[IA64] signal(ia64_ia32): add a signal stack overflow check

The similar check has been added to x86_32(i386) in commit
id 83bd0102.
So we add this check to ia64_ia32 and improve it a liitle bit in that
we need to check for stack overflow only when the signal is on stack.
Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/ia32/ia32_signal.c

@@ -766,8 +766,19 @@ get_sigframe (struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (!on_sig_stack(esp))
+		int onstack = sas_ss_flags(esp);
+
+		if (onstack == 0)
 			esp = current->sas_ss_sp + current->sas_ss_size;
+		else if (onstack == SS_ONSTACK) {
+			/*
+			 * If we are on the alternate signal stack and would
+			 * overflow it, don't. Return an always-bogus address
+			 * instead so we will die with SIGSEGV.
+			 */
+			if (!likely(on_sig_stack(esp - frame_size)))
+				return (void __user *) -1L;
+		}
 	}
 	/* Legacy stack switching not supported */