Re: [PATCH, RFC] Enable libsanitizer on powerpc{,64}

[Peter Bergner <bergner at vnet dot ibm dot com>]

On Tue, 2012-11-20 at 18:18 +0400, Evgeniy Stepanov wrote:

> I wonder if under some conditions we may get a different number of
> extra frames (inlining comes to mind). What do you think of removing
> any number of frames that belong to the runtime library - we have
> memory layout info for that?

How about the following hack that needs to be cleaned up, but does
work for me.  It scans through the trace looking for the frame pointer
that is passed in and if it finds it, it pops the stack up to that
point.  If it doesn't find it (a bug?), it just leaves the trace
alone.

Maybe it fixes the ARM Android issue you just ran into?

Peter



diff -urpN -X /home/bergner/cvs/dontdiff gcc-fsf-mainline-kcc/libsanitizer/asan/asan_linux.cc gcc-fsf-mainline-asan/libsanitizer/asan/asan_linux.cc
--- gcc-fsf-mainline-kcc/libsanitizer/asan/asan_linux.cc	2012-11-20 12:52:33.961664485 -0600
+++ gcc-fsf-mainline-asan/libsanitizer/asan/asan_linux.cc	2012-11-20 11:28:00.646245908 -0600
@@ -141,12 +141,19 @@ uptr Unwind_GetIP(struct _Unwind_Context
 #endif
 }
 
+uptr Unwind_GetBP(struct _Unwind_Context *ctx) {
+  return _Unwind_GetCFA(ctx);
+}
+
 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx,
     void *param) {
   StackTrace *b = (StackTrace*)param;
   CHECK(b->size < b->max_size);
   uptr pc = Unwind_GetIP(ctx);
-  b->trace[b->size++] = pc;
+  uptr bp = Unwind_GetBP(ctx);
+  b->trace[b->size] = pc;
+  b->frame[b->size] = bp;
+  b->size++;
   if (b->size == b->max_size) return UNWIND_STOP;
   return UNWIND_CONTINUE;
 }
@@ -158,8 +165,13 @@ void GetStackTrace(StackTrace *stack, up
     stack->max_size = max_s;
 #if defined(__arm__) || defined(__powerpc__) || defined(__powerpc64__)
     _Unwind_Backtrace(Unwind_Trace, stack);
-    // Pop off the two ASAN functions from the backtrace.
-    stack->PopStackFrames(2);
+    // Attempt to pop off the ASAN functions from the backtrace.
+    uptr cnt;
+    for (cnt = 0; cnt < stack->size; cnt++)
+      if (stack->frame[cnt] == bp) {
+	stack->PopStackFrames(cnt);
+	break;
+      }
 #else
     if (!asan_inited) return;
     if (AsanThread *t = asanThreadRegistry().GetCurrent())
diff -urpN -X /home/bergner/cvs/dontdiff gcc-fsf-mainline-kcc/libsanitizer/sanitizer_common/sanitizer_stacktrace.cc gcc-fsf-mainline-asan/libsanitizer/sanitizer_common/sanitizer_stacktrace.cc
--- gcc-fsf-mainline-kcc/libsanitizer/sanitizer_common/sanitizer_stacktrace.cc	2012-11-20 11:42:08.834439704 -0600
+++ gcc-fsf-mainline-asan/libsanitizer/sanitizer_common/sanitizer_stacktrace.cc	2012-11-20 12:59:29.896106625 -0600
@@ -144,7 +144,8 @@ void StackTrace::PopStackFrames(uptr cou
   CHECK(size > count);
   size -= count;
   for (uptr i = 0; i < size; i++) {
-    trace[i] = trace[i + count];
+    trace[i] = trace[i+count];
+    frame[i] = frame[i+count];
   }
 }
 
diff -urpN -X /home/bergner/cvs/dontdiff gcc-fsf-mainline-kcc/libsanitizer/sanitizer_common/sanitizer_stacktrace.h gcc-fsf-mainline-asan/libsanitizer/sanitizer_common/sanitizer_stacktrace.h
--- gcc-fsf-mainline-kcc/libsanitizer/sanitizer_common/sanitizer_stacktrace.h	2012-11-20 11:42:08.821389243 -0600
+++ gcc-fsf-mainline-asan/libsanitizer/sanitizer_common/sanitizer_stacktrace.h	2012-11-20 11:12:44.551390980 -0600
@@ -23,6 +23,7 @@ struct StackTrace {
   uptr size;
   uptr max_size;
   uptr trace[kStackTraceMax];
+  uptr frame[kStackTraceMax];	// For use by _Unwind_Backtrace architectures.
   static void PrintStack(const uptr *addr, uptr size,
                          bool symbolize, const char *strip_file_prefix,
                          SymbolizeCallback symbolize_callback);