[libFuzzer] Periodically purge allocator's quarantine to prolong fuzzing sessions.
Summary:
Fuzzing targets that allocate/deallocate a lot of memory tend to consume
a lot of RSS when ASan quarantine is enabled. Purging quarantine between
iterations and returning memory to OS keeps RSS down and should not
reduce the quarantine effectiveness provided the fuzz target does not
preserve state between iterations (in this case this feature can be turned off).
Based on D39153.
Reviewers: vitalybuka
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D39155
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@316382 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerDriver.cpp b/FuzzerDriver.cpp
index 29248dc..18c73ca 100644
--- a/FuzzerDriver.cpp
+++ b/FuzzerDriver.cpp
@@ -578,6 +578,7 @@
Options.ReloadIntervalSec = Flags.reload;
Options.OnlyASCII = Flags.only_ascii;
Options.DetectLeaks = Flags.detect_leaks;
+ Options.PurgeAllocatorIntervalSec = Flags.purge_allocator_interval;
Options.TraceMalloc = Flags.trace_malloc;
Options.RssLimitMb = Flags.rss_limit_mb;
if (Flags.runs >= 0)
diff --git a/FuzzerExtFunctions.def b/FuzzerExtFunctions.def
index 3bc5302..25a655b 100644
--- a/FuzzerExtFunctions.def
+++ b/FuzzerExtFunctions.def
@@ -33,6 +33,7 @@
(void (*malloc_hook)(const volatile void *, size_t),
void (*free_hook)(const volatile void *)),
false);
+EXT_FUNC(__sanitizer_purge_allocator, void, (), false);
EXT_FUNC(__sanitizer_print_memory_profile, int, (size_t, size_t), false);
EXT_FUNC(__sanitizer_print_stack_trace, void, (), true);
EXT_FUNC(__sanitizer_symbolize_pc, void,
diff --git a/FuzzerFlags.def b/FuzzerFlags.def
index efbc067..e4bca46 100644
--- a/FuzzerFlags.def
+++ b/FuzzerFlags.def
@@ -114,6 +114,10 @@
"Be careful, this will also close e.g. asan's stderr/stdout.")
FUZZER_FLAG_INT(detect_leaks, 1, "If 1, and if LeakSanitizer is enabled "
"try to detect memory leaks during fuzzing (i.e. not only at shut down).")
+FUZZER_FLAG_INT(purge_allocator_interval, 1, "Purge allocator caches and "
+ "quarantines every <N> seconds. When rss_limit_mb is specified (>0), "
+ "purging starts when RSS exceeds 50% of rss_limit_mb. Pass "
+ "purge_allocator_interval=-1 to disable this functionality.")
FUZZER_FLAG_INT(trace_malloc, 0, "If >= 1 will print all mallocs/frees. "
"If >= 2 will also print stack traces.")
FUZZER_FLAG_INT(rss_limit_mb, 2048, "If non-zero, the fuzzer will exit upon"
diff --git a/FuzzerInternal.h b/FuzzerInternal.h
index 34fdeb8..97c1408 100644
--- a/FuzzerInternal.h
+++ b/FuzzerInternal.h
@@ -96,6 +96,7 @@
void CrashOnOverwrittenData();
void InterruptCallback();
void MutateAndTestOne();
+ void PurgeAllocator();
void ReportNewCoverage(InputInfo *II, const Unit &U);
void PrintPulseAndReportSlowInput(const uint8_t *Data, size_t Size);
void WriteToOutputCorpus(const Unit &U);
@@ -124,6 +125,8 @@
bool HasMoreMallocsThanFrees = false;
size_t NumberOfLeakDetectionAttempts = 0;
+ system_clock::time_point LastAllocatorPurgeAttemptTime = system_clock::now();
+
UserCallback CB;
InputCorpus &Corpus;
MutationDispatcher &MD;
diff --git a/FuzzerLoop.cpp b/FuzzerLoop.cpp
index 30844e3..58e8168 100644
--- a/FuzzerLoop.cpp
+++ b/FuzzerLoop.cpp
@@ -587,7 +587,7 @@
size_t NewSize = 0;
NewSize = MD.Mutate(CurrentUnitData, Size, CurrentMaxMutationLen);
assert(NewSize > 0 && "Mutator returned empty unit");
- assert(NewSize <= CurrentMaxMutationLen && "Mutator return overisized unit");
+ assert(NewSize <= CurrentMaxMutationLen && "Mutator return oversized unit");
Size = NewSize;
II.NumExecutedMutations++;
if (RunOne(CurrentUnitData, Size, /*MayDeleteFile=*/true, &II))
@@ -598,6 +598,25 @@
}
}
+void Fuzzer::PurgeAllocator() {
+ if (Options.PurgeAllocatorIntervalSec < 0 ||
+ !EF->__sanitizer_purge_allocator) {
+ return;
+ }
+ if (duration_cast<seconds>(system_clock::now() -
+ LastAllocatorPurgeAttemptTime).count() <
+ Options.PurgeAllocatorIntervalSec) {
+ return;
+ }
+
+ if (Options.RssLimitMb <= 0 ||
+ GetPeakRSSMb() > static_cast<size_t>(Options.RssLimitMb) / 2) {
+ EF->__sanitizer_purge_allocator();
+ }
+
+ LastAllocatorPurgeAttemptTime = system_clock::now();
+}
+
void Fuzzer::ReadAndExecuteSeedCorpora(const Vector<std::string> &CorpusDirs) {
const size_t kMaxSaneLen = 1 << 20;
const size_t kMinDefaultLen = 4096;
@@ -699,6 +718,8 @@
// Perform several mutations and runs.
MutateAndTestOne();
+
+ PurgeAllocator();
}
PrintStats("DONE ", "\n");
diff --git a/FuzzerOptions.h b/FuzzerOptions.h
index e57c7df..73953e1 100644
--- a/FuzzerOptions.h
+++ b/FuzzerOptions.h
@@ -54,6 +54,7 @@
bool DumpCoverage = false;
bool UseClangCoverage = false;
bool DetectLeaks = true;
+ int PurgeAllocatorIntervalSec = 1;
int UseFeatureFrequency = false;
int TraceMalloc = 0;
bool HandleAbrt = false;