/*
 * Machine check injection support.
 * Copyright 2008 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 *
 * Authors:
 * Andi Kleen
 * Ying Huang
 */
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/preempt.h>
#include <linux/smp.h>
#include <linux/notifier.h>
#include <linux/kdebug.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include <linux/gfp.h>
#include <asm/mce.h>
#include <asm/apic.h>
#include <asm/nmi.h>

/* Update fake mce registers on current CPU. */
static void inject_mce(struct mce *m)
{
	struct mce *i = &per_cpu(injectm, m->extcpu);

	/* Make sure no one reads partially written injectm */
	i->finished = 0;
	mb();
	m->finished = 0;
	/* First set the fields after finished */
	i->extcpu = m->extcpu;
	mb();
	/* Now write record in order, finished last (except above) */
	memcpy(i, m, sizeof(struct mce));
	/* Finally activate it */
	mb();
	i->finished = 1;
}

static void raise_poll(struct mce *m)
{
	unsigned long flags;
	mce_banks_t b;

	memset(&b, 0xff, sizeof(mce_banks_t));
	local_irq_save(flags);
	machine_check_poll(0, &b);
	local_irq_restore(flags);
	m->finished = 0;
}

static void raise_exception(struct mce *m, struct pt_regs *pregs)
{
	struct pt_regs regs;
	unsigned long flags;

	if (!pregs) {
		memset(&regs, 0, sizeof(struct pt_regs));
		regs.ip = m->ip;
		regs.cs = m->cs;
		pregs = &regs;
	}
	/* in mcheck exeception handler, irq will be disabled */
	local_irq_save(flags);
	do_machine_check(pregs, 0);
	local_irq_restore(flags);
	m->finished = 0;
}

static cpumask_var_t mce_inject_cpumask;
static DEFINE_MUTEX(mce_inject_mutex);

static int mce_raise_notify(unsigned int cmd, struct pt_regs *regs)
{
	int cpu = smp_processor_id();
	struct mce *m = this_cpu_ptr(&injectm);
	if (!cpumask_test_cpu(cpu, mce_inject_cpumask))
		return NMI_DONE;
	cpumask_clear_cpu(cpu, mce_inject_cpumask);
	if (m->inject_flags & MCJ_EXCEPTION)
		raise_exception(m, regs);
	else if (m->status)
		raise_poll(m);
	return NMI_HANDLED;
}

static void mce_irq_ipi(void *info)
{
	int cpu = smp_processor_id();
	struct mce *m = this_cpu_ptr(&injectm);

	if (cpumask_test_cpu(cpu, mce_inject_cpumask) &&
			m->inject_flags & MCJ_EXCEPTION) {
		cpumask_clear_cpu(cpu, mce_inject_cpumask);
		raise_exception(m, NULL);
	}
}

/* Inject mce on current CPU */
static int raise_local(void)
{
	struct mce *m = this_cpu_ptr(&injectm);
	int context = MCJ_CTX(m->inject_flags);
	int ret = 0;
	int cpu = m->extcpu;

	if (m->inject_flags & MCJ_EXCEPTION) {
		pr_info("Triggering MCE exception on CPU %d\n", cpu);
		switch (context) {
		case MCJ_CTX_IRQ:
			/*
			 * Could do more to fake interrupts like
			 * calling irq_enter, but the necessary
			 * machinery isn't exported currently.
			 */
			/*FALL THROUGH*/
		case MCJ_CTX_PROCESS:
			raise_exception(m, NULL);
			break;
		default:
			pr_info("Invalid MCE context\n");
			ret = -EINVAL;
		}
		pr_info("MCE exception done on CPU %d\n", cpu);
	} else if (m->status) {
		pr_info("Starting machine check poll CPU %d\n", cpu);
		raise_poll(m);
		mce_notify_irq();
		pr_info("Machine check poll done on CPU %d\n", cpu);
	} else
		m->finished = 0;

	return ret;
}

static void raise_mce(struct mce *m)
{
	int context = MCJ_CTX(m->inject_flags);

	inject_mce(m);

	if (context == MCJ_CTX_RANDOM)
		return;

	if (m->inject_flags & (MCJ_IRQ_BROADCAST | MCJ_NMI_BROADCAST)) {
		unsigned long start;
		int cpu;

		get_online_cpus();
		cpumask_copy(mce_inject_cpumask, cpu_online_mask);
		cpumask_clear_cpu(get_cpu(), mce_inject_cpumask);
		for_each_online_cpu(cpu) {
			struct mce *mcpu = &per_cpu(injectm, cpu);
			if (!mcpu->finished ||
			    MCJ_CTX(mcpu->inject_flags) != MCJ_CTX_RANDOM)
				cpumask_clear_cpu(cpu, mce_inject_cpumask);
		}
		if (!cpumask_empty(mce_inject_cpumask)) {
			if (m->inject_flags & MCJ_IRQ_BROADCAST) {
				/*
				 * don't wait because mce_irq_ipi is necessary
				 * to be sync with following raise_local
				 */
				preempt_disable();
				smp_call_function_many(mce_inject_cpumask,
					mce_irq_ipi, NULL, 0);
				preempt_enable();
			} else if (m->inject_flags & MCJ_NMI_BROADCAST)
				apic->send_IPI_mask(mce_inject_cpumask,
						NMI_VECTOR);
		}
		start = jiffies;
		while (!cpumask_empty(mce_inject_cpumask)) {
			if (!time_before(jiffies, start + 2*HZ)) {
				pr_err("Timeout waiting for mce inject %lx\n",
					*cpumask_bits(mce_inject_cpumask));
				break;
			}
			cpu_relax();
		}
		raise_local();
		put_cpu();
		put_online_cpus();
	} else {
		preempt_disable();
		raise_local();
		preempt_enable();
	}
}

/* Error injection interface */
static ssize_t mce_write(struct file *filp, const char __user *ubuf,
			 size_t usize, loff_t *off)
{
	struct mce m;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	/*
	 * There are some cases where real MSR reads could slip
	 * through.
	 */
	if (!boot_cpu_has(X86_FEATURE_MCE) || !boot_cpu_has(X86_FEATURE_MCA))
		return -EIO;

	if ((unsigned long)usize > sizeof(struct mce))
		usize = sizeof(struct mce);
	if (copy_from_user(&m, ubuf, usize))
		return -EFAULT;

	if (m.extcpu >= num_possible_cpus() || !cpu_online(m.extcpu))
		return -EINVAL;

	/*
	 * Need to give user space some time to set everything up,
	 * so do it a jiffie or two later everywhere.
	 */
	schedule_timeout(2);

	mutex_lock(&mce_inject_mutex);
	raise_mce(&m);
	mutex_unlock(&mce_inject_mutex);
	return usize;
}

static int inject_init(void)
{
	if (!alloc_cpumask_var(&mce_inject_cpumask, GFP_KERNEL))
		return -ENOMEM;
	pr_info("Machine check injector initialized\n");
	register_mce_write_callback(mce_write);
	register_nmi_handler(NMI_LOCAL, mce_raise_notify, 0,
				"mce_notify");
	return 0;
}

module_init(inject_init);
/*
 * Cannot tolerate unloading currently because we cannot
 * guarantee all openers of mce_chrdev will get a reference to us.
 */
MODULE_LICENSE("GPL");