arm64: Add dump_backtrace() in show_regs

Generic code expects show_regs() to dump the stack, but arm64's
show_regs() does not. This makes it hard to debug softlockups and
other issues that result in show_regs() being called.

This patch updates arm64's show_regs() to dump the stack, as common
code expects.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
[will: folded in bug_handler fix from mrutland]
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/stacktrace.h

@@ -30,5 +30,6 @@ struct stackframe {
 extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame);
 extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 			    int (*fn)(struct stackframe *, void *), void *data);
+extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
 
 #endif	/* __ASM_STACKTRACE_H */

arch/arm64/kernel/process.c

@@ -210,6 +210,7 @@ void __show_regs(struct pt_regs *regs)
 void show_regs(struct pt_regs * regs)
 {
 	__show_regs(regs);
+	dump_backtrace(regs, NULL);
 }
 
 static void tls_thread_flush(void)

arch/arm64/kernel/traps.c

@@ -140,7 +140,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
 	}
 }
 
-static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
 	struct stackframe frame;
 	unsigned long irq_stack_ptr;
@@ -728,8 +728,6 @@ static int bug_handler(struct pt_regs *regs, unsigned int esr)
 		break;
 
 	case BUG_TRAP_TYPE_WARN:
-		/* Ideally, report_bug() should backtrace for us... but no. */
-		dump_backtrace(regs, NULL);
 		break;
 
 	default: