[compiler-rt] r243601 - [sanitizer] add a weak hook for memcmp interceptor, to be used primarily for fuzzing. More hooks will be added later. So far this is a Linux-only feature

[Kostya Serebryany]

Author: kcc
Date: Wed Jul 29 20:19:17 2015
New Revision: 243601

URL: http://llvm.org/viewvc/llvm-project?rev=243601&view=rev
Log:
[sanitizer] add a weak hook for memcmp interceptor, to be used primarily for fuzzing. More hooks will be added later. So far this is a Linux-only feature

Modified:
    compiler-rt/trunk/include/sanitizer/common_interface_defs.h
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h

Modified: compiler-rt/trunk/include/sanitizer/common_interface_defs.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/include/sanitizer/common_interface_defs.h?rev=243601&r1=243600&r2=243601&view=diff
==============================================================================
--- compiler-rt/trunk/include/sanitizer/common_interface_defs.h (original)
+++ compiler-rt/trunk/include/sanitizer/common_interface_defs.h Wed Jul 29 20:19:17 2015
@@ -111,6 +111,15 @@ extern "C" {
   // Sets the callback to be called right before death on error.
   // Passing 0 will unset the callback.
   void __sanitizer_set_death_callback(void (*callback)(void));
+
+  // Interceptor hooks.
+  // Whenever a libc function interceptor is called it checks if the
+  // corresponding weak hook is defined, and it so -- calls it.
+  // The primary use case is data-flow-guided fuzzing, where the fuzzer needs
+  // 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);
 #ifdef __cplusplus
 }  // extern "C"
 #endif

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc?rev=243601&r1=243600&r2=243601&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc Wed Jul 29 20:19:17 2015
@@ -39,6 +39,16 @@
 
 #include <stdarg.h>
 
+#if SANITIZER_INTERCEPTOR_HOOKS
+#define CALL_WEAK_INTERCEPTOR_HOOK4(f, ...)                                    \
+  do {                                                                         \
+    if (f)                                                                     \
+      f(__VA_ARGS__);                                                          \
+  } while (false);
+#else
+#define CALL_WEAK_INTERCEPTOR_HOOK4(f, a1, a2, a3, a4)
+#endif  // SANITIZER_INTERCEPTOR_HOOKS
+
 #if SANITIZER_WINDOWS && !defined(va_copy)
 #define va_copy(dst, src) ((dst) = (src))
 #endif // _WIN32
@@ -363,11 +373,20 @@ INTERCEPTOR(char *, strpbrk, const char
 #endif
 
 #if SANITIZER_INTERCEPT_MEMCMP
+
+extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+void __sanitizer_weak_hook_memcmp(uptr called_pc, const void *s1,
+                                  const void *s2, uptr n);
+}  // extern "C"
+
 INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, memcmp, a1, a2, size);
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return internal_memcmp(a1, a2, size);
+  CALL_WEAK_INTERCEPTOR_HOOK4(__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

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h?rev=243601&r1=243600&r2=243601&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h Wed Jul 29 20:19:17 2015
@@ -254,5 +254,6 @@
 
 #define SANITIZER_INTERCEPT_MLOCKX SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_FOPENCOOKIE SI_LINUX_NOT_ANDROID
+#define SANITIZER_INTERCEPTOR_HOOKS SI_LINUX
 
 #endif  // #ifndef SANITIZER_PLATFORM_INTERCEPTORS_H