kdb,debug_core: Allow the debug core to receive a panic notification

It is highly desirable to trap into kdb on panic.  The debug core will
attempt to register as the first in line for the panic notifier.

CC: Ingo Molnar <mingo@elte.hu>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index b38bb25..64b5588 100644 (file)
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -762,11 +762,28 @@ static struct sysrq_key_op sysrq_dbg_op = {
 };
 #endif
 
+static int kgdb_panic_event(struct notifier_block *self,
+                           unsigned long val,
+                           void *data)
+{
+       if (dbg_kdb_mode)
+               kdb_printf("PANIC: %s\n", (char *)data);
+       kgdb_breakpoint();
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block kgdb_panic_event_nb = {
+       .notifier_call  = kgdb_panic_event,
+       .priority       = INT_MAX,
+};
+
 static void kgdb_register_callbacks(void)
 {
        if (!kgdb_io_module_registered) {
                kgdb_io_module_registered = 1;
                kgdb_arch_init();
+               atomic_notifier_chain_register(&panic_notifier_list,
+                                              &kgdb_panic_event_nb);
 #ifdef CONFIG_MAGIC_SYSRQ
                register_sysrq_key('g', &sysrq_dbg_op);
 #endif
@@ -786,6 +803,8 @@ static void kgdb_unregister_callbacks(void)
         */
        if (kgdb_io_module_registered) {
                kgdb_io_module_registered = 0;
+               atomic_notifier_chain_unregister(&panic_notifier_list,
+                                              &kgdb_panic_event_nb);
                kgdb_arch_exit();
 #ifdef CONFIG_MAGIC_SYSRQ
                unregister_sysrq_key('g', &sysrq_dbg_op);