1 files changed, 71 insertions, 0 deletions
diff --git a/lib/Fuzzer/FuzzerTracePC.cpp b/lib/Fuzzer/FuzzerTracePC.cpp
new file mode 100644
index 0000000000000..46c43d0c17f08
--- /dev/null
+++ b/lib/Fuzzer/FuzzerTracePC.cpp
@@ -0,0 +1,71 @@
+//===- FuzzerTracePC.cpp - PC tracing--------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// Trace PCs.
+// This module implements __sanitizer_cov_trace_pc, a callback required
+// for -fsanitize-coverage=trace-pc instrumentation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "FuzzerInternal.h"
+
+namespace fuzzer {
+
+void PcCoverageMap::Reset() { memset(Map, 0, sizeof(Map)); }
+
+void PcCoverageMap::Update(uintptr_t Addr) {
+  uintptr_t Idx = Addr % kMapSizeInBits;
+  uintptr_t WordIdx = Idx / kBitsInWord;
+  uintptr_t BitIdx = Idx % kBitsInWord;
+  Map[WordIdx] |= 1UL << BitIdx;
+}
+
+size_t PcCoverageMap::MergeFrom(const PcCoverageMap &Other) {
+  uintptr_t Res = 0;
+  for (size_t i = 0; i < kMapSizeInWords; i++)
+    Res += __builtin_popcountl(Map[i] |= Other.Map[i]);
+  return Res;
+}
+
+static PcCoverageMap CurrentMap;
+static thread_local uintptr_t Prev;
+
+void PcMapResetCurrent() {
+  if (Prev) {
+    Prev = 0;
+    CurrentMap.Reset();
+  }
+}
+
+size_t PcMapMergeInto(PcCoverageMap *Map) {
+  if (!Prev)
+    return 0;
+  return Map->MergeFrom(CurrentMap);
+}
+
+static void HandlePC(uint32_t PC) {
+  // We take 12 bits of PC and mix it with the previous PCs.
+  uintptr_t Next = (Prev << 5) ^ (PC & 4095);
+  CurrentMap.Update(Next);
+  Prev = Next;
+}
+
+} // namespace fuzzer
+
+extern "C" {
+void __sanitizer_cov_trace_pc() {
+  fuzzer::HandlePC(static_cast<uint32_t>(
+      reinterpret_cast<uintptr_t>(__builtin_return_address(0))));
+}
+
+void __sanitizer_cov_trace_pc_indir(int *) {
+  // Stub to allow linking with code built with
+  // -fsanitize=indirect-calls,trace-pc.
+  // This isn't used currently.
+}
+}