[NFC][lsan] Change Mac root regions scan

Author: vitalybuka

compiler-rt/lib/lsan/lsan_common.cpp

@@ -527,8 +527,11 @@ static void ProcessThreads(SuspendedThreadsList const &suspended_threads,
 
 #  endif  // SANITIZER_FUCHSIA
 
-void ScanRootRegion(Frontier *frontier, const Region &root_region,
-                    uptr region_begin, uptr region_end, bool is_readable) {
+bool HasRootRegions() { return !root_regions.empty(); }
+
+static void ScanRootRegion(Frontier *frontier, const Region &root_region,
+                           uptr region_begin, uptr region_end,
+                           bool is_readable) {
   uptr intersection_begin = Max(root_region.begin, region_begin);
   uptr intersection_end = Min(region_end, root_region.end);
   if (intersection_begin >= intersection_end)
@@ -542,6 +545,16 @@ void ScanRootRegion(Frontier *frontier, const Region &root_region,
                          kReachable);
 }
 
+void ScanRootRegions(Frontier *frontier,
+                     const InternalMmapVectorNoCtor<Region> &mapped_regions) {
+  if (!flags()->use_root_regions || mapped_regions.empty())
+    return;
+
+  for (const auto &m : mapped_regions)
+    for (const auto &r : root_regions)
+      ScanRootRegion(frontier, r, m.begin, m.end, true);
+}
+
 static void ProcessRootRegion(Frontier *frontier, const Region &root_region) {
   MemoryMappingLayout proc_maps(/*cache_enabled*/ true);
   MemoryMappedSegment segment;

compiler-rt/lib/lsan/lsan_common.h

@@ -256,9 +256,9 @@ struct CheckForLeaksParam {
   bool success = false;
 };
 
-InternalMmapVectorNoCtor<Region> const *GetRootRegions();
-void ScanRootRegion(Frontier *frontier, const Region &region, uptr region_begin,
-                    uptr region_end, bool is_readable);
+bool HasRootRegions();
+void ScanRootRegions(Frontier *frontier,
+                     const InternalMmapVectorNoCtor<Region> &region);
 // Run stoptheworld while holding any platform-specific locks, as well as the
 // allocator and thread registry locks.
 void LockStuffAndStopTheWorld(StopTheWorldCallback callback,

compiler-rt/lib/lsan/lsan_common_mac.cpp

@@ -165,7 +165,8 @@ void ProcessPlatformSpecificAllocations(Frontier *frontier) {
   vm_address_t address = 0;
   kern_return_t err = KERN_SUCCESS;
 
-  InternalMmapVectorNoCtor<Region> const *root_regions = GetRootRegions();
+  InternalMmapVectorNoCtor<Region> mapped_regions;
+  bool use_root_regions = flags()->use_root_regions && HasRootRegions();
 
   RegionScanState scan_state;
   while (err == KERN_SUCCESS) {
@@ -203,8 +204,7 @@ void ProcessPlatformSpecificAllocations(Frontier *frontier) {
 
     // Recursing over the full memory map is very slow, break out
     // early if we don't need the full iteration.
-    if (scan_state.seen_regions == SeenRegion::All &&
-        !(flags()->use_root_regions && root_regions->size() > 0)) {
+    if (scan_state.seen_regions == SeenRegion::All && !use_root_regions) {
       break;
     }
 
@@ -215,15 +215,12 @@ void ProcessPlatformSpecificAllocations(Frontier *frontier) {
     //
     // TODO(fjricci) - remove this once sanitizer_procmaps_mac has the same
     // behavior as sanitizer_procmaps_linux and traverses all memory regions
-    if (flags()->use_root_regions) {
-      for (uptr i = 0; i < root_regions->size(); i++) {
-        ScanRootRegion(frontier, (*root_regions)[i], address, end_address,
-                       info.protection & kProtectionRead);
-      }
-    }
+    if (use_root_regions && (info.protection & kProtectionRead))
+      mapped_regions.push_back({address, end_address});
 
     address = end_address;
   }
+  ScanRootRegions(frontier, mapped_regions);
 }
 
 // On darwin, we can intercept _exit gracefully, and return a failing exit code