[scudo][standalone] Fix Android logging

Kostya Kortchinsky · Kostya Kortchinsky · commit a1f6ff26814b · 2020-01-28T11:03:39.000-08:00
Summary: Zygote & children's stderr is lost, so use Bionic's provided allocation free syslog function for `outputRaw`. Get rid of the mutex as it's not vital and could cause issues with `fork`. Reviewers: cferris, pcc, eugenis, hctim, morehouse Subscribers: #sanitizers, llvm-commits Tags: #sanitizers, #llvm Differential Revision: https://reviews.llvm.org/D73561
diff --git a/compiler-rt/lib/scudo/standalone/linux.cpp b/compiler-rt/lib/scudo/standalone/linux.cpp
@@ -164,10 +164,17 @@ bool getRandom(void *Buffer, uptr Length, UNUSED bool Blocking) {
   return (ReadBytes == static_cast<ssize_t>(Length));
 }
 
+// Allocation free syslog-like API.
+extern "C" WEAK int async_safe_write_log(int pri, const char *tag,
+                                         const char *msg);
+
 void outputRaw(const char *Buffer) {
-  static HybridMutex Mutex;
-  ScopedLock L(Mutex);
-  write(2, Buffer, strlen(Buffer));
+  if (&async_safe_write_log) {
+    constexpr s32 AndroidLogInfo = 4;
+    async_safe_write_log(AndroidLogInfo, "scudo", Buffer);
+  } else {
+    write(2, Buffer, strlen(Buffer));
+  }
 }
 
 extern "C" WEAK void android_set_abort_message(const char *);
