[asan] when a fake stack is being unmapped also flush the corresponding shadow

llvm-svn: 197040

compiler-rt/lib/asan/asan_allocator2.cc

@@ -42,12 +42,7 @@ struct AsanMapUnmapCallback {
     PoisonShadow(p, size, 0);
     // We are about to unmap a chunk of user memory.
     // Mark the corresponding shadow memory as not needed.
-    // Since asan's mapping is compacting, the shadow chunk may be
-    // not page-aligned, so we only flush the page-aligned portion.
-    uptr page_size = GetPageSizeCached();
-    uptr shadow_beg = RoundUpTo(MemToShadow(p), page_size);
-    uptr shadow_end = RoundDownTo(MemToShadow(p + size), page_size);
-    FlushUnneededShadowMemory(shadow_beg, shadow_end - shadow_beg);
+    FlushUnneededASanShadowMemory(p, size);
     // Statistics.
     AsanStats &thread_stats = GetCurrentThreadStats();
     thread_stats.munmaps++;

compiler-rt/lib/asan/asan_fake_stack.cc

@@ -61,7 +61,9 @@ void FakeStack::Destroy(int tid) {
                  NumberOfFrames(stack_size_log(), class_id));
     Report("T%d: FakeStack destroyed: %s\n", tid, str.data());
   }
-  UnmapOrDie(this, RequiredSize(stack_size_log_));
+  uptr size = RequiredSize(stack_size_log_);
+  FlushUnneededASanShadowMemory(reinterpret_cast<uptr>(this), size);
+  UnmapOrDie(this, size);
 }
 
 void FakeStack::PoisonAll(u8 magic) {

compiler-rt/lib/asan/asan_poisoning.cc

@@ -50,6 +50,15 @@ struct ShadowSegmentEndpoint {
   }
 };
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+    // Since asan's mapping is compacting, the shadow chunk may be
+    // not page-aligned, so we only flush the page-aligned portion.
+    uptr page_size = GetPageSizeCached();
+    uptr shadow_beg = RoundUpTo(MemToShadow(p), page_size);
+    uptr shadow_end = RoundDownTo(MemToShadow(p + size), page_size);
+    FlushUnneededShadowMemory(shadow_beg, shadow_end - shadow_beg);
+}
+
 }  // namespace __asan
 
 // ---------------------- Interface ---------------- {{{1

compiler-rt/lib/asan/asan_poisoning.h

@@ -57,4 +57,8 @@ ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
   }
 }
 
+// Calls __sanitizer::FlushUnneededShadowMemory() on
+// [MemToShadow(p), MemToShadow(p+size)] with proper rounding.
+void FlushUnneededASanShadowMemory(uptr p, uptr size);
+
 }  // namespace __asan