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-rw-r--r--tools/fuzzing/libfuzzer/FuzzerInterceptors.cpp235
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diff --git a/tools/fuzzing/libfuzzer/FuzzerInterceptors.cpp b/tools/fuzzing/libfuzzer/FuzzerInterceptors.cpp
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+++ b/tools/fuzzing/libfuzzer/FuzzerInterceptors.cpp
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+//===-- 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();
+ }
+}
+
+static int internal_strcmp_strncmp(const char *s1, const char *s2, bool strncmp,
+ size_t n) {
+ size_t i = 0;
+ while (true) {
+ if (strncmp) {
+ if (i == n)
+ break;
+ i++;
+ }
+ unsigned c1 = *s1;
+ unsigned c2 = *s2;
+ if (c1 != c2)
+ return (c1 < c2) ? -1 : 1;
+ if (c1 == 0)
+ break;
+ s1++;
+ s2++;
+ }
+ return 0;
+}
+
+static int internal_strncmp(const char *s1, const char *s2, size_t n) {
+ return internal_strcmp_strncmp(s1, s2, true, n);
+}
+
+static int internal_strcmp(const char *s1, const char *s2) {
+ return internal_strcmp_strncmp(s1, s2, false, 0);
+}
+
+static int internal_memcmp(const void *s1, const void *s2, size_t n) {
+ const uint8_t *t1 = static_cast<const uint8_t *>(s1);
+ const uint8_t *t2 = static_cast<const uint8_t *>(s2);
+ for (size_t i = 0; i < n; ++i, ++t1, ++t2)
+ if (*t1 != *t2)
+ return *t1 < *t2 ? -1 : 1;
+ return 0;
+}
+
+static size_t internal_strlen(const char *s) {
+ size_t i = 0;
+ while (s[i])
+ i++;
+ return i;
+}
+
+static char *internal_strstr(const char *haystack, const char *needle) {
+ // This is O(N^2), but we are not using it in hot places.
+ size_t len1 = internal_strlen(haystack);
+ size_t len2 = internal_strlen(needle);
+ if (len1 < len2)
+ return nullptr;
+ for (size_t pos = 0; pos <= len1 - len2; pos++) {
+ if (internal_memcmp(haystack + pos, needle, len2) == 0)
+ return const_cast<char *>(haystack) + pos;
+ }
+ return nullptr;
+}
+
+extern "C" {
+
+DEFINE_REAL(int, bcmp, const void *, const void *, size_t)
+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 bcmp(const char *s1, const char *s2, size_t n) {
+ if (!FuzzerInited)
+ return internal_memcmp(s1, s2, n);
+ int result = REAL(bcmp)(s1, s2, n);
+ __sanitizer_weak_hook_memcmp(GET_CALLER_PC(), s1, s2, n, result);
+ return result;
+}
+
+ATTRIBUTE_INTERFACE int memcmp(const void *s1, const void *s2, size_t n) {
+ if (!FuzzerInited)
+ return internal_memcmp(s1, s2, n);
+ 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) {
+ if (!FuzzerInited)
+ return internal_strncmp(s1, s2, n);
+ 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) {
+ if (!FuzzerInited)
+ return internal_strcmp(s1, s2);
+ 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) {
+ if (!FuzzerInited)
+ return internal_strstr(s1, s2);
+ 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(bcmp) = reinterpret_cast<memcmp_type>(
+ getFuncAddr("bcmp", reinterpret_cast<uintptr_t>(&bcmp)));
+ 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