[PATCH] D22258: [compiler-rt] Enhance funcion padding detection for function interception
Etienne Bergeron via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 11 22:37:32 PDT 2016
etienneb created this revision.
etienneb added a reviewer: rnk.
etienneb added subscribers: chrisha, wang0109, llvm-commits.
Many CRT (64-bits) functions contains a "hint-nop". The current padding
detection is not able to recognize the 10-bytes padding and the HotPatch
hooking technique cannot be used.
Other patterns may be discover and may be added later.
http://reviews.llvm.org/D22258
Files:
lib/interception/interception_win.cc
Index: lib/interception/interception_win.cc
===================================================================
--- lib/interception/interception_win.cc
+++ lib/interception/interception_win.cc
@@ -202,6 +202,29 @@
return true;
}
+static const u8 kHintNop10Bytes[] = {
+ 0x66, 0x66, 0x0F, 0x1F, 0x84,
+ 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+template<class T>
+NOINLINE static bool FunctionHasPrefix(uptr address, const T &pattern) {
+ u8* function = (u8*)address - sizeof(pattern);
+ for (size_t i = 0; i < sizeof(pattern); ++i)
+ if (function[i] != pattern[i])
+ return false;
+ return true;
+}
+
+NOINLINE static bool FunctionHasPadding(uptr address, uptr size) {
+ if (IsMemoryPadding(address - size, size))
+ return true;
+ if (size <= sizeof(kHintNop10Bytes) &&
+ FunctionHasPrefix(address, kHintNop10Bytes))
+ return true;
+ return false;
+}
+
static void WritePadding(uptr from, uptr size) {
_memset((void*)from, 0xCC, (size_t)size);
}
@@ -617,7 +640,7 @@
// Validate that the function is hot patchable.
size_t instruction_size = GetInstructionSize(old_func);
if (instruction_size < kShortJumpInstructionLength ||
- !IsMemoryPadding(header, kHotPatchHeaderLen))
+ !FunctionHasPadding(old_func, kHotPatchHeaderLen))
return false;
if (orig_old_func) {
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