[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/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