[lsan] Be more conservative in SuspendedThreadsListMac::GetRegistersAndSP

[lgrey]

Summary

Currently, we only return REGISTERS_UNAVAILABLE_FATAL if we receive KERN_INVALID_ARGUMENT from thread_status. In reality, there are other possible return values (MACH_SEND_INVALID_DEST for example) that make it dangerous to read memory. This can be demonstrated by running create_thread_leak.cpp in standalone mode where it will appear to hang due to a EXC_BAD_ACCESS while scanning the stack.

This change reverses the current logic to treat MIG_ARRAY_TOO_LARGE as non-fatal, and all other errors as fatal.

[lgrey]

yln@, looks like kubamracek@ hasn't been active recently, can you take a look? :)

[aeubanks]

makes sense, as long as all the tests pass with this change

[hans]

Looks reasonable to me too.

[hans]

It seems Leonard is out at the moment, so I'll go ahead and commit this on his behalf.

compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_mac.cpp

PtraceRegistersStatus SuspendedThreadsListMac::GetRegistersAndSP(
   thread_t thread = GetThread(index);
   regs_struct regs;
   int err;
   mach_msg_type_number_t reg_count = sizeof(regs) / sizeof(natural_t);
   err = thread_get_state(thread, regs_flavor, (thread_state_t)&regs,
                          &reg_count);
   if (err != KERN_SUCCESS) {
     VReport(1, "Error - unable to get registers for a thread\n");
-    // KERN_INVALID_ARGUMENT indicates that either the flavor is invalid,
-    // or the thread does not exist. The other possible error case,
     // MIG_ARRAY_TOO_LARGE, means that the state is too large, but it's
     // still safe to proceed.
-    return err == KERN_INVALID_ARGUMENT ? REGISTERS_UNAVAILABLE_FATAL
-                                        : REGISTERS_UNAVAILABLE;
+    return err == MIG_ARRAY_TOO_LARGE ? REGISTERS_UNAVAILABLE
+                                      : REGISTERS_UNAVAILABLE_FATAL;
   }
 
   buffer->resize(RoundUpTo(sizeof(regs), sizeof(uptr)) / sizeof(uptr));
   internal_memcpy(buffer->data(), &regs, sizeof(regs));
 #if defined(__aarch64__) && defined(arm_thread_state64_get_sp)
   *sp = arm_thread_state64_get_sp(regs);
 #else
   *sp = regs.SP_REG;