[Sanitizers][Darwin] Add READ/WRITE detection on arm64 for darwin.

[thetruestblue]

Summary

On arm64 the read/write flag is set on the esr register. Adding this flag check for arm64 enables a more accurate print out for sanitizer signal reports and matches the behavior on x86.

Fixes bug: https://github.com/llvm/llvm-project/issues/27917

These tests are now passing on for asan, tsan, and ubsan on Darwin arm64 and arm64e:

		Posix/illegal_read_test.cpp
		Posix/illegal_write_test.cpp

rdar://92104440

[thetruestblue]

Found macro name for arm64 esr WNR mask

[yln]

Great, thanks!

llvm issues now live on Github. Here is the imported one from the Bugzilla: https://github.com/llvm/llvm-project/issues/27917
You can make yourself the Assignee, leave a reference to this revision in a comment, and close the issue.

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

#endif
   // The report is added to CrashLog as part of logging all of Printf output.
 #endif
 }
 
 SignalContext::WriteFlag SignalContext::GetWriteFlag() const {
 #if defined(__x86_64__) || defined(__i386__)
   ucontext_t *ucontext = static_cast<ucontext_t*>(context);
   return ucontext->uc_mcontext->__es.__err & 2 /*T_PF_WRITE*/ ? Write : Read;
+#elif defined(__arm64__)
+  ucontext_t *ucontext = static_cast<ucontext_t*>(context);
+  return ucontext->uc_mcontext->__es.__esr & 0x40 /*ESR WnR*/ ? Write : Read;
 #else
   return Unknown;
 #endif
 }
 
 bool SignalContext::IsTrueFaultingAddress() const {
   auto si = static_cast<const siginfo_t *>(siginfo);
   // "Real" SIGSEGV codes (e.g., SEGV_MAPERR, SEGV_MAPERR) are non-zero.