| /* |
| american fuzzy lop++ - GCC plugin instrumentation bootstrap |
| --------------------------------------------------------- |
| |
| Written by Austin Seipp <aseipp@pobox.com> and |
| Laszlo Szekeres <lszekeres@google.com> and |
| Michal Zalewski |
| |
| GCC integration design is based on the LLVM design, which comes |
| from Laszlo Szekeres. |
| |
| 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. |
| |
| */ |
| |
| #ifdef __ANDROID__ |
| #include "android-ashmem.h" |
| #endif |
| #include "../config.h" |
| #include "../types.h" |
| |
| #ifdef USEMMAP |
| #include <stdio.h> |
| #endif |
| #include <stdlib.h> |
| #include <signal.h> |
| #include <unistd.h> |
| #include <string.h> |
| #include <assert.h> |
| |
| #include <sys/mman.h> |
| #ifndef USEMMAP |
| #include <sys/shm.h> |
| #endif |
| #include <sys/wait.h> |
| #include <sys/types.h> |
| |
| #include <sys/mman.h> |
| #include <fcntl.h> |
| |
| /* 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; |
| |
| #ifdef __ANDROID__ |
| u32 __afl_prev_loc; |
| u32 __afl_final_loc; |
| #else |
| __thread u32 __afl_prev_loc; |
| __thread u32 __afl_final_loc; |
| #endif |
| |
| /* Trace a basic block with some ID */ |
| void __afl_trace(const u32 x) { |
| |
| #if 1 /* enable for neverZero feature. */ |
| __afl_area_ptr[__afl_prev_loc ^ x] += |
| 1 + ((u8)(1 + __afl_area_ptr[__afl_prev_loc ^ x]) == 0); |
| #else |
| ++__afl_area_ptr[__afl_prev_loc ^ x]; |
| #endif |
| |
| __afl_prev_loc = (x >> 1); |
| return; |
| |
| } |
| |
| /* 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) { |
| |
| #ifdef USEMMAP |
| const char * shm_file_path = id_str; |
| int shm_fd = -1; |
| unsigned char *shm_base = NULL; |
| |
| /* create the shared memory segment as if it was a file */ |
| shm_fd = shm_open(shm_file_path, O_RDWR, 0600); |
| if (shm_fd == -1) { |
| |
| fprintf(stderr, "shm_open() failed\n"); |
| exit(1); |
| |
| } |
| |
| /* map the shared memory segment to the address space of the process */ |
| shm_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0); |
| if (shm_base == MAP_FAILED) { |
| |
| close(shm_fd); |
| shm_fd = -1; |
| |
| fprintf(stderr, "mmap() failed\n"); |
| exit(2); |
| |
| } |
| |
| __afl_area_ptr = shm_base; |
| #else |
| u32 shm_id = atoi(id_str); |
| |
| __afl_area_ptr = shmat(shm_id, NULL, 0); |
| #endif |
| |
| /* 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) { |
| |
| u8 tmp[4] = {0, 0, 0, 0}; |
| u32 map_size = MAP_SIZE; |
| s32 child_pid; |
| |
| u8 child_stopped = 0; |
| |
| void (*old_sigchld_handler)(int) = signal(SIGCHLD, SIG_DFL); |
| |
| /* 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 (MAP_SIZE <= 0x800000) { |
| |
| map_size = (FS_OPT_ENABLED | FS_OPT_MAPSIZE | FS_OPT_SET_MAPSIZE(MAP_SIZE)); |
| memcpy(tmp, &map_size, 4); |
| |
| } |
| |
| 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) { |
| |
| signal(SIGCHLD, old_sigchld_handler); |
| |
| 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.md. */ |
| |
| 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(101))) void __afl_auto_init(void) { |
| |
| is_persistent = !!getenv(PERSIST_ENV_VAR); |
| |
| if (getenv(DEFER_ENV_VAR)) return; |
| |
| __afl_manual_init(); |
| |
| } |
| |
