[SanitizeCoverage] Enable stack-depth coverage for -fsanitize=fuzzer

Summary:
- Don't sanitize __sancov_lowest_stack.
- Don't instrument leaf functions.
- Add CoverageStackDepth to Fuzzer and FuzzerNoLink.
- Only enable on Linux.

Reviewers: vitalybuka, kcc, george.karpenkov

Reviewed By: kcc

Subscribers: kubamracek, cfe-commits, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D37156

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@312185 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc b/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
index 469656766..3c5f29b28 100644
--- a/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
+++ b/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
@@ -211,5 +211,10 @@ SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_8bit_counters_init, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_pcs_init, void) {}
 }  // extern "C"
+// Weak definition for code instrumented with -fsanitize-coverage=stack-depth
+// and later linked with code containing a strong definition.
+// E.g., -fsanitize=fuzzer-no-link
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+SANITIZER_TLS_INITIAL_EXEC_ATTRIBUTE uptr __sancov_lowest_stack;
 
 #endif  // !SANITIZER_FUCHSIA