| /* |
| american fuzzy lop - LLVM instrumentation bootstrap |
| --------------------------------------------------- |
| |
| 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 code is the rewrite of afl-as.h's main_payload. |
| |
| */ |
| |
| #include "../config.h" |
| #include "../types.h" |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <signal.h> |
| #include <unistd.h> |
| #include <string.h> |
| #include <assert.h> |
| |
| #include <sys/mman.h> |
| #include <sys/shm.h> |
| #include <sys/wait.h> |
| #include <sys/types.h> |
| |
| /* This is a somewhat ugly hack for the experimental 'trace-pc-guard' mode. |
| Basically, we need to make sure that the forkserver is initialized after |
| the LLVM-generated runtime initialization pass, not before. */ |
| |
| #ifdef USE_TRACE_PC |
| # define CONST_PRIO 5 |
| #else |
| # define CONST_PRIO 0 |
| #endif /* ^USE_TRACE_PC */ |
| |
| |
| /* Globals needed by the injected instrumentation. The __afl_area_initial region |
| is used for instrumentation output before __afl_map_shm() has a chance to run. |
| It will end up as .comm, so it shouldn't be too wasteful. */ |
| |
| u8 __afl_area_initial[MAP_SIZE]; |
| u8* __afl_area_ptr = __afl_area_initial; |
| |
| __thread u32 __afl_prev_loc; |
| |
| |
| /* Running in persistent mode? */ |
| |
| static u8 is_persistent; |
| |
| |
| /* SHM setup. */ |
| |
| static void __afl_map_shm(void) { |
| |
| u8 *id_str = getenv(SHM_ENV_VAR); |
| |
| /* If we're running under AFL, attach to the appropriate region, replacing the |
| early-stage __afl_area_initial region that is needed to allow some really |
| hacky .init code to work correctly in projects such as OpenSSL. */ |
| |
| if (id_str) { |
| |
| u32 shm_id = atoi(id_str); |
| |
| __afl_area_ptr = shmat(shm_id, NULL, 0); |
| |
| /* Whooooops. */ |
| |
| if (__afl_area_ptr == (void *)-1) _exit(1); |
| |
| /* Write something into the bitmap so that even with low AFL_INST_RATIO, |
| our parent doesn't give up on us. */ |
| |
| __afl_area_ptr[0] = 1; |
| |
| } |
| |
| } |
| |
| |
| /* Fork server logic. */ |
| |
| static void __afl_start_forkserver(void) { |
| |
| static u8 tmp[4]; |
| s32 child_pid; |
| |
| u8 child_stopped = 0; |
| |
| /* Phone home and tell the parent that we're OK. If parent isn't there, |
| assume we're not running in forkserver mode and just execute program. */ |
| |
| if (write(FORKSRV_FD + 1, tmp, 4) != 4) return; |
| |
| while (1) { |
| |
| u32 was_killed; |
| int status; |
| |
| /* Wait for parent by reading from the pipe. Abort if read fails. */ |
| |
| if (read(FORKSRV_FD, &was_killed, 4) != 4) _exit(1); |
| |
| /* If we stopped the child in persistent mode, but there was a race |
| condition and afl-fuzz already issued SIGKILL, write off the old |
| process. */ |
| |
| if (child_stopped && was_killed) { |
| child_stopped = 0; |
| if (waitpid(child_pid, &status, 0) < 0) _exit(1); |
| } |
| |
| if (!child_stopped) { |
| |
| /* Once woken up, create a clone of our process. */ |
| |
| child_pid = fork(); |
| if (child_pid < 0) _exit(1); |
| |
| /* In child process: close fds, resume execution. */ |
| |
| if (!child_pid) { |
| |
| close(FORKSRV_FD); |
| close(FORKSRV_FD + 1); |
| return; |
| |
| } |
| |
| } else { |
| |
| /* Special handling for persistent mode: if the child is alive but |
| currently stopped, simply restart it with SIGCONT. */ |
| |
| kill(child_pid, SIGCONT); |
| child_stopped = 0; |
| |
| } |
| |
| /* In parent process: write PID to pipe, then wait for child. */ |
| |
| if (write(FORKSRV_FD + 1, &child_pid, 4) != 4) _exit(1); |
| |
| if (waitpid(child_pid, &status, is_persistent ? WUNTRACED : 0) < 0) |
| _exit(1); |
| |
| /* In persistent mode, the child stops itself with SIGSTOP to indicate |
| a successful run. In this case, we want to wake it up without forking |
| again. */ |
| |
| if (WIFSTOPPED(status)) child_stopped = 1; |
| |
| /* Relay wait status to pipe, then loop back. */ |
| |
| if (write(FORKSRV_FD + 1, &status, 4) != 4) _exit(1); |
| |
| } |
| |
| } |
| |
| |
| /* A simplified persistent mode handler, used as explained in README.llvm. */ |
| |
| int __afl_persistent_loop(unsigned int max_cnt) { |
| |
| static u8 first_pass = 1; |
| static u32 cycle_cnt; |
| |
| if (first_pass) { |
| |
| /* Make sure that every iteration of __AFL_LOOP() starts with a clean slate. |
| On subsequent calls, the parent will take care of that, but on the first |
| iteration, it's our job to erase any trace of whatever happened |
| before the loop. */ |
| |
| if (is_persistent) { |
| |
| memset(__afl_area_ptr, 0, MAP_SIZE); |
| __afl_area_ptr[0] = 1; |
| __afl_prev_loc = 0; |
| } |
| |
| cycle_cnt = max_cnt; |
| first_pass = 0; |
| return 1; |
| |
| } |
| |
| if (is_persistent) { |
| |
| if (--cycle_cnt) { |
| |
| raise(SIGSTOP); |
| |
| __afl_area_ptr[0] = 1; |
| __afl_prev_loc = 0; |
| |
| return 1; |
| |
| } else { |
| |
| /* When exiting __AFL_LOOP(), make sure that the subsequent code that |
| follows the loop is not traced. We do that by pivoting back to the |
| dummy output region. */ |
| |
| __afl_area_ptr = __afl_area_initial; |
| |
| } |
| |
| } |
| |
| return 0; |
| |
| } |
| |
| |
| /* This one can be called from user code when deferred forkserver mode |
| is enabled. */ |
| |
| void __afl_manual_init(void) { |
| |
| static u8 init_done; |
| |
| if (!init_done) { |
| |
| __afl_map_shm(); |
| __afl_start_forkserver(); |
| init_done = 1; |
| |
| } |
| |
| } |
| |
| |
| /* Proper initialization routine. */ |
| |
| __attribute__((constructor(CONST_PRIO))) void __afl_auto_init(void) { |
| |
| is_persistent = !!getenv(PERSIST_ENV_VAR); |
| |
| if (getenv(DEFER_ENV_VAR)) return; |
| |
| __afl_manual_init(); |
| |
| } |
| |
| |
| /* The following stuff deals with supporting -fsanitize-coverage=trace-pc-guard. |
| It remains non-operational in the traditional, plugin-backed LLVM mode. |
| For more info about 'trace-pc-guard', see README.llvm. |
| |
| The first function (__sanitizer_cov_trace_pc_guard) is called back on every |
| edge (as opposed to every basic block). */ |
| |
| void __sanitizer_cov_trace_pc_guard(uint32_t* guard) { |
| __afl_area_ptr[*guard]++; |
| } |
| |
| |
| /* Init callback. Populates instrumentation IDs. Note that we're using |
| ID of 0 as a special value to indicate non-instrumented bits. That may |
| still touch the bitmap, but in a fairly harmless way. */ |
| |
| void __sanitizer_cov_trace_pc_guard_init(uint32_t* start, uint32_t* stop) { |
| |
| u32 inst_ratio = 100; |
| u8* x; |
| |
| if (start == stop || *start) return; |
| |
| x = getenv("AFL_INST_RATIO"); |
| if (x) inst_ratio = atoi(x); |
| |
| if (!inst_ratio || inst_ratio > 100) { |
| fprintf(stderr, "[-] ERROR: Invalid AFL_INST_RATIO (must be 1-100).\n"); |
| abort(); |
| } |
| |
| /* Make sure that the first element in the range is always set - we use that |
| to avoid duplicate calls (which can happen as an artifact of the underlying |
| implementation in LLVM). */ |
| |
| *(start++) = R(MAP_SIZE - 1) + 1; |
| |
| while (start < stop) { |
| |
| if (R(100) < inst_ratio) *start = R(MAP_SIZE - 1) + 1; |
| else *start = 0; |
| |
| start++; |
| |
| } |
| |
| } |