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[libFuzzer] Add feature to not use AFL's deferred forkserver. 

A small but substantial minority of libFuzzer-based fuzzers run code that
does not play well with fork in global constructors or LLVMFuzzerInitialize.
This patch allows these fuzzers to use afl_driver by allowing them to
opt-out of using AFL's deferred forkserver which deferres calling fork until
after this code.

Patch By: metzman

Differential Revision: https://reviews.llvm.org/D45744

llvm-svn: 330652
This commit is contained in:
Matt Morehouse 2018-04-23 21:36:21 +00:00
parent 6ed0fad999
commit f66221c6ec
1 changed files with 13 additions and 1 deletions
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14
compiler-rt/lib/fuzzer/afl/afl_driver.cpp
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@ -138,6 +138,17 @@ static const int kNumExtraStats = 2;
static const char *kExtraStatsFormatString = "peak_rss_mb : %u\n"
"slowest_unit_time_sec : %u\n";
// Experimental feature to use afl_driver without AFL's deferred mode.
// Needs to run before __afl_auto_init.
__attribute__((constructor(0))) void __decide_deferred_forkserver(void) {
if (getenv("AFL_DRIVER_DONT_DEFER")) {
if (unsetenv("__AFL_DEFER_FORKSRV")) {
perror("Failed to unset __AFL_DEFER_FORKSRV");
abort();
}
}
}
// Copied from FuzzerUtil.cpp.
size_t GetPeakRSSMb() {
struct rusage usage;
@ -315,7 +326,8 @@ int main(int argc, char **argv) {
maybe_duplicate_stderr();
maybe_initialize_extra_stats();
__afl_manual_init();
if (!getenv("AFL_DRIVER_DONT_DEFER"))
__afl_manual_init();
int N = 1000;
if (argc == 2 && argv[1][0] == '-')