FMT, ...) (void)0
+#endif
+
+extern int __strace;
+
+void __stracef(const char *, ...);
+const char *__strace_stat(int, const struct stat *);
+const char *__strace_sigaction(char *, size_t, int, const struct sigaction *);
+const char *__strace_sigset(char[41], size_t, int, const sigset_t *);
+const char *__strace_rlimit_name(int);
+const char *__strace_rlimit(char[41], size_t, int, const struct rlimit *);
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_CALLS_STRACE_INTERNAL_H_ */
diff --git a/libc/calls/strace_rlimit.c b/libc/calls/strace_rlimit.c
new file mode 100644
index 00000000000..58b4aea71fb
--- /dev/null
+++ b/libc/calls/strace_rlimit.c
@@ -0,0 +1,40 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/calls/struct/rlimit.h"
+#include "libc/fmt/itoa.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/sysv/consts/rlimit.h"
+
+const char *__strace_rlimit_name(int resource) {
+  static char buf[12];
+  if (resource == RLIMIT_AS) return "RLIMIT_AS";
+  if (resource == RLIMIT_CPU) return "RLIMIT_CPU";
+  if (resource == RLIMIT_FSIZE) return "RLIMIT_FSIZE";
+  FormatInt32(buf, resource);
+  return buf;
+}
+
+privileged const char *__strace_rlimit(char buf[64], size_t bufsize, int rc,
+                                       const struct rlimit *rlim) {
+  if (rc == -1) return "n/a";
+  if (!rlim) return "NULL";
+  ksnprintf(buf, bufsize, "{%'lu, %'lu}", rlim->rlim_cur, rlim->rlim_max);
+  return buf;
+}
diff --git a/libc/calls/strace_sigaction.greg.c b/libc/calls/strace_sigaction.greg.c
new file mode 100644
index 00000000000..e34df149b88
--- /dev/null
+++ b/libc/calls/strace_sigaction.greg.c
@@ -0,0 +1,31 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/kprintf.h"
+
+privileged const char *__strace_sigaction(char *buf, size_t bufsize, int rc,
+                                          const struct sigaction *sa) {
+  char maskbuf[41];
+  if (rc == -1) return "n/a";
+  if (!sa) return "NULL";
+  ksnprintf(buf, bufsize, "{.sa_handler=%p, .sa_flags=%#lx, .sa_mask=%s}",
+            sa->sa_handler, sa->sa_flags,
+            __strace_sigset(maskbuf, sizeof(maskbuf), rc, &sa->sa_mask));
+  return buf;
+}
diff --git a/libc/calls/strace_sigset.greg.c b/libc/calls/strace_sigset.greg.c
new file mode 100644
index 00000000000..f083d75c63d
--- /dev/null
+++ b/libc/calls/strace_sigset.greg.c
@@ -0,0 +1,28 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/kprintf.h"
+
+privileged const char *__strace_sigset(char buf[41], size_t bufsize, int rc,
+                                       const sigset_t *ss) {
+  if (rc == -1) return "n/a";
+  if (!ss) return "NULL";
+  ksnprintf(buf, bufsize, "{%#lx, %#lx}", ss->__bits[0], ss->__bits[1]);
+  return buf;
+}
diff --git a/libc/calls/strace_stat.greg.c b/libc/calls/strace_stat.greg.c
new file mode 100644
index 00000000000..475e2c0234a
--- /dev/null
+++ b/libc/calls/strace_stat.greg.c
@@ -0,0 +1,29 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/kprintf.h"
+
+privileged const char *__strace_stat(int rc, const struct stat *st) {
+  static char buf[256];
+  if (rc == -1) return "n/a";
+  if (!st) return "NULL";
+  ksnprintf(buf, sizeof(buf), "{.st_size=%'ld, .st_mode=%#o, .st_ino=%'lu}",
+            st->st_size, st->st_mode, st->st_ino);
+  return buf;
+}
diff --git a/libc/calls/sysdebug.internal.h b/libc/calls/sysdebug.internal.h
deleted file mode 100644
index bc9efeb3c8b..00000000000
--- a/libc/calls/sysdebug.internal.h
+++ /dev/null
@@ -1,15 +0,0 @@
-#ifndef COSMOPOLITAN_LIBC_CALLS_SYSDEBUG_INTERNAL_H_
-#define COSMOPOLITAN_LIBC_CALLS_SYSDEBUG_INTERNAL_H_
-#include "libc/log/libfatal.internal.h"
-
-#ifndef DEBUGSYS
-#define DEBUGSYS 0
-#endif
-
-#if DEBUGSYS
-#define SYSDEBUG(FMT, ...) kprintf("SYS: " FMT "\n", ##__VA_ARGS__)
-#else
-#define SYSDEBUG(FMT, ...) (void)0
-#endif
-
-#endif /* COSMOPOLITAN_LIBC_CALLS_SYSDEBUG_INTERNAL_H_ */
diff --git a/libc/calls/wait4-nt.c b/libc/calls/wait4-nt.c
index a5fa862c2e7..a55a4a46ec7 100644
--- a/libc/calls/wait4-nt.c
+++ b/libc/calls/wait4-nt.c
@@ -19,8 +19,8 @@
 #include "libc/assert.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/rusage.h"
-#include "libc/calls/sysdebug.internal.h"
 #include "libc/fmt/conv.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/accounting.h"
@@ -71,12 +71,12 @@ textwindows int sys_wait4_nt(int pid, int *opt_out_wstatus, int options,
       i = WaitForMultipleObjects(count, handles, false, -1);
     }
     if (i == kNtWaitFailed) {
-      SYSDEBUG("WaitForMultipleObjects failed %d", GetLastError());
+      STRACE("%s failed %u", "WaitForMultipleObjects", GetLastError());
       return __winerr();
     }
     assert(__isfdkind(pids[i], kFdProcess));
     if (!GetExitCodeProcess(handles[i], &dwExitCode)) {
-      SYSDEBUG("GetExitCodeProcess failed %d", GetLastError());
+      STRACE("%s failed %u", "GetExitCodeProcess", GetLastError());
       return __winerr();
     }
     if (dwExitCode == kNtStillActive) continue;
@@ -92,7 +92,7 @@ textwindows int sys_wait4_nt(int pid, int *opt_out_wstatus, int options,
         opt_out_rusage->ru_stime =
             WindowsDurationToTimeVal(ReadFileTime(kernelfiletime));
       } else {
-        SYSDEBUG("GetProcessTimes failed %d", GetLastError());
+        STRACE("%s failed %u", "GetProcessTimes", GetLastError());
       }
     }
     CloseHandle(g_fds.p[pids[i]].handle);
diff --git a/libc/calls/wait4.c b/libc/calls/wait4.c
index f74f75c6b62..a6c83dcacd3 100644
--- a/libc/calls/wait4.c
+++ b/libc/calls/wait4.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/wait4.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
@@ -38,21 +38,20 @@
  */
 int wait4(int pid, int *opt_out_wstatus, int options,
           struct rusage *opt_out_rusage) {
-  int rc, ws;
+  int rc, ws = 0;
   if (IsAsan() &&
       ((opt_out_wstatus &&
         !__asan_is_valid(opt_out_wstatus, sizeof(*opt_out_wstatus))) ||
        (opt_out_rusage &&
         !__asan_is_valid(opt_out_rusage, sizeof(*opt_out_rusage))))) {
-    return efault();
-  }
-  ws = 0;
-  if (!IsWindows()) {
+    rc = efault();
+  } else if (!IsWindows()) {
     rc = sys_wait4(pid, &ws, options, opt_out_rusage);
   } else {
     rc = sys_wait4_nt(pid, &ws, options, opt_out_rusage);
   }
-  SYSDEBUG("waitpid(%d, [0x%x], %d) -> [%d]", pid, ws, options, rc);
-  if (opt_out_wstatus) *opt_out_wstatus = ws;
+  if (rc != -1 && opt_out_wstatus) *opt_out_wstatus = ws;
+  STRACE("wait4(%d, [%#x], %d, %p) → %d% m", pid, ws, options, opt_out_rusage,
+         rc);
   return rc;
 }
diff --git a/libc/calls/wincrash.c b/libc/calls/wincrash.c
index 32259c4d1dc..62aa0b55ccf 100644
--- a/libc/calls/wincrash.c
+++ b/libc/calls/wincrash.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/typedef/sigaction_f.h"
 #include "libc/calls/ucontext.h"
 #include "libc/nt/enum/exceptionhandleractions.h"
@@ -31,7 +31,7 @@ textwindows unsigned __wincrash(struct NtExceptionPointers *ep) {
     ucontext_t ctx;
     struct siginfo si;
   } g;
-  SYSDEBUG("__wincrash");
+  STRACE("__wincrash");
   switch (ep->ExceptionRecord->ExceptionCode) {
     case kNtSignalBreakpoint:
       sig = SIGTRAP;
diff --git a/libc/intrin/asan.c b/libc/intrin/asan.c
index 73a0879fa04..3ce36c7eff2 100644
--- a/libc/intrin/asan.c
+++ b/libc/intrin/asan.c
@@ -23,6 +23,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/iovec.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
@@ -1378,6 +1379,7 @@ textstartup void __asan_init(int argc, char **argv, char **envp,
   __asan_shadow_string_list(envp);
   __asan_shadow_auxv(auxv);
   __asan_install_malloc_hooks();
+  STRACE("cosmopolitan memory safety module initialized");
 }
 
 static textstartup void __asan_ctor(void) {
diff --git a/libc/intrin/exit.greg.c b/libc/intrin/exit.greg.c
index a0a77023891..86ca692bb17 100644
--- a/libc/intrin/exit.greg.c
+++ b/libc/intrin/exit.greg.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #define ShouldUseMsabiAttribute() 1
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/nexgen32e/vendor.internal.h"
@@ -37,6 +38,7 @@
  * @noreturn
  */
 privileged noinstrument noasan noubsan wontreturn void _Exit(int exitcode) {
+  STRACE("_Exit(%d)", exitcode);
   if ((!IsWindows() && !IsMetal()) || (IsMetal() && IsGenuineCosmo())) {
     asm volatile("syscall"
                  : /* no outputs */
diff --git a/libc/intrin/getenv.c b/libc/intrin/getenv.c
index 3aa83de4a48..d6e3e6eb44e 100644
--- a/libc/intrin/getenv.c
+++ b/libc/intrin/getenv.c
@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/runtime/runtime.h"
 
@@ -63,6 +63,6 @@ char *getenv(const char *s) {
   } else {
     r = GetEnv(s, ToUpper);
   }
-  SYSDEBUG("getenv(%#s) → %#s", s, r);
+  STRACE("getenv(%#s) → %#s", s, r);
   return r;
 }
diff --git a/libc/intrin/psrldq.c b/libc/intrin/psrldq.c
index 505d870e169..9ed38136adc 100644
--- a/libc/intrin/psrldq.c
+++ b/libc/intrin/psrldq.c
@@ -27,7 +27,6 @@
  * @mayalias
  */
 void(psrldq)(uint8_t b[16], const uint8_t a[16], unsigned long n) {
-  unsigned i;
   if (n > 16) n = 16;
   __builtin_memcpy(b, a + n, 16 - n);
   __builtin_memset(b + (16 - n), 0, n);
diff --git a/libc/intrin/quick_exit.c b/libc/intrin/quick_exit.c
index 54e37e1729f..1970c534cba 100644
--- a/libc/intrin/quick_exit.c
+++ b/libc/intrin/quick_exit.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/bits/weaken.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/nt/console.h"
 #include "libc/nt/runtime.h"
@@ -35,6 +36,7 @@ const char kConsoleHandles[2] = {kNtStdInputHandle, kNtStdOutputHandle};
 wontreturn void quick_exit(int exitcode) {
   int i;
   const uintptr_t *p;
+  STRACE("quick_exit(%d)", exitcode);
   if (weaken(fflush)) {
     weaken(fflush)(0);
   }
diff --git a/libc/intrin/somanyasan.S b/libc/intrin/somanyasan.S
index 41d41d4c43a..a473f4a8bc1 100644
--- a/libc/intrin/somanyasan.S
+++ b/libc/intrin/somanyasan.S
@@ -184,7 +184,7 @@ __asan_version_mismatch_check_v8:
 	.endfn	__asan_version_mismatch_check_v8,globl
 
 //	Initializes Address Sanitizer runtime earlier if linked.
-	.init.start 301,_init_asan
+	.init.start 303,_init_asan
 	push	%rdi
 	push	%rsi
 	mov	%r12,%rdi
@@ -194,7 +194,7 @@ __asan_version_mismatch_check_v8:
 	call	__asan_init
 	pop	%rsi
 	pop	%rdi
-	.init.end 301,_init_asan
+	.init.end 303,_init_asan
 
 __asan_before_dynamic_init:
 	push	%rbp
diff --git a/libc/intrin/stracef.greg.c b/libc/intrin/stracef.greg.c
new file mode 100644
index 00000000000..ab5fbc4fe8d
--- /dev/null
+++ b/libc/intrin/stracef.greg.c
@@ -0,0 +1,28 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/kprintf.h"
+
+privileged void __stracef(const char *fmt, ...) {
+  va_list v;
+  if (__strace <= 0) return;
+  va_start(v, fmt);
+  kvprintf(fmt, v);
+  va_end(v);
+}
diff --git a/libc/log/libfatal.internal.h b/libc/log/libfatal.internal.h
index 7e8a77a5ddf..f53aad990a5 100644
--- a/libc/log/libfatal.internal.h
+++ b/libc/log/libfatal.internal.h
@@ -242,6 +242,26 @@ forceinline char *__strstr(const char *haystack, const char *needle) {
   return 0;
 }
 
+forceinline char *__getenv(char **p, const char *s) {
+  size_t i, j;
+  if (p) {
+    for (i = 0; p[i]; ++i) {
+      for (j = 0;; ++j) {
+        if (!s[j]) {
+          if (p[i][j] == '=') {
+            return p[i] + j + 1;
+          }
+          break;
+        }
+        if ((s[j] & 255) != __ToUpper(p[i][j] & 255)) {
+          break;
+        }
+      }
+    }
+  }
+  return 0;
+}
+
 forceinline const char *__strchr(const char *s, unsigned char c) {
   char *r;
   for (;; ++s) {
diff --git a/libc/mem/putenv.c b/libc/mem/putenv.c
index b2f6c41a978..27ff7724037 100644
--- a/libc/mem/putenv.c
+++ b/libc/mem/putenv.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/alg/alg.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/internal.h"
@@ -121,6 +121,6 @@ void __freeenv(void *p) {
 int putenv(char *s) {
   int rc;
   rc = PutEnvImpl(strdup(s), true);
-  SYSDEBUG("putenv(%#s) → %d", s, rc);
+  STRACE("putenv(%#s) → %d", s, rc);
   return rc;
 }
diff --git a/libc/mem/setenv.c b/libc/mem/setenv.c
index c7e24ff260b..bb9c33cdcd3 100644
--- a/libc/mem/setenv.c
+++ b/libc/mem/setenv.c
@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/mem/internal.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
@@ -37,6 +37,6 @@ int setenv(const char *name, const char *value, int overwrite) {
   s = malloc(namelen + valuelen + 2);
   memcpy(mempcpy(mempcpy(s, name, namelen), "=", 1), value, valuelen + 1);
   rc = PutEnvImpl(s, overwrite);
-  SYSDEBUG("setenv(%#s, %#s, %d) → %d", name, value, overwrite, rc);
+  STRACE("setenv(%#s, %#s, %d) → %d", name, value, overwrite, rc);
   return rc;
 }
diff --git a/libc/runtime/arememoryintervalsok.c b/libc/runtime/arememoryintervalsok.c
index 8c20eb62304..1a4969a1438 100644
--- a/libc/runtime/arememoryintervalsok.c
+++ b/libc/runtime/arememoryintervalsok.c
@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/runtime/memtrack.internal.h"
 
 noasan bool AreMemoryIntervalsOk(const struct MemoryIntervals *mm) {
@@ -24,7 +24,7 @@ noasan bool AreMemoryIntervalsOk(const struct MemoryIntervals *mm) {
   int i;
   for (i = 0; i < mm->i; ++i) {
     if (mm->p[i].y < mm->p[i].x) {
-      SYSDEBUG("AreMemoryIntervalsOk() y should be >= x!");
+      STRACE("AreMemoryIntervalsOk() y should be >= x!");
       return false;
     }
     if (i) {
@@ -34,7 +34,7 @@ noasan bool AreMemoryIntervalsOk(const struct MemoryIntervals *mm) {
         }
       } else {
         if (!(mm->p[i - 1].y + 1 <= mm->p[i].x)) {
-          SYSDEBUG("AreMemoryIntervalsOk() out of order or overlap!");
+          STRACE("AreMemoryIntervalsOk() out of order or overlap!");
           return false;
         }
       }
diff --git a/libc/runtime/clearenv.c b/libc/runtime/clearenv.c
index 46308f92a19..c37f1fb5349 100644
--- a/libc/runtime/clearenv.c
+++ b/libc/runtime/clearenv.c
@@ -16,12 +16,14 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
 #include "libc/runtime/runtime.h"
 
 /**
  * Removes all environment variables.
  */
 int clearenv(void) {
+  STRACE("clearenv() → 0");
   environ = NULL;
   return 0;
 }
diff --git a/libc/runtime/cosmo.S b/libc/runtime/cosmo.S
index 5760a93b049..f9685696424 100644
--- a/libc/runtime/cosmo.S
+++ b/libc/runtime/cosmo.S
@@ -21,6 +21,7 @@
 #include "libc/notice.inc"
 #include "libc/sysv/consts/prot.h"
 #include "libc/sysv/consts/map.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 .text.startup
 
@@ -37,6 +38,10 @@ cosmo:	push	%rbp
 	mov	%rsi,%r13
 	mov	%rdx,%r14
 	mov	%rcx,%r15
+#ifdef SYSDEBUG
+	call	__strace_init
+	mov	%eax,%r12d
+#endif /* SYSDEBUG */
 #ifdef __FAST_MATH__
 	push	%rax
 	stmxcsr	(%rsp)
@@ -72,7 +77,7 @@ cosmo:	push	%rbp
 	.endfn	cosmo,weak
 
 #ifdef __PG__
-	.init.start 800,_init_ftrace
+	.init.start 306,_init_ftrace
 	push	%rdi
 	push	%rsi
 	mov	%r12d,%edi
@@ -86,5 +91,21 @@ cosmo:	push	%rbp
 	mov	%eax,%r12d
 	pop	%rsi
 	pop	%rdi
-	.init.end 800,_init_ftrace
+	.init.end 306,_init_ftrace
+#endif
+
+#if IsModeDbg()
+#ifdef SYSDEBUG
+	.init.start 307,_init_printargs
+	push	%rdi
+	push	%rsi
+	mov	%r12d,%edi
+	mov	%r13,%rsi
+	mov	%r14,%rdx
+	mov	%r15,%rcx
+	call	__printargs
+	pop	%rsi
+	pop	%rdi
+	.init.end 307,_init_printargs
+#endif
 #endif
diff --git a/libc/runtime/dsohandle.S b/libc/runtime/dsohandle.S
index 6e9d6d6aec8..136dd405bdc 100644
--- a/libc/runtime/dsohandle.S
+++ b/libc/runtime/dsohandle.S
@@ -19,7 +19,9 @@
 #include "libc/macros.internal.h"
 #include "libc/notice.inc"
 
+	.underrun
 //	Uniquely identifies each artifact linked in an address space.
 __dso_handle:
 	.quad	__dso_handle
 	.endobj	__dso_handle,globl,hidden
+	.overrun
diff --git a/libc/runtime/exit.c b/libc/runtime/exit.c
index 6818ff1fcc3..3dcaad2ce10 100644
--- a/libc/runtime/exit.c
+++ b/libc/runtime/exit.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/bits/weaken.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
 
@@ -32,6 +33,7 @@
  * @noreturn
  */
 wontreturn void exit(int exitcode) {
+  STRACE("exit(%d)", exitcode);
   if (weaken(__cxa_finalize)) {
     weaken(__cxa_finalize)(NULL);
   }
diff --git a/libc/runtime/finddebugbinary.c b/libc/runtime/finddebugbinary.c
index 5df30e39d21..72c87233c42 100644
--- a/libc/runtime/finddebugbinary.c
+++ b/libc/runtime/finddebugbinary.c
@@ -22,46 +22,37 @@
 #include "libc/runtime/symbols.internal.h"
 #include "libc/str/str.h"
 
-static char *g_comdbg;
-static char g_comdbg_buf[PATH_MAX + 1];
-
-static optimizesize textstartup void g_comdbg_init() {
+/**
+ * Returns path of binary with the debug information, or null.
+ *
+ * @return path to debug binary, or NULL
+ */
+const char *FindDebugBinary(void) {
+  static bool once;
+  static char *res;
+  static char buf[PATH_MAX + 1];
   char *p;
   size_t n;
-  static bool once;
   if (!once) {
-    if (!(g_comdbg = getenv("COMDBG"))) {
+    if (!(res = getenv("COMDBG"))) {
       p = program_executable_name;
       n = strlen(p);
       if (n > 4 && READ32LE(p + n - 4) == READ32LE(".dbg")) {
-        g_comdbg = p;
+        res = p;
       } else if (n > 4 && READ32LE(p + n - 4) == READ32LE(".com") &&
                  n + 4 <= PATH_MAX) {
-        mempcpy(mempcpy(g_comdbg_buf, p, n), ".dbg", 5);
-        if (fileexists(g_comdbg_buf)) {
-          g_comdbg = g_comdbg_buf;
+        mempcpy(mempcpy(buf, p, n), ".dbg", 5);
+        if (fileexists(buf)) {
+          res = buf;
         }
       } else if (n + 8 <= PATH_MAX) {
-        mempcpy(mempcpy(g_comdbg_buf, p, n), ".com.dbg", 9);
-        if (fileexists(g_comdbg_buf)) {
-          g_comdbg = g_comdbg_buf;
+        mempcpy(mempcpy(buf, p, n), ".com.dbg", 9);
+        if (fileexists(buf)) {
+          res = buf;
         }
       }
     }
     once = true;
   }
+  return res;
 }
-
-/**
- * Returns path of binary with the debug information, or null.
- *
- * @return path to debug binary, or NULL
- */
-const char *FindDebugBinary(void) {
-  g_comdbg_init();
-  return g_comdbg;
-}
-
-const void *const g_comdbg_ctor[] initarray = {
-    g_comdbg_init,
-};
diff --git a/libc/runtime/fork-nt.c b/libc/runtime/fork-nt.c
index c455c792c53..7aefaa140f2 100644
--- a/libc/runtime/fork-nt.c
+++ b/libc/runtime/fork-nt.c
@@ -21,7 +21,7 @@
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/ntspawn.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/fmt/itoa.h"
 #include "libc/macros.internal.h"
 #include "libc/nexgen32e/nt2sysv.h"
@@ -60,7 +60,7 @@ static textwindows noasan char16_t *ParseInt(char16_t *p, int64_t *x) {
 }
 
 static dontinline textwindows noasan bool ForkIo(int64_t h, void *buf, size_t n,
-                                               bool32 (*f)()) {
+                                                 bool32 (*f)()) {
   char *p;
   size_t i;
   uint32_t x;
@@ -73,17 +73,15 @@ static dontinline textwindows noasan bool ForkIo(int64_t h, void *buf, size_t n,
 }
 
 static dontinline textwindows noasan void WriteAll(int64_t h, void *buf,
-                                                 size_t n) {
-  if (!ForkIo(h, buf, n, WriteFile)) {
-    SYSDEBUG("fork() WriteFile(%zu) failed %d\n", n, GetLastError());
-  }
+                                                   size_t n) {
+  bool rc = ForkIo(h, buf, n, WriteFile);
+  STRACE("%s(%ld, %'zu) %d% m", "WriteFile", h, n);
 }
 
 static textwindows dontinline noasan void ReadAll(int64_t h, void *buf,
-                                                size_t n) {
-  if (!ForkIo(h, buf, n, ReadFile)) {
-    SYSDEBUG("fork() ReadFile(%zu) failed %d\n", n, GetLastError());
-  }
+                                                  size_t n) {
+  bool rc = ForkIo(h, buf, n, ReadFile);
+  STRACE("%s(%ld, %'zu) %d% m", "ReadFile", h, n);
 }
 
 textwindows noasan noinstrument void WinMainForked(void) {
@@ -99,6 +97,7 @@ textwindows noasan noinstrument void WinMainForked(void) {
   varlen = GetEnvironmentVariable(u"_FORK", var, ARRAYLEN(var));
   if (!varlen) return;
   if (varlen >= ARRAYLEN(var)) ExitProcess(123);
+  STRACE("WinMainForked()");
   SetEnvironmentVariable(u"_FORK", NULL);
   ParseInt(ParseInt(var, &reader), &writer);
   ReadAll(reader, jb, sizeof(jb));
diff --git a/libc/runtime/fork.c b/libc/runtime/fork.c
index 5d47e474ac7..14a94670bdf 100644
--- a/libc/runtime/fork.c
+++ b/libc/runtime/fork.c
@@ -20,7 +20,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/nt/process.h"
 
@@ -55,12 +55,12 @@ int fork(void) {
     }
     parent = __pid;
     __pid = dx;
-    SYSDEBUG("fork() → 0 (child of %d)", parent);
+    STRACE("fork() → 0 (child of %d)", parent);
     if (weaken(__onfork)) {
       weaken(__onfork)();
     }
   } else {
-    SYSDEBUG("fork() → %d% m", ax);
+    STRACE("fork() → %d% m", ax);
   }
   return ax;
 }
diff --git a/libc/runtime/ftrace-hook.S b/libc/runtime/ftrace-hook.S
index f17c1bb7a00..a679c52b13f 100644
--- a/libc/runtime/ftrace-hook.S
+++ b/libc/runtime/ftrace-hook.S
@@ -21,7 +21,7 @@
 
 ftrace_hook:
 	cmp	$0,g_ftrace(%rip)
-	je	1f
+	jg	1f
 	ret
 1:	push	%rbp
 	mov	%rsp,%rbp
diff --git a/libc/runtime/ftraceinit.c b/libc/runtime/ftraceinit.greg.c
similarity index 84%
rename from libc/runtime/ftraceinit.c
rename to libc/runtime/ftraceinit.greg.c
index cd6af1c9ff8..48bbc05aae9 100644
--- a/libc/runtime/ftraceinit.c
+++ b/libc/runtime/ftraceinit.greg.c
@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 
@@ -31,26 +32,10 @@
  *
  * @see libc/runtime/_init.S for documentation
  */
-textstartup int ftrace_init(int argc, char *argv[]) {
-  int i;
-  bool foundflag;
-  foundflag = false;
-  for (i = 1; i <= argc; ++i) {
-    if (!foundflag) {
-      if (argv[i]) {
-        if (strcmp(argv[i], "--ftrace") == 0) {
-          foundflag = true;
-        } else if (strcmp(argv[i], "----ftrace") == 0) {
-          strcpy(argv[i], "--ftrace");
-        }
-      }
-    } else {
-      argv[i - 1] = argv[i];
-    }
-  }
-  if (foundflag) {
-    --argc;
+textstartup int ftrace_init(void) {
+  if (__intercept_flag(&__argc, __argv, "--ftrace")) {
     ftrace_install();
+    ++g_ftrace;
   }
-  return argc;
+  return __argc;
 }
diff --git a/libc/runtime/interceptflag.greg.c b/libc/runtime/interceptflag.greg.c
new file mode 100644
index 00000000000..026ea4dbede
--- /dev/null
+++ b/libc/runtime/interceptflag.greg.c
@@ -0,0 +1,46 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/log/libfatal.internal.h"
+#include "libc/runtime/internal.h"
+#include "libc/str/str.h"
+
+textstartup bool __intercept_flag(int *argc, char *argv[], const char *flag) {
+  /* asan isn't initialized yet at runlevel 300 */
+  char *a;
+  int i, j;
+  bool found;
+  found = false;
+  for (j = i = 1; i <= *argc;) {
+    a = argv[j++];
+    if (a && !__strcmp(a, flag)) {
+      found = true;
+      --*argc;
+    } else {
+      /*
+       * e.g. turns ----strace → --strace for execve.
+       * todo: update this to allow ------strace etc.
+       */
+      if (a && a[0] == '-' && a[1] == '-' && !__strcmp(a + 2, flag)) {
+        a = flag;
+      }
+      argv[i++] = a;
+    }
+  }
+  return found;
+}
diff --git a/libc/runtime/internal.h b/libc/runtime/internal.h
index 3b0e05e9714..1942922d158 100644
--- a/libc/runtime/internal.h
+++ b/libc/runtime/internal.h
@@ -27,6 +27,7 @@ long _setstack(void *, void *, ...) hidden;
 int GetDosArgv(const char16_t *, char *, size_t, char **, size_t) hidden;
 Elf64_Ehdr *MapElfRead(const char *, struct MappedFile *) hidden;
 int GetDosEnviron(const char16_t *, char *, size_t, char **, size_t) hidden;
+bool __intercept_flag(int *, char *[], const char *);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/libc/runtime/memtrack.c b/libc/runtime/memtrack.c
index 127bef8a7e3..a3b2783f9e9 100644
--- a/libc/runtime/memtrack.c
+++ b/libc/runtime/memtrack.c
@@ -21,7 +21,7 @@
 #include "libc/bits/likely.h"
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -76,13 +76,13 @@ static noasan bool ExtendMemoryIntervals(struct MemoryIntervals *mm) {
       shad = (char *)(((intptr_t)base >> 3) + 0x7fff8000);
       dm = sys_mmap(shad, gran >> 3, prot, flags, -1, 0);
       if (!dm.addr) {
-        SYSDEBUG("ExtendMemoryIntervals() fail #1");
+        STRACE("ExtendMemoryIntervals() fail #1");
         return false;
       }
     }
     dm = sys_mmap(base, gran, prot, flags, -1, 0);
     if (!dm.addr) {
-      SYSDEBUG("ExtendMemoryIntervals() fail #2");
+      STRACE("ExtendMemoryIntervals() fail #2");
       return false;
     }
     MoveMemoryIntervals(dm.addr, mm->p, mm->i);
@@ -95,13 +95,13 @@ static noasan bool ExtendMemoryIntervals(struct MemoryIntervals *mm) {
       shad = (char *)(((intptr_t)base >> 3) + 0x7fff8000);
       dm = sys_mmap(shad, gran >> 3, prot, flags, -1, 0);
       if (!dm.addr) {
-        SYSDEBUG("ExtendMemoryIntervals() fail #3");
+        STRACE("ExtendMemoryIntervals() fail #3");
         return false;
       }
     }
     dm = sys_mmap(base, gran, prot, flags, -1, 0);
     if (!dm.addr) {
-      SYSDEBUG("ExtendMemoryIntervals() fail #4");
+      STRACE("ExtendMemoryIntervals() fail #4");
       return false;
     }
     mm->n = (size + gran) / sizeof(*mm->p);
diff --git a/libc/runtime/memtrack.internal.h b/libc/runtime/memtrack.internal.h
index 1fb01f23845..18ae776f124 100644
--- a/libc/runtime/memtrack.internal.h
+++ b/libc/runtime/memtrack.internal.h
@@ -1,5 +1,6 @@
 #ifndef COSMOPOLITAN_LIBC_RUNTIME_MEMTRACK_H_
 #define COSMOPOLITAN_LIBC_RUNTIME_MEMTRACK_H_
+#include "libc/assert.h"
 #include "libc/dce.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/enum/version.h"
@@ -164,6 +165,7 @@ forceinline unsigned FindMemoryInterval(const struct MemoryIntervals *mm,
       r = m;
     }
   }
+  assert(l == mm->i || x <= mm->p[l].y);
   return l;
 }
 
@@ -171,7 +173,7 @@ forceinline bool IsMemtracked(int x, int y) {
   unsigned i;
   i = FindMemoryInterval(&_mmi, x);
   if (i == _mmi.i) return false;
-  if (!(_mmi.p[i].x <= x && x <= _mmi.p[i].y)) return false;
+  if (x < _mmi.p[i].x) return false;
   for (;;) {
     if (y <= _mmi.p[i].y) return true;
     if (++i == _mmi.i) return false;
diff --git a/libc/runtime/memtracknt.c b/libc/runtime/memtracknt.c
index f6dc682ca3b..3873f1cfad3 100644
--- a/libc/runtime/memtracknt.c
+++ b/libc/runtime/memtracknt.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/nt/memory.h"
 #include "libc/nt/runtime.h"
 #include "libc/runtime/memtrack.internal.h"
@@ -37,8 +37,8 @@ noasan void ReleaseMemoryNt(struct MemoryIntervals *mm, int l, int r) {
   for (i = l; i <= r; ++i) {
     addr = GetFrameAddr(mm->p[i].x);
     last = GetFrameAddr(mm->p[i].y);
-    SYSDEBUG("UnmapViewOfFile(addr:0x%x, size:0x%x, hand:0x%x)", addr,
-             last - addr + FRAMESIZE, mm->p[i].h);
+    STRACE("UnmapViewOfFile(%p, size:%'zu, hand:%ld)", addr,
+           last - addr + FRAMESIZE, mm->p[i].h);
     ok = UnmapViewOfFile(addr);
     assert(ok);
     ok = CloseHandle(mm->p[i].h);
diff --git a/libc/runtime/mmap.c b/libc/runtime/mmap.c
index ee58ac8cf13..0b02674417c 100644
--- a/libc/runtime/mmap.c
+++ b/libc/runtime/mmap.c
@@ -21,7 +21,7 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -40,7 +40,6 @@
 
 #define IP(X)      (intptr_t)(X)
 #define VIP(X)     (void *)IP(X)
-#define SMALL(n)   ((n) <= 0xffffffffffff)
 #define ALIGNED(p) (!(IP(p) & (FRAMESIZE - 1)))
 #define ADDR(x)    ((int64_t)((uint64_t)(x) << 32) >> 16)
 #define SHADE(x)   (((intptr_t)(x) >> 3) + 0x7fff8000)
@@ -60,7 +59,7 @@ noasan static bool NeedAutomap(char *p, size_t n) {
          IsMapped(p, n);
 }
 
-noasan static bool ChooseInterval(int x, int n, int *res) {
+noasan static bool ChooseMemoryInterval(int x, int n, int *res) {
   int i;
   if (_mmi.i) {
     i = FindMemoryInterval(&_mmi, x);
@@ -89,18 +88,17 @@ noasan static bool ChooseInterval(int x, int n, int *res) {
 
 noasan static bool Automap(int n, int *res) {
   *res = -1;
-  if (ChooseInterval(FRAME(kAutomapStart), n, res)) {
+  if (ChooseMemoryInterval(FRAME(kAutomapStart), n, res)) {
     assert(*res >= FRAME(kAutomapStart));
     if (*res + n <= FRAME(kAutomapStart + (kAutomapStart - 1))) {
       return true;
     } else {
-      SYSDEBUG("mmap(0x%p, 0x%x) ENOMEM (automap interval exhausted)",
-               ADDR(*res), ADDR(n + 1));
+      STRACE("mmap(%.12p, %p) ENOMEM (automap interval exhausted)", ADDR(*res),
+             ADDR(n + 1));
       return false;
     }
   } else {
-    SYSDEBUG("mmap(0x%p, 0x%x) ENOMEM (automap failed)", ADDR(*res),
-             ADDR(n + 1));
+    STRACE("mmap(%.12p, %p) ENOMEM (automap failed)", ADDR(*res), ADDR(n + 1));
     return false;
   }
 }
@@ -111,28 +109,28 @@ static noasan void *MapMemory(void *addr, size_t size, int prot, int flags,
   dm = sys_mmap(addr, size, prot, f, fd, off);
   if (UNLIKELY(dm.addr == MAP_FAILED)) {
     if (IsWindows() && (flags & MAP_FIXED)) {
-      SYSDEBUG("mmap(0x%p, 0x%x) -> %s (%s)", addr, size, strerror(errno),
-               "can't recover from MAP_FIXED errors on Windows");
+      STRACE("mmap(%.12p, %'ld) → %s (%s)", addr, size, strerror(errno),
+             "can't recover from MAP_FIXED errors on Windows");
       assert(!"MapMemory() failed");
       Die();
     }
     return MAP_FAILED;
   }
   if (UNLIKELY(dm.addr != addr)) {
-    SYSDEBUG("KERNEL DIDN'T RESPECT MAP_FIXED");
+    STRACE("KERNEL DIDN'T RESPECT MAP_FIXED");
     assert(!"MapMemory() failed");
     Die();
   }
   if (!IsWindows() && (flags & MAP_FIXED)) {
     if (UntrackMemoryIntervals(addr, size)) {
-      SYSDEBUG("FIXED UNTRACK FAILED %s", strerror(errno));
+      STRACE("FIXED UNTRACK FAILED %s", strerror(errno));
       assert(!"MapMemory() failed");
       Die();
     }
   }
   if (TrackMemoryInterval(&_mmi, x, x + (n - 1), dm.maphandle, prot, flags)) {
     if (sys_munmap(addr, n) == -1) {
-      SYSDEBUG("TRACK MUNMAP FAILED %s", strerror(errno));
+      STRACE("TRACK MUNMAP FAILED %s", strerror(errno));
       assert(!"MapMemory() failed");
       Die();
     }
@@ -151,21 +149,21 @@ static noasan void *MapMemory(void *addr, size_t size, int prot, int flags,
  * punch holes into existing mappings.
  */
 static textwindows dontinline noasan void *MapMemories(char *addr, size_t size,
-                                                     int prot, int flags,
-                                                     int fd, int64_t off, int f,
-                                                     int x, size_t n) {
+                                                       int prot, int flags,
+                                                       int fd, int64_t off,
+                                                       int f, int x, size_t n) {
   struct DirectMap dm;
   size_t i, m = (n - 1) * FRAMESIZE;
   assert(m < size && m + FRAMESIZE >= size);
   dm = sys_mmap(addr + m, size - m, prot, f, fd, fd == -1 ? 0 : off + m);
   if (dm.addr == MAP_FAILED) {
-    SYSDEBUG("MapMemories(%p+%x/%x) %s", addr, m, size, strerror(errno));
+    STRACE("MapMemories(%.12p+%lx/%lx) %m", addr, m, size);
     return MAP_FAILED;
   }
   if (TrackMemoryInterval(&_mmi, x + (n - 1), x + (n - 1), dm.maphandle, prot,
                           flags) == -1) {
-    SYSDEBUG("MapMemories(%p+%x/%x) unrecoverable failure #1 %s", addr, m, size,
-             strerror(errno));
+    STRACE("MapMemories(%.12p+%lx/%lx) unrecoverable failure #1 %m", addr, m,
+           size);
     assert(!"MapMemories() failed");
     Die();
   }
@@ -174,8 +172,8 @@ static textwindows dontinline noasan void *MapMemories(char *addr, size_t size,
     if (dm.addr == MAP_FAILED ||
         TrackMemoryInterval(&_mmi, x + i / FRAMESIZE, x + i / FRAMESIZE,
                             dm.maphandle, prot, flags) == -1) {
-      SYSDEBUG("MapMemories(%p+%x/%x) unrecoverable failure #2 %s", addr, i,
-               size, strerror(errno));
+      STRACE("MapMemories(%p+%x/%x) unrecoverable failure #2 %m", addr, i,
+             size);
       assert(!"MapMemories() failed");
       Die();
     }
@@ -221,56 +219,56 @@ noasan void *mmap(void *addr, size_t size, int prot, int flags, int fd,
   int a, b, i, f, m, n, x;
   char mode[8], *p = addr;
   if (UNLIKELY(!size)) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (size=0)", p, size);
+    STRACE("mmap(%.12p, %'zu) EINVAL (size=0)", p, size);
     return VIP(einval());
   }
-  if (UNLIKELY(!SMALL(size))) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (size isn't 48-bit)", p, size);
+  if (UNLIKELY(!IsLegalSize(size))) {
+    STRACE("mmap(%.12p, %'zu) EINVAL (size isn't 48-bit)", p, size);
     return VIP(einval());
   }
   if (UNLIKELY(!IsLegalPointer(p))) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (p isn't 48-bit)", p, size);
+    STRACE("mmap(%.12p, %'zu) EINVAL (p isn't 48-bit)", p, size);
     return VIP(einval());
   }
   if (UNLIKELY(!ALIGNED(p))) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (p isn't 64kb aligned)", p, size);
+    STRACE("mmap(%.12p, %'zu) EINVAL (p isn't 64kb aligned)", p, size);
     return VIP(einval());
   }
   if (UNLIKELY(fd < -1)) {
-    SYSDEBUG("mmap(0x%p, 0x%x, fd=%d) EBADF", p, size, (long)fd);
+    STRACE("mmap(%.12p, %'zu, fd=%d) EBADF", p, size, fd);
     return VIP(ebadf());
   }
   if (UNLIKELY(!((fd != -1) ^ !!(flags & MAP_ANONYMOUS)))) {
-    SYSDEBUG("mmap(0x%p, 0x%x, %s, %d, %d) EINVAL (fd anonymous mismatch)", p,
-             size, DescribeMapping(prot, flags, mode), (long)fd, off);
+    STRACE("mmap(%.12p, %'zu, %s, %d, %'ld) EINVAL (fd anonymous mismatch)", p,
+           size, DescribeMapping(prot, flags, mode), fd, off);
     return VIP(einval());
   }
   if (UNLIKELY(!(!!(flags & MAP_PRIVATE) ^ !!(flags & MAP_SHARED)))) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (MAP_SHARED ^ MAP_PRIVATE)", p, size);
+    STRACE("mmap(%.12p, %'zu) EINVAL (MAP_SHARED ^ MAP_PRIVATE)", p, size);
     return VIP(einval());
   }
   if (UNLIKELY(off < 0)) {
-    SYSDEBUG("mmap(0x%p, 0x%x, off=%d) EINVAL (neg off)", p, size, off);
+    STRACE("mmap(%.12p, %'zu, off=%'ld) EINVAL (neg off)", p, size, off);
     return VIP(einval());
   }
   if (UNLIKELY(INT64_MAX - size < off)) {
-    SYSDEBUG("mmap(0x%p, 0x%x, off=%d) EINVAL (too large)", p, size, off);
+    STRACE("mmap(%.12p, %'zu, off=%'ld) EINVAL (too large)", p, size, off);
     return VIP(einval());
   }
   if (UNLIKELY(!ALIGNED(off))) {
-    SYSDEBUG("mmap(0x%p, 0x%x) EINVAL (p isn't 64kb aligned)", p, size);
+    STRACE("mmap(%.12p, %'zu) EINVAL (p isn't 64kb aligned)", p, size);
     return VIP(einval());
   }
   if ((flags & MAP_FIXED_NOREPLACE) && IsMapped(p, size)) {
     if (OverlapsImageSpace(p, size)) {
-      SYSDEBUG("mmap(0x%p, 0x%x) EFAULT (overlaps image)", p, size);
+      STRACE("mmap(%.12p, %'zu) EFAULT (overlaps image)", p, size);
     } else {
-      SYSDEBUG("mmap(0x%p, 0x%x) EFAULT (overlaps existing)", p, size);
+      STRACE("mmap(%.12p, %'zu) EFAULT (overlaps existing)", p, size);
     }
     return VIP(efault());
   }
-  SYSDEBUG("mmap(0x%p, 0x%x, %s, %d, %d)", p, size,
-           DescribeMapping(prot, flags, mode), (long)fd, off);
+  STRACE("mmap(%.12p, %'zu, %s, %d, %'ld)% m", p, size,
+         DescribeMapping(prot, flags, mode), fd, off);
   if (fd == -1) {
     size = ROUNDUP(size, FRAMESIZE);
     if (IsWindows()) {
@@ -283,7 +281,7 @@ noasan void *mmap(void *addr, size_t size, int prot, int flags, int fd,
     x = FRAME(p);
     if (IsWindows()) {
       if (UntrackMemoryIntervals(p, size)) {
-        SYSDEBUG("FIXED UNTRACK FAILED %s", strerror(errno));
+        STRACE("FIXED UNTRACK FAILED %m");
         assert(!"mmap() failed");
         Die();
       }
diff --git a/libc/runtime/mremap.c b/libc/runtime/mremap.c
index dc9b8ead12f..82dad601e93 100644
--- a/libc/runtime/mremap.c
+++ b/libc/runtime/mremap.c
@@ -21,10 +21,9 @@
 #include "libc/bits/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
-#include "libc/log/libfatal.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/runtime.h"
 #include "libc/runtime/directmap.internal.h"
@@ -36,7 +35,6 @@
 
 #define IP(X)      (intptr_t)(X)
 #define VIP(X)     (void *)IP(X)
-#define SMALL(n)   ((n) <= 0xffffffffffff)
 #define ALIGNED(p) (!(IP(p) & (FRAMESIZE - 1)))
 #define ADDR(x)    ((int64_t)((uint64_t)(x) << 32) >> 16)
 #define SHADE(x)   (((intptr_t)(x) >> 3) + 0x7fff8000)
@@ -76,43 +74,44 @@ void *mremap(void *p, size_t n, size_t m, int f, ... /* void *q */) {
   size_t i, j, k;
   struct DirectMap dm;
   int a, b, prot, flags;
+  assert(!__vforked);
   if (UNLIKELY(!m)) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EINVAL (m=0)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EINVAL (m=0)", p, n, m, f);
     return VIP(einval());
   }
   if (UNLIKELY(!n)) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EOPNOTSUPP (n=0)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EOPNOTSUPP (n=0)", p, n, m, f);
     return VIP(eopnotsupp());
   }
   if (UNLIKELY(!ALIGNED(n))) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EOPNOTSUPP (n align)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EOPNOTSUPP (n align)", p, n, m, f);
     return VIP(eopnotsupp());
   }
   if (UNLIKELY(!ALIGNED(m))) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EOPNOTSUPP (n align)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EOPNOTSUPP (n align)", p, n, m, f);
     return VIP(eopnotsupp());
   }
   if (UNLIKELY(!ALIGNED(p))) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EINVAL (64kb align)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EINVAL (64kb align)", p, n, m, f);
     return VIP(einval());
   }
-  if (UNLIKELY(!SMALL(n))) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EINVAL (n too big)", p, n, m, f);
+  if (UNLIKELY(!IsLegalSize(n))) {
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EINVAL (n too big)", p, n, m, f);
     return VIP(enomem());
   }
-  if (UNLIKELY(!SMALL(m))) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EINVAL (m too big)", p, n, m, f);
+  if (UNLIKELY(!IsLegalSize(m))) {
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EINVAL (m too big)", p, n, m, f);
     return VIP(enomem());
   }
   if (f & ~(MREMAP_MAYMOVE | MREMAP_FIXED)) {
-    SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x) EINVAL (bad flag)", p, n, m, f);
+    STRACE("mremap(%p, %'zu, %'zu, %#b) EINVAL (bad flag)", p, n, m, f);
     return VIP(einval());
   }
   if (!IsMemtracked(FRAME(p), FRAME((intptr_t)p + (n - 1)))) {
-    SYSDEBUG("munmap(0x%x, 0x%x) EFAULT (interval not tracked)", p, n);
+    STRACE("munmap(%p, %'zu) EFAULT (interval not tracked)", p, n);
     return VIP(efault());
   }
-  SYSDEBUG("mremap(0x%p, 0x%x, 0x%x, 0x%x)", p, n, m, f);
+  STRACE("mremap(%p, %'zu, %'zu, %#b)", p, n, m, f);
   i = FindMemoryInterval(&_mmi, FRAME(p));
   if (i >= _mmi.i) return VIP(efault());
   flags = _mmi.p[i].flags;
@@ -174,8 +173,8 @@ void *mremap(void *p, size_t n, size_t m, int f, ... /* void *q */) {
     }
     q = sys_mremap((void *)p, n, m, MREMAP_MAYMOVE | MREMAP_FIXED,
                    (void *)ADDR(a));
-    SYSDEBUG("sys_mremap(0x%p, 0x%x, 0x%x, 0x%x, 0x%x) -> 0x%p", p, n, m,
-             MREMAP_MAYMOVE | MREMAP_FIXED, ADDR(a));
+    STRACE("sys_mremap(%p, %'zu, %'zu, %#b, %p) → %p", p, n, m,
+           MREMAP_MAYMOVE | MREMAP_FIXED, ADDR(a), q);
     if (q == MAP_FAILED) return 0;
     if (ReleaseMemoryIntervals(&_mmi, (uintptr_t)p >> 16,
                                ((uintptr_t)p + n - FRAMESIZE) >> 16, 0) != -1 &&
diff --git a/libc/runtime/munmap.c b/libc/runtime/munmap.c
index 45098727ea9..6073bc9690f 100644
--- a/libc/runtime/munmap.c
+++ b/libc/runtime/munmap.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/bits/likely.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -31,10 +31,8 @@
 #include "libc/sysv/errfuns.h"
 
 #define IP(X)      (intptr_t)(X)
-#define SMALL(n)   ((n) <= 0xffffffffffff)
 #define ALIGNED(p) (!(IP(p) & (FRAMESIZE - 1)))
 #define ADDR(x)    ((int64_t)((uint64_t)(x) << 32) >> 16)
-#define SHADE(x)   (((intptr_t)(x) >> 3) + 0x7fff8000)
 #define FRAME(x)   ((int)((intptr_t)(x) >> 16))
 
 /**
@@ -56,28 +54,29 @@ noasan int munmap(void *v, size_t n) {
   int rc;
   char poison, *p = v;
   intptr_t a, b, x, y;
+  assert(!__vforked);
   if (UNLIKELY(!n)) {
-    SYSDEBUG("munmap(0x%p, 0x%x) %s (n=0)", p, n);
+    STRACE("munmap(%.12p, %'zu) %s (n=0)", p, n);
     return einval();
   }
-  if (UNLIKELY(!SMALL(n))) {
-    SYSDEBUG("munmap(0x%p, 0x%x) EINVAL (n isn't 48-bit)", p, n);
+  if (UNLIKELY(!IsLegalSize(n))) {
+    STRACE("munmap(%.12p, %'zu) EINVAL (n isn't 48-bit)", p, n);
     return einval();
   }
   if (UNLIKELY(!IsLegalPointer(p))) {
-    SYSDEBUG("munmap(0x%p, 0x%x) EINVAL (p isn't 48-bit)", p, n);
+    STRACE("munmap(%.12p, %'zu) EINVAL (p isn't 48-bit)", p, n);
     return einval();
   }
   if (UNLIKELY(!IsLegalPointer(p + (n - 1)))) {
-    SYSDEBUG("munmap(0x%p, 0x%x) EINVAL (p+(n-1) isn't 48-bit)", p, n);
+    STRACE("munmap(%.12p, %'zu) EINVAL (p+(n-1) isn't 48-bit)", p, n);
     return einval();
   }
   if (UNLIKELY(!ALIGNED(p))) {
-    SYSDEBUG("munmap(0x%p, 0x%x) EINVAL (p isn't 64kb aligned)", p, n);
+    STRACE("munmap(%.12p, %'zu) EINVAL (p isn't 64kb aligned)", p, n);
     return einval();
   }
   if (!IsMemtracked(FRAME(p), FRAME(p + (n - 1)))) {
-    SYSDEBUG("munmap(0x%p, 0x%x) EFAULT (interval not tracked)", p, n);
+    STRACE("munmap(%.12p, %'zu) EFAULT (interval not tracked)", p, n);
     return efault();
   }
   if (UntrackMemoryIntervals(p, n) != -1) {
@@ -85,7 +84,7 @@ noasan int munmap(void *v, size_t n) {
       rc = sys_munmap(p, n);
       if (rc != -1) {
         if (IsAsan() && !OverlapsShadowSpace(p, n)) {
-          a = SHADE(p);
+          a = ((intptr_t)p >> 3) + 0x7fff8000;
           b = a + (n >> 3);
           if (IsMemtracked(FRAME(a), FRAME(b - 1))) {
             x = ROUNDUP(a, FRAMESIZE);
@@ -100,7 +99,7 @@ noasan int munmap(void *v, size_t n) {
               __repstosb((void *)a, kAsanUnmapped, b - a);
             }
           } else {
-            SYSDEBUG("unshadow(0x%x, 0x%x) EFAULT", a, b - a);
+            STRACE("unshadow(%.12p, %p) EFAULT", a, b - a);
           }
         }
       }
@@ -110,7 +109,7 @@ noasan int munmap(void *v, size_t n) {
   } else {
     rc = -1;
   }
-  SYSDEBUG("munmap(0x%p, 0x%x) -> %d %s", p, n, (long)rc,
-           rc == -1 ? strerror(errno) : "");
+  STRACE("munmap(%.12p, %'zu) → %d %s", p, n, rc,
+         rc == -1 ? strerror(errno) : "");
   return rc;
 }
diff --git a/libc/runtime/opensymboltable.c b/libc/runtime/opensymboltable.c
index 6d2d229c494..d615ed020f9 100644
--- a/libc/runtime/opensymboltable.c
+++ b/libc/runtime/opensymboltable.c
@@ -20,7 +20,7 @@
 #include "libc/assert.h"
 #include "libc/bits/bits.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/elf/def.h"
 #include "libc/elf/scalar.h"
@@ -187,7 +187,7 @@ noasan struct SymbolTable *OpenSymbolTable(const char *filename) {
 RaiseEnoexec:
   errno = ENOEXEC;
 SystemError:
-  SYSDEBUG("OpenSymbolTable() %s", strerror(errno));
+  STRACE("OpenSymbolTable() %m");
   if (map != MAP_FAILED) {
     munmap(map, st.st_size);
   }
diff --git a/libc/runtime/printargs.c b/libc/runtime/printargs.c
new file mode 100644
index 00000000000..986be211545
--- /dev/null
+++ b/libc/runtime/printargs.c
@@ -0,0 +1,116 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/runtime.h"
+#include "libc/runtime/stack.h"
+#include "libc/sysv/consts/auxv.h"
+
+static const struct AuxiliaryValue {
+  const char *fmt;
+  long *id;
+  const char *name;
+} kAuxiliaryValues[] = {
+    {"%-14p", &AT_EXECFD, "AT_EXECFD"},
+    {"%-14p", &AT_PHDR, "AT_PHDR"},
+    {"%-14p", &AT_PHENT, "AT_PHENT"},
+    {"%-14p", &AT_PHNUM, "AT_PHNUM"},
+    {"%-14p", &AT_PAGESZ, "AT_PAGESZ"},
+    {"%-14p", &AT_BASE, "AT_BASE"},
+    {"%-14p", &AT_ENTRY, "AT_ENTRY"},
+    {"%-14p", &AT_NOTELF, "AT_NOTELF"},
+    {"%-14d", &AT_UID, "AT_UID"},
+    {"%-14d", &AT_EUID, "AT_EUID"},
+    {"%-14d", &AT_GID, "AT_GID"},
+    {"%-14d", &AT_EGID, "AT_EGID"},
+    {"%-14d", &AT_CLKTCK, "AT_CLKTCK"},
+    {"%-14d", &AT_OSRELDATE, "AT_OSRELDATE"},
+    {"%-14p", &AT_PLATFORM, "AT_PLATFORM"},
+    {"%-14p", &AT_DCACHEBSIZE, "AT_DCACHEBSIZE"},
+    {"%-14p", &AT_ICACHEBSIZE, "AT_ICACHEBSIZE"},
+    {"%-14p", &AT_UCACHEBSIZE, "AT_UCACHEBSIZE"},
+    {"%-14p", &AT_SECURE, "AT_SECURE"},
+    {"%-14s", &AT_BASE_PLATFORM, "AT_BASE_PLATFORM"},
+    {"%-14p", &AT_RANDOM, "AT_RANDOM"},
+    {"%-14s", &AT_EXECFN, "AT_EXECFN"},
+    {"%-14p", &AT_SYSINFO_EHDR, "AT_SYSINFO_EHDR"},
+    {"%-14p", &AT_FLAGS, "AT_FLAGS"},
+    {"%-14p", &AT_HWCAP, "AT_HWCAP"},
+    {"%-14p", &AT_HWCAP2, "AT_HWCAP2"},
+    {"%-14p", &AT_STACKBASE, "AT_STACKBASE"},
+    {"%-14p", &AT_CANARY, "AT_CANARY"},
+    {"%-14p", &AT_CANARYLEN, "AT_CANARYLEN"},
+    {"%-14ld", &AT_NCPUS, "AT_NCPUS"},
+    {"%-14p", &AT_PAGESIZES, "AT_PAGESIZES"},
+    {"%-14d", &AT_PAGESIZESLEN, "AT_PAGESIZESLEN"},
+    {"%-14p", &AT_TIMEKEEP, "AT_TIMEKEEP"},
+    {"%-14p", &AT_STACKPROT, "AT_STACKPROT"},
+    {"%-14p", &AT_EHDRFLAGS, "AT_EHDRFLAGS"},
+};
+
+static const struct AuxiliaryValue *DescribeAuxv(unsigned long x) {
+  int i;
+  for (i = 0; i < ARRAYLEN(kAuxiliaryValues); ++i) {
+    if (*kAuxiliaryValues[i].id && x == *kAuxiliaryValues[i].id) {
+      return kAuxiliaryValues + i;
+    }
+  }
+  return NULL;
+}
+
+textstartup void __printargs(int argc, char **argv, char **envp,
+                             intptr_t *auxv) {
+#ifdef SYSDEBUG
+  long key;
+  char **env;
+  unsigned i;
+  intptr_t *auxp;
+  char path[PATH_MAX];
+  struct AuxiliaryValue *auxinfo;
+  STRACE("ARGUMENTS (%p)", argv);
+  for (i = 0; i < argc; ++i) {
+    STRACE(" ☼ %s", argv[i]);
+  }
+  STRACE("ENVIRONMENT (%p)", envp);
+  for (env = envp; *env; ++env) {
+    STRACE(" ☼ %s", *env);
+  }
+  STRACE("AUXILIARY (%p)", auxv);
+  for (auxp = auxv; *auxp; auxp += 2) {
+    if ((auxinfo = DescribeAuxv(auxp[0]))) {
+      ksnprintf(path, sizeof(path), auxinfo->fmt, auxp[1]);
+      STRACE(" ☼ %16s[%4ld] = %s", auxinfo->name, auxp[0], path);
+    } else {
+      STRACE(" ☼ %16s[%4ld] = %014p", "unknown", auxp[0], auxp[1]);
+    }
+  }
+  STRACE("SPECIALS");
+  STRACE(" ☼ %21s = %#s", "kTmpPath", kTmpPath);
+  STRACE(" ☼ %21s = %#s", "kNtSystemDirectory", kNtSystemDirectory);
+  STRACE(" ☼ %21s = %#s", "kNtWindowsDirectory", kNtWindowsDirectory);
+  STRACE(" ☼ %21s = %#s", "program_executable_name", program_executable_name);
+  STRACE(" ☼ %21s = %#s", "GetInterpreterExecutableName()",
+         GetInterpreterExecutableName(path, sizeof(path)));
+  STRACE(" ☼ %21s = %p", "RSP", __builtin_frame_address(0));
+  STRACE(" ☼ %21s = %p", "GetStackAddr()", GetStackAddr(0));
+  STRACE(" ☼ %21s = %p", "GetStaticStackAddr(0)", GetStaticStackAddr(0));
+  STRACE(" ☼ %21s = %p", "GetStackSize()", GetStackSize());
+#endif
+}
diff --git a/libc/runtime/straceinit.greg.c b/libc/runtime/straceinit.greg.c
new file mode 100644
index 00000000000..5c43e462a60
--- /dev/null
+++ b/libc/runtime/straceinit.greg.c
@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/bits/safemacros.internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/fmt/conv.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/log/libfatal.internal.h"
+#include "libc/runtime/internal.h"
+#include "libc/str/str.h"
+
+/**
+ * Enables plaintext system call logging  if `--strace` flag is passed.
+ */
+textstartup int __strace_init(int argc, char **argv, char **envp, long *auxv) {
+  /* asan isn't initialized yet at runlevel 300 */
+  if (__intercept_flag(&argc, argv, "--strace") ||
+      __atoul(nulltoempty(__getenv(envp, "STRACE")))) {
+    ++__strace;
+  }
+  return argc;
+}
diff --git a/libc/runtime/vfork.S b/libc/runtime/vfork.S
index 197d6f763b0..11c6e1cfb56 100644
--- a/libc/runtime/vfork.S
+++ b/libc/runtime/vfork.S
@@ -17,14 +17,10 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/dce.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/macros.internal.h"
 .privileged
 
-#ifdef __FSANITIZE_ADDRESS__
-vfork:	jmp	fork			# TODO: asan and vfork don't mix?
-	.endfn	vfork,globl
-#else
-
 //	Forks process without copying page tables.
 //
 //	This is the same as fork() except it's optimized for the case
@@ -40,11 +36,24 @@ vfork:	jmp	fork			# TODO: asan and vfork don't mix?
 //	@returnstwice
 //	@vforksafe
 vfork:
+#ifdef __FSANITIZE_ADDRESS__
+	jmp	fork			# TODO: asan and vfork don't mix?
+	.endfn	vfork,globl
+#else
 #if SupportsWindows()
 	testb	IsWindows()
-	jnz	sys_fork_nt
+	jnz	sys_fork_nt		# and we're lucky to have that
 #endif
+#if SupportsOpenbsd()
+	testb	IsOpenbsd()
+	jnz	fork			# fake vfork plus msyscall issues
+#endif
+#ifdef SYSDEBUG
+	ezlea	.Llog,di
+	call	__stracef
+#endif /* SYSDEBUG */
 	mov	__NR_vfork(%rip),%eax
+	mov	errno(%rip),%r8d	# avoid question of @vforksafe errno
 	pop	%rsi			# saves return address in a register
 #if SupportsBsd()
 	testb	IsBsd()
@@ -56,7 +65,8 @@ vfork:
 	cmp	$-4095,%eax
 	jae	systemfive_error
 #endif
-0:	ezlea	__vforked,di
+0:	mov	%r8d,errno(%rip)
+	ezlea	__vforked,di
 	test	%eax,%eax
 	jz	1f
 	decl	(%rdi)
@@ -81,4 +91,11 @@ vfork.bsd:
 	.endfn	vfork.bsd
 #endif /* BSD */
 
+#ifdef SYSDEBUG
+	.rodata.str1.1
+.Llog:	.ascii	STRACE_PROLOGUE
+	.asciz	"vfork()%n"
+	.previous
+#endif /* DEBUGSYS */
+
 #endif /* __FSANITIZE_ADDRESS__ */
diff --git a/libc/runtime/winmain.greg.c b/libc/runtime/winmain.greg.c
index 35ffb0810ce..72c8fdb04b9 100644
--- a/libc/runtime/winmain.greg.c
+++ b/libc/runtime/winmain.greg.c
@@ -20,6 +20,7 @@
 #include "libc/bits/pushpop.h"
 #include "libc/bits/weaken.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/fmt/fmt.h"
 #include "libc/intrin/kprintf.h"
@@ -127,6 +128,7 @@ static noasan textwindows wontreturn noinstrument void WinMainNew(void) {
   stacksize = GetStackSize();
   allocsize = argsize + stacksize;
   allocaddr = stackaddr - argsize;
+  STRACE("WinMainNew() mapping arg block / stack");
   MapViewOfFileExNuma(
       (_mmi.p[0].h = CreateFileMappingNuma(
            -1, &kNtIsInheritable, kNtPageExecuteReadwrite, allocsize >> 32,
@@ -139,6 +141,7 @@ static noasan textwindows wontreturn noinstrument void WinMainNew(void) {
   _mmi.p[0].flags = MAP_PRIVATE | MAP_ANONYMOUS;
   _mmi.i = 1;
   wa = (struct WinArgs *)allocaddr;
+  STRACE("WinMainNew() loading arg block");
   count = GetDosArgv(GetCommandLine(), wa->argblock, ARRAYLEN(wa->argblock),
                      wa->argv, ARRAYLEN(wa->argv));
   for (i = 0; wa->argv[0][i]; ++i) {
@@ -147,11 +150,13 @@ static noasan textwindows wontreturn noinstrument void WinMainNew(void) {
     }
   }
   env16 = GetEnvironmentStrings();
+  STRACE("WinMainNew() loading environment");
   GetDosEnviron(env16, wa->envblock, ARRAYLEN(wa->envblock) - 8, wa->envp,
                 ARRAYLEN(wa->envp) - 1);
   FreeEnvironmentStrings(env16);
   wa->auxv[0][0] = pushpop(AT_EXECFN);
   wa->auxv[0][1] = (intptr_t)wa->argv[0];
+  STRACE("WinMainNew() switching stacks");
   _jmpstack((char *)stackaddr + stacksize, cosmo, count, wa->argv, wa->envp,
             wa->auxv);
 }
@@ -198,6 +203,7 @@ noasan textwindows noinstrument int64_t WinMain(int64_t hInstance,
   ts = rdtsc();
   __nomultics = true;
   __pid = GetCurrentProcessId();
+  STRACE("WinMain()");
   MakeLongDoubleLongAgain();
   if (weaken(WinSockInit)) weaken(WinSockInit)();
   if (weaken(WinMainForked)) weaken(WinMainForked)();
diff --git a/libc/sock/accept4.c b/libc/sock/accept4.c
index 1d24bb048a4..85c87189817 100644
--- a/libc/sock/accept4.c
+++ b/libc/sock/accept4.c
@@ -17,10 +17,12 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/sysv/errfuns.h"
 
 /**
@@ -35,14 +37,20 @@
  * @asyncsignalsafe
  */
 int accept4(int fd, void *out_addr, uint32_t *inout_addrsize, int flags) {
-  if (!out_addr) return efault();
-  if (!inout_addrsize) return efault();
-  if (IsAsan() && !__asan_is_valid(out_addr, *inout_addrsize)) return efault();
-  if (!IsWindows()) {
-    return sys_accept4(fd, out_addr, inout_addrsize, flags);
+  int rc;
+  char addrbuf[72];
+  if (!out_addr || !inout_addrsize ||
+      (IsAsan() && !__asan_is_valid(out_addr, *inout_addrsize))) {
+    rc = efault();
+  } else if (!IsWindows()) {
+    rc = sys_accept4(fd, out_addr, inout_addrsize, flags);
   } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_accept_nt(&g_fds.p[fd], out_addr, inout_addrsize, flags);
+    rc = sys_accept_nt(&g_fds.p[fd], out_addr, inout_addrsize, flags);
   } else {
-    return ebadf();
+    rc = ebadf();
   }
+  STRACE("accept4(%d, [%s]) -> %d% m", fd,
+         __describe_sockaddr(out_addr, inout_addrsize ? *inout_addrsize : 0),
+         rc);
+  return rc;
 }
diff --git a/libc/sock/bind.c b/libc/sock/bind.c
index 28cb9c689df..a65c7bc6c32 100644
--- a/libc/sock/bind.c
+++ b/libc/sock/bind.c
@@ -18,10 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/str/str.h"
 #include "libc/sysv/errfuns.h"
 
@@ -36,26 +38,30 @@
  * @asyncsignalsafe
  */
 int bind(int fd, const void *addr, uint32_t addrsize) {
-  if (!addr) return efault();
-  if (IsAsan() && !__asan_is_valid(addr, addrsize)) return efault();
-  if (addrsize == sizeof(struct sockaddr_in)) {
+  int rc;
+  char addrbuf[72];
+  if (!addr || (IsAsan() && !__asan_is_valid(addr, addrsize))) {
+    rc = efault();
+  } else if (addrsize >= sizeof(struct sockaddr_in)) {
     if (!IsWindows()) {
       if (!IsBsd()) {
-        return sys_bind(fd, addr, addrsize);
+        rc = sys_bind(fd, addr, addrsize);
       } else {
         char addr2[sizeof(
             struct sockaddr_un_bsd)]; /* sockaddr_un_bsd is the largest */
         assert(addrsize <= sizeof(addr2));
         memcpy(&addr2, addr, addrsize);
         sockaddr2bsd(&addr2[0]);
-        return sys_bind(fd, &addr2, addrsize);
+        rc = sys_bind(fd, &addr2, addrsize);
       }
     } else if (__isfdkind(fd, kFdSocket)) {
-      return sys_bind_nt(&g_fds.p[fd], addr, addrsize);
+      rc = sys_bind_nt(&g_fds.p[fd], addr, addrsize);
     } else {
-      return ebadf();
+      rc = ebadf();
     }
   } else {
-    return einval();
+    rc = einval();
   }
+  STRACE("bind(%d, %s) -> %d% m", fd, __describe_sockaddr(addr, addrsize), rc);
+  return rc;
 }
diff --git a/libc/sock/connect.c b/libc/sock/connect.c
index 2793124817a..41e39882f77 100644
--- a/libc/sock/connect.c
+++ b/libc/sock/connect.c
@@ -16,9 +16,11 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/sysv/errfuns.h"
 
 /**
@@ -32,15 +34,20 @@
  * @asyncsignalsafe
  */
 int connect(int fd, const void *addr, uint32_t addrsize) {
-  uint32_t ip;
-  if (!addr) return efault();
-  if (IsAsan() && !__asan_is_valid(addr, addrsize)) return efault();
-  _firewall(addr, addrsize);
-  if (!IsWindows()) {
-    return sys_connect(fd, addr, addrsize);
-  } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_connect_nt(&g_fds.p[fd], addr, addrsize);
+  int rc;
+  if (addr && !(IsAsan() && !__asan_is_valid(addr, addrsize))) {
+    _firewall(addr, addrsize);
+    if (!IsWindows()) {
+      rc = sys_connect(fd, addr, addrsize);
+    } else if (__isfdkind(fd, kFdSocket)) {
+      rc = sys_connect_nt(&g_fds.p[fd], addr, addrsize);
+    } else {
+      rc = ebadf();
+    }
   } else {
-    return ebadf();
+    rc = efault();
   }
+  STRACE("connect(%d, %s) -> %d% m", fd, __describe_sockaddr(addr, addrsize),
+         rc);
+  return rc;
 }
diff --git a/libc/sock/getpeername.c b/libc/sock/getpeername.c
index 444a3e60c55..0fbf32df7ec 100644
--- a/libc/sock/getpeername.c
+++ b/libc/sock/getpeername.c
@@ -17,10 +17,12 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/sysv/errfuns.h"
 
 /**
@@ -29,12 +31,19 @@
  * @see getsockname()
  */
 int getpeername(int fd, void *out_addr, uint32_t *out_addrsize) {
-  if (IsAsan() && !__asan_is_valid(out_addr, *out_addrsize)) return efault();
-  if (!IsWindows()) {
-    return sys_getpeername(fd, out_addr, out_addrsize);
+  int rc;
+  if (!out_addr || !out_addrsize ||
+      (IsAsan() && (!__asan_is_valid(out_addrsize, 4) ||
+                    !__asan_is_valid(out_addr, *out_addrsize)))) {
+    rc = efault();
+  } else if (!IsWindows()) {
+    rc = sys_getpeername(fd, out_addr, out_addrsize);
   } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_getpeername_nt(&g_fds.p[fd], out_addr, out_addrsize);
+    rc = sys_getpeername_nt(&g_fds.p[fd], out_addr, out_addrsize);
   } else {
-    return ebadf();
+    rc = ebadf();
   }
+  STRACE("getpeername(%d, [%s]) -> %d% m", fd,
+         __describe_sockaddr(out_addr, out_addrsize ? *out_addrsize : 0), rc);
+  return rc;
 }
diff --git a/libc/sock/getsockname.c b/libc/sock/getsockname.c
index 49c7e9dbe4d..fac44ca1a71 100644
--- a/libc/sock/getsockname.c
+++ b/libc/sock/getsockname.c
@@ -17,10 +17,12 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/sysv/errfuns.h"
 
 /**
@@ -29,12 +31,19 @@
  * @see getpeername()
  */
 int getsockname(int fd, void *out_addr, uint32_t *out_addrsize) {
-  if (IsAsan() && !__asan_is_valid(out_addr, *out_addrsize)) return efault();
-  if (!IsWindows()) {
-    return sys_getsockname(fd, out_addr, out_addrsize);
+  int rc;
+  if (!out_addrsize || !out_addrsize ||
+      (IsAsan() && (!__asan_is_valid(out_addrsize, 4) ||
+                    !__asan_is_valid(out_addr, *out_addrsize)))) {
+    rc = efault();
+  } else if (!IsWindows()) {
+    rc = sys_getsockname(fd, out_addr, out_addrsize);
   } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_getsockname_nt(&g_fds.p[fd], out_addr, out_addrsize);
+    rc = sys_getsockname_nt(&g_fds.p[fd], out_addr, out_addrsize);
   } else {
-    return ebadf();
+    rc = ebadf();
   }
+  STRACE("getsockname(%d, [%s]) -> %d% m", fd,
+         __describe_sockaddr(out_addr, out_addrsize ? *out_addrsize : 0), rc);
+  return rc;
 }
diff --git a/libc/sock/inet_ntop.c b/libc/sock/inet_ntop.c
index 3e8fbe99c8f..afbc88d946d 100644
--- a/libc/sock/inet_ntop.c
+++ b/libc/sock/inet_ntop.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/fmt/itoa.h"
+#include "libc/str/str.h"
 #include "libc/sysv/consts/af.h"
 #include "libc/sysv/errfuns.h"
 
@@ -34,16 +35,17 @@ const char *inet_ntop(int af, const void *src, char *dst, uint32_t size) {
   unsigned char *ip;
   int i, t, a, b, c, d;
   p = dst;
+  if (!size) return dst;
   if ((ip = src)) {
     if (af == AF_INET) {
       if (size >= 16) {
-        p += uint64toarray_radix10(ip[0], p);
+        p = FormatUint32(p, ip[0]);
         *p++ = '.';
-        p += uint64toarray_radix10(ip[1], p);
+        p = FormatUint32(p, ip[1]);
         *p++ = '.';
-        p += uint64toarray_radix10(ip[2], p);
+        p = FormatUint32(p, ip[2]);
         *p++ = '.';
-        p += uint64toarray_radix10(ip[3], p);
+        p = FormatUint32(p, ip[3]);
         *p = '\0';
         return dst;
       } else {
@@ -98,6 +100,5 @@ const char *inet_ntop(int af, const void *src, char *dst, uint32_t size) {
   } else {
     einval();
   }
-  if (size) dst[0] = '\0';
-  return NULL;
+  return 0;
 }
diff --git a/libc/sock/internal.h b/libc/sock/internal.h
index 312826592c4..7126f579873 100644
--- a/libc/sock/internal.h
+++ b/libc/sock/internal.h
@@ -1,6 +1,5 @@
 #ifndef COSMOPOLITAN_LIBC_SOCK_INTERNAL_H_
 #define COSMOPOLITAN_LIBC_SOCK_INTERNAL_H_
-#include "libc/bits/bits.h"
 #include "libc/calls/internal.h"
 #include "libc/nt/thunk/msabi.h"
 #include "libc/nt/winsock.h"
@@ -148,12 +147,10 @@ int sys_close_epoll(int) hidden;
  */
 forceinline void sockaddr2bsd(void *saddr) {
   char *p;
-  uint16_t fam;
   if (saddr) {
     p = saddr;
-    fam = READ16LE(p);
+    p[1] = p[0];
     p[0] = sizeof(struct sockaddr_in_bsd);
-    p[1] = fam;
   }
 }
 
@@ -161,11 +158,11 @@ forceinline void sockaddr2bsd(void *saddr) {
  * Converts sockaddr_in_bsd (XNU/BSD) → sockaddr (Linux/Windows).
  */
 forceinline void sockaddr2linux(void *saddr) {
-  char *p, fam;
+  char *p;
   if (saddr) {
     p = saddr;
-    fam = p[1];
-    WRITE16LE(p, fam);
+    p[0] = p[1];
+    p[1] = 0;
   }
 }
 
diff --git a/libc/sock/listen.c b/libc/sock/listen.c
index 65c1465c118..a3500345f0a 100644
--- a/libc/sock/listen.c
+++ b/libc/sock/listen.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
@@ -34,11 +35,14 @@
  * @return 0 on success or -1 w/ errno
  */
 int listen(int fd, int backlog) {
+  int rc;
   if (!IsWindows()) {
-    return sys_listen(fd, backlog);
+    rc = sys_listen(fd, backlog);
   } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_listen_nt(&g_fds.p[fd], backlog);
+    rc = sys_listen_nt(&g_fds.p[fd], backlog);
   } else {
-    return ebadf();
+    rc = ebadf();
   }
+  STRACE("listen(%d, %d) → %d% m", fd, backlog, rc);
+  return rc;
 }
diff --git a/libc/sock/poll.c b/libc/sock/poll.c
index 38fa964f7d0..bf5e5e23f13 100644
--- a/libc/sock/poll.c
+++ b/libc/sock/poll.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/sock/internal.h"
@@ -38,16 +39,18 @@
  * @asyncsignalsafe
  */
 int poll(struct pollfd *fds, uint64_t nfds, int32_t timeout_ms) {
+  int rc;
   if (IsAsan() && !__asan_is_valid(fds, nfds * sizeof(struct pollfd))) {
-    return efault();
-  }
-  if (!IsWindows()) {
+    rc = efault();
+  } else if (!IsWindows()) {
     if (!IsMetal()) {
-      return sys_poll(fds, nfds, timeout_ms);
+      rc = sys_poll(fds, nfds, timeout_ms);
     } else {
-      return sys_poll_metal(fds, nfds, timeout_ms);
+      rc = sys_poll_metal(fds, nfds, timeout_ms);
     }
   } else {
-    return sys_poll_nt(fds, nfds, timeout_ms);
+    rc = sys_poll_nt(fds, nfds, timeout_ms);
   }
+  STRACE("poll(%p, %'lu, %'d) → %d% m", fds, nfds, timeout_ms, rc);
+  return rc;
 }
diff --git a/libc/sock/shutdown.c b/libc/sock/shutdown.c
index 2183b2f2fa3..7c9f3df8ca1 100644
--- a/libc/sock/shutdown.c
+++ b/libc/sock/shutdown.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
@@ -31,11 +32,14 @@
  * @asyncsignalsafe
  */
 int shutdown(int fd, int how) {
+  int rc;
   if (!IsWindows()) {
-    return sys_shutdown(fd, how);
+    rc = sys_shutdown(fd, how);
   } else if (__isfdkind(fd, kFdSocket)) {
-    return sys_shutdown_nt(&g_fds.p[fd], how);
+    rc = sys_shutdown_nt(&g_fds.p[fd], how);
   } else {
-    return ebadf();
+    rc = ebadf();
   }
+  STRACE("shutdown(%d, %d) -> %d% m", fd, how, rc);
+  return rc;
 }
diff --git a/libc/sock/sock.h b/libc/sock/sock.h
index 6eb96b9cac5..95c9d7bcc79 100644
--- a/libc/sock/sock.h
+++ b/libc/sock/sock.h
@@ -136,31 +136,30 @@ char *inet_ntoa(struct in_addr);
 int parseport(const char *);
 uint32_t *GetHostIps(void);
 
-int socket(int, int, int) nodiscard;
-int accept(int, void *, uint32_t *) nodiscard;
-int accept4(int, void *, uint32_t *, int) nodiscard;
+int socket(int, int, int);
+int accept(int, void *, uint32_t *);
+int accept4(int, void *, uint32_t *, int);
 int bind(int, const void *, uint32_t);
 int connect(int, const void *, uint32_t);
 int listen(int, int);
 int shutdown(int, int);
-int getsockname(int, void *, uint32_t *) paramsnonnull();
-int getpeername(int, void *, uint32_t *) paramsnonnull();
-ssize_t send(int, const void *, size_t, int) paramsnonnull();
+int getsockname(int, void *, uint32_t *);
+int getpeername(int, void *, uint32_t *);
+ssize_t send(int, const void *, size_t, int);
 ssize_t recv(int, void *, size_t, int);
-ssize_t recvmsg(int, struct msghdr *, int) paramsnonnull();
+ssize_t recvmsg(int, struct msghdr *, int);
 ssize_t recvfrom(int, void *, size_t, uint32_t, void *, uint32_t *);
-ssize_t sendmsg(int, const struct msghdr *, int) paramsnonnull();
+ssize_t sendmsg(int, const struct msghdr *, int);
 ssize_t readv(int, const struct iovec *, int);
 ssize_t writev(int, const struct iovec *, int);
 ssize_t sendfile(int, int, int64_t *, size_t);
-int getsockopt(int, int, int, void *, uint32_t *) paramsnonnull((5));
+int getsockopt(int, int, int, void *, uint32_t *);
 int setsockopt(int, int, int, const void *, uint32_t);
-int socketpair(int, int, int, int[2]) paramsnonnull();
-int poll(struct pollfd *, uint64_t, int32_t) paramsnonnull();
+int socketpair(int, int, int, int[2]);
+int poll(struct pollfd *, uint64_t, int32_t);
 int ppoll(struct pollfd *, uint64_t, const struct timespec *,
-          const struct sigset *) paramsnonnull((1, 4));
-ssize_t sendto(int, const void *, size_t, uint32_t, const void *, uint32_t)
-    paramsnonnull((2));
+          const struct sigset *);
+ssize_t sendto(int, const void *, size_t, uint32_t, const void *, uint32_t);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/libc/sock/sockdebug.c b/libc/sock/sockdebug.c
new file mode 100644
index 00000000000..42e5c12c77f
--- /dev/null
+++ b/libc/sock/sockdebug.c
@@ -0,0 +1,114 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/struct/sockaddr6.h"
+#include "libc/errno.h"
+#include "libc/fmt/itoa.h"
+#include "libc/macros.internal.h"
+#include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/af.h"
+#include "libc/sysv/consts/ipproto.h"
+#include "libc/sysv/consts/sock.h"
+
+const char *__describe_socket_family(int family) {
+  static char buf[12];
+  if (family == AF_UNIX) return "AF_UNIX";
+  if (family == AF_INET) return "AF_INET";
+  if (family == AF_INET6) return "AF_INET6";
+  FormatInt32(buf, family);
+  return buf;
+}
+
+const char *__describe_socket_type(int type) {
+  int x;
+  char *p;
+  static char buf[12 + 1 + 12 + 1 + 13 + 1];
+  p = buf;
+  x = type & ~(SOCK_CLOEXEC | SOCK_NONBLOCK);
+  if (x == SOCK_STREAM) {
+    p = stpcpy(p, "SOCK_STREAM");
+  } else if (x == SOCK_DGRAM) {
+    p = stpcpy(p, "SOCK_DGRAM");
+  } else if (x == SOCK_RAW) {
+    p = stpcpy(p, "SOCK_RAW");
+  } else {
+    p = FormatInt32(p, x);
+  }
+  if (type & SOCK_CLOEXEC) p = stpcpy(p, "|SOCK_CLOEXEC");
+  if (type & SOCK_NONBLOCK) p = stpcpy(p, "|SOCK_NONBLOCK");
+  return buf;
+}
+
+const char *__describe_socket_protocol(int family) {
+  static char buf[12];
+  if (family == IPPROTO_IP) return "IPPROTO_IP";
+  if (family == IPPROTO_ICMP) return "IPPROTO_ICMP";
+  if (family == IPPROTO_TCP) return "IPPROTO_TCP";
+  if (family == IPPROTO_UDP) return "IPPROTO_UDP";
+  if (family == IPPROTO_RAW) return "IPPROTO_RAW";
+  if (family == IPPROTO_IPV6) return "IPPROTO_IPv6";
+  FormatInt32(buf, family);
+  return buf;
+}
+
+const char *__describe_sockaddr(const struct sockaddr *sa, size_t sasize) {
+  int e;
+  size_t n;
+  uint16_t port;
+  char *p, ip[72];
+  static char buf[128];
+  e = errno;
+  stpcpy(buf, "NULL");
+  if (sa && sasize >= sizeof(sa->sa_family)) {
+    stpcpy(buf, __describe_socket_family(sa->sa_family));
+    if (sa->sa_family == AF_INET && sasize >= sizeof(struct sockaddr_in)) {
+      const struct sockaddr_in *in;
+      in = (const struct sockaddr_in *)sa;
+      if (inet_ntop(AF_INET, &in->sin_addr, ip, sizeof(ip))) {
+        p = buf;
+        p = stpcpy(p, ip);
+        *p++ = ':';
+        p = FormatUint32(p, in->sin_port);
+      }
+    } else if (sa->sa_family == AF_INET6 &&
+               sasize >= sizeof(struct sockaddr_in6)) {
+      const struct sockaddr_in6 *in6;
+      in6 = (const struct sockaddr_in6 *)sa;
+      if (inet_ntop(AF_INET6, &in6->sin6_addr, ip, sizeof(ip))) {
+        p = buf;
+        *p++ = '[';
+        p = stpcpy(p, ip);
+        *p++ = ']';
+        *p++ = ':';
+        p = FormatUint32(p, in6->sin6_port);
+      }
+    } else if (sa->sa_family == AF_UNIX &&
+               sasize >= sizeof(struct sockaddr_un)) {
+      const struct sockaddr_un *unix;
+      unix = (const struct sockaddr_un *)sa;
+      n = strnlen(unix->sun_path, sizeof(unix->sun_path));
+      n = MIN(n, sizeof(buf) - 1);
+      memcpy(buf, unix->sun_path, n);
+      buf[n] = 0;
+    }
+  }
+  errno = e;
+  return buf;
+}
diff --git a/libc/sock/sockdebug.h b/libc/sock/sockdebug.h
new file mode 100644
index 00000000000..f85b99bff9c
--- /dev/null
+++ b/libc/sock/sockdebug.h
@@ -0,0 +1,14 @@
+#ifndef COSMOPOLITAN_LIBC_SOCK_SOCKDEBUG_H_
+#define COSMOPOLITAN_LIBC_SOCK_SOCKDEBUG_H_
+#include "libc/sock/sock.h"
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+const char *__describe_sockaddr(const struct sockaddr *, size_t);
+const char *__describe_socket_family(int);
+const char *__describe_socket_type(int);
+const char *__describe_socket_protocol(int);
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_SOCK_SOCKDEBUG_H_ */
diff --git a/libc/sock/socket.c b/libc/sock/socket.c
index f668a5f000f..e7b6a4d13b1 100644
--- a/libc/sock/socket.c
+++ b/libc/sock/socket.c
@@ -16,11 +16,12 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
+#include "libc/sock/sockdebug.h"
 #include "libc/sysv/consts/af.h"
-#include "libc/sysv/errfuns.h"
 
 /**
  * Creates new system resource for network communication, e.g.
@@ -38,17 +39,15 @@
  * @asyncsignalsafe
  */
 int socket(int family, int type, int protocol) {
-  if (family == AF_UNSPEC) {
-    family = AF_INET;
-  } else if (family == AF_INET6) {
-    /* Recommend IPv6 on frontend serving infrastructure only. That's
-       what Google Cloud does. It's more secure. It also means poll()
-       will work on Windows, which doesn't allow mixing third layers. */
-    return epfnosupport();
-  }
+  int rc;
+  if (family == AF_UNSPEC) family = AF_INET;
   if (!IsWindows()) {
-    return sys_socket(family, type, protocol);
+    rc = sys_socket(family, type, protocol);
   } else {
-    return sys_socket_nt(family, type, protocol);
+    rc = sys_socket_nt(family, type, protocol);
   }
+  STRACE("socket(%s, %s, %s) -> %d% m", __describe_socket_family(family),
+         __describe_socket_type(type), __describe_socket_protocol(protocol),
+         rc);
+  return rc;
 }
diff --git a/libc/stdio/fopen.c b/libc/stdio/fopen.c
index 722d26480cc..3e78067fc90 100644
--- a/libc/stdio/fopen.c
+++ b/libc/stdio/fopen.c
@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
@@ -59,7 +59,7 @@ FILE *fopen(const char *pathname, const char *mode) {
   FILE *f;
   bool noclose;
   int fd, flags;
-  SYSDEBUG("fopen(%s)", pathname);
+  STRACE("fopen(%s)", pathname);
   flags = fopenflags(mode);
   pathname = fixpathname(pathname, flags);
   if ((fd = openpathname(pathname, flags, &noclose)) != -1) {
diff --git a/libc/str/istext.c b/libc/str/istext.c
index 0a75f602197..460626572c7 100644
--- a/libc/str/istext.c
+++ b/libc/str/istext.c
@@ -21,7 +21,7 @@
 /**
  * Returns true if buffer is most likely plaintext.
  */
-bool IsText(const void *data, size_t size) {
+bool _istext(const void *data, size_t size) {
   const unsigned char *p, *pe;
   for (p = data, pe = p + size; p < pe; ++p) {
     if (*p <= 3) {
diff --git a/libc/str/isutf8.c b/libc/str/isutf8.c
index 983ce72822c..9155c5e4a46 100644
--- a/libc/str/isutf8.c
+++ b/libc/str/isutf8.c
@@ -23,7 +23,7 @@
  *
  * This function will return false if a pure ascii string is passed.
  */
-bool IsUtf8(const void *data, size_t size) {
+bool _isutf8(const void *data, size_t size) {
   const unsigned char *p, *pe;
   for (p = data, pe = p + size; p + 2 <= pe; ++p) {
     if (p[0] >= 0300) {
diff --git a/libc/str/str.h b/libc/str/str.h
index 1f63ad42777..fca378aa857 100644
--- a/libc/str/str.h
+++ b/libc/str/str.h
@@ -203,8 +203,8 @@ char *strtoupper(char *) paramsnonnull();
 char *chomp(char *);
 char16_t *chomp16(char16_t *);
 wchar_t *wchomp(wchar_t *);
-bool IsText(const void *, size_t);
-bool IsUtf8(const void *, size_t);
+bool _istext(const void *, size_t);
+bool _isutf8(const void *, size_t);
 bool _isabspath(const char *) strlenesque;
 bool escapedos(char16_t *, unsigned, const char16_t *, unsigned);
 
diff --git a/libc/runtime/describeos.c b/libc/sysv/describeos.greg.c
similarity index 86%
rename from libc/runtime/describeos.c
rename to libc/sysv/describeos.greg.c
index ded8f318542..1b0f37c6a2c 100644
--- a/libc/runtime/describeos.c
+++ b/libc/sysv/describeos.greg.c
@@ -17,23 +17,21 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/dce.h"
-#include "libc/runtime/runtime.h"
-#include "libc/str/str.h"
 
-char *describeos(char *buf, size_t size) {
-  const char *s;
+const char *__describe_os(void) {
   if (IsLinux()) {
-    s = "gnu/systemd";
+    return "gnu/systemd";
   } else if (IsXnu()) {
-    s = "xnu's not unix";
+    return "xnu's not unix!";
   } else if (IsFreebsd()) {
-    s = "freebesiyatadishmaya";
+    return "free besiyata dishmaya";
+  } else if (IsNetbsd()) {
+    return "net besiyata dishmaya";
   } else if (IsOpenbsd()) {
-    s = "openbsd";
+    return "open besiyata dishmaya";
   } else if (IsWindows()) {
-    s = "the new technology";
+    return "the new technology";
   } else {
-    s = "wut";
+    return "wut";
   }
-  return memccpy(buf, s, '\0', size);
 }
diff --git a/libc/sysv/strace.greg.c b/libc/sysv/strace.greg.c
new file mode 100644
index 00000000000..cd75bfa5fc0
--- /dev/null
+++ b/libc/sysv/strace.greg.c
@@ -0,0 +1,21 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
+
+int __strace;
diff --git a/libc/sysv/systemfive.S b/libc/sysv/systemfive.S
index f2b5f9bcabb..8a899572018 100644
--- a/libc/sysv/systemfive.S
+++ b/libc/sysv/systemfive.S
@@ -16,13 +16,14 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
-#include "libc/sysv/consts/prot.h"
-#include "libc/sysv/consts/nr.h"
-#include "libc/sysv/consts/map.h"
 #include "libc/macros.internal.h"
-#include "libc/sysv/consts/prot.h"
 #include "libc/nexgen32e/macros.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/nr.h"
+#include "libc/sysv/consts/prot.h"
+#include "libc/sysv/consts/prot.h"
 
 /*                                           ▄▄▄
                        ▄▄▄                    ▀▓▓▒▄
@@ -306,8 +307,29 @@ _init_systemfive_magnums:
 	jnz	3b
 	xchg	%rbx,%rax
 	stosq
+#ifdef SYSDEBUG
+	inc	%r8d
+#endif
 	jmp	2b
-5:	pop	%rdi
+5:	nop
+#ifdef SYSDEBUG
+	push	%rdi
+	push	%rsi
+	push	%r8
+	call	__describe_os
+	mov	%rax,%rdx
+	pop	%r8
+	.weak	__stracef
+	ezlea	__stracef,ax
+	test	%rax,%rax
+	jz	5f
+	ezlea	.Llog,di
+	mov	%r8d,%esi
+	call	*%rax
+5:	pop	%rsi
+	pop	%rdi
+#endif /* DEBUGSYS */
+	pop	%rdi
 	pop	%rsi
 	pop	%rbx
 //	𝑠𝑙𝑖𝑑𝑒
@@ -325,8 +347,12 @@ _init_systemfive_pid:
 	.endfn	_init_systemfive_pid
 #endif
 #if SupportsSystemv() && !defined(TINY)
-_init_systemfive_stack:					# determinism ftw!
-#if SupportsWindows() || SupportsMetal()
+
+//	Create a stack with deterministic readable addresses.
+//	If ape_execve() already created us a stack that meets
+//	the requirements of STATIC_STACK_SIZE() then we skip.
+_init_systemfive_stack:
+#if SupportsWindows() || SupportsMetal() || SupportsOpenbsd()
 	testb	$WINDOWS|METAL,__hostos(%rip)
 	jnz	_init_systemfive_done
 #endif
@@ -512,6 +538,14 @@ syscon_windows:/*
 	.globl	syscon_windows
 #endif
 
+#ifdef SYSDEBUG
+	.rodata.str1.1
+.Llog:	.ascii	STRACE_PROLOGUE
+	.ascii	"bell system five system call support"
+	.asciz	" %'u magnums loaded on %s%n"
+	.previous
+#endif /* DEBUGSYS */
+
 	.weak	ape_stack_vaddr
 	.weak	ape_stack_memsz
 	.weak	ape_stack_align
diff --git a/libc/sysv/sysv.mk b/libc/sysv/sysv.mk
index 1b01db90e7f..42d389fc766 100644
--- a/libc/sysv/sysv.mk
+++ b/libc/sysv/sysv.mk
@@ -22,6 +22,7 @@ LIBC_SYSV_ARTIFACTS += LIBC_SYSV_A
 LIBC_SYSV_A = o/$(MODE)/libc/sysv/sysv.a
 LIBC_SYSV_A_HDRS = $(filter %.h,$(LIBC_SYSV_A_FILES))
 LIBC_SYSV_A_INCS = $(filter %.inc,$(LIBC_SYSV_A_FILES))
+LIBC_SYSV_A_SRCS_C = $(filter %.c,$(LIBC_SYSV_A_FILES))
 LIBC_SYSV_A_SRCS_A = $(filter %.s,$(LIBC_SYSV_A_FILES))
 LIBC_SYSV_A_SRCS_S = $(filter %.S,$(LIBC_SYSV_A_FILES))
 LIBC_SYSV_A_CHECKS = $(LIBC_SYSV_A).pkg
@@ -36,15 +37,19 @@ LIBC_SYSV_A_FILES :=					\
 	libc/sysv/restorert.S				\
 	libc/sysv/syscall.S				\
 	libc/sysv/systemfive.S				\
+	libc/sysv/strace.greg.c				\
+	libc/sysv/describeos.greg.c			\
 	$(wildcard libc/sysv/consts/*)			\
 	$(wildcard libc/sysv/errfuns/*)
 
 LIBC_SYSV_A_SRCS =					\
 	$(LIBC_SYSV_A_SRCS_A)				\
+	$(LIBC_SYSV_A_SRCS_C)				\
 	$(LIBC_SYSV_A_SRCS_S)
 
 LIBC_SYSV_A_OBJS =					\
 	$(LIBC_SYSV_A_SRCS_A:%.s=o/$(MODE)/%.o)		\
+	$(LIBC_SYSV_A_SRCS_C:%.c=o/$(MODE)/%.o)		\
 	$(LIBC_SYSV_A_SRCS_S:%.S=o/$(MODE)/%.o)
 
 LIBC_SYSV_A_DEPS :=					\
diff --git a/libc/unicode/unicode-properties.txt b/libc/unicode/unicode-properties.txt
index bbd3eaea283..f208c7cfb9f 100644
--- a/libc/unicode/unicode-properties.txt
+++ b/libc/unicode/unicode-properties.txt
@@ -28,3 +28,10 @@ Cf = Other, format
 Cs = Other, surrogate
 Co = Other, private use
 Cn = Other, not assigned (including noncharacters)
+
+W  Wide      Naturally wide character, e.g. Hiragana.
+Na Narrow    Naturally narrow character, e.g. ISO Basic Latin alphabet.
+F  Fullwidth Wide variant with compatibility normalisation to naturally narrow character, e.g. fullwidth Latin script.
+H  Halfwidth Narrow variant with compatibility normalisation to naturally wide character, e.g. half-width kana. Includes U+20A9 (₩) as an exception.
+A  Ambiguous Characters included in East Asian DBCS codes but also in European SBCS codes, e.g. Greek alphabet. Duospaced behaviour can consequently vary.
+N  Neutral   Characters which do not appear in East Asian DBCS codes, e.g. Devanagari.
diff --git a/libc/x/x.h b/libc/x/x.h
index 3166a0bb584..a4d2b5ea2ab 100644
--- a/libc/x/x.h
+++ b/libc/x/x.h
@@ -122,6 +122,11 @@ int xvspawn(void (*)(void *), void *, struct rusage *);
 #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
 #define xasprintf(FMT, ...) (xasprintf)(PFLINK(FMT), ##__VA_ARGS__)
 #define xvasprintf(FMT, VA) (xvasprintf)(PFLINK(FMT), VA)
+#define xsigaction(SIG, HANDLER, FLAGS, MASK, OLD) \
+  ({                                               \
+    __SIGACTION_YOINK(SIG);                        \
+    xsigaction(SIG, HANDLER, FLAGS, MASK, OLD);    \
+  })
 #endif
 
 COSMOPOLITAN_C_END_
diff --git a/libc/x/xsigaction.c b/libc/x/xsigaction.c
index de964a8577a..3a64fda0f3e 100644
--- a/libc/x/xsigaction.c
+++ b/libc/x/xsigaction.c
@@ -39,8 +39,8 @@
  * @asyncsignalsafe
  * @vforksafe
  */
-int xsigaction(int sig, void *handler, uint64_t flags, uint64_t mask,
-               struct sigaction *old) {
+int(xsigaction)(int sig, void *handler, uint64_t flags, uint64_t mask,
+                struct sigaction *old) {
   /* This API is superior to sigaction() because (1) it offers feature
      parity; (2) compiler emits 1/3rd as much binary code at call-site;
      and (3) it removes typing that just whines without added saftey. */
diff --git a/libc/zipos/zipos.internal.h b/libc/zipos/zipos.internal.h
index e659160bab5..9d1cb41230f 100644
--- a/libc/zipos/zipos.internal.h
+++ b/libc/zipos/zipos.internal.h
@@ -1,7 +1,7 @@
 #ifndef COSMOPOLITAN_LIBC_ZIPOS_ZIPOS_H_
 #define COSMOPOLITAN_LIBC_ZIPOS_ZIPOS_H_
 #include "libc/calls/calls.h"
-#include "libc/calls/sysdebug.internal.h"
+#include "libc/calls/strace.internal.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
diff --git a/test/libc/sock/inet_ntop_test.c b/test/libc/sock/inet_ntop_test.c
index 261bbcd700c..a98ab7671c4 100644
--- a/test/libc/sock/inet_ntop_test.c
+++ b/test/libc/sock/inet_ntop_test.c
@@ -41,17 +41,17 @@ TEST(inet_ntop, testBadFamily) {
   uint8_t localhost[4] = {127, 0, 0, 1};
   ASSERT_EQ(NULL, inet_ntop(666, localhost, buf, sizeof(buf)));
   EXPECT_EQ(EAFNOSUPPORT, errno);
-  ASSERT_STREQ("", buf);
+  ASSERT_STREQ("hi", buf);
 }
 
 TEST(inet_ntop, testNoSpace) {
   char *buf = memcpy(malloc(16), "hi", 3);
   uint8_t localhost[4] = {127, 0, 0, 1};
-  ASSERT_EQ(NULL, inet_ntop(AF_INET, localhost, buf, 0));
+  EXPECT_EQ(NULL, inet_ntop(AF_INET, localhost, buf, 1));
   EXPECT_EQ(ENOSPC, errno);
   ASSERT_STREQ("hi", buf);
   ASSERT_EQ(NULL, inet_ntop(AF_INET, localhost, buf, 7));
-  ASSERT_STREQ("", buf);
+  ASSERT_STREQ("hi", buf);
   free(buf);
 }
 
diff --git a/third_party/chibicc/test/test.mk b/third_party/chibicc/test/test.mk
index 61824fda495..e42be50b0ae 100644
--- a/third_party/chibicc/test/test.mk
+++ b/third_party/chibicc/test/test.mk
@@ -39,6 +39,7 @@ THIRD_PARTY_CHIBICC_TEST_CHECKS =						\
 	$(THIRD_PARTY_CHIBICC_TEST_HDRS:%=o/$(MODE)/%.ok)
 
 THIRD_PARTY_CHIBICC_TEST_DIRECTDEPS =						\
+	LIBC_CALLS								\
 	LIBC_FMT								\
 	LIBC_INTRIN								\
 	LIBC_MEM								\
diff --git a/tool/build/lib/elfwriter_zip.c b/tool/build/lib/elfwriter_zip.c
index 0f48e002720..3501bb0d199 100644
--- a/tool/build/lib/elfwriter_zip.c
+++ b/tool/build/lib/elfwriter_zip.c
@@ -155,8 +155,8 @@ void elfwriter_zip(struct ElfWriter *elf, const char *symbol, const char *name,
   lfilehdrsize = kZipLfileHdrMinSize + namesize;
   crc = crc32_z(0, data, uncompsize);
   GetDosLocalTime(mtim.tv_sec, &mtime, &mdate);
-  if (IsUtf8(name, namesize)) gflags |= kZipGflagUtf8;
-  if (S_ISREG(mode) && IsText(data, size)) {
+  if (_isutf8(name, namesize)) gflags |= kZipGflagUtf8;
+  if (S_ISREG(mode) && _istext(data, size)) {
     iattrs |= kZipIattrText;
   }
   commentsize = kZipCdirHdrLinkableSize - (CFILE_HDR_SIZE + namesize);
diff --git a/tool/net/redbean.c b/tool/net/redbean.c
index 0eaf4a705d9..8eefef98942 100644
--- a/tool/net/redbean.c
+++ b/tool/net/redbean.c
@@ -3322,8 +3322,8 @@ static void StoreAsset(char *path, size_t pathlen, char *data, size_t datalen,
   INFOF("Storing asset %`'s", path);
 
   disk = gflags = iattrs = 0;
-  if (IsUtf8(path, pathlen)) gflags |= kZipGflagUtf8;
-  if (IsText(data, datalen)) iattrs |= kZipIattrText;
+  if (_isutf8(path, pathlen)) gflags |= kZipGflagUtf8;
+  if (_istext(data, datalen)) iattrs |= kZipIattrText;
   crc = crc32_z(0, data, datalen);
   if (datalen < 100) {
     method = kZipCompressionNone;