Port to 2.1 - Fix performance regression in Guid.NewGuid on OSX

src/Native/Unix/Common/pal_config.h.in

@@ -28,6 +28,7 @@
 #cmakedefine01 HAVE_TIOCGWINSZ
 #cmakedefine01 HAVE_SCHED_GETAFFINITY
 #cmakedefine01 HAVE_SCHED_SETAFFINITY
+#cmakedefine01 HAVE_ARC4RANDOM
 #cmakedefine01 KEVENT_HAS_VOID_UDATA
 #cmakedefine01 HAVE_FDS_BITS
 #cmakedefine01 HAVE_PRIVATE_FDS_BITS

src/Native/Unix/System.Native/pal_random.cpp

@@ -11,6 +11,7 @@
 #include <time.h>
 #include <errno.h>
 
+#include "pal_config.h"
 /*
 
 Generate random bytes. The generated bytes are not cryptographically strong.
@@ -20,6 +21,9 @@ extern "C" void SystemNative_GetNonCryptographicallySecureRandomBytes(uint8_t* b
 {
     assert(buffer != NULL);
 
+#if HAVE_ARC4RANDOM
+    arc4random_buf(buffer, (size_t)bufferLength);
+#else
     static volatile int rand_des = -1;
     long num = 0;
     static bool sMissingDevURandom;
@@ -93,4 +97,5 @@ extern "C" void SystemNative_GetNonCryptographicallySecureRandomBytes(uint8_t* b
         *(buffer + i) ^= num;
         num >>= 8;
     }
+#endif // HAS_ARC4RANDOM
 }

src/Native/Unix/configure.cmake

@@ -140,6 +140,10 @@ check_function_exists(
     sched_setaffinity
     HAVE_SCHED_SETAFFINITY)
 
+check_function_exists(
+    arc4random
+    HAVE_ARC4RANDOM)
+
 check_symbol_exists(
     TIOCGWINSZ
     "sys/ioctl.h"