[sanitizer/coverage] Add AFL-style coverage counters (search heuristic for fuzzing).
Introduce -mllvm -sanitizer-coverage-8bit-counters=1
which adds imprecise thread-unfriendly 8-bit coverage counters.
The run-time library maps these 8-bit counters to 8-bit bitsets in the same way
AFL (http://lcamtuf.coredump.cx/afl/technical_details.txt) does:
counter values are divided into 8 ranges and based on the counter
value one of the bits in the bitset is set.
The AFL ranges are used here: 1, 2, 3, 4-7, 8-15, 16-31, 32-127, 128+.
These counters provide a search heuristic for single-threaded
coverage-guided fuzzers, we do not expect them to be useful for other purposes.
Depending on the value of -fsanitize-coverage=[123] flag,
these counters will be added to the function entry blocks (=1),
every basic block (=2), or every edge (=3).
Use these counters as an optional search heuristic in the Fuzzer library.
Add a test where this heuristic is critical.
llvm-svn: 231166
diff --git a/llvm/lib/Fuzzer/FuzzerDriver.cpp b/llvm/lib/Fuzzer/FuzzerDriver.cpp
index 1746afd..9ccd744 100644
--- a/llvm/lib/Fuzzer/FuzzerDriver.cpp
+++ b/llvm/lib/Fuzzer/FuzzerDriver.cpp
@@ -158,6 +158,7 @@
Options.DoCrossOver = Flags.cross_over;
Options.MutateDepth = Flags.mutate_depth;
Options.ExitOnFirst = Flags.exit_on_first;
+ Options.UseCounters = Flags.use_counters;
Options.UseFullCoverageSet = Flags.use_full_coverage_set;
Options.UseCoveragePairs = Flags.use_coverage_pairs;
Options.PreferSmallDuringInitialShuffle =
diff --git a/llvm/lib/Fuzzer/FuzzerFlags.def b/llvm/lib/Fuzzer/FuzzerFlags.def
index 068f245..08176af 100644
--- a/llvm/lib/Fuzzer/FuzzerFlags.def
+++ b/llvm/lib/Fuzzer/FuzzerFlags.def
@@ -32,6 +32,7 @@
FUZZER_FLAG(
int, save_minimized_corpus, 0,
"If 1, the minimized corpus is saved into the first input directory")
+FUZZER_FLAG(int, use_counters, 0, "Use coverage counters")
FUZZER_FLAG(int, use_full_coverage_set, 0,
"Experimental: Maximize the number of different full"
" coverage sets as opposed to maximizing the total coverage."
diff --git a/llvm/lib/Fuzzer/FuzzerInternal.h b/llvm/lib/Fuzzer/FuzzerInternal.h
index 980b00e..e4e5eb7 100644
--- a/llvm/lib/Fuzzer/FuzzerInternal.h
+++ b/llvm/lib/Fuzzer/FuzzerInternal.h
@@ -48,6 +48,7 @@
bool DoCrossOver = true;
int MutateDepth = 5;
bool ExitOnFirst = false;
+ bool UseCounters = false;
bool UseFullCoverageSet = false;
bool UseCoveragePairs = false;
int PreferSmallDuringInitialShuffle = -1;
@@ -95,6 +96,15 @@
std::vector<Unit> Corpus;
std::unordered_set<uintptr_t> FullCoverageSets;
std::unordered_set<uint64_t> CoveragePairs;
+
+ // For UseCounters
+ std::vector<uint8_t> CounterBitmap;
+ size_t TotalBits() { // Slow. Call it only for printing stats.
+ size_t Res = 0;
+ for (auto x : CounterBitmap) Res += __builtin_popcount(x);
+ return Res;
+ }
+
UserCallback Callback;
FuzzingOptions Options;
system_clock::time_point ProcessStartTime = system_clock::now();
diff --git a/llvm/lib/Fuzzer/FuzzerLoop.cpp b/llvm/lib/Fuzzer/FuzzerLoop.cpp
index 70b63eb..563fbf4 100644
--- a/llvm/lib/Fuzzer/FuzzerLoop.cpp
+++ b/llvm/lib/Fuzzer/FuzzerLoop.cpp
@@ -138,17 +138,28 @@
}
size_t Fuzzer::RunOneMaximizeTotalCoverage(const Unit &U) {
+ size_t NumCounters = __sanitizer_get_number_of_counters();
+ if (Options.UseCounters) {
+ CounterBitmap.resize(NumCounters);
+ __sanitizer_update_counter_bitset_and_clear_counters(0);
+ }
size_t OldCoverage = __sanitizer_get_total_unique_coverage();
Callback(U.data(), U.size());
size_t NewCoverage = __sanitizer_get_total_unique_coverage();
+ size_t NumNewBits = 0;
+ if (Options.UseCounters)
+ NumNewBits = __sanitizer_update_counter_bitset_and_clear_counters(
+ CounterBitmap.data());
+
if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) && Options.Verbosity) {
size_t Seconds = secondsSinceProcessStartUp();
std::cerr
<< "#" << TotalNumberOfRuns
<< "\tcov: " << NewCoverage
+ << "\tbits: " << TotalBits()
<< "\texec/s: " << (Seconds ? TotalNumberOfRuns / Seconds : 0) << "\n";
}
- if (NewCoverage > OldCoverage)
+ if (NewCoverage > OldCoverage || NumNewBits)
return NewCoverage;
return 0;
}
@@ -189,6 +200,7 @@
if (Options.Verbosity) {
std::cerr << "#" << TotalNumberOfRuns
<< "\tNEW: " << NewCoverage
+ << " B: " << TotalBits()
<< " L: " << U->size()
<< " S: " << Corpus.size()
<< " I: " << i
diff --git a/llvm/lib/Fuzzer/test/CMakeLists.txt b/llvm/lib/Fuzzer/test/CMakeLists.txt
index bed9cd8..08130c6 100644
--- a/llvm/lib/Fuzzer/test/CMakeLists.txt
+++ b/llvm/lib/Fuzzer/test/CMakeLists.txt
@@ -5,6 +5,7 @@
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O0 -fsanitize-coverage=4")
set(Tests
+ CounterTest
FourIndependentBranchesTest
FullCoverageSetTest
InfiniteTest
diff --git a/llvm/lib/Fuzzer/test/CounterTest.cpp b/llvm/lib/Fuzzer/test/CounterTest.cpp
new file mode 100644
index 0000000..332ccfe
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/CounterTest.cpp
@@ -0,0 +1,14 @@
+// Test for a fuzzer: must find the case where a particular basic block is
+// executed many times.
+#include <iostream>
+
+extern "C" void TestOneInput(const uint8_t *Data, size_t Size) {
+ int Num = 0;
+ for (size_t i = 0; i < Size; i++)
+ if (Data[i] == 'A' + i)
+ Num++;
+ if (Num >= 4) {
+ std::cerr << "BINGO!\n";
+ exit(1);
+ }
+}
diff --git a/llvm/lib/Fuzzer/test/fuzzer.test b/llvm/lib/Fuzzer/test/fuzzer.test
index 1e42e72..45691f5 100644
--- a/llvm/lib/Fuzzer/test/fuzzer.test
+++ b/llvm/lib/Fuzzer/test/fuzzer.test
@@ -17,3 +17,6 @@
RUN: not ./LLVMFuzzer-FourIndependentBranchesTest -timeout=15 -seed=1 -use_coverage_pairs=1 2>&1 | FileCheck %s --check-prefix=FourIndependentBranchesTest
FourIndependentBranchesTest: BINGO
+
+RUN: not ./LLVMFuzzer-CounterTest -use_counters=1 -max_len=6 -seed=1 -timeout=15 2>&1 | FileCheck %s --check-prefix=CounterTest
+CounterTest: BINGO