1 files changed, 36 insertions, 3 deletions

diff --git a/libsanitizer/asan/asan_poisoning.h b/libsanitizer/asan/asan_poisoning.h
index da79a0ff2e4..30e39e9077c 100644
--- a/libsanitizer/asan/asan_poisoning.h
+++ b/libsanitizer/asan/asan_poisoning.h
@@ -13,9 +13,14 @@
 #include "asan_interceptors.h"
 #include "asan_internal.h"
 #include "asan_mapping.h"
+#include "sanitizer_common/sanitizer_flags.h"
 
 namespace __asan {
 
+// Enable/disable memory poisoning.
+void SetCanPoisonMemory(bool value);
+bool CanPoisonMemory();
+
 // Poisons the shadow memory for "size" bytes starting from "addr".
 void PoisonShadow(uptr addr, uptr size, u8 value);
 
@@ -31,16 +36,40 @@ void PoisonShadowPartialRightRedzone(uptr addr,
 // performance-critical code with care.
 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
                                     u8 value) {
-  DCHECK(flags()->poison_heap);
+  DCHECK(CanPoisonMemory());
   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
   uptr shadow_end = MEM_TO_SHADOW(
       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
-  REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
+  // FIXME: Page states are different on Windows, so using the same interface
+  // for mapping shadow and zeroing out pages doesn't "just work", so we should
+  // probably provide higher-level interface for these operations.
+  // For now, just memset on Windows.
+  if (value ||
+      SANITIZER_WINDOWS == 1 ||
+      shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
+    REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
+  } else {
+    uptr page_size = GetPageSizeCached();
+    uptr page_beg = RoundUpTo(shadow_beg, page_size);
+    uptr page_end = RoundDownTo(shadow_end, page_size);
+
+    if (page_beg >= page_end) {
+      REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
+    } else {
+      if (page_beg != shadow_beg) {
+        REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
+      }
+      if (page_end != shadow_end) {
+        REAL(memset)((void *)page_end, 0, shadow_end - page_end);
+      }
+      ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
+    }
+  }
 }
 
 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
-  DCHECK(flags()->poison_heap);
+  DCHECK(CanPoisonMemory());
   bool poison_partial = flags()->poison_partial;
   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
   for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
@@ -55,4 +84,8 @@ ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
   }
 }
 
+// Calls __sanitizer::FlushUnneededShadowMemory() on
+// [MemToShadow(p), MemToShadow(p+size)] with proper rounding.
+void FlushUnneededASanShadowMemory(uptr p, uptr size);
+
 }  // namespace __asan