kgdb: Add module event hooks

Allow gdb to auto load kernel modules when it is attached,
which makes it trivially easy to debug module init functions
or pre-set breakpoints in a kernel module that has not loaded yet.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 0557f24c6bca0d1da04f620c163a70010930737e..8bfa373cd5fdfdb2a0bcc88819898751b4876a15 100644 (file)
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -688,6 +688,22 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
        return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 }
 
+/*
+ * GDB places a breakpoint at this function to know dynamically
+ * loaded objects. It's not defined static so that only one instance with this
+ * name exists in the kernel.
+ */
+
+static int module_event(struct notifier_block *self, unsigned long val,
+       void *data)
+{
+       return 0;
+}
+
+static struct notifier_block dbg_module_load_nb = {
+       .notifier_call  = module_event,
+};
+
 int kgdb_nmicallback(int cpu, void *regs)
 {
 #ifdef CONFIG_SMP
@@ -816,6 +832,7 @@ static void kgdb_register_callbacks(void)
                kgdb_arch_init();
                if (!dbg_is_early)
                        kgdb_arch_late();
+               register_module_notifier(&dbg_module_load_nb);
                register_reboot_notifier(&dbg_reboot_notifier);
                atomic_notifier_chain_register(&panic_notifier_list,
                                               &kgdb_panic_event_nb);
@@ -839,6 +856,7 @@ static void kgdb_unregister_callbacks(void)
        if (kgdb_io_module_registered) {
                kgdb_io_module_registered = 0;
                unregister_reboot_notifier(&dbg_reboot_notifier);
+               unregister_module_notifier(&dbg_module_load_nb);
                atomic_notifier_chain_unregister(&panic_notifier_list,
                                               &kgdb_panic_event_nb);
                kgdb_arch_exit();