| //===-- 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 |