Reimplement Thread Static Data ASan routines with TLS

Summary:
Thread Static Data cannot be used in early init on NetBSD
and FreeBSD. Reuse the ASan TSD API for compatibility with
existing code with an alternative implementation using Thread
Local Storage.

New version uses Thread Local Storage to store a pointer
with thread specific data. The destructor from TSD has been
replaced with a TLS destrucutor that is called upon thread
exit.

Reviewers: joerg, vitalybuka, jfb

Reviewed By: vitalybuka

Subscribers: dim, emaste, ro, jfb, devnexen, kubamracek, mgorny, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D55596

llvm-svn: 349619

1 files changed, 46 insertions, 0 deletions

diff --git a/compiler-rt/lib/asan/asan_posix.cc b/compiler-rt/lib/asan/asan_posix.cc
index 17c28b0aea2..ca99c04b3ad 100644
--- a/compiler-rt/lib/asan/asan_posix.cc
+++ b/compiler-rt/lib/asan/asan_posix.cc
@@ -40,6 +40,51 @@ void AsanOnDeadlySignal(int signo, void *siginfo, void *context) {
 
 // ---------------------- TSD ---------------- {{{1
 
+#if SANITIZER_NETBSD || SANITIZER_FREEBSD
+// Thread Static Data cannot be used in early init on NetBSD and FreeBSD.
+// Reuse the Asan TSD API for compatibility with existing code
+// with an alternative implementation.
+
+static void (*tsd_destructor)(void *tsd) = nullptr;
+
+struct tsd_key {
+  tsd_key() : key(nullptr) {}
+  ~tsd_key() {
+    CHECK(tsd_destructor);
+    if (key)
+      (*tsd_destructor)(key);
+  }
+  void *key;
+};
+
+static thread_local struct tsd_key key;
+
+void AsanTSDInit(void (*destructor)(void *tsd)) {
+  CHECK(!tsd_destructor);
+  tsd_destructor = destructor;
+}
+
+void *AsanTSDGet() {
+  CHECK(tsd_destructor);
+  return key.key;
+}
+
+void AsanTSDSet(void *tsd) {
+  CHECK(tsd_destructor);
+  CHECK(tsd);
+  CHECK(!key.key);
+  key.key = tsd;
+}
+
+void PlatformTSDDtor(void *tsd) {
+  CHECK(tsd_destructor);
+  CHECK_EQ(key.key, tsd);
+  key.key = nullptr;
+  // Make sure that signal handler can not see a stale current thread pointer.
+  atomic_signal_fence(memory_order_seq_cst);
+  AsanThread::TSDDtor(tsd);
+}
+#else
 static pthread_key_t tsd_key;
 static bool tsd_key_inited = false;
 void AsanTSDInit(void (*destructor)(void *tsd)) {
@@ -67,6 +112,7 @@ void PlatformTSDDtor(void *tsd) {
   }
   AsanThread::TSDDtor(tsd);
 }
+#endif
 }  // namespace __asan
 
 #endif  // SANITIZER_POSIX