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author | Andrea Fioraldi <andreafioraldi@gmail.com> | 2019-08-27 13:31:35 +0200 |
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committer | Andrea Fioraldi <andreafioraldi@gmail.com> | 2019-08-27 13:31:35 +0200 |
commit | 0e59a591693901ec6a69c7de2e9de2dcca52c101 (patch) | |
tree | 6a0a3be742f26e7cf6cbfcc1779a85e29c6d9db1 /afl-as.c | |
parent | d3d0682310b840b027083133837bcd9be0638281 (diff) | |
download | afl++-0e59a591693901ec6a69c7de2e9de2dcca52c101.tar.gz |
include and src folders
Diffstat (limited to 'afl-as.c')
-rw-r--r-- | afl-as.c | 550 |
1 files changed, 0 insertions, 550 deletions
diff --git a/afl-as.c b/afl-as.c deleted file mode 100644 index 94595f24..00000000 --- a/afl-as.c +++ /dev/null @@ -1,550 +0,0 @@ -/* - american fuzzy lop - wrapper for GNU as - --------------------------------------- - - Written and maintained by Michal Zalewski <lcamtuf@google.com> - - Copyright 2013, 2014, 2015 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 - - The sole purpose of this wrapper is to preprocess assembly files generated - by GCC / clang and inject the instrumentation bits included from afl-as.h. It - is automatically invoked by the toolchain when compiling programs using - afl-gcc / afl-clang. - - Note that it's an explicit non-goal to instrument hand-written assembly, - be it in separate .s files or in __asm__ blocks. The only aspiration this - utility has right now is to be able to skip them gracefully and allow the - compilation process to continue. - - That said, see experimental/clang_asm_normalize/ for a solution that may - allow clang users to make things work even with hand-crafted assembly. Just - note that there is no equivalent for GCC. - - */ - -#define AFL_MAIN - -#include "config.h" -#include "types.h" -#include "debug.h" -#include "alloc-inl.h" - -#include "afl-as.h" - -#include <stdio.h> -#include <unistd.h> -#include <stdlib.h> -#include <string.h> -#include <time.h> -#include <ctype.h> -#include <fcntl.h> - -#include <sys/wait.h> -#include <sys/time.h> - -static u8** as_params; /* Parameters passed to the real 'as' */ - -static u8* input_file; /* Originally specified input file */ -static u8* modified_file; /* Instrumented file for the real 'as' */ - -static u8 be_quiet, /* Quiet mode (no stderr output) */ - clang_mode, /* Running in clang mode? */ - pass_thru, /* Just pass data through? */ - just_version, /* Just show version? */ - sanitizer; /* Using ASAN / MSAN */ - -static u32 inst_ratio = 100, /* Instrumentation probability (%) */ - as_par_cnt = 1; /* Number of params to 'as' */ - -/* If we don't find --32 or --64 in the command line, default to - instrumentation for whichever mode we were compiled with. This is not - perfect, but should do the trick for almost all use cases. */ - -#ifdef __x86_64__ - -static u8 use_64bit = 1; - -#else - -static u8 use_64bit = 0; - -#ifdef __APPLE__ -# error "Sorry, 32-bit Apple platforms are not supported." -#endif /* __APPLE__ */ - -#endif /* ^__x86_64__ */ - - -/* Examine and modify parameters to pass to 'as'. Note that the file name - is always the last parameter passed by GCC, so we exploit this property - to keep the code simple. */ - -static void edit_params(int argc, char** argv) { - - u8 *tmp_dir = getenv("TMPDIR"), *afl_as = getenv("AFL_AS"); - u32 i; - -#ifdef __APPLE__ - - u8 use_clang_as = 0; - - /* On MacOS X, the Xcode cctool 'as' driver is a bit stale and does not work - with the code generated by newer versions of clang that are hand-built - by the user. See the thread here: http://goo.gl/HBWDtn. - - To work around this, when using clang and running without AFL_AS - specified, we will actually call 'clang -c' instead of 'as -q' to - compile the assembly file. - - The tools aren't cmdline-compatible, but at least for now, we can - seemingly get away with this by making only very minor tweaks. Thanks - to Nico Weber for the idea. */ - - if (clang_mode && !afl_as) { - - use_clang_as = 1; - - afl_as = getenv("AFL_CC"); - if (!afl_as) afl_as = getenv("AFL_CXX"); - if (!afl_as) afl_as = "clang"; - - } - -#endif /* __APPLE__ */ - - /* Although this is not documented, GCC also uses TEMP and TMP when TMPDIR - is not set. We need to check these non-standard variables to properly - handle the pass_thru logic later on. */ - - if (!tmp_dir) tmp_dir = getenv("TEMP"); - if (!tmp_dir) tmp_dir = getenv("TMP"); - if (!tmp_dir) tmp_dir = "/tmp"; - - as_params = ck_alloc((argc + 32) * sizeof(u8*)); - - as_params[0] = afl_as ? afl_as : (u8*)"as"; - - as_params[argc] = 0; - - for (i = 1; i < argc - 1; i++) { - - if (!strcmp(argv[i], "--64")) use_64bit = 1; - else if (!strcmp(argv[i], "--32")) use_64bit = 0; - -#ifdef __APPLE__ - - /* The Apple case is a bit different... */ - - if (!strcmp(argv[i], "-arch") && i + 1 < argc) { - - if (!strcmp(argv[i + 1], "x86_64")) use_64bit = 1; - else if (!strcmp(argv[i + 1], "i386")) - FATAL("Sorry, 32-bit Apple platforms are not supported."); - - } - - /* Strip options that set the preference for a particular upstream - assembler in Xcode. */ - - if (clang_mode && (!strcmp(argv[i], "-q") || !strcmp(argv[i], "-Q"))) - continue; - -#endif /* __APPLE__ */ - - as_params[as_par_cnt++] = argv[i]; - - } - -#ifdef __APPLE__ - - /* When calling clang as the upstream assembler, append -c -x assembler - and hope for the best. */ - - if (use_clang_as) { - - as_params[as_par_cnt++] = "-c"; - as_params[as_par_cnt++] = "-x"; - as_params[as_par_cnt++] = "assembler"; - - } - -#endif /* __APPLE__ */ - - input_file = argv[argc - 1]; - - if (input_file[0] == '-') { - - if (!strcmp(input_file + 1, "-version")) { - just_version = 1; - modified_file = input_file; - goto wrap_things_up; - } - - if (input_file[1]) FATAL("Incorrect use (not called through afl-gcc?)"); - else input_file = NULL; - - } else { - - /* Check if this looks like a standard invocation as a part of an attempt - to compile a program, rather than using gcc on an ad-hoc .s file in - a format we may not understand. This works around an issue compiling - NSS. */ - - if (strncmp(input_file, tmp_dir, strlen(tmp_dir)) && - strncmp(input_file, "/var/tmp/", 9) && - strncmp(input_file, "/tmp/", 5)) pass_thru = 1; - - } - - modified_file = alloc_printf("%s/.afl-%u-%u.s", tmp_dir, getpid(), - (u32)time(NULL)); - -wrap_things_up: - - as_params[as_par_cnt++] = modified_file; - as_params[as_par_cnt] = NULL; - -} - - -/* Process input file, generate modified_file. Insert instrumentation in all - the appropriate places. */ - -static void add_instrumentation(void) { - - static u8 line[MAX_LINE]; - - FILE* inf; - FILE* outf; - s32 outfd; - u32 ins_lines = 0; - - u8 instr_ok = 0, skip_csect = 0, skip_next_label = 0, - skip_intel = 0, skip_app = 0, instrument_next = 0; - -#ifdef __APPLE__ - - u8* colon_pos; - -#endif /* __APPLE__ */ - - if (input_file) { - - inf = fopen(input_file, "r"); - if (!inf) PFATAL("Unable to read '%s'", input_file); - - } else inf = stdin; - - outfd = open(modified_file, O_WRONLY | O_EXCL | O_CREAT, 0600); - - if (outfd < 0) PFATAL("Unable to write to '%s'", modified_file); - - outf = fdopen(outfd, "w"); - - if (!outf) PFATAL("fdopen() failed"); - - while (fgets(line, MAX_LINE, inf)) { - - /* In some cases, we want to defer writing the instrumentation trampoline - until after all the labels, macros, comments, etc. If we're in this - mode, and if the line starts with a tab followed by a character, dump - the trampoline now. */ - - if (!pass_thru && !skip_intel && !skip_app && !skip_csect && instr_ok && - instrument_next && line[0] == '\t' && isalpha(line[1])) { - - fprintf(outf, use_64bit ? trampoline_fmt_64 : trampoline_fmt_32, - R(MAP_SIZE)); - - instrument_next = 0; - ins_lines++; - - } - - /* Output the actual line, call it a day in pass-thru mode. */ - - fputs(line, outf); - - if (pass_thru) continue; - - /* All right, this is where the actual fun begins. For one, we only want to - instrument the .text section. So, let's keep track of that in processed - files - and let's set instr_ok accordingly. */ - - if (line[0] == '\t' && line[1] == '.') { - - /* OpenBSD puts jump tables directly inline with the code, which is - a bit annoying. They use a specific format of p2align directives - around them, so we use that as a signal. */ - - if (!clang_mode && instr_ok && !strncmp(line + 2, "p2align ", 8) && - isdigit(line[10]) && line[11] == '\n') skip_next_label = 1; - - if (!strncmp(line + 2, "text\n", 5) || - !strncmp(line + 2, "section\t.text", 13) || - !strncmp(line + 2, "section\t__TEXT,__text", 21) || - !strncmp(line + 2, "section __TEXT,__text", 21)) { - instr_ok = 1; - continue; - } - - if (!strncmp(line + 2, "section\t", 8) || - !strncmp(line + 2, "section ", 8) || - !strncmp(line + 2, "bss\n", 4) || - !strncmp(line + 2, "data\n", 5)) { - instr_ok = 0; - continue; - } - - } - - /* Detect off-flavor assembly (rare, happens in gdb). When this is - encountered, we set skip_csect until the opposite directive is - seen, and we do not instrument. */ - - if (strstr(line, ".code")) { - - if (strstr(line, ".code32")) skip_csect = use_64bit; - if (strstr(line, ".code64")) skip_csect = !use_64bit; - - } - - /* Detect syntax changes, as could happen with hand-written assembly. - Skip Intel blocks, resume instrumentation when back to AT&T. */ - - if (strstr(line, ".intel_syntax")) skip_intel = 1; - if (strstr(line, ".att_syntax")) skip_intel = 0; - - /* Detect and skip ad-hoc __asm__ blocks, likewise skipping them. */ - - if (line[0] == '#' || line[1] == '#') { - - if (strstr(line, "#APP")) skip_app = 1; - if (strstr(line, "#NO_APP")) skip_app = 0; - - } - - /* If we're in the right mood for instrumenting, check for function - names or conditional labels. This is a bit messy, but in essence, - we want to catch: - - ^main: - function entry point (always instrumented) - ^.L0: - GCC branch label - ^.LBB0_0: - clang branch label (but only in clang mode) - ^\tjnz foo - conditional branches - - ...but not: - - ^# BB#0: - clang comments - ^ # BB#0: - ditto - ^.Ltmp0: - clang non-branch labels - ^.LC0 - GCC non-branch labels - ^.LBB0_0: - ditto (when in GCC mode) - ^\tjmp foo - non-conditional jumps - - Additionally, clang and GCC on MacOS X follow a different convention - with no leading dots on labels, hence the weird maze of #ifdefs - later on. - - */ - - if (skip_intel || skip_app || skip_csect || !instr_ok || - line[0] == '#' || line[0] == ' ') continue; - - /* Conditional branch instruction (jnz, etc). We append the instrumentation - right after the branch (to instrument the not-taken path) and at the - branch destination label (handled later on). */ - - if (line[0] == '\t') { - - if (line[1] == 'j' && line[2] != 'm' && R(100) < inst_ratio) { - - fprintf(outf, use_64bit ? trampoline_fmt_64 : trampoline_fmt_32, - R(MAP_SIZE)); - - ins_lines++; - - } - - continue; - - } - - /* Label of some sort. This may be a branch destination, but we need to - read carefully and account for several different formatting - conventions. */ - -#ifdef __APPLE__ - - /* Apple: L<whatever><digit>: */ - - if ((colon_pos = strstr(line, ":"))) { - - if (line[0] == 'L' && isdigit(*(colon_pos - 1))) { - -#else - - /* Everybody else: .L<whatever>: */ - - if (strstr(line, ":")) { - - if (line[0] == '.') { - -#endif /* __APPLE__ */ - - /* .L0: or LBB0_0: style jump destination */ - -#ifdef __APPLE__ - - /* Apple: L<num> / LBB<num> */ - - if ((isdigit(line[1]) || (clang_mode && !strncmp(line, "LBB", 3))) - && R(100) < inst_ratio) { - -#else - - /* Apple: .L<num> / .LBB<num> */ - - if ((isdigit(line[2]) || (clang_mode && !strncmp(line + 1, "LBB", 3))) - && R(100) < inst_ratio) { - -#endif /* __APPLE__ */ - - /* An optimization is possible here by adding the code only if the - label is mentioned in the code in contexts other than call / jmp. - That said, this complicates the code by requiring two-pass - processing (messy with stdin), and results in a speed gain - typically under 10%, because compilers are generally pretty good - about not generating spurious intra-function jumps. - - We use deferred output chiefly to avoid disrupting - .Lfunc_begin0-style exception handling calculations (a problem on - MacOS X). */ - - if (!skip_next_label) instrument_next = 1; else skip_next_label = 0; - - } - - } else { - - /* Function label (always instrumented, deferred mode). */ - - instrument_next = 1; - - } - - } - - } - - if (ins_lines) - fputs(use_64bit ? main_payload_64 : main_payload_32, outf); - - if (input_file) fclose(inf); - fclose(outf); - - if (!be_quiet) { - - if (!ins_lines) WARNF("No instrumentation targets found%s.", - pass_thru ? " (pass-thru mode)" : ""); - else OKF("Instrumented %u locations (%s-bit, %s mode, ratio %u%%).", - ins_lines, use_64bit ? "64" : "32", - getenv("AFL_HARDEN") ? "hardened" : - (sanitizer ? "ASAN/MSAN" : "non-hardened"), - inst_ratio); - - } - -} - - -/* Main entry point */ - -int main(int argc, char** argv) { - - s32 pid; - u32 rand_seed; - int status; - u8* inst_ratio_str = getenv("AFL_INST_RATIO"); - - struct timeval tv; - struct timezone tz; - - clang_mode = !!getenv(CLANG_ENV_VAR); - - if (isatty(2) && !getenv("AFL_QUIET")) { - - SAYF(cCYA "afl-as" VERSION cRST " by <lcamtuf@google.com>\n"); - - } else be_quiet = 1; - - if (argc < 2) { - - SAYF("\n" - "This is a helper application for afl-fuzz. It is a wrapper around GNU 'as',\n" - "executed by the toolchain whenever using afl-gcc or afl-clang. You probably\n" - "don't want to run this program directly.\n\n" - - "Rarely, when dealing with extremely complex projects, it may be advisable to\n" - "set AFL_INST_RATIO to a value less than 100 in order to reduce the odds of\n" - "instrumenting every discovered branch.\n\n"); - - exit(1); - - } - - gettimeofday(&tv, &tz); - - rand_seed = tv.tv_sec ^ tv.tv_usec ^ getpid(); - - srandom(rand_seed); - - edit_params(argc, argv); - - if (inst_ratio_str) { - - if (sscanf(inst_ratio_str, "%u", &inst_ratio) != 1 || inst_ratio > 100) - FATAL("Bad value of AFL_INST_RATIO (must be between 0 and 100)"); - - } - - if (getenv(AS_LOOP_ENV_VAR)) - FATAL("Endless loop when calling 'as' (remove '.' from your PATH)"); - - setenv(AS_LOOP_ENV_VAR, "1", 1); - - /* When compiling with ASAN, we don't have a particularly elegant way to skip - ASAN-specific branches. But we can probabilistically compensate for - that... */ - - if (getenv("AFL_USE_ASAN") || getenv("AFL_USE_MSAN")) { - sanitizer = 1; - if (!getenv("AFL_INST_RATIO")) - inst_ratio /= 3; - } - - if (!just_version) add_instrumentation(); - - if (!(pid = fork())) { - - execvp(as_params[0], (char**)as_params); - FATAL("Oops, failed to execute '%s' - check your PATH", as_params[0]); - - } - - if (pid < 0) PFATAL("fork() failed"); - - if (waitpid(pid, &status, 0) <= 0) PFATAL("waitpid() failed"); - - if (!getenv("AFL_KEEP_ASSEMBLY")) unlink(modified_file); - - exit(WEXITSTATUS(status)); - -} - |