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[win/asan] Don't intercept memset etc. in ntdll #120397

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Merged
merged 2 commits into from
Dec 20, 2024
Merged

[win/asan] Don't intercept memset etc. in ntdll #120397

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91b49f1
[win/asan] Don't intercept memset etc. in ntdll
zmodem Dec 17, 2024
8959e64
use an internal strcmp
zmodem Dec 19, 2024
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32 changes: 28 additions & 4 deletions compiler-rt/lib/interception/interception_win.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,18 @@ static char* _strchr(char* str, char c) {
return nullptr;
}

static int _strcmp(const char *s1, const char *s2) {
while (true) {
unsigned c1 = *s1;
unsigned c2 = *s2;
if (c1 != c2) return (c1 < c2) ? -1 : 1;
if (c1 == 0) break;
s1++;
s2++;
}
return 0;
}

static void _memset(void *p, int value, size_t sz) {
for (size_t i = 0; i < sz; ++i)
((char*)p)[i] = (char)value;
Expand Down Expand Up @@ -1177,8 +1189,7 @@ static void **InterestingDLLsAvailable() {
"libc++.dll", // libc++
"libunwind.dll", // libunwind
# endif
// NTDLL should go last as it exports some functions that we should
// override in the CRT [presumably only used internally].
// NTDLL must go last as it gets special treatment in OverrideFunction.
"ntdll.dll",
NULL
};
Expand Down Expand Up @@ -1235,7 +1246,7 @@ uptr InternalGetProcAddress(void *module, const char *func_name) {

for (DWORD i = 0; i < exports->NumberOfNames; i++) {
RVAPtr<char> name(module, names[i]);
if (!strcmp(func_name, name)) {
if (!_strcmp(func_name, name)) {
DWORD index = ordinals[i];
RVAPtr<char> func(module, functions[index]);

Expand Down Expand Up @@ -1281,9 +1292,22 @@ uptr InternalGetProcAddress(void *module, const char *func_name) {

bool OverrideFunction(
const char *func_name, uptr new_func, uptr *orig_old_func) {
static const char *kNtDllIgnore[] = {
"memcmp", "memcpy", "memmove", "memset"
};

bool hooked = false;
void **DLLs = InterestingDLLsAvailable();
for (size_t i = 0; DLLs[i]; ++i) {
if (DLLs[i + 1] == nullptr) {
// This is the last DLL, i.e. NTDLL. It exports some functions that
// we only want to override in the CRT.
for (const char *ignored : kNtDllIgnore) {
if (_strcmp(func_name, ignored) == 0)
return hooked;
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Nit, let's just break or continue so the reader doesn't have to think about what hooked is, we just hit the shared return codepath.

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It's a nested loop, I think returning is the most straight-forward.

}
}

uptr func_addr = InternalGetProcAddress(DLLs[i], func_name);
if (func_addr &&
OverrideFunction(func_addr, new_func, orig_old_func)) {
Expand Down Expand Up @@ -1337,7 +1361,7 @@ bool OverrideImportedFunction(const char *module_to_patch,
RVAPtr<IMAGE_IMPORT_BY_NAME> import_by_name(
module, name_table->u1.ForwarderString);
const char *funcname = &import_by_name->Name[0];
if (strcmp(funcname, function_name) == 0)
if (_strcmp(funcname, function_name) == 0)
break;
}
}
Expand Down
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