kgdb,debug_core: add the ability to control the reboot notifier
Sometimes it is desirable to stop the kernel debugger before allowing
a system to reboot either with kdb or kgdb. This patch adds the
ability to turn the reboot notifier on and off or enter the debugger
and stop kernel execution before rebooting.
It is possible to change the setting after booting the kernel with the
following:
echo 1 > /sys/module/debug_core/parameters/kgdbreboot
It is also possible to change this setting using kdb / kgdb to
manipulate the variable directly.
Using KDB:
mm kgdbreboot 1
Using gdb:
set kgdbreboot=1
Reported-by: Jan Kiszka <jan.kiszka@siemens.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 3c1ad4e..3f88a45 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -76,6 +76,8 @@
struct kgdb_io *dbg_io_ops;
static DEFINE_SPINLOCK(kgdb_registration_lock);
+/* Action for the reboot notifiter, a global allow kdb to change it */
+static int kgdbreboot;
/* kgdb console driver is loaded */
static int kgdb_con_registered;
/* determine if kgdb console output should be used */
@@ -97,6 +99,7 @@
early_param("kgdbcon", opt_kgdb_con);
module_param(kgdb_use_con, int, 0644);
+module_param(kgdbreboot, int, 0644);
/*
* Holds information about breakpoints in a kernel. These breakpoints are
@@ -788,8 +791,21 @@
static int
dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
{
+ /*
+ * Take the following action on reboot notify depending on value:
+ * 1 == Enter debugger
+ * 0 == [the default] detatch debug client
+ * -1 == Do nothing... and use this until the board resets
+ */
+ switch (kgdbreboot) {
+ case 1:
+ kgdb_breakpoint();
+ case -1:
+ goto done;
+ }
if (!dbg_kdb_mode)
gdbstub_exit(code);
+done:
return NOTIFY_DONE;
}
