1 files changed, 433 insertions, 0 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
new file mode 100644
index 000000000000..7ec5bd140b87
--- /dev/null
+++ b/arch/x86/kernel/nmi.c
@@ -0,0 +1,433 @@
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
+ *  Copyright (C) 2011	Don Zickus Red Hat, Inc.
+ *
+ *  Pentium III FXSR, SSE support
+ *	Gareth Hughes <gareth@valinux.com>, May 2000
+ */
+
+/*
+ * Handle hardware traps and faults.
+ */
+#include <linux/spinlock.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/nmi.h>
+#include <linux/delay.h>
+#include <linux/hardirq.h>
+#include <linux/slab.h>
+
+#include <linux/mca.h>
+
+#if defined(CONFIG_EDAC)
+#include <linux/edac.h>
+#endif
+
+#include <linux/atomic.h>
+#include <asm/traps.h>
+#include <asm/mach_traps.h>
+#include <asm/nmi.h>
+
+#define NMI_MAX_NAMELEN	16
+struct nmiaction {
+	struct list_head list;
+	nmi_handler_t handler;
+	unsigned int flags;
+	char *name;
+};
+
+struct nmi_desc {
+	spinlock_t lock;
+	struct list_head head;
+};
+
+static struct nmi_desc nmi_desc[NMI_MAX] = 
+{
+	{
+		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[0].lock),
+		.head = LIST_HEAD_INIT(nmi_desc[0].head),
+	},
+	{
+		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[1].lock),
+		.head = LIST_HEAD_INIT(nmi_desc[1].head),
+	},
+
+};
+
+struct nmi_stats {
+	unsigned int normal;
+	unsigned int unknown;
+	unsigned int external;
+	unsigned int swallow;
+};
+
+static DEFINE_PER_CPU(struct nmi_stats, nmi_stats);
+
+static int ignore_nmis;
+
+int unknown_nmi_panic;
+/*
+ * Prevent NMI reason port (0x61) being accessed simultaneously, can
+ * only be used in NMI handler.
+ */
+static DEFINE_RAW_SPINLOCK(nmi_reason_lock);
+
+static int __init setup_unknown_nmi_panic(char *str)
+{
+	unknown_nmi_panic = 1;
+	return 1;
+}
+__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
+
+#define nmi_to_desc(type) (&nmi_desc[type])
+
+static int notrace __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2b)
+{
+	struct nmi_desc *desc = nmi_to_desc(type);
+	struct nmiaction *a;
+	int handled=0;
+
+	rcu_read_lock();
+
+	/*
+	 * NMIs are edge-triggered, which means if you have enough
+	 * of them concurrently, you can lose some because only one
+	 * can be latched at any given time.  Walk the whole list
+	 * to handle those situations.
+	 */
+	list_for_each_entry_rcu(a, &desc->head, list)
+		handled += a->handler(type, regs);
+
+	rcu_read_unlock();
+
+	/* return total number of NMI events handled */
+	return handled;
+}
+
+static int __setup_nmi(unsigned int type, struct nmiaction *action)
+{
+	struct nmi_desc *desc = nmi_to_desc(type);
+	unsigned long flags;
+
+	spin_lock_irqsave(&desc->lock, flags);
+
+	/*
+	 * most handlers of type NMI_UNKNOWN never return because
+	 * they just assume the NMI is theirs.  Just a sanity check
+	 * to manage expectations
+	 */
+	WARN_ON_ONCE(type == NMI_UNKNOWN && !list_empty(&desc->head));
+
+	/*
+	 * some handlers need to be executed first otherwise a fake
+	 * event confuses some handlers (kdump uses this flag)
+	 */
+	if (action->flags & NMI_FLAG_FIRST)
+		list_add_rcu(&action->list, &desc->head);
+	else
+		list_add_tail_rcu(&action->list, &desc->head);
+	
+	spin_unlock_irqrestore(&desc->lock, flags);
+	return 0;
+}
+
+static struct nmiaction *__free_nmi(unsigned int type, const char *name)
+{
+	struct nmi_desc *desc = nmi_to_desc(type);
+	struct nmiaction *n;
+	unsigned long flags;
+
+	spin_lock_irqsave(&desc->lock, flags);
+
+	list_for_each_entry_rcu(n, &desc->head, list) {
+		/*
+		 * the name passed in to describe the nmi handler
+		 * is used as the lookup key
+		 */
+		if (!strcmp(n->name, name)) {
+			WARN(in_nmi(),
+				"Trying to free NMI (%s) from NMI context!\n", n->name);
+			list_del_rcu(&n->list);
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&desc->lock, flags);
+	synchronize_rcu();
+	return (n);
+}
+
+int register_nmi_handler(unsigned int type, nmi_handler_t handler,
+			unsigned long nmiflags, const char *devname)
+{
+	struct nmiaction *action;
+	int retval = -ENOMEM;
+
+	if (!handler)
+		return -EINVAL;
+
+	action = kzalloc(sizeof(struct nmiaction), GFP_KERNEL);
+	if (!action)
+		goto fail_action;
+
+	action->handler = handler;
+	action->flags = nmiflags;
+	action->name = kstrndup(devname, NMI_MAX_NAMELEN, GFP_KERNEL);
+	if (!action->name)
+		goto fail_action_name;
+
+	retval = __setup_nmi(type, action);
+
+	if (retval)
+		goto fail_setup_nmi;
+
+	return retval;
+
+fail_setup_nmi:
+	kfree(action->name);
+fail_action_name:
+	kfree(action);
+fail_action:	
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(register_nmi_handler);
+
+void unregister_nmi_handler(unsigned int type, const char *name)
+{
+	struct nmiaction *a;
+
+	a = __free_nmi(type, name);
+	if (a) {
+		kfree(a->name);
+		kfree(a);
+	}
+}
+
+EXPORT_SYMBOL_GPL(unregister_nmi_handler);
+
+static notrace __kprobes void
+pci_serr_error(unsigned char reason, struct pt_regs *regs)
+{
+	pr_emerg("NMI: PCI system error (SERR) for reason %02x on CPU %d.\n",
+		 reason, smp_processor_id());
+
+	/*
+	 * On some machines, PCI SERR line is used to report memory
+	 * errors. EDAC makes use of it.
+	 */
+#if defined(CONFIG_EDAC)
+	if (edac_handler_set()) {
+		edac_atomic_assert_error();
+		return;
+	}
+#endif
+
+	if (panic_on_unrecovered_nmi)
+		panic("NMI: Not continuing");
+
+	pr_emerg("Dazed and confused, but trying to continue\n");
+
+	/* Clear and disable the PCI SERR error line. */
+	reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_SERR;
+	outb(reason, NMI_REASON_PORT);
+}
+
+static notrace __kprobes void
+io_check_error(unsigned char reason, struct pt_regs *regs)
+{
+	unsigned long i;
+
+	pr_emerg(
+	"NMI: IOCK error (debug interrupt?) for reason %02x on CPU %d.\n",
+		 reason, smp_processor_id());
+	show_registers(regs);
+
+	if (panic_on_io_nmi)
+		panic("NMI IOCK error: Not continuing");
+
+	/* Re-enable the IOCK line, wait for a few seconds */
+	reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_IOCHK;
+	outb(reason, NMI_REASON_PORT);
+
+	i = 20000;
+	while (--i) {
+		touch_nmi_watchdog();
+		udelay(100);
+	}
+
+	reason &= ~NMI_REASON_CLEAR_IOCHK;
+	outb(reason, NMI_REASON_PORT);
+}
+
+static notrace __kprobes void
+unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
+{
+	int handled;
+
+	/*
+	 * Use 'false' as back-to-back NMIs are dealt with one level up.
+	 * Of course this makes having multiple 'unknown' handlers useless
+	 * as only the first one is ever run (unless it can actually determine
+	 * if it caused the NMI)
+	 */
+	handled = nmi_handle(NMI_UNKNOWN, regs, false);
+	if (handled) {
+		__this_cpu_add(nmi_stats.unknown, handled);
+		return;
+	}
+
+	__this_cpu_add(nmi_stats.unknown, 1);
+
+#ifdef CONFIG_MCA
+	/*
+	 * Might actually be able to figure out what the guilty party
+	 * is:
+	 */
+	if (MCA_bus) {
+		mca_handle_nmi();
+		return;
+	}
+#endif
+	pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
+		 reason, smp_processor_id());
+
+	pr_emerg("Do you have a strange power saving mode enabled?\n");
+	if (unknown_nmi_panic || panic_on_unrecovered_nmi)
+		panic("NMI: Not continuing");
+
+	pr_emerg("Dazed and confused, but trying to continue\n");
+}
+
+static DEFINE_PER_CPU(bool, swallow_nmi);
+static DEFINE_PER_CPU(unsigned long, last_nmi_rip);
+
+static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
+{
+	unsigned char reason = 0;
+	int handled;
+	bool b2b = false;
+
+	/*
+	 * CPU-specific NMI must be processed before non-CPU-specific
+	 * NMI, otherwise we may lose it, because the CPU-specific
+	 * NMI can not be detected/processed on other CPUs.
+	 */
+
+	/*
+	 * Back-to-back NMIs are interesting because they can either
+	 * be two NMI or more than two NMIs (any thing over two is dropped
+	 * due to NMI being edge-triggered).  If this is the second half
+	 * of the back-to-back NMI, assume we dropped things and process
+	 * more handlers.  Otherwise reset the 'swallow' NMI behaviour
+	 */
+	if (regs->ip == __this_cpu_read(last_nmi_rip))
+		b2b = true;
+	else
+		__this_cpu_write(swallow_nmi, false);
+
+	__this_cpu_write(last_nmi_rip, regs->ip);
+
+	handled = nmi_handle(NMI_LOCAL, regs, b2b);
+	__this_cpu_add(nmi_stats.normal, handled);
+	if (handled) {
+		/*
+		 * There are cases when a NMI handler handles multiple
+		 * events in the current NMI.  One of these events may
+		 * be queued for in the next NMI.  Because the event is
+		 * already handled, the next NMI will result in an unknown
+		 * NMI.  Instead lets flag this for a potential NMI to
+		 * swallow.
+		 */
+		if (handled > 1)
+			__this_cpu_write(swallow_nmi, true);
+		return;
+	}
+
+	/* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
+	raw_spin_lock(&nmi_reason_lock);
+	reason = get_nmi_reason();
+
+	if (reason & NMI_REASON_MASK) {
+		if (reason & NMI_REASON_SERR)
+			pci_serr_error(reason, regs);
+		else if (reason & NMI_REASON_IOCHK)
+			io_check_error(reason, regs);
+#ifdef CONFIG_X86_32
+		/*
+		 * Reassert NMI in case it became active
+		 * meanwhile as it's edge-triggered:
+		 */
+		reassert_nmi();
+#endif
+		__this_cpu_add(nmi_stats.external, 1);
+		raw_spin_unlock(&nmi_reason_lock);
+		return;
+	}
+	raw_spin_unlock(&nmi_reason_lock);
+
+	/*
+	 * Only one NMI can be latched at a time.  To handle
+	 * this we may process multiple nmi handlers at once to
+	 * cover the case where an NMI is dropped.  The downside
+	 * to this approach is we may process an NMI prematurely,
+	 * while its real NMI is sitting latched.  This will cause
+	 * an unknown NMI on the next run of the NMI processing.
+	 *
+	 * We tried to flag that condition above, by setting the
+	 * swallow_nmi flag when we process more than one event.
+	 * This condition is also only present on the second half
+	 * of a back-to-back NMI, so we flag that condition too.
+	 *
+	 * If both are true, we assume we already processed this
+	 * NMI previously and we swallow it.  Otherwise we reset
+	 * the logic.
+	 *
+	 * There are scenarios where we may accidentally swallow
+	 * a 'real' unknown NMI.  For example, while processing
+	 * a perf NMI another perf NMI comes in along with a
+	 * 'real' unknown NMI.  These two NMIs get combined into
+	 * one (as descibed above).  When the next NMI gets
+	 * processed, it will be flagged by perf as handled, but
+	 * noone will know that there was a 'real' unknown NMI sent
+	 * also.  As a result it gets swallowed.  Or if the first
+	 * perf NMI returns two events handled then the second
+	 * NMI will get eaten by the logic below, again losing a
+	 * 'real' unknown NMI.  But this is the best we can do
+	 * for now.
+	 */
+	if (b2b && __this_cpu_read(swallow_nmi))
+		__this_cpu_add(nmi_stats.swallow, 1);
+	else
+		unknown_nmi_error(reason, regs);
+}
+
+dotraplinkage notrace __kprobes void
+do_nmi(struct pt_regs *regs, long error_code)
+{
+	nmi_enter();
+
+	inc_irq_stat(__nmi_count);
+
+	if (!ignore_nmis)
+		default_do_nmi(regs);
+
+	nmi_exit();
+}
+
+void stop_nmi(void)
+{
+	ignore_nmis++;
+}
+
+void restart_nmi(void)
+{
+	ignore_nmis--;
+}
+
+/* reset the back-to-back NMI logic */
+void local_touch_nmi(void)
+{
+	__this_cpu_write(last_nmi_rip, 0);
+}