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Unified Diff: third_party/afl/src/llvm_mode/afl-clang-fast.c

Issue 2075883002: Add American Fuzzy Lop (afl) to third_party/afl/ (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Fix nits Created 4 years, 6 months ago
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Index: third_party/afl/src/llvm_mode/afl-clang-fast.c
diff --git a/third_party/afl/src/llvm_mode/afl-clang-fast.c b/third_party/afl/src/llvm_mode/afl-clang-fast.c
new file mode 100644
index 0000000000000000000000000000000000000000..b9cedea954ad3d26d259f2b7b054d7f7d793ea07
--- /dev/null
+++ b/third_party/afl/src/llvm_mode/afl-clang-fast.c
@@ -0,0 +1,327 @@
+/*
+ american fuzzy lop - LLVM-mode wrapper for clang
+ ------------------------------------------------
+
+ Written by Laszlo Szekeres <lszekeres@google.com> and
+ Michal Zalewski <lcamtuf@google.com>
+
+ LLVM integration design comes from Laszlo Szekeres.
+
+ Copyright 2015, 2016 Google Inc. All rights reserved.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at:
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ This program is a drop-in replacement for clang, similar in most respects
+ to ../afl-gcc. It tries to figure out compilation mode, adds a bunch
+ of flags, and then calls the real compiler.
+
+ */
+
+#define AFL_MAIN
+
+#include "../config.h"
+#include "../types.h"
+#include "../debug.h"
+#include "../alloc-inl.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+static u8* obj_path; /* Path to runtime libraries */
+static u8** cc_params; /* Parameters passed to the real CC */
+static u32 cc_par_cnt = 1; /* Param count, including argv0 */
+
+
+/* Try to find the runtime libraries. If that fails, abort. */
+
+static void find_obj(u8* argv0) {
+
+ u8 *afl_path = getenv("AFL_PATH");
+ u8 *slash, *tmp;
+
+ if (afl_path) {
+
+ tmp = alloc_printf("%s/afl-llvm-rt.o", afl_path);
+
+ if (!access(tmp, R_OK)) {
+ obj_path = afl_path;
+ ck_free(tmp);
+ return;
+ }
+
+ ck_free(tmp);
+
+ }
+
+ slash = strrchr(argv0, '/');
+
+ if (slash) {
+
+ u8 *dir;
+
+ *slash = 0;
+ dir = ck_strdup(argv0);
+ *slash = '/';
+
+ tmp = alloc_printf("%s/afl-llvm-rt.o", dir);
+
+ if (!access(tmp, R_OK)) {
+ obj_path = dir;
+ ck_free(tmp);
+ return;
+ }
+
+ ck_free(tmp);
+ ck_free(dir);
+
+ }
+
+ if (!access(AFL_PATH "/afl-llvm-rt.o", R_OK)) {
+ obj_path = AFL_PATH;
+ return;
+ }
+
+ FATAL("Unable to find 'afl-llvm-rt.o' or 'afl-llvm-pass.so'. Please set AFL_PATH");
+
+}
+
+
+/* Copy argv to cc_params, making the necessary edits. */
+
+static void edit_params(u32 argc, char** argv) {
+
+ u8 fortify_set = 0, asan_set = 0, x_set = 0, maybe_linking = 1, bit_mode = 0;
+ u8 *name;
+
+ cc_params = ck_alloc((argc + 64) * sizeof(u8*));
+
+ name = strrchr(argv[0], '/');
+ if (!name) name = argv[0]; else name++;
+
+ if (!strcmp(name, "afl-clang-fast++")) {
+ u8* alt_cxx = getenv("AFL_CXX");
+ cc_params[0] = alt_cxx ? alt_cxx : (u8*)"clang++";
+ } else {
+ u8* alt_cc = getenv("AFL_CC");
+ cc_params[0] = alt_cc ? alt_cc : (u8*)"clang";
+ }
+
+ /* There are two ways to compile afl-clang-fast. In the traditional mode, we
+ use afl-llvm-pass.so to inject instrumentation. In the experimental
+ 'trace-pc' mode, we use native LLVM instrumentation callbacks instead.
+ The latter is a very recent addition - see:
+
+ http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs */
+
+#ifdef USE_TRACE_PC
+ cc_params[cc_par_cnt++] = "-fsanitize-coverage=bb,trace-pc";
+#else
+ cc_params[cc_par_cnt++] = "-Xclang";
+ cc_params[cc_par_cnt++] = "-load";
+ cc_params[cc_par_cnt++] = "-Xclang";
+ cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-pass.so", obj_path);
+#endif /* ^USE_TRACE_PC */
+
+ cc_params[cc_par_cnt++] = "-Qunused-arguments";
+
+ while (--argc) {
+ u8* cur = *(++argv);
+
+ if (!strcmp(cur, "-m32")) bit_mode = 32;
+ if (!strcmp(cur, "-m64")) bit_mode = 64;
+
+ if (!strcmp(cur, "-x")) x_set = 1;
+
+ if (!strcmp(cur, "-c") || !strcmp(cur, "-S") || !strcmp(cur, "-E") ||
+ !strcmp(cur, "-v")) maybe_linking = 0;
+
+ if (!strcmp(cur, "-fsanitize=address") ||
+ !strcmp(cur, "-fsanitize=memory")) asan_set = 1;
+
+ if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1;
+
+ if (!strcmp(cur, "-shared")) maybe_linking = 0;
+
+ cc_params[cc_par_cnt++] = cur;
+
+ }
+
+ if (getenv("AFL_HARDEN")) {
+
+ cc_params[cc_par_cnt++] = "-fstack-protector-all";
+
+ if (!fortify_set)
+ cc_params[cc_par_cnt++] = "-D_FORTIFY_SOURCE=2";
+
+ }
+
+ if (!asan_set) {
+
+ if (getenv("AFL_USE_ASAN")) {
+
+ cc_params[cc_par_cnt++] = "-fsanitize=address";
+
+ if (getenv("AFL_USE_MSAN"))
+ FATAL("ASAN and MSAN are mutually exclusive");
+
+ } else if (getenv("AFL_USE_MSAN")) {
+
+ cc_params[cc_par_cnt++] = "-fsanitize=memory";
+
+ if (getenv("AFL_USE_ASAN"))
+ FATAL("ASAN and MSAN are mutually exclusive");
+
+ }
+
+ }
+
+#ifdef USE_TRACE_PC
+
+ if (getenv("AFL_INST_RATIO"))
+ FATAL("AFL_INST_RATIO not available at compile time with 'trace-pc'.");
+
+#endif /* USE_TRACE_PC */
+
+ if (!getenv("AFL_DONT_OPTIMIZE")) {
+
+ cc_params[cc_par_cnt++] = "-g";
+ cc_params[cc_par_cnt++] = "-O3";
+ cc_params[cc_par_cnt++] = "-funroll-loops";
+
+ }
+
+ cc_params[cc_par_cnt++] = "-D__AFL_HAVE_MANUAL_CONTROL=1";
+ cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1";
+ cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1";
+
+ /* When the user tries to use persistent or deferred forkserver modes by
+ appending a single line to the program, we want to reliably inject a
+ signature into the binary (to be picked up by afl-fuzz) and we want
+ to call a function from the runtime .o file. This is unnecessarily
+ painful for three reasons:
+
+ 1) We need to convince the compiler not to optimize out the signature.
+ This is done with __attribute__((used)).
+
+ 2) We need to convince the linker, when called with -Wl,--gc-sections,
+ not to do the same. This is done by forcing an assignment to a
+ 'volatile' pointer.
+
+ 3) We need to declare __afl_persistent_loop() in the global namespace,
+ but doing this within a method in a class is hard - :: and extern "C"
+ are forbidden and __attribute__((alias(...))) doesn't work. Hence the
+ __asm__ aliasing trick.
+
+ */
+
+ cc_params[cc_par_cnt++] = "-D__AFL_LOOP(_A)="
+ "({ static volatile char *_B __attribute__((used)); "
+ " _B = (char*)\"" PERSIST_SIG "\"; "
+#ifdef __APPLE__
+ "__attribute__((visibility(\"default\"))) "
+ "int _L(unsigned int) __asm__(\"___afl_persistent_loop\"); "
+#else
+ "__attribute__((visibility(\"default\"))) "
+ "int _L(unsigned int) __asm__(\"__afl_persistent_loop\"); "
+#endif /* ^__APPLE__ */
+ "_L(_A); })";
+
+ cc_params[cc_par_cnt++] = "-D__AFL_INIT()="
+ "do { static volatile char *_A __attribute__((used)); "
+ " _A = (char*)\"" DEFER_SIG "\"; "
+#ifdef __APPLE__
+ "__attribute__((visibility(\"default\"))) "
+ "void _I(void) __asm__(\"___afl_manual_init\"); "
+#else
+ "__attribute__((visibility(\"default\"))) "
+ "void _I(void) __asm__(\"__afl_manual_init\"); "
+#endif /* ^__APPLE__ */
+ "_I(); } while (0)";
+
+ if (maybe_linking) {
+
+ if (x_set) {
+ cc_params[cc_par_cnt++] = "-x";
+ cc_params[cc_par_cnt++] = "none";
+ }
+
+ switch (bit_mode) {
+
+ case 0:
+ cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt.o", obj_path);
+ break;
+
+ case 32:
+ cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-32.o", obj_path);
+
+ if (access(cc_params[cc_par_cnt - 1], R_OK))
+ FATAL("-m32 is not supported by your compiler");
+
+ break;
+
+ case 64:
+ cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-64.o", obj_path);
+
+ if (access(cc_params[cc_par_cnt - 1], R_OK))
+ FATAL("-m64 is not supported by your compiler");
+
+ break;
+
+ }
+
+ }
+
+ cc_params[cc_par_cnt] = NULL;
+
+}
+
+
+/* Main entry point */
+
+int main(int argc, char** argv) {
+
+ if (isatty(2) && !getenv("AFL_QUIET")) {
+
+ SAYF(cCYA "afl-clang-fast " cBRI VERSION cRST " by <lszekeres@google.com>\n");
+
+ }
+
+ if (argc < 2) {
+
+ SAYF("\n"
+ "This is a helper application for afl-fuzz. It serves as a drop-in replacement\n"
+ "for clang, letting you recompile third-party code with the required runtime\n"
+ "instrumentation. A common use pattern would be one of the following:\n\n"
+
+ " CC=%s/afl-clang-fast ./configure\n"
+ " CXX=%s/afl-clang-fast++ ./configure\n\n"
+
+ "In contrast to the traditional afl-clang tool, this version is implemented as\n"
+ "an LLVM pass and tends to offer improved performance with slow programs.\n\n"
+
+ "You can specify custom next-stage toolchain via AFL_CC and AFL_CXX. Setting\n"
+ "AFL_HARDEN enables hardening optimizations in the compiled code.\n\n",
+ BIN_PATH, BIN_PATH);
+
+ exit(1);
+
+ }
+
+
+ find_obj(argv[0]);
+
+ edit_params(argc, argv);
+
+ execvp(cc_params[0], (char**)cc_params);
+
+ FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
+
+ return 0;
+
+}
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