1 files changed, 41 insertions, 0 deletions
diff --git a/lib/fuzzer/FuzzerExtraCounters.cpp b/lib/fuzzer/FuzzerExtraCounters.cpp
new file mode 100644
index 000000000000..0e7a7761bf80
--- /dev/null
+++ b/lib/fuzzer/FuzzerExtraCounters.cpp
@@ -0,0 +1,41 @@
+//===- FuzzerExtraCounters.cpp - Extra coverage counters ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// Extra coverage counters defined by user code.
+//===----------------------------------------------------------------------===//
+
+#include "FuzzerDefs.h"
+
+#if LIBFUZZER_LINUX || LIBFUZZER_NETBSD
+__attribute__((weak)) extern uint8_t __start___libfuzzer_extra_counters;
+__attribute__((weak)) extern uint8_t __stop___libfuzzer_extra_counters;
+
+namespace fuzzer {
+uint8_t *ExtraCountersBegin() { return &__start___libfuzzer_extra_counters; }
+uint8_t *ExtraCountersEnd() { return &__stop___libfuzzer_extra_counters; }
+ATTRIBUTE_NO_SANITIZE_ALL
+void ClearExtraCounters() {  // hand-written memset, don't asan-ify.
+  uintptr_t *Beg = reinterpret_cast<uintptr_t*>(ExtraCountersBegin());
+  uintptr_t *End = reinterpret_cast<uintptr_t*>(ExtraCountersEnd());
+  for (; Beg < End; Beg++) {
+    *Beg = 0;
+    __asm__ __volatile__("" : : : "memory");
+  }
+}
+
+}  // namespace fuzzer
+
+#else
+// TODO: implement for other platforms.
+namespace fuzzer {
+uint8_t *ExtraCountersBegin() { return nullptr; }
+uint8_t *ExtraCountersEnd() { return nullptr; }
+void ClearExtraCounters() {}
+}  // namespace fuzzer
+
+#endif