[compiler-rt] Intercept the bcmp() function.

Summary:
I have not introduced a separate hook for `bcmp()` as I don't think there
should be any reason for a sanitizer to treat it differently from `memcmp()`.

This is only enabled when building on POSIX with GNU extensions.

Context: this is to avoid losing coverage when emitting `bcmp() == 0` instead
of `memcmp() == 0` in llvm, see https://reviews.llvm.org/D56593.

Reviewers: mgorny, krytarowski, vitalybuka, dvyukov

Subscribers: kubamracek, dberris, delcypher, jdoerfert, #sanitizers, llvm-commits, jyknight

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D58379

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@354851 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 31 insertions, 7 deletions

diff --git a/lib/sanitizer_common/sanitizer_common_interceptors.inc b/lib/sanitizer_common/sanitizer_common_interceptors.inc
index 8c5c2114e..6e0538d5c 100644
--- a/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -819,16 +819,14 @@ INTERCEPTOR(void *, memcpy, void *dst, const void *src, uptr size) {
 #endif
 
 #if SANITIZER_INTERCEPT_MEMCMP
-
 DECLARE_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, uptr called_pc,
                               const void *s1, const void *s2, uptr n,
                               int result)
 
-INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
-  if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
-    return internal_memcmp(a1, a2, size);
-  void *ctx;
-  COMMON_INTERCEPTOR_ENTER(ctx, memcmp, a1, a2, size);
+// Common code for `memcmp` and `bcmp`.
+int MemcmpInterceptorCommon(void *ctx,
+                            int (*real_fn)(const void *, const void *, uptr),
+                            const void *a1, const void *a2, uptr size) {
   if (common_flags()->intercept_memcmp) {
     if (common_flags()->strict_memcmp) {
       // Check the entire regions even if the first bytes of the buffers are
@@ -854,17 +852,39 @@ INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
       return r;
     }
   }
-  int result = REAL(memcmp(a1, a2, size));
+  int result = real_fn(a1, a2, size);
   CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, GET_CALLER_PC(), a1,
                              a2, size, result);
   return result;
 }
 
+INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
+  if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
+    return internal_memcmp(a1, a2, size);
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, memcmp, a1, a2, size);
+  return MemcmpInterceptorCommon(ctx, REAL(memcmp), a1, a2, size);
+}
+
 #define INIT_MEMCMP COMMON_INTERCEPT_FUNCTION(memcmp)
 #else
 #define INIT_MEMCMP
 #endif
 
+#if SANITIZER_INTERCEPT_BCMP
+INTERCEPTOR(int, bcmp, const void *a1, const void *a2, uptr size) {
+  if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
+    return internal_memcmp(a1, a2, size);
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, bcmp, a1, a2, size);
+  return MemcmpInterceptorCommon(ctx, REAL(bcmp), a1, a2, size);
+}
+
+#define INIT_BCMP COMMON_INTERCEPT_FUNCTION(bcmp)
+#else
+#define INIT_BCMP
+#endif
+
 #if SANITIZER_INTERCEPT_MEMCHR
 INTERCEPTOR(void*, memchr, const void *s, int c, SIZE_T n) {
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
@@ -9473,6 +9493,7 @@ static void InitializeCommonInterceptors() {
   INIT_MEMCPY;
   INIT_MEMCHR;
   INIT_MEMCMP;
+  INIT_BCMP;
   INIT_MEMRCHR;
   INIT_MEMMEM;
   INIT_READ;
diff --git a/lib/sanitizer_common/sanitizer_platform_interceptors.h b/lib/sanitizer_common/sanitizer_platform_interceptors.h
index c9ed53d6b..b49eb555a 100644
--- a/lib/sanitizer_common/sanitizer_platform_interceptors.h
+++ b/lib/sanitizer_common/sanitizer_platform_interceptors.h
@@ -142,6 +142,9 @@
 #define SANITIZER_INTERCEPT_MEMMOVE 1
 #define SANITIZER_INTERCEPT_MEMCPY 1
 #define SANITIZER_INTERCEPT_MEMCMP SI_NOT_FUCHSIA
+#define SANITIZER_INTERCEPT_BCMP \
+  SANITIZER_INTERCEPT_MEMCMP &&  \
+      ((SI_POSIX && _GNU_SOURCE) || SI_NETBSD || SI_OPENBSD || SI_FREEBSD)
 #define SANITIZER_INTERCEPT_STRNDUP SI_POSIX
 #define SANITIZER_INTERCEPT___STRNDUP SI_LINUX_NOT_FREEBSD
 #if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && \