[PATCH] D11552: Fix fast stack-unwinding for Power

[Bill Schmidt]

wschmidt created this revision.
wschmidt added reviewers: echristo, nemanjai, kbarton, seurer, hfinkel, eugenis, kcc, samsonov.
wschmidt added a subscriber: llvm-commits.
wschmidt set the repository for this revision to rL LLVM.

PowerPC differs from other architectures in that the callee-saved return address is stored in the caller's stack frame, not the callee's.  This patch adjusts the logic to find the LR in the correct place for PowerPC.

Patch joint with Bill Seurer.  This replaces review.llvm.org/D9259.

Repository:
  rL LLVM

http://reviews.llvm.org/D11552

Files:
  lib/sanitizer_common/sanitizer_stacktrace.cc
  lib/sanitizer_common/sanitizer_stacktrace.h

Index: lib/sanitizer_common/sanitizer_stacktrace.h
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.h
+++ lib/sanitizer_common/sanitizer_stacktrace.h
@@ -19,8 +19,7 @@
 
 static const u32 kStackTraceMax = 256;
 
-#if SANITIZER_LINUX && (defined(__aarch64__) || defined(__powerpc__) || \
-                        defined(__powerpc64__) || defined(__sparc__) || \
+#if SANITIZER_LINUX && (defined(__aarch64__) || defined(__sparc__) || \
                         defined(__mips__))
 # define SANITIZER_CAN_FAST_UNWIND 0
 #elif SANITIZER_WINDOWS
Index: lib/sanitizer_common/sanitizer_stacktrace.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.cc
+++ lib/sanitizer_common/sanitizer_stacktrace.cc
@@ -83,7 +83,15 @@
   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
          IsAligned((uptr)frame, sizeof(*frame)) &&
          size < max_depth) {
+#ifdef __powerpc__
+    uhwptr *caller_frame = (uhwptr*)frame[0];
+    if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
+        !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
+      break;
+    uhwptr pc1 = caller_frame[2];
+#else
     uhwptr pc1 = frame[1];
+#endif
     if (pc1 != pc) {
       trace_buffer[size++] = (uptr) pc1;
     }


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