mce-inject.c

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/*
 * 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 = &__get_cpu_var(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 = &__get_cpu_var(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 = &__get_cpu_var(injectm);
    int context = MCJ_CTX(m->inject_flags);
    int ret = 0;
    int cpu = m->extcpu;

    if (m->inject_flags & MCJ_EXCEPTION) {
        printk(KERN_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:
            printk(KERN_INFO "Invalid MCE context\n");
            ret = -EINVAL;
        }
        printk(KERN_INFO "MCE exception done on CPU %d\n", cpu);
    } else if (m->status) {
        printk(KERN_INFO "Starting machine check poll CPU %d\n", cpu);
        raise_poll(m);
        mce_notify_irq();
        printk(KERN_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;

#ifdef CONFIG_X86_LOCAL_APIC
    if (m->inject_flags & (MCJ_IRQ_BRAODCAST | 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_BRAODCAST) {
                /*
                 * 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)) {
                printk(KERN_ERR
                "Timeout waiting for mce inject %lx\n",
                    *cpumask_bits(mce_inject_cpumask));
                break;
            }
            cpu_relax();
        }
        raise_local();
        put_cpu();
        put_online_cpus();
    } else
#endif
    {
        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;
    printk(KERN_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");