[libFuzzer] extend the weak memcmp/strcmp/strncmp interceptors to receive the result of the computations. With that, don't do any mutations if memcmp/etc returned 0

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@257423 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 25 insertions, 15 deletions

diff --git a/include/sanitizer/common_interface_defs.h b/include/sanitizer/common_interface_defs.h
index b736ed9e5..b2a4bb7b8 100644
--- a/include/sanitizer/common_interface_defs.h
+++ b/include/sanitizer/common_interface_defs.h
@@ -125,9 +125,11 @@ extern "C" {
   // to know what is being passed to libc functions, e.g. memcmp.
   // FIXME: implement more hooks.
   void __sanitizer_weak_hook_memcmp(void *called_pc, const void *s1,
-                                    const void *s2, size_t n);
+                                    const void *s2, size_t n, int result);
   void __sanitizer_weak_hook_strncmp(void *called_pc, const char *s1,
-                                    const char *s2, size_t n);
+                                    const char *s2, size_t n, int result);
+  void __sanitizer_weak_hook_strcmp(void *called_pc, const char *s1,
+                                    const char *s2, int result);
 #ifdef __cplusplus
 }  // extern "C"
 #endif
diff --git a/lib/sanitizer_common/sanitizer_common_interceptors.inc b/lib/sanitizer_common/sanitizer_common_interceptors.inc
index 4639ddc92..2a748cdc6 100644
--- a/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -214,13 +214,11 @@ static inline int CharCmpX(unsigned char c1, unsigned char c2) {
 }
 
 DECLARE_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strcmp, uptr called_pc,
-                              const char *s1, const char *s2)
+                              const char *s1, const char *s2, int result)
 
 INTERCEPTOR(int, strcmp, const char *s1, const char *s2) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, strcmp, s1, s2);
-  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strcmp, GET_CALLER_PC(), s1,
-                             s2);
   unsigned char c1, c2;
   uptr i;
   for (i = 0;; i++) {
@@ -230,19 +228,21 @@ INTERCEPTOR(int, strcmp, const char *s1, const char *s2) {
   }
   COMMON_INTERCEPTOR_READ_STRING(ctx, s1, i + 1);
   COMMON_INTERCEPTOR_READ_STRING(ctx, s2, i + 1);
-  return CharCmpX(c1, c2);
+  int result = CharCmpX(c1, c2);
+  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strcmp, GET_CALLER_PC(), s1,
+                             s2, result);
+  return result;
 }
 
 DECLARE_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strncmp, uptr called_pc,
-                              const char *s1, const char *s2, uptr n)
+                              const char *s1, const char *s2, uptr n,
+                              int result)
 
 INTERCEPTOR(int, strncmp, const char *s1, const char *s2, uptr size) {
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return internal_strncmp(s1, s2, size);
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, strncmp, s1, s2, size);
-  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strncmp, GET_CALLER_PC(), s1,
-                             s2, size);
   unsigned char c1 = 0, c2 = 0;
   uptr i;
   for (i = 0; i < size; i++) {
@@ -252,7 +252,10 @@ INTERCEPTOR(int, strncmp, const char *s1, const char *s2, uptr size) {
   }
   COMMON_INTERCEPTOR_READ_RANGE(ctx, s1, Min(i + 1, size));
   COMMON_INTERCEPTOR_READ_RANGE(ctx, s2, Min(i + 1, size));
-  return CharCmpX(c1, c2);
+  int result = CharCmpX(c1, c2);
+  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_strncmp, GET_CALLER_PC(), s1,
+                             s2, size, result);
+  return result;
 }
 
 #define INIT_STRCMP COMMON_INTERCEPT_FUNCTION(strcmp)
@@ -400,15 +403,14 @@ INTERCEPTOR(char *, strpbrk, const char *s1, const char *s2) {
 #if SANITIZER_INTERCEPT_MEMCMP
 
 DECLARE_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, uptr called_pc,
-                              const void *s1, const void *s2, uptr n)
+                              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);
-  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, GET_CALLER_PC(), a1,
-                             a2, size);
   if (common_flags()->intercept_memcmp) {
     if (common_flags()->strict_memcmp) {
       // Check the entire regions even if the first bytes of the buffers are
@@ -428,10 +430,16 @@ INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
       }
       COMMON_INTERCEPTOR_READ_RANGE(ctx, s1, Min(i + 1, size));
       COMMON_INTERCEPTOR_READ_RANGE(ctx, s2, Min(i + 1, size));
-      return CharCmpX(c1, c2);
+      int r = CharCmpX(c1, c2);
+      CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, GET_CALLER_PC(),
+                                 a1, a2, size, r);
+      return r;
     }
   }
-  return REAL(memcmp(a1, a2, size));
+  int result = REAL(memcmp(a1, a2, size));
+  CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, GET_CALLER_PC(), a1,
+                             a2, size, result);
+  return result;
 }
 
 #define INIT_MEMCMP COMMON_INTERCEPT_FUNCTION(memcmp)