[llvm-commits] [ASan] Replace CRT .dll malloc with our implementation at asan_init() time (issue 5708059)

[timurrrr at google.com]

Reviewers: glider,

Message:
Hi Alexander,

Can you please review this small CL?

Thanks,
Timur

Description:
Replace CRT .dll malloc with our implementation

Please review this at http://codereview.appspot.com/5708059/

Affected files:
   M lib/asan/asan_malloc_win.cc


Index: lib/asan/asan_malloc_win.cc
diff --git a/lib/asan/asan_malloc_win.cc b/lib/asan/asan_malloc_win.cc
index  
40429f481e284221972754996284040f8ce9f7a3..42c54dc5d1818aeea6bddccf22df324a9a560a44  
100644
--- a/lib/asan/asan_malloc_win.cc
+++ b/lib/asan/asan_malloc_win.cc
@@ -18,12 +18,7 @@
  #include "asan_internal.h"
  #include "asan_stack.h"

-namespace __asan {
-void ReplaceSystemMalloc() {
-  // FIXME: investigate whether any action is needed.
-  // Currenlty, we fail to intercept malloc() called from intercepted  
_strdup().
-}
-}  // namespace __asan
+#include "interception/interception.h"

  // ---------------------- Replacement functions ---------------- {{{1
  using namespace __asan;  // NOLINT
@@ -55,4 +50,37 @@ void *realloc(void *ptr, size_t size) {
  }
  }  // extern "C"

+using __interception::GetRealFunctionAddress;
+
+// We don't want to include "windows.h" in this file to avoid extra  
attributes
+// set on malloc/free etc (e.g. dllimport), so declare a few things  
manually:
+extern "C" int __stdcall VirtualProtect(void* addr, size_t size,
+                                        DWORD prot, DWORD *old_prot);
+const int PAGE_EXECUTE_READWRITE = 0x40;
+
+namespace __asan {
+void ReplaceSystemMalloc() {
+#ifdef _WIN64
+# error ReplaceSystemMalloc was not tested on x64
+#endif
+  char *crt_malloc;
+  if (GetRealFunctionAddress("malloc", (void**)&crt_malloc)) {
+    // Replace malloc in the CRT dll with a jump to our malloc.
+    DWORD old_prot, unused;
+    CHECK(VirtualProtect(crt_malloc, 16, PAGE_EXECUTE_READWRITE,  
&old_prot));
+    REAL(memset)(crt_malloc, 0xCC /* int 3 */, 16);  // just in case.
+
+    uintptr_t jmp_offset = (uintptr_t)malloc - (uintptr_t)crt_malloc - 5;
+    crt_malloc[0] = 0xE9;  // jmp, should be followed by an offset.
+    REAL(memcpy)(crt_malloc + 1, &jmp_offset, sizeof(jmp_offset));
+
+    CHECK(VirtualProtect(crt_malloc, 16, old_prot, &unused));
+
+    // FYI: FlushInstructionCache is needed on Itanium etc but not on  
x86/x64.
+  }
+
+  // FIXME: investigate whether anything else is needed.
+}
+}  // namespace __asan
+
  #endif  // _WIN32