Account for stack redzone when computing sp on darwin

[fjricci]

Summary

thread_get_register_pointer_values handles the redzone computation
automatically, but is marked as an unavailable API function. This
patch replicates its logic accounting for the stack redzone on
x86_64.

Should fix flakiness in the use_stack_threaded test for lsan on darwin.

[kcc]

Whenever possible, prefer if() to #if
In this case, there is a SANITIZER_ macro for this condition.

[fjricci]

Ah, okay, I didn't realize that aarch64 has a redzone as well (thread_get_register_pointer_values is only for x86). Will update.

[fjricci]

Remove ifdef

[fjricci]

Remove accidental inclusion of extra files

[fjricci]

Committed as rL302898

lib/sanitizer_common/sanitizer_stoptheworld_mac.cc

if (err != KERN_SUCCESS) {
     // still safe to proceed.
     return err == KERN_INVALID_ARGUMENT ? REGISTERS_UNAVAILABLE_FATAL
                                         : REGISTERS_UNAVAILABLE;
   }
 
   internal_memcpy(buffer, &regs, sizeof(regs));
   *sp = regs.SP_REG;
 
+  // On x86_64 and aarch64, we must account for the stack redzone, which is 128
+  // bytes.
+  if (SANITIZER_WORDSIZE == 64) *sp -= 128;
+
   return REGISTERS_AVAILABLE;
 }
 
 uptr SuspendedThreadsListMac::RegisterCount() const {
   return MACHINE_THREAD_STATE_COUNT;
 }
 } // namespace __sanitizer
 
 #endif  // SANITIZER_MAC && (defined(__x86_64__) || defined(__aarch64__)) ||
         //                   defined(__i386))