[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
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@330652 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/afl/afl_driver.cpp b/afl/afl_driver.cpp
index 9f50ddd..fa494c0 100644
--- a/afl/afl_driver.cpp
+++ b/afl/afl_driver.cpp
@@ -138,6 +138,17 @@
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 @@
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] == '-')