From 4ce918e3942f0333ccb7d65d6265f4fc5f5324be Mon Sep 17 00:00:00 2001
From: Julian Lettner <jlettner@apple.com>
Date: Tue, 5 Mar 2019 00:41:15 +0000
Subject: [PATCH] [NFC][Sanitizer] Cleanup ASan's GetStackTrace implementation

Cleanup ASan's  __sanitizer::BufferedStackTrace::UnwindImpl (formerly
GetStackTrace) implementation. Start with ASan because it is the most
complex implementation.

GetStackTrace implementations seem to have started out as exact copies
of the original implementation in ASan, but have diverged in subtle
ways. My goal is to parameterize this algorithm (via templating or
callbacks) so we can share the implementation and get rid of the
inversed dependency (sanitizer_common depends on concrete
implementations in asan, ubsan, etc.). This should also help us to avoid
those pesky linker errors caused by undefined, duplicate, and weak
symbols on Windows.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D58861

llvm-svn: 355355
---
 compiler-rt/lib/asan/asan_stack.cc            | 33 ++++++++-----------
 .../sanitizer_common/sanitizer_stacktrace.h   |  5 +++
 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_stack.cc b/compiler-rt/lib/asan/asan_stack.cc
index 72caf1f8bc81..0bcba419da8b 100644
--- a/compiler-rt/lib/asan/asan_stack.cc
+++ b/compiler-rt/lib/asan/asan_stack.cc
@@ -31,28 +31,23 @@ u32 GetMallocContextSize() {
 void __sanitizer::BufferedStackTrace::UnwindImpl(
     uptr pc, uptr bp, void *context, bool request_fast, u32 max_depth) {
   using namespace __asan;
-#if SANITIZER_WINDOWS
-  Unwind(max_depth, pc, 0, context, 0, 0, false);
-#else
-  AsanThread *t;
   size = 0;
-  if (LIKELY(asan_inited)) {
-    if ((t = GetCurrentThread()) && !t->isUnwinding()) {
-      uptr stack_top = t->stack_top();
-      uptr stack_bottom = t->stack_bottom();
-      ScopedUnwinding unwind_scope(t);
-      if (!SANITIZER_MIPS || IsValidFrame(bp, stack_top, stack_bottom)) {
-        if (StackTrace::WillUseFastUnwind(request_fast))
-          Unwind(max_depth, pc, bp, nullptr, stack_top, stack_bottom, true);
-        else
-          Unwind(max_depth, pc, 0, context, 0, 0, false);
-      }
-    } else if (!t && !request_fast) {
-      /* If GetCurrentThread() has failed, try to do slow unwind anyways. */
-      Unwind(max_depth, pc, bp, context, 0, 0, false);
+  if (UNLIKELY(!asan_inited)) return;
+
+  AsanThread *t = GetCurrentThread();
+  if (t && !t->isUnwinding() && WillUseFastUnwind(request_fast)) {
+    uptr top = t->stack_top();
+    uptr bottom = t->stack_bottom();
+    ScopedUnwinding unwind_scope(t);
+    if (!SANITIZER_MIPS || IsValidFrame(bp, top, bottom)) {
+      UnwindFast(pc, bp, top, bottom, max_depth);
+      return;
     }
   }
-#endif // SANITIZER_WINDOWS
+
+#if SANITIZER_CAN_SLOW_UNWIND
+    UnwindSlowWithOptionalContext(pc, context, max_depth);
+#endif
 }
 
 // ------------------ Interface -------------- {{{1
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h b/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h
index 4d19979f2c5a..ec63b66cfec2 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h
@@ -134,6 +134,11 @@ struct BufferedStackTrace : public StackTrace {
   void UnwindSlow(uptr pc, u32 max_depth);
   void UnwindSlow(uptr pc, void *context, u32 max_depth);
 
+  void UnwindSlowWithOptionalContext(uptr pc, void *context, u32 max_depth) {
+    if (context) UnwindSlow(pc, context, max_depth);
+    else         UnwindSlow(pc, max_depth);
+  }
+
   void PopStackFrames(uptr count);
   uptr LocatePcInTrace(uptr pc);