commit 15478fd3a87d731b4dbe9438444f2afa3338df09
author Nicolas Capens <capn@google.com> Thu May 27 13:50:51 2021 -0400
committer Nicolas Capens <nicolascapens@google.com> Thu May 27 19:33:45 2021 +0000
tree 91bcd5c69b7921a633d8d57c366388e698d40a3a
parent 9dd7a5171793ca09a52bb5c9037a759f1e0b1ffa

Marl: Suppress MemorySanitizer false-positive

Worker::current is a static thread_local which gets intialized to null,
which gets checked for in Scheduler::Fiber::current(). Unfortunately
MemorySanitizer does not observe the initialization when Marl is used
within a shared library, when the Linux dynamic loader is not
instrumented and its TLS initialization is not otherwise intercepted and
handled correctly.

This change decorates Scheduler::Fiber::current() with
__attribute__((no_sanitize_memory)) to suppress instrumenting it with
use-of-uninitialized-data checks.

Bug: chromium:1211047
Change-Id: I61b584922d9aba5d67991ce916c69102734f2b61
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/54610
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

third_party/marl/include/marl/sanitizers.h

diff --git a/third_party/marl/include/marl/sanitizers.h b/third_party/marl/include/marl/sanitizers.h
index 3f26d4a..aea997e 100644
--- a/third_party/marl/include/marl/sanitizers.h
+++ b/third_party/marl/include/marl/sanitizers.h
@@ -78,4 +78,13 @@
 #define THREAD_SANITIZER_ONLY(x)
 #endif  // THREAD_SANITIZER_ENABLED
 
+// The CLANG_NO_SANITIZE_MEMORY macro suppresses MemorySanitizer checks for
+// use-of-uninitialized-data. It can be used to decorate functions with known
+// false positives.
+#ifdef __clang__
+#define CLANG_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
+#else
+#define CLANG_NO_SANITIZE_MEMORY
+#endif
+
 #endif  // marl_sanitizers_h

third_party/marl/src/scheduler.cpp

diff --git a/third_party/marl/src/scheduler.cpp b/third_party/marl/src/scheduler.cpp
index 027565d..af98159 100644
--- a/third_party/marl/src/scheduler.cpp
+++ b/third_party/marl/src/scheduler.cpp
@@ -234,6 +234,9 @@
   MARL_ASSERT(worker != nullptr, "No Scheduler::Worker bound");
 }
 
+// TODO(chromium:1211047): Testing the static thread_local Worker::current for
+// null causes a MemorySantizer false positive.
+CLANG_NO_SANITIZE_MEMORY
 Scheduler::Fiber* Scheduler::Fiber::current() {
   auto worker = Worker::getCurrent();
   return worker != nullptr ? worker->getCurrentFiber() : nullptr;