Teach stackinfo::walk() how to virtually unwind the tls sigstack

This improves how stackinfo::dumpstack() dumps _sigbe and sigdelayed frames

	* exceptions.cc (stack_info): Add sigstackptr member.
	(walk): Unwind sigstackptr inside _sigbe and sigdelayed.
	* gendef (_sigdelayed_end): Add symbol to mark end of sigdelayed.

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>

winsup/cygwin/ChangeLog

@@ -1,3 +1,9 @@
+2015-03-12  Jon TURNEY  <jon.turney@dronecode.org.uk>
+
+	* exceptions.cc (stack_info): Add sigstackptr member.
+	(walk): Unwind sigstackptr inside _sigbe and sigdelayed.
+	* gendef (_sigdelayed_end): Add symbol to mark end of sigdelayed.
+
 2015-03-13  Corinna Vinschen  <corinna@vinschen.de>
 
 	* include/cygwin/sys_time.h: Remove.  Definitions moved to newlib's

winsup/cygwin/exceptions.cc

@@ -45,6 +45,8 @@ details. */
 #define CALL_HANDLER_RETRY_INNER 10
 
 char debugger_command[2 * NT_MAX_PATH + 20];
+extern u_char _sigbe;
+extern u_char _sigdelayed_end;
 
 static BOOL WINAPI ctrl_c_handler (DWORD);
 
@@ -224,6 +226,7 @@ class stack_info
 #ifdef __x86_64__
   CONTEXT c;
   UNWIND_HISTORY_TABLE hist;
+  __stack_t *sigstackptr;
 #endif
 public:
   STACKFRAME sf;		 /* For storing the stack information */
@@ -252,6 +255,7 @@ stack_info::init (PUINT_PTR framep, bool wantargs, PCONTEXT ctx)
       memset (&c, 0, sizeof c);
       c.ContextFlags = CONTEXT_ALL;
     }
+  sigstackptr = _my_tls.stackptr;
 #endif
   memset (&sf, 0, sizeof (sf));
   if (ctx)
@@ -287,6 +291,15 @@ stack_info::walk ()
   sf.AddrStack.Offset = c.Rsp;
   sf.AddrFrame.Offset = c.Rbp;
 
+  if ((c.Rip >= (DWORD64)&_sigbe) && (c.Rip < (DWORD64)&_sigdelayed_end))
+    {
+      /* _sigbe and sigdelayed don't have SEH unwinding data, so virtually
+         unwind the tls sigstack */
+      c.Rip = sigstackptr[-1];
+      sigstackptr--;
+      return 1;
+    }
+
   f = RtlLookupFunctionEntry (c.Rip, &imagebase, &hist);
   if (f)
     RtlVirtualUnwind (0, imagebase, c.Rip, f, &c, &hdl, &establisher, NULL);

winsup/cygwin/gendef

@@ -311,6 +311,8 @@ sigdelayed:
 	xchgq	%r10,(%rsp)
 	ret
 	.seh_endproc
+_sigdelayed_end:
+	.global _sigdelayed_end
 
 # _cygtls::pop
 	.global _ZN7_cygtls3popEv