Re: Sparc ASAN

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

On Tue, 2012-11-20 at 23:19 -0500, David Miller wrote:
> The address violation detection seems to work properly and the only
> thing that seems to be left are some backtrace/unwind issues.  These
> are perhaps similar to the unwind bits that the powerpc folks ran
> into.

David, does the following patch (will have some fuzz since I removed
one ppc only hunk from the patch) fix your backtrace issue?  I'll note
you'll have to add "|| defined(__sparc__)" to the #if ... or as
it's probably going to turn out, just replace the whole thing
with a "#if !defined(__i386__) && !defined(__x86_64__)".

Peter


Index: libsanitizer/asan/asan_linux.cc
===================================================================
--- libsanitizer/asan/asan_linux.cc	(revision 193678)
+++ libsanitizer/asan/asan_linux.cc	(working copy)
@@ -134,11 +141,27 @@
 #endif
 }
 
+uptr Unwind_GetBP(struct _Unwind_Context *ctx) {
+  return _Unwind_GetCFA(ctx);
+}
+
+struct Unwind_Trace_Info {
+  StackTrace *stack;
+  uptr bp;
+};
+
 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx,
     void *param) {
-  StackTrace *b = (StackTrace*)param;
+  Unwind_Trace_Info *p = (Unwind_Trace_Info *)param;
+  StackTrace *b = p->stack;
+  uptr pc = Unwind_GetIP(ctx);
+  if (Unwind_GetBP(ctx) == p->bp) {
+    // We just encountered the frame pointer we want to start
+    // our backtrace with, so empty the backtrace before adding
+    // this frame to the backtrace.
+    b->size = 0;
+  }
   CHECK(b->size < b->max_size);
-  uptr pc = Unwind_GetIP(ctx);
   b->trace[b->size++] = pc;
   if (b->size == b->max_size) return UNWIND_STOP;
   return UNWIND_CONTINUE;
@@ -149,8 +172,11 @@
   stack->trace[0] = pc;
   if ((max_s) > 1) {
     stack->max_size = max_s;
-#ifdef __arm__
-    _Unwind_Backtrace(Unwind_Trace, stack);
+#if defined(__arm__) || defined(__powerpc__) || defined(__powerpc64__)
+    Unwind_Trace_Info param;
+    param.stack = stack;
+    param.bp = bp;
+    _Unwind_Backtrace(Unwind_Trace, &param);
 #else
     if (!asan_inited) return;
     if (AsanThread *t = asanThreadRegistry().GetCurrent())