[libFuzzer] new experimental feature: value profiling. Profiles values that affect control flow and treats new values as new coverage.
llvm-svn: 278839
diff --git a/llvm/lib/Fuzzer/FuzzerTraceState.cpp b/llvm/lib/Fuzzer/FuzzerTraceState.cpp
index 6f87fca..9eae068 100644
--- a/llvm/lib/Fuzzer/FuzzerTraceState.cpp
+++ b/llvm/lib/Fuzzer/FuzzerTraceState.cpp
@@ -173,6 +173,7 @@
static bool RecordingTraces = false;
static bool RecordingMemcmp = false;
static bool RecordingMemmem = false;
+static bool RecordingValueProfile = false;
static bool DoingMyOwnMemmem = false;
struct ScopedDoingMyOwnMemmem {
@@ -529,11 +530,60 @@
return Len;
}
+// Value profile.
+// We keep track of various values that affect control flow.
+// These values are inserted into a bit-set-based hash map (ValueBitMap VP).
+// Every new bit in the map is treated as a new coverage.
+//
+// For memcmp/strcmp/etc the interesting value is the length of the common
+// prefix of the parameters.
+// For cmp instructions the interesting value is a XOR of the parameters.
+// The interesting value is mixed up with the PC and is then added to the map.
+static ValueBitMap VP;
+
+void EnableValueProfile() { RecordingValueProfile = true; }
+
+size_t VPMapMergeFromCurrent(ValueBitMap &M) {
+ if (!RecordingValueProfile) return 0;
+ return M.MergeFrom(VP);
+}
+
+static void AddValueForMemcmp(void *caller_pc, const void *s1, const void *s2,
+ size_t n) {
+ if (!n) return;
+ size_t Len = std::min(n, (size_t)32);
+ const char *A1 = reinterpret_cast<const char *>(s1);
+ const char *A2 = reinterpret_cast<const char *>(s2);
+ size_t LastSameByte = 0;
+ for (; LastSameByte < Len; LastSameByte++)
+ if (A1[LastSameByte] != A2[LastSameByte])
+ break;
+ size_t PC = reinterpret_cast<size_t>(caller_pc);
+ VP.AddValue((PC & 4095) | (LastSameByte << 12));
+}
+
+static void AddValueForStrcmp(void *caller_pc, const char *s1, const char *s2,
+ size_t n) {
+ if (!n) return;
+ size_t Len = std::min(n, (size_t)32);
+ size_t LastSameByte = 0;
+ for (; LastSameByte < Len; LastSameByte++)
+ if (s1[LastSameByte] != s2[LastSameByte] || s1[LastSameByte] == 0)
+ break;
+ size_t PC = reinterpret_cast<size_t>(caller_pc);
+ VP.AddValue((PC & 4095) | (LastSameByte << 12));
+}
+
+static void AddValueForCmp(uintptr_t PC, uint64_t Arg1, uint64_t Arg2) {
+ VP.AddValue((PC & 4095) | (__builtin_popcountl(Arg1 ^ Arg2) << 12));
+}
+
} // namespace fuzzer
using fuzzer::TS;
using fuzzer::RecordingTraces;
using fuzzer::RecordingMemcmp;
+using fuzzer::RecordingValueProfile;
extern "C" {
void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
@@ -597,6 +647,8 @@
#if LLVM_FUZZER_DEFINES_SANITIZER_WEAK_HOOOKS
void __sanitizer_weak_hook_memcmp(void *caller_pc, const void *s1,
const void *s2, size_t n, int result) {
+ if (RecordingValueProfile)
+ fuzzer::AddValueForMemcmp(caller_pc, s1, s2, n);
if (!RecordingMemcmp) return;
if (result == 0) return; // No reason to mutate.
if (n <= 1) return; // Not interesting.
@@ -606,6 +658,8 @@
void __sanitizer_weak_hook_strncmp(void *caller_pc, const char *s1,
const char *s2, size_t n, int result) {
+ if (RecordingValueProfile)
+ fuzzer::AddValueForStrcmp(caller_pc, s1, s2, n);
if (!RecordingMemcmp) return;
if (result == 0) return; // No reason to mutate.
size_t Len1 = fuzzer::InternalStrnlen(s1, n);
@@ -619,6 +673,8 @@
void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
const char *s2, int result) {
+ if (RecordingValueProfile)
+ fuzzer::AddValueForStrcmp(caller_pc, s1, s2, 64);
if (!RecordingMemcmp) return;
if (result == 0) return; // No reason to mutate.
size_t Len1 = strlen(s1);
@@ -656,11 +712,15 @@
__attribute__((visibility("default")))
void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
uint64_t Arg2) {
- if (!RecordingTraces) return;
- uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
- uint64_t CmpSize = (SizeAndType >> 32) / 8;
- uint64_t Type = (SizeAndType << 32) >> 32;
- TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
+ if (RecordingTraces) {
+ uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
+ uint64_t CmpSize = (SizeAndType >> 32) / 8;
+ uint64_t Type = (SizeAndType << 32) >> 32;
+ TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
+ }
+ if (RecordingValueProfile)
+ fuzzer::AddValueForCmp(
+ reinterpret_cast<uintptr_t>(__builtin_return_address(0)), Arg1, Arg2);
}
__attribute__((visibility("default")))