kmod: auto detect whether to apply hack

Makefile

@@ -99,7 +99,7 @@ clean:
 
 out/.options.%:
 	$(mkdir_p)
-	rm out/.options.* || :
+	rm -f out/.options.*
 	touch $@
 
 bpf/vmlinux/system.h:
@@ -121,7 +121,7 @@ out/mimic: $(mimic_obj)
 	$(mkdir_p)
 	$(CC) $(CFLAGS) $(mimic_obj) -o $@ $(LDFLAGS) $(mimic_link_libs)
 
-out/mimic.ko: .FORCE
+out/mimic.ko: .FORCE build-tools
 	$(mkdir_p)
 	$(MAKE) -C kmod
 	cp kmod/mimic.ko $@

kmod/AKMBUILD

@@ -4,5 +4,5 @@ built_modules="$modname.ko"
 
 build() {
   cp -r "$srcdir"/* "$builddir"
-  make $MAKEFLAGS -C "$builddir" KERNEL_UNAME="$kernel_ver" DISTRO_HACK=1
+  make $MAKEFLAGS -C "$builddir" KERNEL_UNAME="$kernel_ver"
 }

kmod/Makefile

@@ -4,7 +4,7 @@ ccflags-y := -D_MIMIC_KMOD
 KERNEL_UNAME ?= $(shell uname -r)
 SYSTEM_BUILD_DIR := /lib/modules/$(KERNEL_UNAME)/build
 
-# Notes on distro hack:
+# Notes on hack:
 #
 # - Debian does not ship vmlinux nor resolve_btfids in
 #   linux-headers like Arch Linux does, so we need to refer to externally
@@ -20,33 +20,49 @@ SYSTEM_BUILD_DIR := /lib/modules/$(KERNEL_UNAME)/build
 # Other distributions lacking components necessary to build kernel module BTF
 # can also use the hack in packaging.
 
-ifdef DISTRO_HACK
+ifneq ($(wildcard $(SYSTEM_BUILD_DIR)/vmlinux),)
+vmlinux_exists := 1
+else
+vmlinux_exists := 0
+endif
+ifneq ($(wildcard $(SYSTEM_BUILD_DIR)/tools/bpf/resolve_btfids/resolve_btfids),)
+resolve_btfids_exists := 1
+else
+resolve_btfids_exists := 0
+endif
 
+ifeq ($(vmlinux_exists)$(resolve_btfids_exists),11)
+build_dir := $(SYSTEM_BUILD_DIR)
+else
+enable_hack := 1
 build_dir := build
 
-VMLINUX_TO_BTF ?= /usr/lib/mimic/vmlinux-to-btf
 RESOLVE_BTFIDS ?= /usr/lib/mimic/resolve_btfids
 
-export EXTRACT_VMLINUX ?= /usr/lib/mimic/extract-vmlinux
-export EXTRACT_BTF ?= /usr/lib/mimic/extract-btf
+path_extension := PATH="$$PATH:/usr/lib/mimic:$(CURDIR)/../out:$(CURDIR)/../tools"
+VMLINUX_TO_BTF ?= $(path_extension) vmlinux-to-btf
+export EXTRACT_VMLINUX ?= $(path_extension) extract-vmlinux
+export EXTRACT_BTF ?= $(path_extension) extract-btf
 export VMLINUX_SUFFIX ?= -$(KERNEL_UNAME)
 
-else
-build_dir := $(SYSTEM_BUILD_DIR)
 endif
 
 all:
-ifdef DISTRO_HACK
-	cp -rL $(SYSTEM_BUILD_DIR) $(build_dir) || true
-	$(VMLINUX_TO_BTF) $(build_dir)
-	if [ ! -f $(build_dir)/tools/bpf/resolve_btfids/resolve_btfids ]; then \
-		install -Dm755 $(RESOLVE_BTFIDS) $(build_dir)/tools/bpf/resolve_btfids/resolve_btfids; \
-	fi
+ifdef enable_hack
+	-cp -rL $(SYSTEM_BUILD_DIR) $(build_dir)
+ifeq ($(vmlinux_exists),0)
+	$(VMLINUX_TO_BTF) >$(build_dir)/vmlinux
 endif
+ifeq ($(resolve_btfids_exists),0)
+ifeq ($(wildcard $(RESOLVE_BTFIDS)),)
+	@echo "ERROR: `resolve_btfids` not found. Please compile it from Linux kernel source and re-run make with RESOLVE_BTFIDS=<path>."
+	@exit 1
+endif
+	install -Dm755 $(RESOLVE_BTFIDS) $(build_dir)/tools/bpf/resolve_btfids/resolve_btfids
+endif  # resolve_btfids_exists
+endif  # enable_hack
 	$(MAKE) -C $(build_dir) M=$(CURDIR) modules
 
 clean:
-ifdef DISTRO_HACK
-	rm -rf $(build_dir)
-endif
+	rm -rf build
 	[ ! -d $(SYSTEM_BUILD_DIR) ] || $(MAKE) -C $(SYSTEM_BUILD_DIR) M=$(CURDIR) clean

kmod/dkms.conf

@@ -1,6 +1,6 @@
 PACKAGE_NAME="mimic"
 PACKAGE_VERSION="0.4.2"
-MAKE[0]="make KERNEL_UNAME=$kernelver DISTRO_HACK=1"
+MAKE[0]="make KERNEL_UNAME=$kernelver"
 CLEAN="make clean"
 BUILT_MODULE_NAME[0]="mimic"
 DEST_MODULE_LOCATION[0]="/kernel/drivers/misc"

tools/vendor-vmlinux-h

@@ -45,7 +45,7 @@ do_vendor() {
   )
 
   BOOT_DIR="out/$debian_arch/boot" VMLINUX_SUFFIX="-${uname_r_ver}-${flavor}" \
-    tools/vmlinux-to-btf "out/$debian_arch" "$endianness"
+    tools/vmlinux-to-btf "$endianness" >"out/$debian_arch/vmlinux"
 
   mkdir -p bpf/vmlinux
   cat >"bpf/vmlinux/$arch.h" <<EOF

tools/vmlinux-to-btf

@@ -5,33 +5,30 @@
 #
 # See kmod/Makefile for usage with automatic kernel building tool e.g. DKMS.
 
-module_dir="$1"
-endianness="$2"
+endianness="$1"
 : "${VMLINUX_SUFFIX:=-$(uname -r)}"
 : "${EXTRACT_VMLINUX:="tools/extract-vmlinux"}"
 : "${EXTRACT_BTF:="out/extract-btf"}"
 : "${BOOT_DIR:="/boot"}"
 
-if [ ! -f "$module_dir/vmlinux" ]; then
-  if [ -f "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX" ]; then
-    "$EXTRACT_VMLINUX" "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX" >"$module_dir/vmlinux"
-    [ $? -eq 0 ] || "$EXTRACT_BTF" "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX" "$endianness" >"$module_dir/vmlinux"
+if [ -f "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX" ]; then
+  "$EXTRACT_VMLINUX" "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX"
+  [ $? -eq 0 ] || "$EXTRACT_BTF" "$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX" "$endianness"
+  if [ $? -ne 0 ]; then
+    >&2 echo "ERROR: cannot extract BTF from '$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX'"
+    exit 1
+  fi
+elif [ -f "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" ]; then
+  if readelf -h "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" >/dev/null 2>&1; then
+    cp "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" "$module_dir/vmlinux"
+  else
+    "$EXTRACT_BTF" "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" "$endianness"
     if [ $? -ne 0 ]; then
-      >&2 echo "ERROR: cannot extract BTF from '$BOOT_DIR/vmlinuz$VMLINUX_SUFFIX'"
+      >&2 echo "ERROR: cannot extract BTF from '$BOOT_DIR/vmlinux$VMLINUX_SUFFIX'"
       exit 1
     fi
-  elif [ -f "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" ]; then
-    if readelf -h "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" >/dev/null 2>/dev/null; then
-      cp "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" "$module_dir/vmlinux"
-    else
-      "$EXTRACT_BTF" "$BOOT_DIR/vmlinux$VMLINUX_SUFFIX" "$endianness" >"$module_dir/vmlinux"
-      if [ $? -ne 0 ]; then
-        >&2 echo "ERROR: cannot extract BTF from '$BOOT_DIR/vmlinux$VMLINUX_SUFFIX'"
-        exit 1
-      fi
-    fi
-  else
-    >&2 echo "ERROR: no boot image found"
-    exit 1
   fi
+else
+  >&2 echo "ERROR: no boot image found"
+  exit 1
 fi