--- /dev/null
+//===-- FuzzerInterceptors.cpp --------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Intercept certain libc functions to aid fuzzing.
+// Linked only when other RTs that define their own interceptors are not linked.
+//===----------------------------------------------------------------------===//
+
+#include "FuzzerPlatform.h"
+
+#if LIBFUZZER_LINUX
+
+#define GET_CALLER_PC() __builtin_return_address(0)
+
+#define PTR_TO_REAL(x) real_##x
+#define REAL(x) __interception::PTR_TO_REAL(x)
+#define FUNC_TYPE(x) x##_type
+#define DEFINE_REAL(ret_type, func, ...) \
+ typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
+ namespace __interception { \
+ FUNC_TYPE(func) PTR_TO_REAL(func); \
+ }
+
+#include <cassert>
+#include <cstdint>
+#include <dlfcn.h> // for dlsym()
+#include <sanitizer/common_interface_defs.h>
+
+static void *getFuncAddr(const char *name, uintptr_t wrapper_addr) {
+ void *addr = dlsym(RTLD_NEXT, name);
+ if (!addr) {
+ // If the lookup using RTLD_NEXT failed, the sanitizer runtime library is
+ // later in the library search order than the DSO that we are trying to
+ // intercept, which means that we cannot intercept this function. We still
+ // want the address of the real definition, though, so look it up using
+ // RTLD_DEFAULT.
+ addr = dlsym(RTLD_DEFAULT, name);
+
+ // In case `name' is not loaded, dlsym ends up finding the actual wrapper.
+ // We don't want to intercept the wrapper and have it point to itself.
+ if (reinterpret_cast<uintptr_t>(addr) == wrapper_addr)
+ addr = nullptr;
+ }
+ return addr;
+}
+
+static int FuzzerInited = 0;
+static bool FuzzerInitIsRunning;
+
+static void fuzzerInit();
+
+static void ensureFuzzerInited() {
+ assert(!FuzzerInitIsRunning);
+ if (!FuzzerInited) {
+ fuzzerInit();
+ }
+}
+
+extern "C" {
+
+DEFINE_REAL(int, memcmp, const void *, const void *, size_t)
+DEFINE_REAL(int, strncmp, const char *, const char *, size_t)
+DEFINE_REAL(int, strcmp, const char *, const char *)
+DEFINE_REAL(int, strncasecmp, const char *, const char *, size_t)
+DEFINE_REAL(int, strcasecmp, const char *, const char *)
+DEFINE_REAL(char *, strstr, const char *, const char *)
+DEFINE_REAL(char *, strcasestr, const char *, const char *)
+DEFINE_REAL(void *, memmem, const void *, size_t, const void *, size_t)
+
+ATTRIBUTE_INTERFACE int memcmp(const void *s1, const void *s2, size_t n) {
+ ensureFuzzerInited();
+ int result = REAL(memcmp)(s1, s2, n);
+ __sanitizer_weak_hook_memcmp(GET_CALLER_PC(), s1, s2, n, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE int strncmp(const char *s1, const char *s2, size_t n) {
+ ensureFuzzerInited();
+ int result = REAL(strncmp)(s1, s2, n);
+ __sanitizer_weak_hook_strncmp(GET_CALLER_PC(), s1, s2, n, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE int strcmp(const char *s1, const char *s2) {
+ ensureFuzzerInited();
+ int result = REAL(strcmp)(s1, s2);
+ __sanitizer_weak_hook_strcmp(GET_CALLER_PC(), s1, s2, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE int strncasecmp(const char *s1, const char *s2, size_t n) {
+ ensureFuzzerInited();
+ int result = REAL(strncasecmp)(s1, s2, n);
+ __sanitizer_weak_hook_strncasecmp(GET_CALLER_PC(), s1, s2, n, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE int strcasecmp(const char *s1, const char *s2) {
+ ensureFuzzerInited();
+ int result = REAL(strcasecmp)(s1, s2);
+ __sanitizer_weak_hook_strcasecmp(GET_CALLER_PC(), s1, s2, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE char *strstr(const char *s1, const char *s2) {
+ ensureFuzzerInited();
+ char *result = REAL(strstr)(s1, s2);
+ __sanitizer_weak_hook_strstr(GET_CALLER_PC(), s1, s2, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE char *strcasestr(const char *s1, const char *s2) {
+ ensureFuzzerInited();
+ char *result = REAL(strcasestr)(s1, s2);
+ __sanitizer_weak_hook_strcasestr(GET_CALLER_PC(), s1, s2, result);
+
+ return result;
+}
+
+ATTRIBUTE_INTERFACE
+void *memmem(const void *s1, size_t len1, const void *s2, size_t len2) {
+ ensureFuzzerInited();
+ void *result = REAL(memmem)(s1, len1, s2, len2);
+ __sanitizer_weak_hook_memmem(GET_CALLER_PC(), s1, len1, s2, len2, result);
+
+ return result;
+}
+
+__attribute__((section(".preinit_array"),
+ used)) static void (*__local_fuzzer_preinit)(void) = fuzzerInit;
+
+} // extern "C"
+
+static void fuzzerInit() {
+ assert(!FuzzerInitIsRunning);
+ if (FuzzerInited)
+ return;
+ FuzzerInitIsRunning = true;
+
+ REAL(memcmp) = reinterpret_cast<memcmp_type>(
+ getFuncAddr("memcmp", reinterpret_cast<uintptr_t>(&memcmp)));
+ REAL(strncmp) = reinterpret_cast<strncmp_type>(
+ getFuncAddr("strncmp", reinterpret_cast<uintptr_t>(&strncmp)));
+ REAL(strcmp) = reinterpret_cast<strcmp_type>(
+ getFuncAddr("strcmp", reinterpret_cast<uintptr_t>(&strcmp)));
+ REAL(strncasecmp) = reinterpret_cast<strncasecmp_type>(
+ getFuncAddr("strncasecmp", reinterpret_cast<uintptr_t>(&strncasecmp)));
+ REAL(strcasecmp) = reinterpret_cast<strcasecmp_type>(
+ getFuncAddr("strcasecmp", reinterpret_cast<uintptr_t>(&strcasecmp)));
+ REAL(strstr) = reinterpret_cast<strstr_type>(
+ getFuncAddr("strstr", reinterpret_cast<uintptr_t>(&strstr)));
+ REAL(strcasestr) = reinterpret_cast<strcasestr_type>(
+ getFuncAddr("strcasestr", reinterpret_cast<uintptr_t>(&strcasestr)));
+ REAL(memmem) = reinterpret_cast<memmem_type>(
+ getFuncAddr("memmem", reinterpret_cast<uintptr_t>(&memmem)));
+
+ FuzzerInitIsRunning = false;
+ FuzzerInited = 1;
+}
+
+#endif
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