Index: lib/fuzzer/FuzzerDriver.cpp
===================================================================
--- lib/fuzzer/FuzzerDriver.cpp
+++ lib/fuzzer/FuzzerDriver.cpp
@@ -617,6 +617,7 @@
Options.PrintFinalStats = Flags.print_final_stats;
Options.PrintCorpusStats = Flags.print_corpus_stats;
Options.PrintCoverage = Flags.print_coverage;
+ Options.PrintUnstableStats = Flags.print_unstable_stats;
Options.DumpCoverage = Flags.dump_coverage;
if (Flags.exit_on_src_pos)
Options.ExitOnSrcPos = Flags.exit_on_src_pos;
Index: lib/fuzzer/FuzzerFlags.def
===================================================================
--- lib/fuzzer/FuzzerFlags.def
+++ lib/fuzzer/FuzzerFlags.def
@@ -110,6 +110,8 @@
FUZZER_FLAG_INT(dump_coverage, 0, "Deprecated."
" If 1, dump coverage information as a"
" .sancov file at exit.")
+FUZZER_FLAG_INT(print_unstable_stats, 0, "Experimental."
+ " If 1, print unstable statistics at exit.")
FUZZER_FLAG_INT(handle_segv, 1, "If 1, try to intercept SIGSEGV.")
FUZZER_FLAG_INT(handle_bus, 1, "If 1, try to intercept SIGBUS.")
FUZZER_FLAG_INT(handle_abrt, 1, "If 1, try to intercept SIGABRT.")
Index: lib/fuzzer/FuzzerInternal.h
===================================================================
--- lib/fuzzer/FuzzerInternal.h
+++ lib/fuzzer/FuzzerInternal.h
@@ -67,6 +67,7 @@
static void StaticGracefulExitCallback();
void ExecuteCallback(const uint8_t *Data, size_t Size);
+ void CheckForUnstableCounters(const uint8_t *Data, size_t Size);
bool RunOne(const uint8_t *Data, size_t Size, bool MayDeleteFile = false,
InputInfo *II = nullptr, bool *FoundUniqFeatures = nullptr);
Index: lib/fuzzer/FuzzerLoop.cpp
===================================================================
--- lib/fuzzer/FuzzerLoop.cpp
+++ lib/fuzzer/FuzzerLoop.cpp
@@ -352,6 +352,8 @@
void Fuzzer::PrintFinalStats() {
if (Options.PrintCoverage)
TPC.PrintCoverage();
+ if (Options.PrintUnstableStats)
+ TPC.PrintUnstableStats();
if (Options.DumpCoverage)
TPC.DumpCoverage();
if (Options.PrintCorpusStats)
@@ -444,6 +446,29 @@
}
}
+void Fuzzer::CheckForUnstableCounters(const uint8_t *Data, size_t Size) {
+ auto CBSetupAndRun = [&]() {
+ ScopedEnableMsanInterceptorChecks S;
+ UnitStartTime = system_clock::now();
+ TPC.ResetMaps();
+ RunningCB = true;
+ CB(Data, Size);
+ RunningCB = false;
+ UnitStopTime = system_clock::now();
+ };
+
+ // Copy original run counters into our unstable counters
+ TPC.InitializeUnstableCounters();
+
+ // First Rerun
+ CBSetupAndRun();
+ TPC.UpdateUnstableCounters();
+
+ // Second Rerun
+ CBSetupAndRun();
+ TPC.UpdateUnstableCounters();
+}
+
bool Fuzzer::RunOne(const uint8_t *Data, size_t Size, bool MayDeleteFile,
InputInfo *II, bool *FoundUniqFeatures) {
if (!Size)
@@ -466,6 +491,12 @@
*FoundUniqFeatures = FoundUniqFeaturesOfII;
PrintPulseAndReportSlowInput(Data, Size);
size_t NumNewFeatures = Corpus.NumFeatureUpdates() - NumUpdatesBefore;
+
+ // If print_unstable_stats, execute the same input two more times to detect
+ // unstable edges.
+ if (NumNewFeatures && Options.PrintUnstableStats)
+ CheckForUnstableCounters(Data, Size);
+
if (NumNewFeatures) {
TPC.UpdateObservedPCs();
Corpus.AddToCorpus({Data, Data + Size}, NumNewFeatures, MayDeleteFile,
Index: lib/fuzzer/FuzzerOptions.h
===================================================================
--- lib/fuzzer/FuzzerOptions.h
+++ lib/fuzzer/FuzzerOptions.h
@@ -54,6 +54,7 @@
bool PrintFinalStats = false;
bool PrintCorpusStats = false;
bool PrintCoverage = false;
+ bool PrintUnstableStats = false;
bool DumpCoverage = false;
bool DetectLeaks = true;
int PurgeAllocatorIntervalSec = 1;
Index: lib/fuzzer/FuzzerTracePC.h
===================================================================
--- lib/fuzzer/FuzzerTracePC.h
+++ lib/fuzzer/FuzzerTracePC.h
@@ -103,6 +103,7 @@
void PrintCoverage();
void DumpCoverage();
+ void PrintUnstableStats();
template<class CallBack>
void IterateCoveredFunctions(CallBack CB);
@@ -135,7 +136,17 @@
void SetFocusFunction(const std::string &FuncName);
bool ObservedFocusFunction();
+ void InitializeUnstableCounters();
+ void UpdateUnstableCounters();
+
private:
+ // Value used to represent unstable edge.
+ static constexpr int16_t kUnstableCounter = -1;
+
+ // Uses 16-bit signed type to be able to accommodate any possible value from
+ // uint8_t counter and -1 constant as well.
+ int16_t UnstableCounters[kNumPCs];
+
bool UseCounters = false;
uint32_t UseValueProfileMask = false;
bool DoPrintNewPCs = false;
Index: lib/fuzzer/FuzzerTracePC.cpp
===================================================================
--- lib/fuzzer/FuzzerTracePC.cpp
+++ lib/fuzzer/FuzzerTracePC.cpp
@@ -59,6 +59,37 @@
return Res;
}
+// Initializes unstable counters by copying Inline8bitCounters to unstable
+// counters.
+void TracePC::InitializeUnstableCounters() {
+ if (NumInline8bitCounters && NumInline8bitCounters == NumPCsInPCTables) {
+ size_t UnstableIdx = 0;
+ for (size_t i = 0; i < NumModulesWithInline8bitCounters; i++) {
+ uint8_t *Beg = ModuleCounters[i].Start;
+ size_t Size = ModuleCounters[i].Stop - Beg;
+ assert(Size == (size_t)(ModulePCTable[i].Stop - ModulePCTable[i].Start));
+ for (size_t j = 0; j < Size; j++, UnstableIdx++)
+ if (UnstableCounters[UnstableIdx] != kUnstableCounter)
+ UnstableCounters[UnstableIdx] = Beg[j];
+ }
+ }
+}
+
+// Compares the current counters with counters from previous runs
+// and records differences as unstable edges.
+void TracePC::UpdateUnstableCounters() {
+ if (NumInline8bitCounters && NumInline8bitCounters == NumPCsInPCTables) {
+ size_t UnstableIdx = 0;
+ for (size_t i = 0; i < NumModulesWithInline8bitCounters; i++) {
+ uint8_t *Beg = ModuleCounters[i].Start;
+ size_t Size = ModuleCounters[i].Stop - Beg;
+ assert(Size == (size_t)(ModulePCTable[i].Stop - ModulePCTable[i].Start));
+ for (size_t j = 0; j < Size; j++, UnstableIdx++)
+ if (Beg[j] != UnstableCounters[UnstableIdx])
+ UnstableCounters[UnstableIdx] = kUnstableCounter;
+ }
+ }
+}
void TracePC::HandleInline8bitCountersInit(uint8_t *Start, uint8_t *Stop) {
if (Start == Stop) return;
@@ -310,6 +341,15 @@
}
}
+void TracePC::PrintUnstableStats() {
+ size_t count = 0;
+ for (size_t i = 0; i < NumInline8bitCounters; i++)
+ if (UnstableCounters[i] == kUnstableCounter)
+ count++;
+ Printf("stat::stability_rate: %.2f\n",
+ 100 - static_cast<float>(count * 100) / NumInline8bitCounters);
+}
+
// Value profile.
// We keep track of various values that affect control flow.
// These values are inserted into a bit-set-based hash map.
Index: test/fuzzer/PrintUnstableStatsTest.cpp
===================================================================
--- test/fuzzer/PrintUnstableStatsTest.cpp
+++ test/fuzzer/PrintUnstableStatsTest.cpp
@@ -0,0 +1,69 @@
+#include <assert.h>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+
+int x = 0;
+bool skip0 = false;
+bool skip1 = false;
+bool skip2 = false;
+
+__attribute__((noinline)) void det0() { x++; }
+__attribute__((noinline)) void det1() { x++; }
+__attribute__((noinline)) void det2() { x++; }
+__attribute__((noinline)) void det3() { x++; }
+__attribute__((noinline)) void det4() { x++; }
+
+__attribute__((noinline)) void ini0() { x++; }
+__attribute__((noinline)) void ini1() { x++; }
+__attribute__((noinline)) void ini2() { x++; }
+
+__attribute__((noinline)) void t0() { x++; }
+__attribute__((noinline)) void t1() { x++; }
+__attribute__((noinline)) void t2() { x++; }
+__attribute__((noinline)) void t3() { x++; }
+__attribute__((noinline)) void t4() { x++; }
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+ if (Size == 1 && Data[0] == 'A' && !skip0) {
+ skip0 = true;
+ ini0();
+ }
+ if (Size == 1 && Data[0] == 'B' && !skip1) {
+ skip1 = true;
+ ini1();
+ }
+ if (Size == 1 && Data[0] == 'C' && !skip2) {
+ skip2 = true;
+ ini2();
+ }
+
+ det0();
+ det1();
+ int a = rand();
+ det2();
+
+ switch (a % 5) {
+ case 0:
+ t0();
+ break;
+ case 1:
+ t1();
+ break;
+ case 2:
+ t2();
+ break;
+ case 3:
+ t3();
+ break;
+ case 4:
+ t4();
+ break;
+ default:
+ assert(false);
+ }
+
+ det3();
+ det4();
+ return 0;
+}
Index: test/fuzzer/print_unstable_stats.test
===================================================================
--- test/fuzzer/print_unstable_stats.test
+++ test/fuzzer/print_unstable_stats.test
@@ -0,0 +1,3 @@
+RUN: %cpp_compiler %S/PrintUnstableStatsTest.cpp -o %t-PrintUnstableStatsTest
+RUN: %run %t-PrintUnstableStatsTest -print_unstable_stats=1 -runs=100000 2>&1 | FileCheck %s --check-prefix=LONG
+LONG: stat::stability_rate: 27.59