GWP-ASan: Report a different TID on macOS

The TID returned by PlatformThread::CurrentId() uses
`pthread_mach_thread_np(pthread_self())` which does not match the one
used by crashpad (and hence reported server-side.) Record a matching
TID instead.

Bug: 934888
Change-Id: I9606827874c6072fc8ba1dc9a1ed6b67e27a0898
Reviewed-on: https://chromium-review.googlesource.com/c/1484351
Auto-Submit: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635667}

components/gwp_asan/client/guarded_page_allocator.cc

@@ -20,9 +20,29 @@
 #include "components/gwp_asan/common/crash_key_name.h"
 #include "components/gwp_asan/common/pack_stack_trace.h"
 
+#if defined(OS_MACOSX)
+#include <pthread.h>
+#endif
+
 namespace gwp_asan {
 namespace internal {
 
+namespace {
+
+// Report a tid that matches what crashpad collects which may differ from what
+// base::PlatformThread::CurrentId() returns.
+uint64_t ReportTid() {
+#if !defined(OS_MACOSX)
+  return base::PlatformThread::CurrentId();
+#else
+  uint64_t tid = base::kInvalidThreadId;
+  pthread_threadid_np(nullptr, &tid);
+  return tid;
+#endif
+}
+
+}  // namespace
+
 // TODO: Delete out-of-line constexpr defininitons once C++17 is in use.
 constexpr size_t GuardedPageAllocator::kGpaAllocAlignment;
 
@@ -182,7 +202,7 @@ void GuardedPageAllocator::RecordAllocationInSlot(size_t slot,
   slots_[slot].alloc.trace_len = Pack(reinterpret_cast<uintptr_t*>(trace), len,
                                       slots_[slot].alloc.packed_trace,
                                       sizeof(slots_[slot].alloc.packed_trace));
-  slots_[slot].alloc.tid = base::PlatformThread::CurrentId();
+  slots_[slot].alloc.tid = ReportTid();
   slots_[slot].alloc.trace_collected = true;
 
   slots_[slot].dealloc.tid = base::kInvalidThreadId;
@@ -199,7 +219,7 @@ void GuardedPageAllocator::RecordDeallocationInSlot(size_t slot) {
       Pack(reinterpret_cast<uintptr_t*>(trace), len,
            slots_[slot].dealloc.packed_trace,
            sizeof(slots_[slot].dealloc.packed_trace));
-  slots_[slot].dealloc.tid = base::PlatformThread::CurrentId();
+  slots_[slot].dealloc.tid = ReportTid();
   slots_[slot].dealloc.trace_collected = true;
 }
 

components/gwp_asan/common/allocator_state.h

@@ -67,7 +67,7 @@ class AllocatorState {
     struct AllocationInfo {
       // (De)allocation thread id or base::kInvalidThreadId if no (de)allocation
       // occurred.
-      base::PlatformThreadId tid = base::kInvalidThreadId;
+      uint64_t tid = base::kInvalidThreadId;
       // Packed stack trace.
       uint8_t packed_trace[kMaxPackedTraceLength];
       // Length used to encode the packed stack trace.