Implement global pointer scanning for darwin leak sanitizer

[fjricci]

Thanks for all the reviews - there are roughly 15 patches left to go in my implementation, and then things should quiet down greatly.

[fjricci]

Refactor to eliminate duplicated code between darwin and linux

Didn't originally think to do this.

[kubamracek]

lib/lsan/lsan_common_mac.cc

103–104

Is this clang-format'd?

[fjricci]

lib/lsan/lsan_common_mac.cc

103–104

I'm not sure - I'll re-run before I merge.

lib/lsan/lsan_common_mac.cc

 AllocatorCache *GetAllocatorCache() { return &get_tls_val(true)->cache; }
 
 // Required on Linux for initialization of TLS behavior, but should not be
 // required on Darwin.
 void InitializePlatformSpecificModules() {}
 
 // Scans global variables for heap pointers.
 void ProcessGlobalRegions(Frontier *frontier) {
-  CHECK(0 && "unimplemented");
+  MemoryMappingLayout memory_mapping(false);
+  InternalMmapVector<LoadedModule> modules(/*initial_capacity*/ 128);
+  memory_mapping.DumpListOfModules(&modules);
+  for (uptr i = 0; i < modules.size(); ++i) {
+    // Even when global scanning is disabled, we still need to scan
+    // system libraries for stashed pointers
+    if (!flags()->use_globals && modules[i].instrumented())
+      continue;
+
+    for (const __sanitizer::LoadedModule::AddressRange &range
+         : modules[i].ranges()) {
+      if (range.executable)
+        continue;
+
+      uptr allocator_begin = 0, allocator_end = 0;
+      GetAllocatorGlobalRange(&allocator_begin, &allocator_end);
+      if (range.beg <= allocator_begin && allocator_begin < range.end) {
+        CHECK_LE(allocator_begin, allocator_end);
+        CHECK_LE(allocator_end, range.end);
+        if (range.beg < allocator_begin)
+          ScanRangeForPointers(range.beg, allocator_begin, frontier, "GLOBAL",
+                               kReachable);
+        if (allocator_end < range.end)
+          ScanRangeForPointers(allocator_end, range.end, frontier, "GLOBAL",
+                               kReachable);
+      } else {
+        ScanRangeForPointers(range.beg, range.end, frontier, "GLOBAL",
+                             kReachable);
+      }
+    }
+  }
 }
 
 void ProcessPlatformSpecificAllocations(Frontier *frontier) {
   CHECK(0 && "unimplemented");
 }
 
 void DoStopTheWorld(StopTheWorldCallback callback, void *argument) {
   CHECK(0 && "unimplemented");
 }
 
 } // namespace __lsan
 
 #endif // CAN_SANITIZE_LEAKS && SANITIZER_MAC