[compiler-rt] r222572 - [ASan] Get fake stack code working with GCC 4.8.2.

[Jay Foad]

Author: foad
Date: Fri Nov 21 15:25:09 2014
New Revision: 222572

URL: http://llvm.org/viewvc/llvm-project?rev=222572&view=rev
Log:
[ASan] Get fake stack code working with GCC 4.8.2.

Summary:
TestCases/Linux/heavy_uar_test.cc was failing on my
PowerPC64 box with GCC 4.8.2, because the compiler recognised
a memset-like loop and turned it into a call to memset, which
got intercepted by __asan_memset, which got upset because it was
being called on an address in high shadow memory.

Use break_optimization to stop the compiler from doing this.

Reviewers: kcc, samsonov

Reviewed By: kcc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6266

Modified:
    compiler-rt/trunk/lib/asan/asan_fake_stack.cc
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_libc.cc

Modified: compiler-rt/trunk/lib/asan/asan_fake_stack.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_fake_stack.cc?rev=222572&r1=222571&r2=222572&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_fake_stack.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_fake_stack.cc Fri Nov 21 15:25:09 2014
@@ -27,8 +27,10 @@ ALWAYS_INLINE void SetShadow(uptr ptr, u
   CHECK_EQ(SHADOW_SCALE, 3);  // This code expects SHADOW_SCALE=3.
   u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
   if (class_id <= 6) {
-    for (uptr i = 0; i < (1U << class_id); i++)
+    for (uptr i = 0; i < (1U << class_id); i++) {
       shadow[i] = magic;
+      SanitizerBreakOptimization(0);  // Make sure this does not become memset.
+    }
   } else {
     // The size class is too big, it's cheaper to poison only size bytes.
     PoisonShadow(ptr, size, static_cast<u8>(magic));

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h?rev=222572&r1=222571&r2=222572&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h Fri Nov 21 15:25:09 2014
@@ -535,6 +535,20 @@ INLINE void AndroidLogWrite(const char *
 INLINE void GetExtraActivationFlags(char *buf, uptr size) { *buf = '\0'; }
 INLINE void SanitizerInitializeUnwinder() {}
 #endif
+
+// Make the compiler think that something is going on there.
+// Use this inside a loop that looks like memset/memcpy/etc to prevent the
+// compiler from recognising it and turning it into an actual call to
+// memset/memcpy/etc.
+static inline void SanitizerBreakOptimization(void *arg) {
+#if _MSC_VER
+  // FIXME: make sure this is actually enough.
+  __asm;
+#else
+  __asm__ __volatile__("" : : "r" (arg) : "memory");
+#endif
+}
+
 }  // namespace __sanitizer
 
 inline void *operator new(__sanitizer::operator_new_size_type size,

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_libc.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_libc.cc?rev=222572&r1=222571&r2=222572&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_libc.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_libc.cc Fri Nov 21 15:25:09 2014
@@ -16,16 +16,6 @@
 
 namespace __sanitizer {
 
-// Make the compiler think that something is going on there.
-static inline void break_optimization(void *arg) {
-#if _MSC_VER
-  // FIXME: make sure this is actually enough.
-  __asm;
-#else
-  __asm__ __volatile__("" : : "r" (arg) : "memory");
-#endif
-}
-
 s64 internal_atoll(const char *nptr) {
   return internal_simple_strtoll(nptr, (char**)0, 10);
 }
@@ -78,7 +68,7 @@ void internal_bzero_aligned16(void *s, u
   CHECK_EQ((reinterpret_cast<uptr>(s) | n) & 15, 0);
   for (S16 *p = reinterpret_cast<S16*>(s), *end = p + n / 16; p < end; p++) {
     p->a = p->b = 0;
-    break_optimization(0);  // Make sure this does not become memset.
+    SanitizerBreakOptimization(0);  // Make sure this does not become memset.
   }
 }