[tsan] Detect races on modifying accesses in Swift code

This patch allows the Swift compiler to emit calls to `__tsan_external_write` before starting any modifying access, which will cause TSan to detect races on arrays, dictionaries and other classes defined in non-instrumented modules. Races on collections from the Swift standard library and user-defined structs and a frequent cause of subtle bugs and it's important that TSan detects those on top of existing LLVM IR instrumentation, which already detects races in direct memory accesses.

Differential Revision: https://reviews.llvm.org/D31630



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@302050 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 39 insertions, 8 deletions

diff --git a/lib/tsan/rtl/tsan_external.cc b/lib/tsan/rtl/tsan_external.cc
index 2d32b6dac..6c0e9477e 100644
--- a/lib/tsan/rtl/tsan_external.cc
+++ b/lib/tsan/rtl/tsan_external.cc
@@ -17,14 +17,30 @@ namespace __tsan {
 
 #define CALLERPC ((uptr)__builtin_return_address(0))
 
-const char *registered_tags[kExternalTagMax];
-static atomic_uint32_t used_tags{kExternalTagFirstUserAvailable};  // NOLINT.
+struct TagData {
+  const char *object_type;
+  const char *header;
+};
 
-const char *GetObjectTypeFromTag(uptr tag) {
-  if (tag == 0) return nullptr;
+static TagData registered_tags[kExternalTagMax] = {
+  {},
+  {"Swift variable", "Swift access race"},
+};
+static atomic_uint32_t used_tags{kExternalTagFirstUserAvailable};  // NOLINT.
+static TagData *GetTagData(uptr tag) {
   // Invalid/corrupted tag?  Better return NULL and let the caller deal with it.
   if (tag >= atomic_load(&used_tags, memory_order_relaxed)) return nullptr;
-  return registered_tags[tag];
+  return &registered_tags[tag];
+}
+
+const char *GetObjectTypeFromTag(uptr tag) {
+  TagData *tag_data = GetTagData(tag);
+  return tag_data ? tag_data->object_type : nullptr;
+}
+
+const char *GetReportHeaderFromTag(uptr tag) {
+  TagData *tag_data = GetTagData(tag);
+  return tag_data ? tag_data->header : nullptr;
 }
 
 void InsertShadowStackFrameForTag(ThreadState *thr, uptr tag) {
@@ -34,9 +50,9 @@ void InsertShadowStackFrameForTag(ThreadState *thr, uptr tag) {
 uptr TagFromShadowStackFrame(uptr pc) {
   uptr tag_count = atomic_load(&used_tags, memory_order_relaxed);
   void *pc_ptr = (void *)pc;
-  if (pc_ptr < &registered_tags[0] || pc_ptr >= &registered_tags[tag_count])
+  if (pc_ptr < GetTagData(0) || pc_ptr > GetTagData(tag_count - 1))
     return 0;
-  return (const char **)pc_ptr - &registered_tags[0];
+  return (TagData *)pc_ptr - GetTagData(0);
 }
 
 #if !SANITIZER_GO
@@ -60,11 +76,26 @@ SANITIZER_INTERFACE_ATTRIBUTE
 void *__tsan_external_register_tag(const char *object_type) {
   uptr new_tag = atomic_fetch_add(&used_tags, 1, memory_order_relaxed);
   CHECK_LT(new_tag, kExternalTagMax);
-  registered_tags[new_tag] = internal_strdup(object_type);
+  GetTagData(new_tag)->object_type = internal_strdup(object_type);
+  char header[127] = {0};
+  internal_snprintf(header, sizeof(header), "race on %s", object_type);
+  GetTagData(new_tag)->header = internal_strdup(header);
   return (void *)new_tag;
 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
+void __tsan_external_register_header(void *tag, const char *header) {
+  CHECK_GE((uptr)tag, kExternalTagFirstUserAvailable);
+  CHECK_LT((uptr)tag, kExternalTagMax);
+  atomic_uintptr_t *header_ptr =
+      (atomic_uintptr_t *)&GetTagData((uptr)tag)->header;
+  header = internal_strdup(header);
+  char *old_header =
+      (char *)atomic_exchange(header_ptr, (uptr)header, memory_order_seq_cst);
+  if (old_header) internal_free(old_header);
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE
 void __tsan_external_assign_tag(void *addr, void *tag) {
   CHECK_LT(tag, atomic_load(&used_tags, memory_order_relaxed));
   Allocator *a = allocator();