tile: include the syscall number in the backtrace

This information is easily available in the backtrace data and can
be helpful when trying to figure out the backtrace, particularly
if we're early in kernel entry or late in kernel exit.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

arch/tile/kernel/stack.c

@@ -78,8 +78,7 @@ static bool read_memory_func(void *result, unsigned long address,
 /* Return a pt_regs pointer for a valid fault handler frame */
 static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
 {
-	const char *fault = NULL;  /* happy compiler */
-	char fault_buf[64];
+	char fault[64];
 	unsigned long sp = kbt->it.sp;
 	struct pt_regs *p;
 
@@ -90,14 +89,14 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
 	if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
 		return NULL;
 	p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
-	if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
-		fault = "syscall";
-	else {
-		if (kbt->verbose) {     /* else we aren't going to use it */
-			snprintf(fault_buf, sizeof(fault_buf),
+	if (kbt->verbose) {     /* else we aren't going to use it */
+		if (p->faultnum == INT_SWINT_1 ||
+		    p->faultnum == INT_SWINT_1_SIGRETURN)
+			snprintf(fault, sizeof(fault),
+				 "syscall %ld", p->regs[TREG_SYSCALL_NR]);
+		else
+			snprintf(fault, sizeof(fault),
 				 "interrupt %ld", p->faultnum);
-			fault = fault_buf;
-		}
 	}
 	if (EX1_PL(p->ex1) == KERNEL_PL &&
 	    __kernel_text_address(p->pc) &&