[sanitizer] Fix a crash when demangling Swift symbols, take 2

[kubamracek]

Summary

Original patch at http://reviews.llvm.org/D19974 caused failures in MSan.

To invoke the Swift demangler, we use dlsym to locate swift_demangle. However, dlsym malloc's storage and stores it in thread-local storage. Since allocations from the symbolizer are done with the system allocator (at least in TSan, interceptors are skipped when inside the symbolizer), we will crash when we try to deallocate later using the sanitizer allocator again.

To fix this, let's just not call dlsym from the demangler, and call it during initialization.

The dlsym function calls malloc, so it needs to be only used after our allocator is initialized. Adding a Symbolizer::LateInitialize call that is only invoked after all other initializations.

lib/asan/asan_rtl.cc

 #endif  // CAN_SANITIZE_LEAKS
 
 #if CAN_SANITIZE_UB
   __ubsan::InitAsPlugin();
 #endif
 
   InitializeSuppressions();
 
+  Symbolizer::LateInitialize();
+
   VReport(1, "AddressSanitizer Init done\n");
 }
 
 // Initialize as requested from some part of ASan runtime library (interceptors,
 // allocator, etc).
 void AsanInitFromRtl() {
   AsanInitInternal();
 }

lib/sanitizer_common/sanitizer_symbolizer.h

 
 class SymbolizerTool;
 
 class Symbolizer final {
  public:
   /// Initialize and return platform-specific implementation of symbolizer
   /// (if it wasn't already initialized).
   static Symbolizer *GetOrInit();
+  static void LateInitialize();
   // Returns a list of symbolized frames for a given address (containing
   // all inlined functions, if necessary).
   SymbolizedStack *SymbolizePC(uptr address);
   bool SymbolizeData(uptr address, DataInfo *info);
 
   // The module names Symbolizer returns are stable and unique for every given
   // module.  It is safe to store and compare them as pointers.
   bool GetModuleNameAndOffsetForPC(uptr pc, const char **module_name,

lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc

const char *DemangleCXXABI(const char *name) {
   if (__cxxabiv1::__cxa_demangle)
     if (const char *demangled_name =
           __cxxabiv1::__cxa_demangle(name, 0, 0, 0))
       return demangled_name;
 
   return name;
 }
 
-// Attempts to demangle a Swift name. The demangler will return nullptr
-/// if a non-Swift name is passed in.
+// As of now, there are no headers for the Swift runtime. Once they are
+// present, we will weakly link since we do not require Swift runtime to be
+// linked.
+typedef char *(*swift_demangle_ft)(const char *mangledName,
+                                   size_t mangledNameLength, char *outputBuffer,
+                                   size_t *outputBufferSize, uint32_t flags);
+static swift_demangle_ft swift_demangle_f;
+
+// This must not happen lazily at symbolication time, because dlsym uses
+// malloc and thread-local storage, which is not a good thing to do during
+// symbolication.
+static void InitializeSwiftDemangler() {
+  swift_demangle_f = (swift_demangle_ft)dlsym(RTLD_DEFAULT, "swift_demangle");
+}
+
+// Attempts to demangle a Swift name. The demangler will return nullptr if a
+// non-Swift name is passed in.
 const char *DemangleSwift(const char *name) {
-  // Not to call dlsym every time we demangle, check if we are dealing with
-  // Swift mangled name first.
+  // Check if we are dealing with a Swift mangled name first.
   if (name[0] != '_' || name[1] != 'T') {
     return nullptr;
   }
 
-  // As of now, there are no headers for the Swift runtime. Once they are
-  // present, we will weakly link since we do not require Swift runtime to be
-  // linked.
-  typedef char *(*swift_demangle_ft)(const char *mangledName,
-                                     size_t mangledNameLength,
-                                     char *outputBuffer,
-                                     size_t *outputBufferSize,
-                                     uint32_t flags);
-  swift_demangle_ft swift_demangle_f =
-    (swift_demangle_ft) dlsym(RTLD_DEFAULT, "swift_demangle");
   if (swift_demangle_f)
     return swift_demangle_f(name, internal_strlen(name), 0, 0, 0);
 
   return nullptr;
 }
 
 const char *DemangleSwiftAndCXX(const char *name) {
   CHECK(name);

 
 Symbolizer *Symbolizer::PlatformInit() {
   IntrusiveList<SymbolizerTool> list;
   list.clear();
   ChooseSymbolizerTools(&list, &symbolizer_allocator_);
   return new(symbolizer_allocator_) Symbolizer(list);
 }
 
+void Symbolizer::LateInitialize() {
+  Symbolizer::GetOrInit();
+  InitializeSwiftDemangler();
+}
+
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_POSIX

lib/sanitizer_common/sanitizer_symbolizer_win.cc

 Symbolizer *Symbolizer::PlatformInit() {
   IntrusiveList<SymbolizerTool> list;
   list.clear();
   ChooseSymbolizerTools(&list, &symbolizer_allocator_);
 
   return new(symbolizer_allocator_) Symbolizer(list);
 }
 
+void Symbolizer::LateInitialize() {
+  Symbolizer::GetOrInit();
+}
+
 }  // namespace __sanitizer
 
 #endif  // _WIN32

lib/tsan/rtl/tsan_rtl.cc

#endif
   int tid = ThreadCreate(thr, 0, 0, true);
   CHECK_EQ(tid, 0);
   ThreadStart(thr, tid, internal_getpid());
 #if TSAN_CONTAINS_UBSAN
   __ubsan::InitAsPlugin();
 #endif
   ctx->initialized = true;
 
+  Symbolizer::LateInitialize();
+
   if (flags()->stop_on_start) {
     Printf("ThreadSanitizer is suspended at startup (pid %d)."
            " Call __tsan_resume().\n",
            (int)internal_getpid());
     while (__tsan_resumed == 0) {}
   }
 
   OnInitialize();