[PATCH v3 2/2] exit: dump current pt_regs info on global init exit

["qiwu.chen" <qiwuchen55@gmail.com>]

Currently, it's hard to debug panic issues caused by kill init,
since there is no debug info from user mode in current panic msg
such as the user_regs and maps info.

This patch dumps current pt_regs info on global init exit for debugging.

Signed-off-by: qiwu.chen <qiwu.chen@transsion.com>
---
 kernel/exit.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 0d62a53605df..3d5aa88ba517 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -11,6 +11,7 @@
 #include <linux/sched/mm.h>
 #include <linux/sched/stat.h>
 #include <linux/sched/task.h>
+#include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
 #include <linux/sched/cputime.h>
 #include <linux/interrupt.h>
@@ -847,10 +848,12 @@ void __noreturn do_exit(long code)
 		 * If the last thread of global init has exited, panic
 		 * immediately to get a useable coredump.
 		 */
-		if (unlikely(is_global_init(tsk)))
+		if (unlikely(is_global_init(tsk))) {
+			/* dump the pt_regs of current thread for debugging. */
+			show_regs(task_pt_regs(tsk));
 			panic("Attempted to kill init! exitcode=0x%08x\n",
 				tsk->signal->group_exit_code ?: (int)code);
-
+		}
 #ifdef CONFIG_POSIX_TIMERS
 		hrtimer_cancel(&tsk->signal->real_timer);
 		exit_itimers(tsk);
-- 
2.25.1