[compiler-rt] r350102 - Reimplement Thread Static Data MSan routines with TLS

[Kamil Rytarowski via llvm-commits]

Author: kamil
Date: Thu Dec 27 13:43:46 2018
New Revision: 350102

URL: http://llvm.org/viewvc/llvm-project?rev=350102&view=rev
Log:
Reimplement Thread Static Data MSan routines with TLS

Summary:
Thread Static Data cannot be used in early init on NetBSD
and FreeBSD. Reuse the MSan 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: emaste, jfb, llvm-commits, #sanitizers, mgorny

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D55703

Modified:
    compiler-rt/trunk/lib/msan/msan_linux.cc

Modified: compiler-rt/trunk/lib/msan/msan_linux.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/msan/msan_linux.cc?rev=350102&r1=350101&r2=350102&view=diff
==============================================================================
--- compiler-rt/trunk/lib/msan/msan_linux.cc (original)
+++ compiler-rt/trunk/lib/msan/msan_linux.cc Thu Dec 27 13:43:46 2018
@@ -175,6 +175,51 @@ void InstallAtExitHandler() {
 
 // ---------------------- TSD ---------------- {{{1
 
+#if SANITIZER_NETBSD || SANITIZER_FREEBSD
+// Thread Static Data cannot be used in early init on NetBSD and FreeBSD.
+// Reuse the MSan 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);
+  }
+  MsanThread *key;
+};
+
+static thread_local struct tsd_key key;
+
+void MsanTSDInit(void (*destructor)(void *tsd)) {
+  CHECK(!tsd_destructor);
+  tsd_destructor = destructor;
+}
+
+MsanThread *GetCurrentThread() {
+  CHECK(tsd_destructor);
+  return key.key;
+}
+
+void SetCurrentThread(MsanThread *tsd) {
+  CHECK(tsd_destructor);
+  CHECK(tsd);
+  CHECK(!key.key);
+  key.key = tsd;
+}
+
+void MsanTSDDtor(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);
+  MsanThread::TSDDtor(tsd);
+}
+#else
 static pthread_key_t tsd_key;
 static bool tsd_key_inited = false;
 
@@ -211,6 +256,7 @@ void MsanTSDDtor(void *tsd) {
   atomic_signal_fence(memory_order_seq_cst);
   MsanThread::TSDDtor(tsd);
 }
+#endif
 
 } // namespace __msan