Index: compiler-rt/trunk/lib/asan/asan_posix.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_posix.cc
+++ compiler-rt/trunk/lib/asan/asan_posix.cc
@@ -35,56 +35,13 @@
 
 void AsanOnDeadlySignal(int signo, void *siginfo, void *context) {
   ScopedDeadlySignal signal_scope(GetCurrentThread());
-  int code = (int)((siginfo_t*)siginfo)->si_code;
   // Write the first message using fd=2, just in case.
   // It may actually fail to write in case stderr is closed.
   internal_write(2, SanitizerToolName, internal_strlen(SanitizerToolName));
   static const char kDeadlySignal[] = ":DEADLYSIGNAL\n";
   internal_write(2, kDeadlySignal, sizeof(kDeadlySignal) - 1);
   SignalContext sig = SignalContext::Create(siginfo, context);
-
-  // Access at a reasonable offset above SP, or slightly below it (to account
-  // for x86_64 or PowerPC redzone, ARM push of multiple registers, etc) is
-  // probably a stack overflow.
-#ifdef __s390__
-  // On s390, the fault address in siginfo points to start of the page, not
-  // to the precise word that was accessed.  Mask off the low bits of sp to
-  // take it into account.
-  bool IsStackAccess = sig.addr >= (sig.sp & ~0xFFF) &&
-                       sig.addr < sig.sp + 0xFFFF;
-#else
-  bool IsStackAccess = sig.addr + 512 > sig.sp && sig.addr < sig.sp + 0xFFFF;
-#endif
-
-#if __powerpc__
-  // Large stack frames can be allocated with e.g.
-  //   lis r0,-10000
-  //   stdux r1,r1,r0 # store sp to [sp-10000] and update sp by -10000
-  // If the store faults then sp will not have been updated, so test above
-  // will not work, because the fault address will be more than just "slightly"
-  // below sp.
-  if (!IsStackAccess && IsAccessibleMemoryRange(sig.pc, 4)) {
-    u32 inst = *(unsigned *)sig.pc;
-    u32 ra = (inst >> 16) & 0x1F;
-    u32 opcd = inst >> 26;
-    u32 xo = (inst >> 1) & 0x3FF;
-    // Check for store-with-update to sp. The instructions we accept are:
-    //   stbu rs,d(ra)          stbux rs,ra,rb
-    //   sthu rs,d(ra)          sthux rs,ra,rb
-    //   stwu rs,d(ra)          stwux rs,ra,rb
-    //   stdu rs,ds(ra)         stdux rs,ra,rb
-    // where ra is r1 (the stack pointer).
-    if (ra == 1 &&
-        (opcd == 39 || opcd == 45 || opcd == 37 || opcd == 62 ||
-         (opcd == 31 && (xo == 247 || xo == 439 || xo == 183 || xo == 181))))
-      IsStackAccess = true;
-  }
-#endif // __powerpc__
-
-  // We also check si_code to filter out SEGV caused by something else other
-  // then hitting the guard page or unmapped memory, like, for example,
-  // unaligned memory access.
-  if (IsStackAccess && (code == si_SEGV_MAPERR || code == si_SEGV_ACCERR))
+  if (IsStackOverflow(((siginfo_t *)siginfo)->si_code, sig))
     ReportStackOverflow(sig);
   else
     ReportDeadlySignal(signo, sig);
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
@@ -29,8 +29,10 @@
 #endif
 
 namespace __sanitizer {
-struct StackTrace;
+
 struct AddressInfo;
+struct SignalContext;
+struct StackTrace;
 
 // Constants.
 const uptr kWordSize = SANITIZER_WORDSIZE / 8;
@@ -306,6 +308,7 @@
 // Functions related to signal handling.
 typedef void (*SignalHandlerType)(int, void *, void *);
 HandleSignalMode GetHandleSignalMode(int signum);
+bool IsStackOverflow(int code, const SignalContext &sig);
 void InstallDeadlySignalHandlers(SignalHandlerType handler);
 const char *DescribeSignalOrException(int signo);
 // Alternative signal stack (POSIX-only).
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_posix.cc
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_posix.cc
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_posix.cc
@@ -321,6 +321,53 @@
   return "UNKNOWN SIGNAL";
 }
 
+#if !SANITIZER_GO
+bool IsStackOverflow(int code, const SignalContext &sig) {
+  // Access at a reasonable offset above SP, or slightly below it (to account
+  // for x86_64 or PowerPC redzone, ARM push of multiple registers, etc) is
+  // probably a stack overflow.
+#ifdef __s390__
+  // On s390, the fault address in siginfo points to start of the page, not
+  // to the precise word that was accessed.  Mask off the low bits of sp to
+  // take it into account.
+  bool IsStackAccess =
+      sig.addr >= (sig.sp & ~0xFFF) && sig.addr < sig.sp + 0xFFFF;
+#else
+  bool IsStackAccess = sig.addr + 512 > sig.sp && sig.addr < sig.sp + 0xFFFF;
+#endif
+
+#if __powerpc__
+  // Large stack frames can be allocated with e.g.
+  //   lis r0,-10000
+  //   stdux r1,r1,r0 # store sp to [sp-10000] and update sp by -10000
+  // If the store faults then sp will not have been updated, so test above
+  // will not work, because the fault address will be more than just "slightly"
+  // below sp.
+  if (!IsStackAccess && IsAccessibleMemoryRange(sig.pc, 4)) {
+    u32 inst = *(unsigned *)sig.pc;
+    u32 ra = (inst >> 16) & 0x1F;
+    u32 opcd = inst >> 26;
+    u32 xo = (inst >> 1) & 0x3FF;
+    // Check for store-with-update to sp. The instructions we accept are:
+    //   stbu rs,d(ra)          stbux rs,ra,rb
+    //   sthu rs,d(ra)          sthux rs,ra,rb
+    //   stwu rs,d(ra)          stwux rs,ra,rb
+    //   stdu rs,ds(ra)         stdux rs,ra,rb
+    // where ra is r1 (the stack pointer).
+    if (ra == 1 &&
+        (opcd == 39 || opcd == 45 || opcd == 37 || opcd == 62 ||
+         (opcd == 31 && (xo == 247 || xo == 439 || xo == 183 || xo == 181))))
+      IsStackAccess = true;
+  }
+#endif  // __powerpc__
+
+  // We also check si_code to filter out SEGV caused by something else other
+  // then hitting the guard page or unmapped memory, like, for example,
+  // unaligned memory access.
+  return IsStackAccess && (code == si_SEGV_MAPERR || code == si_SEGV_ACCERR);
+}
+#endif  //! SANITIZER_GO
+
 } // namespace __sanitizer
 
 #endif // SANITIZER_POSIX