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afl-showmap.c
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afl-showmap.c
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/*
american fuzzy lop - map display utility
----------------------------------------
Written and maintained by Michal Zalewski <lcamtuf@google.com>
Copyright 2013, 2014, 2015, 2016, 2017 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
A very simple tool that runs the targeted binary and displays
the contents of the trace bitmap in a human-readable form. Useful in
scripts to eliminate redundant inputs and perform other checks.
Exit code is 2 if the target program crashes; 1 if it times out or
there is a problem executing it; or 0 if execution is successful.
*/
#define AFL_MAIN
#include "config.h"
#include "types.h"
#include "debug.h"
#include "alloc-inl.h"
#include "hash.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <signal.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/resource.h>
static s32 forksrv_pid, /* PID of the fork server */
child_pid; /* PID of the tested program */
static s32 fsrv_ctl_fd, /* Fork server control pipe (write) */
fsrv_st_fd; /* Fork server status pipe (read) */
static u8* trace_bits; /* SHM with instrumentation bitmap */
static u8 *out_path, /* Trace output file / dir */
*in_path, /* Program input file / dir */
*doc_path, /* Path to docs */
*target_path, /* Path to target binary */
*at_file; /* Substitution string for @@ */
static u32 exec_tmout; /* Exec timeout (ms) */
static u64 mem_limit = MEM_LIMIT; /* Memory limit (MB) */
static s32 shm_id; /* ID of the SHM region */
static s32 at_file_fd, /* Persistent fd for tmp_input_file */
dev_null_fd = -1; /* Persistent fd for /dev/null */
static u8 quiet_mode, /* Hide non-essential messages? */
edges_only, /* Ignore hit counts? */
cmin_mode, /* Generate output in afl-cmin mode? */
binary_mode, /* Write output as a binary map */
keep_cores; /* Allow coredumps? */
static u8 batch_mode,
no_output,
using_file_arg,
allocated_at_file;
static volatile u8
stop_soon, /* Ctrl-C pressed? */
child_timed_out, /* Child timed out? */
child_crashed; /* Child crashed? */
/* Classify tuple counts. Instead of mapping to individual bits, as in
afl-fuzz.c, we map to more user-friendly numbers between 1 and 8. */
static const u8 count_class_human[256] = {
[0] = 0,
[1] = 1,
[2] = 2,
[3] = 3,
[4 ... 7] = 4,
[8 ... 15] = 5,
[16 ... 31] = 6,
[32 ... 127] = 7,
[128 ... 255] = 8
};
static const u8 count_class_binary[256] = {
[0] = 0,
[1] = 1,
[2] = 2,
[3] = 4,
[4 ... 7] = 8,
[8 ... 15] = 16,
[16 ... 31] = 32,
[32 ... 127] = 64,
[128 ... 255] = 128
};
struct queue_entry {
struct queue_entry *next;
u8 *in_path;
u32 in_len;
u8 *out_path;
};
/* Append new test case to the queue. */
struct queue_entry *queue_top = 0;
struct queue_entry *queue = 0;
int queued_paths = 0;
static void classify_counts(u8* mem, const u8* map) {
u32 i = MAP_SIZE;
if (edges_only) {
while (i--) {
if (*mem) *mem = 1;
mem++;
}
} else {
while (i--) {
*mem = map[*mem];
mem++;
}
}
}
/* Get rid of shared memory (atexit handler). */
static void remove_shm(void) {
shmctl(shm_id, IPC_RMID, NULL);
}
/* Configure shared memory. */
static void setup_shm(void) {
u8* shm_str;
shm_id = shmget(IPC_PRIVATE, MAP_SIZE, IPC_CREAT | IPC_EXCL | 0600);
if (shm_id < 0) PFATAL("shmget() failed");
atexit(remove_shm);
shm_str = alloc_printf("%d", shm_id);
setenv(SHM_ENV_VAR, shm_str, 1);
ck_free(shm_str);
trace_bits = shmat(shm_id, NULL, 0);
if (!trace_bits) PFATAL("shmat() failed");
}
static void setup_at_file(void) {
u8 *use_dir = ".";
if (access(use_dir, R_OK | W_OK | X_OK))
{
use_dir = getenv("TMPDIR");
if (!use_dir)
use_dir = "/tmp";
}
at_file = alloc_printf("%s/.afl-showmap-temp-%u", use_dir, getpid());
unlink(at_file);
at_file_fd = open(at_file, O_RDWR | O_CREAT | O_EXCL, 0600);
if (at_file_fd < 0) PFATAL("Unable to create '%s'", at_file);
allocated_at_file = 1;
}
#define CHK_FORMAT(_divisor, _limit_mult, _fmt, _cast) do { \
if (val < (_divisor) * (_limit_mult)) { \
sprintf(tmp[cur], _fmt, ((_cast)val) / (_divisor)); \
return tmp[cur]; \
} \
} while (0)
/* Describe integer as memory size. */
static u8* DMS(u64 val) {
static u8 tmp[12][16];
static u8 cur;
cur = (cur + 1) % 12;
/* 0-9999 */
CHK_FORMAT(1, 10000, "%llu B", u64);
/* 10.0k - 99.9k */
CHK_FORMAT(1024, 99.95, "%0.01f kB", double);
/* 100k - 999k */
CHK_FORMAT(1024, 1000, "%llu kB", u64);
/* 1.00M - 9.99M */
CHK_FORMAT(1024 * 1024, 9.995, "%0.02f MB", double);
/* 10.0M - 99.9M */
CHK_FORMAT(1024 * 1024, 99.95, "%0.01f MB", double);
/* 100M - 999M */
CHK_FORMAT(1024 * 1024, 1000, "%llu MB", u64);
/* 1.00G - 9.99G */
CHK_FORMAT(1024LL * 1024 * 1024, 9.995, "%0.02f GB", double);
/* 10.0G - 99.9G */
CHK_FORMAT(1024LL * 1024 * 1024, 99.95, "%0.01f GB", double);
/* 100G - 999G */
CHK_FORMAT(1024LL * 1024 * 1024, 1000, "%llu GB", u64);
/* 1.00T - 9.99G */
CHK_FORMAT(1024LL * 1024 * 1024 * 1024, 9.995, "%0.02f TB", double);
/* 10.0T - 99.9T */
CHK_FORMAT(1024LL * 1024 * 1024 * 1024, 99.95, "%0.01f TB", double);
#undef CHK_FORMAT
/* 100T+ */
strcpy(tmp[cur], "infty");
return tmp[cur];
}
/* Write results. */
static u32 write_results(u8 *out_path) {
s32 fd;
u32 i, ret = 0;
if(no_output) {
return 0;
}
u8 cco = !!getenv("AFL_CMIN_CRASHES_ONLY"),
caa = !!getenv("AFL_CMIN_ALLOW_ANY");
if (!strncmp(out_path, "/dev/", 5))
{
fd = open(out_path, O_WRONLY, 0600);
if (fd < 0)
PFATAL("Unable to open '%s'", out_path);
} else
{
unlink(out_path); /* Ignore errors */
fd = open(out_path, O_WRONLY | O_CREAT | O_EXCL, 0600);
if (fd < 0)
PFATAL("Unable to create '%s'", out_path);
}
if (binary_mode) {
for (i = 0; i < MAP_SIZE; i++)
if (trace_bits[i]) ret++;
ck_write(fd, trace_bits, MAP_SIZE, out_path);
close(fd);
} else {
FILE* f = fdopen(fd, "w");
if (!f) PFATAL("fdopen() failed");
for (i = 0; i < MAP_SIZE; i++) {
if (!trace_bits[i]) continue;
ret++;
if (cmin_mode) {
if (child_timed_out) break;
if (!caa && child_crashed != cco) break;
fprintf(f, "%u%u\n", trace_bits[i], i);
} else fprintf(f, "%06u:%u\n", i, trace_bits[i]);
}
fclose(f);
}
return ret;
}
/* Handle timeout signal. */
static void handle_timeout(int sig) {
child_timed_out = 1;
if (child_pid > 0) kill(child_pid, SIGKILL);
}
/* Execute target application. */
static void run_target(char** argv) {
static struct itimerval it;
static u32 prev_timed_out = 0;
int status = 0;
if (!quiet_mode)
SAYF("-- Program output begins --\n" cRST);
memset(trace_bits, 0, MAP_SIZE);
MEM_BARRIER();
s32 res;
if (in_path) {
/* we have the fork server up and running, so simply
tell it to have at it, and then read back PID. */
if ((res = write(fsrv_ctl_fd, &prev_timed_out, 4)) != 4) {
if (stop_soon) return;
RPFATAL(res, "Unable to request new process from fork server (OOM?)");
}
if ((res = read(fsrv_st_fd, &child_pid, 4)) != 4) {
if (stop_soon) return;
RPFATAL(res, "Unable to request new process from fork server (OOM?)");
}
if (child_pid <= 0) FATAL("Fork server is misbehaving (OOM?)");
} else {
child_pid = fork();
if (child_pid < 0) PFATAL("fork() failed");
if (!child_pid) {
struct rlimit r;
if (quiet_mode) {
s32 fd = open("/dev/null", O_RDWR);
if (fd < 0 || dup2(fd, 1) < 0 || dup2(fd, 2) < 0) {
*(u32*)trace_bits = EXEC_FAIL_SIG;
PFATAL("Descriptor initialization failed");
}
close(fd);
}
if (mem_limit) {
r.rlim_max = r.rlim_cur = ((rlim_t)mem_limit) << 20;
#ifdef RLIMIT_AS
setrlimit(RLIMIT_AS, &r); /* Ignore errors */
#else
setrlimit(RLIMIT_DATA, &r); /* Ignore errors */
#endif /* ^RLIMIT_AS */
}
if (!keep_cores) r.rlim_max = r.rlim_cur = 0;
else r.rlim_max = r.rlim_cur = RLIM_INFINITY;
setrlimit(RLIMIT_CORE, &r); /* Ignore errors */
if (!getenv("LD_BIND_LAZY")) setenv("LD_BIND_NOW", "1", 0);
setsid();
execv(target_path, argv);
*(u32*)trace_bits = EXEC_FAIL_SIG;
exit(0);
}
}
/* Configure timeout, wait for child, cancel timeout. */
if (exec_tmout) {
child_timed_out = 0;
it.it_value.tv_sec = (exec_tmout / 1000);
it.it_value.tv_usec = (exec_tmout % 1000) * 1000;
}
setitimer(ITIMER_REAL, &it, NULL);
if(in_path) {
if ((res = read(fsrv_st_fd, &status, 4)) != 4) {
if (stop_soon) return;
RPFATAL(res, "Unable to communicate with fork server (OOM?)");
}
} else {
if (waitpid(child_pid, &status, 0) <= 0) FATAL("waitpid() failed");
}
child_pid = 0;
it.it_value.tv_sec = 0;
it.it_value.tv_usec = 0;
setitimer(ITIMER_REAL, &it, NULL);
MEM_BARRIER();
/* Clean up bitmap, analyze exit condition, etc. */
if (*(u32*)trace_bits == EXEC_FAIL_SIG)
FATAL("Unable to execute '%s'", argv[0]);
classify_counts(trace_bits, binary_mode ?
count_class_binary : count_class_human);
if (!quiet_mode)
SAYF(cRST "-- Program output ends --\n");
if (!child_timed_out && !stop_soon && WIFSIGNALED(status))
child_crashed = 1;
if (!quiet_mode) {
if (child_timed_out)
SAYF(cLRD "\n+++ Program timed off +++\n" cRST);
else if (stop_soon)
SAYF(cLRD "\n+++ Program aborted by user +++\n" cRST);
else if (child_crashed)
SAYF(cLRD "\n+++ Program killed by signal %u +++\n" cRST, WTERMSIG(status));
}
}
/* Handle Ctrl-C and the like. */
static void handle_stop_sig(int sig) {
stop_soon = 1;
if (child_pid > 0) kill(child_pid, SIGKILL);
}
/* Do basic preparations - persistent fds, filenames, etc. */
static void set_up_environment(void) {
setenv("ASAN_OPTIONS", "abort_on_error=1:"
"detect_leaks=0:"
"symbolize=0:"
"allocator_may_return_null=1", 0);
setenv("MSAN_OPTIONS", "exit_code=" STRINGIFY(MSAN_ERROR) ":"
"symbolize=0:"
"abort_on_error=1:"
"allocator_may_return_null=1:"
"msan_track_origins=0", 0);
if (getenv("AFL_PRELOAD")) {
setenv("LD_PRELOAD", getenv("AFL_PRELOAD"), 1);
setenv("DYLD_INSERT_LIBRARIES", getenv("AFL_PRELOAD"), 1);
}
}
/* Setup signal handlers, duh. */
static void setup_signal_handlers(void) {
struct sigaction sa;
sa.sa_handler = NULL;
sa.sa_flags = SA_RESTART;
sa.sa_sigaction = NULL;
sigemptyset(&sa.sa_mask);
/* Various ways of saying "stop". */
sa.sa_handler = handle_stop_sig;
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
/* Exec timeout notifications. */
sa.sa_handler = handle_timeout;
sigaction(SIGALRM, &sa, NULL);
}
/* Detect @@ in args. */
static void detect_file_args(char** argv) {
u32 i = 0;
u8* cwd = getcwd(NULL, 0);
if (!cwd) PFATAL("getcwd() failed");
while (argv[i]) {
u8* aa_loc = strstr(argv[i], "@@");
if (aa_loc) {
using_file_arg = 1;
u8 *aa_subst, *n_arg;
if (!in_path && !at_file)
FATAL("@@ syntax is not supported by this tool.");
if (!at_file)
setup_at_file();
/* Be sure that we're always using fully-qualified paths. */
if (at_file[0] == '/')
aa_subst = at_file;
else
aa_subst = alloc_printf("%s/%s", cwd, at_file);
/* Construct a replacement argv value. */
*aa_loc = 0;
n_arg = alloc_printf("%s%s%s", argv[i], aa_subst, aa_loc + 2);
argv[i] = n_arg;
*aa_loc = '@';
if (at_file[0] != '/')
ck_free(aa_subst);
}
i++;
}
free(cwd); /* not tracked */
}
/* Show banner. */
static void show_banner(void) {
SAYF(cCYA "afl-showmap " cBRI VERSION cRST " by <lcamtuf@google.com>\n");
}
/* Display usage hints. */
static void usage(u8* argv0) {
show_banner();
SAYF("\n%s [ options ] -- /path/to/target_app [ ... ]\n\n"
"Required parameters:\n\n"
" -i file - file or dir to get inputs from\n"
" -o file - file or dir to write the trace data to. Use '-' for no output\n\n"
"Execution control settings:\n\n"
" -t msec - timeout for each run (none)\n"
" -m megs - memory limit for child process (%u MB)\n"
" -Q - use binary-only instrumentation (QEMU mode)\n"
" -U - use Unicorn-based instrumentation (Unicorn mode)\n"
" (Not necessary, here for consistency with other afl-* tools)\n\n"
"Other settings:\n\n"
" -q - sink program's output and don't show messages\n"
" -e - show edge coverage only, ignore hit counts\n"
" -c - allow core dumps\n\n"
"This tool displays raw tuple data captured by AFL instrumentation.\n"
"For additional help, consult %s/README.\n\n" cRST,
argv0, MEM_LIMIT, doc_path);
exit(1);
}
/* Find binary. */
static void find_binary(u8* fname) {
u8* env_path = 0;
struct stat st;
if (strchr(fname, '/') || !(env_path = getenv("PATH"))) {
target_path = ck_strdup(fname);
if (stat(target_path, &st) || !S_ISREG(st.st_mode) ||
!(st.st_mode & 0111) || st.st_size < 4)
FATAL("Program '%s' not found or not executable", fname);
} else {
while (env_path) {
u8 *cur_elem, *delim = strchr(env_path, ':');
if (delim) {
cur_elem = ck_alloc(delim - env_path + 1);
memcpy(cur_elem, env_path, delim - env_path);
delim++;
} else cur_elem = ck_strdup(env_path);
env_path = delim;
if (cur_elem[0])
target_path = alloc_printf("%s/%s", cur_elem, fname);
else
target_path = ck_strdup(fname);
ck_free(cur_elem);
if (!stat(target_path, &st) && S_ISREG(st.st_mode) &&
(st.st_mode & 0111) && st.st_size >= 4) break;
ck_free(target_path);
target_path = 0;
}
if (!target_path) FATAL("Program '%s' not found or not executable", fname);
}
}
/* Fix up argv for QEMU. */
static char** get_qemu_argv(u8* own_loc, char** argv, int argc) {
char** new_argv = ck_alloc(sizeof(char*) * (argc + 4));
u8 *tmp, *cp, *rsl, *own_copy;
/* Workaround for a QEMU stability glitch. */
setenv("QEMU_LOG", "nochain", 1);
memcpy(new_argv + 3, argv + 1, sizeof(char*) * argc);
new_argv[2] = target_path;
new_argv[1] = "--";
/* Now we need to actually find qemu for argv[0]. */
tmp = getenv("AFL_PATH");
if (tmp) {
cp = alloc_printf("%s/afl-qemu-trace", tmp);
if (access(cp, X_OK))
FATAL("Unable to find '%s'", tmp);
target_path = new_argv[0] = cp;
return new_argv;
}
own_copy = ck_strdup(own_loc);
rsl = strrchr(own_copy, '/');
if (rsl) {
*rsl = 0;
cp = alloc_printf("%s/afl-qemu-trace", own_copy);
ck_free(own_copy);
if (!access(cp, X_OK)) {
target_path = new_argv[0] = cp;
return new_argv;
}
} else ck_free(own_copy);
if (!access(BIN_PATH "/afl-qemu-trace", X_OK)) {
target_path = new_argv[0] = BIN_PATH "/afl-qemu-trace";
return new_argv;
}
FATAL("Unable to find 'afl-qemu-trace'.");
}
/* Spin up fork server (instrumented mode only). The idea is explained here:
http://lcamtuf.blogspot.com/2014/10/fuzzing-binaries-without-execve.html
In essence, the instrumentation allows us to skip execve(), and just keep
cloning a stopped child. So, we just execute once, and then send commands
through a pipe. The other part of this logic is in afl-as.h. */
static void init_forkserver(char** argv) {
static struct itimerval it;
int st_pipe[2], ctl_pipe[2];
int status;
s32 rlen;
ACTF("Spinning up the fork server...");
if (pipe(st_pipe) || pipe(ctl_pipe))
PFATAL("pipe() failed");
forksrv_pid = fork();
if (forksrv_pid < 0) PFATAL("fork() failed");
if (!forksrv_pid) {
struct rlimit r;
/* Umpf. On OpenBSD, the default fd limit for root users is set to
soft 128. Let's try to fix that... */
if (!getrlimit(RLIMIT_NOFILE, &r) && r.rlim_cur < FORKSRV_FD + 2) {
r.rlim_cur = FORKSRV_FD + 2;
setrlimit(RLIMIT_NOFILE, &r); /* Ignore errors */
}
if (mem_limit) {
r.rlim_max = r.rlim_cur = ((rlim_t)mem_limit) << 20;
#ifdef RLIMIT_AS
setrlimit(RLIMIT_AS, &r); /* Ignore errors */
#else
/* This takes care of OpenBSD, which doesn't have RLIMIT_AS, but
according to reliable sources, RLIMIT_DATA covers anonymous
maps - so we should be getting good protection against OOM bugs. */
setrlimit(RLIMIT_DATA, &r); /* Ignore errors */
#endif /* ^RLIMIT_AS */
}
/* Dumping cores is slow and can lead to anomalies if SIGKILL is delivered
before the dump is complete. */
r.rlim_max = r.rlim_cur = 0;
setrlimit(RLIMIT_CORE, &r); /* Ignore errors */
/* Isolate the process and configure standard descriptors. If at_path is
specified, stdin is /dev/null; otherwise, at_file_fd is cloned instead. */
setsid();
dup2(dev_null_fd, 1);
dup2(dev_null_fd, 2);
if (using_file_arg) {
dup2(dev_null_fd, 0);
} else {
dup2(at_file_fd, 0);
close(at_file_fd);
}
/* Set up control and status pipes, close the unneeded original fds. */
if (dup2(ctl_pipe[0], FORKSRV_FD) < 0) PFATAL("dup2() failed");
if (dup2(st_pipe[1], FORKSRV_FD + 1) < 0) PFATAL("dup2() failed");
close(ctl_pipe[0]);
close(ctl_pipe[1]);
close(st_pipe[0]);
close(st_pipe[1]);
close(dev_null_fd);
/* This should improve performance a bit, since it stops the linker from
doing extra work post-fork(). */
if (!getenv("LD_BIND_LAZY")) setenv("LD_BIND_NOW", "1", 0);
/* Set sane defaults for ASAN if nothing else specified. */
setenv("ASAN_OPTIONS", "abort_on_error=1:"
"detect_leaks=0:"
"symbolize=0:"
"allocator_may_return_null=1", 0);
/* MSAN is tricky, because it doesn't support abort_on_error=1 at this
point. So, we do this in a very hacky way. */
setenv("MSAN_OPTIONS", "exit_code=" STRINGIFY(MSAN_ERROR) ":"
"symbolize=0:"
"abort_on_error=1:"
"allocator_may_return_null=1:"
"msan_track_origins=0", 0);
execv(target_path, argv);
/* Use a distinctive bitmap signature to tell the parent about execv()
falling through. */
*(u32*)trace_bits = EXEC_FAIL_SIG;
exit(0);
}
/* Close the unneeded endpoints. */
close(ctl_pipe[0]);
close(st_pipe[1]);
fsrv_ctl_fd = ctl_pipe[1];
fsrv_st_fd = st_pipe[0];
/* Wait for the fork server to come up, but don't wait too long. */
it.it_value.tv_sec = ((exec_tmout * FORK_WAIT_MULT) / 1000);
it.it_value.tv_usec = ((exec_tmout * FORK_WAIT_MULT) % 1000) * 1000;
setitimer(ITIMER_REAL, &it, NULL);
rlen = read(fsrv_st_fd, &status, 4);
it.it_value.tv_sec = 0;
it.it_value.tv_usec = 0;
setitimer(ITIMER_REAL, &it, NULL);
/* If we have a four-byte "hello" message from the server, we're all set.
Otherwise, try to figure out what went wrong. */
if (rlen == 4) {
OKF("All right - fork server is up.");
return;
}
if (child_timed_out)
FATAL("Timeout while initializing fork server (adjusting -t may help)");
if (waitpid(forksrv_pid, &status, 0) <= 0) {
PFATAL("waitpid() failed");
}
if (WIFSIGNALED(status)) {
/*if (mem_limit && mem_limit < 500 && uses_asan) {
SAYF("\n" cLRD "[-] " cRST
"Whoops, the target binary crashed suddenly, before receiving any input\n"
" from the fuzzer! Since it seems to be built with ASAN and you have a\n"
" restrictive memory limit configured, this is expected; please read\n"
" %s/notes_for_asan.txt for help.\n", doc_path);
} else */if (!mem_limit) {
SAYF("\n" cLRD "[-] " cRST
"Whoops, the target binary crashed suddenly, before receiving any input\n"
" from the fuzzer! There are several probable explanations:\n\n"
" - The binary is just buggy and explodes entirely on its own. If so, you\n"
" need to fix the underlying problem or find a better replacement.\n\n"
#ifdef __APPLE__
" - On MacOS X, the semantics of fork() syscalls are non-standard and may\n"
" break afl-fuzz performance optimizations when running platform-specific\n"
" targets. To fix this, set AFL_NO_FORKSRV=1 in the environment.\n\n"
#endif /* __APPLE__ */
" - Less likely, there is a horrible bug in the fuzzer. If other options\n"
" fail, poke <lcamtuf@coredump.cx> for troubleshooting tips.\n");
} else {
SAYF("\n" cLRD "[-] " cRST
"Whoops, the target binary crashed suddenly, before receiving any input\n"
" from the fuzzer! There are several probable explanations:\n\n"
" - The current memory limit (%s) is too restrictive, causing the\n"
" target to hit an OOM condition in the dynamic linker. Try bumping up\n"
" the limit with the -m setting in the command line. A simple way confirm\n"
" this diagnosis would be:\n\n"
#ifdef RLIMIT_AS
" ( ulimit -Sv $[%llu << 10]; /path/to/fuzzed_app )\n\n"
#else
" ( ulimit -Sd $[%llu << 10]; /path/to/fuzzed_app )\n\n"
#endif /* ^RLIMIT_AS */
" Tip: you can use http://jwilk.net/software/recidivm to quickly\n"
" estimate the required amount of virtual memory for the binary.\n\n"
" - The binary is just buggy and explodes entirely on its own. If so, you\n"
" need to fix the underlying problem or find a better replacement.\n\n"
#ifdef __APPLE__
" - On MacOS X, the semantics of fork() syscalls are non-standard and may\n"
" break afl-fuzz performance optimizations when running platform-specific\n"
" targets. To fix this, set AFL_NO_FORKSRV=1 in the environment.\n\n"
#endif /* __APPLE__ */
" - Less likely, there is a horrible bug in the fuzzer. If other options\n"
" fail, poke <lcamtuf@coredump.cx> for troubleshooting tips.\n",
DMS(mem_limit << 20), mem_limit - 1);
}