[AVR32] NMI debugging

Change the NMI handler to use the die notifier chain to signal anyone
who cares. Add a simple "nmi debugger" which hooks into this chain and
that may dump registers, task state, etc. when it happens.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

4 files changed, 112 insertions, 3 deletions

diff --git a/arch/avr32/kernel/Makefile b/arch/avr32/kernel/Makefile
index bc224a4e39fe..e4b6d122b033 100644
--- a/arch/avr32/kernel/Makefile
+++ b/arch/avr32/kernel/Makefile
@@ -12,3 +12,4 @@ obj-y				+= init_task.o switch_to.o cpu.o
 obj-$(CONFIG_MODULES)           += module.o avr32_ksyms.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
+obj-$(CONFIG_NMI_DEBUGGING)     += nmi_debug.o
diff --git a/arch/avr32/kernel/irq.c b/arch/avr32/kernel/irq.c
index 61f2de266f62..a8e767d836aa 100644
--- a/arch/avr32/kernel/irq.c
+++ b/arch/avr32/kernel/irq.c
@@ -25,6 +25,17 @@ void ack_bad_irq(unsigned int irq)
         printk("unexpected IRQ %u\n", irq);
 }
 
+/* May be overridden by platform code */
+int __weak nmi_enable(void)
+{
+        return -ENOSYS;
+}
+
+void __weak nmi_disable(void)
+{
+
+}
+
 #ifdef CONFIG_PROC_FS
 int show_interrupts(struct seq_file *p, void *v)
 {
diff --git a/arch/avr32/kernel/nmi_debug.c b/arch/avr32/kernel/nmi_debug.c
new file mode 100644
index 000000000000..3414b8566c29
--- /dev/null
+++ b/arch/avr32/kernel/nmi_debug.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/delay.h>
+#include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+
+#include <asm/irq.h>
+
+enum nmi_action {
+        NMI_SHOW_STATE  = 1 << 0,
+        NMI_SHOW_REGS   = 1 << 1,
+        NMI_DIE         = 1 << 2,
+        NMI_DEBOUNCE    = 1 << 3,
+};
+
+static unsigned long nmi_actions;
+
+static int nmi_debug_notify(struct notifier_block *self,
+                unsigned long val, void *data)
+{
+        struct die_args *args = data;
+
+        if (likely(val != DIE_NMI))
+                return NOTIFY_DONE;
+
+        if (nmi_actions & NMI_SHOW_STATE)
+                show_state();
+        if (nmi_actions & NMI_SHOW_REGS)
+                show_regs(args->regs);
+        if (nmi_actions & NMI_DEBOUNCE)
+                mdelay(10);
+        if (nmi_actions & NMI_DIE)
+                return NOTIFY_BAD;
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block nmi_debug_nb = {
+        .notifier_call = nmi_debug_notify,
+};
+
+static int __init nmi_debug_setup(char *str)
+{
+        char *p, *sep;
+
+        register_die_notifier(&nmi_debug_nb);
+        if (nmi_enable()) {
+                printk(KERN_WARNING "Unable to enable NMI.\n");
+                return 0;
+        }
+
+        if (*str != '=')
+                return 0;
+
+        for (p = str + 1; *p; p = sep + 1) {
+                sep = strchr(p, ',');
+                if (sep)
+                        *sep = 0;
+                if (strcmp(p, "state") == 0)
+                        nmi_actions |= NMI_SHOW_STATE;
+                else if (strcmp(p, "regs") == 0)
+                        nmi_actions |= NMI_SHOW_REGS;
+                else if (strcmp(p, "debounce") == 0)
+                        nmi_actions |= NMI_DEBOUNCE;
+                else if (strcmp(p, "die") == 0)
+                        nmi_actions |= NMI_DIE;
+                else
+                        printk(KERN_WARNING "NMI: Unrecognized action `%s'\n",
+                                p);
+                if (!sep)
+                        break;
+        }
+
+        return 0;
+}
+__setup("nmi_debug", nmi_debug_setup);
diff --git a/arch/avr32/kernel/traps.c b/arch/avr32/kernel/traps.c
index 870c075e6314..cf6f686d9b0b 100644
--- a/arch/avr32/kernel/traps.c
+++ b/arch/avr32/kernel/traps.c
@@ -9,6 +9,7 @@
 #include <linux/bug.h>
 #include <linux/init.h>
 #include <linux/kallsyms.h>
+#include <linux/kdebug.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
 #include <linux/sched.h>
@@ -107,9 +108,23 @@ void _exception(long signr, struct pt_regs *regs, int code,
 
 asmlinkage void do_nmi(unsigned long ecr, struct pt_regs *regs)
 {
-        printk(KERN_ALERT "Got Non-Maskable Interrupt, dumping regs\n");
-        show_regs_log_lvl(regs, KERN_ALERT);
-        show_stack_log_lvl(current, regs->sp, regs, KERN_ALERT);
+        int ret;
+
+        nmi_enter();
+
+        ret = notify_die(DIE_NMI, "NMI", regs, 0, ecr, SIGINT);
+        switch (ret) {
+        case NOTIFY_OK:
+        case NOTIFY_STOP:
+                return;
+        case NOTIFY_BAD:
+                die("Fatal Non-Maskable Interrupt", regs, SIGINT);
+        default:
+                break;
+        }
+
+        printk(KERN_ALERT "Got NMI, but nobody cared. Disabling...\n");
+        nmi_disable();
 }
 
 asmlinkage void do_critical_exception(unsigned long ecr, struct pt_regs *regs)