sh: kgdb: Rework breakpoint handling on top of notifier chain.

This kills off kgdb's breakpoint handler and ties in to the notifier
chain instead.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/kernel/debugtraps.S

@@ -13,7 +13,6 @@
 #include <linux/linkage.h>
 
 #if !defined(CONFIG_KGDB)
-#define breakpoint_trap_handler		debug_trap_handler
 #define singlestep_trap_handler		debug_trap_handler
 #endif
 

arch/sh/kernel/kgdb.c

 /*
  * SuperH KGDB support
  *
- * Copyright (C) 2008  Paul Mundt
+ * Copyright (C) 2008 - 2009  Paul Mundt
  *
  * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
  *
@@ -251,24 +251,60 @@ BUILD_TRAP_HANDLER(singlestep)
 	local_irq_restore(flags);
 }
 
+static int __kgdb_notify(struct die_args *args, unsigned long cmd)
+{
+	int ret;
+
+	switch (cmd) {
+	case DIE_BREAKPOINT:
+		/*
+		 * This means a user thread is single stepping
+		 * a system call which should be ignored
+		 */
+		if (test_thread_flag(TIF_SINGLESTEP))
+			return NOTIFY_DONE;
+
+		ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
+					    args->err, args->regs);
+		if (ret)
+			return NOTIFY_DONE;
+
+		break;
+	}
 
-BUILD_TRAP_HANDLER(breakpoint)
+	return NOTIFY_STOP;
+}
+
+static int
+kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 {
 	unsigned long flags;
-	TRAP_HANDLER_DECL;
+	int ret;
 
 	local_irq_save(flags);
-	kgdb_handle_exception(vec >> 2, SIGTRAP, 0, regs);
+	ret = __kgdb_notify(ptr, cmd);
 	local_irq_restore(flags);
+
+	return ret;
 }
 
+static struct notifier_block kgdb_notifier = {
+	.notifier_call	= kgdb_notify,
+
+	/*
+	 * Lowest-prio notifier priority, we want to be notified last:
+	 */
+	.priority	= -INT_MAX,
+};
+
 int kgdb_arch_init(void)
 {
-	return 0;
+	return register_die_notifier(&kgdb_notifier);
 }
 
 void kgdb_arch_exit(void)
 {
+	unregister_die_notifier(&kgdb_notifier);
 }
 
 struct kgdb_arch arch_kgdb_ops = {