/*
 * MCE grading rules.
 * Copyright 2008, 2009 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.
 *
 * Author: Andi Kleen
 */
#include <linux/kernel.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/debugfs.h>
#include <asm/mce.h>

#include "mce-internal.h"

/*
 * Grade an mce by severity. In general the most severe ones are processed
 * first. Since there are quite a lot of combinations test the bits in a
 * table-driven way. The rules are simply processed in order, first
 * match wins.
 *
 * Note this is only used for machine check exceptions, the corrected
 * errors use much simpler rules. The exceptions still check for the corrected
 * errors, but only to leave them alone for the CMCI handler (except for
 * panic situations)
 */

enum context { IN_KERNEL = 1, IN_USER = 2 };
enum ser { SER_REQUIRED = 1, NO_SER = 2 };

static struct severity {
        u64 mask;
        u64 result;
        unsigned char sev;
        unsigned char mcgmask;
        unsigned char mcgres;
        unsigned char ser;
        unsigned char context;
        unsigned char covered;
        char *msg;
} severities[] = {
#define MCESEV(s, m, c...) { .sev = MCE_ ## s ## _SEVERITY, .msg = m, ## c }
#define  KERNEL         .context = IN_KERNEL
#define  USER           .context = IN_USER
#define  SER            .ser = SER_REQUIRED
#define  NOSER          .ser = NO_SER
#define  BITCLR(x)      .mask = x, .result = 0
#define  BITSET(x)      .mask = x, .result = x
#define  MCGMASK(x, y)  .mcgmask = x, .mcgres = y
#define  MASK(x, y)     .mask = x, .result = y
#define MCI_UC_S (MCI_STATUS_UC|MCI_STATUS_S)
#define MCI_UC_SAR (MCI_STATUS_UC|MCI_STATUS_S|MCI_STATUS_AR)
#define MCI_ADDR (MCI_STATUS_ADDRV|MCI_STATUS_MISCV)

        MCESEV(
                NO, "Invalid",
                BITCLR(MCI_STATUS_VAL)
                ),
        MCESEV(
                NO, "Not enabled",
                BITCLR(MCI_STATUS_EN)
                ),
        MCESEV(
                PANIC, "Processor context corrupt",
                BITSET(MCI_STATUS_PCC)
                ),
        /* When MCIP is not set something is very confused */
        MCESEV(
                PANIC, "MCIP not set in MCA handler",
                MCGMASK(MCG_STATUS_MCIP, 0)
                ),
        /* Neither return not error IP -- no chance to recover -> PANIC */
        MCESEV(
                PANIC, "Neither restart nor error IP",
                MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, 0)
                ),
        MCESEV(
                PANIC, "In kernel and no restart IP",
                KERNEL, MCGMASK(MCG_STATUS_RIPV, 0)
                ),
        MCESEV(
                KEEP, "Corrected error",
                NOSER, BITCLR(MCI_STATUS_UC)
                ),

        /* ignore OVER for UCNA */
        MCESEV(
                KEEP, "Uncorrected no action required",
                SER, MASK(MCI_UC_SAR, MCI_STATUS_UC)
                ),
        MCESEV(
                PANIC, "Illegal combination (UCNA with AR=1)",
                SER,
                MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_STATUS_UC|MCI_STATUS_AR)
                ),
        MCESEV(
                KEEP, "Non signalled machine check",
                SER, BITCLR(MCI_STATUS_S)
                ),

        MCESEV(
                PANIC, "Action required with lost events",
                SER, BITSET(MCI_STATUS_OVER|MCI_UC_SAR)
                ),

        /* known AR MCACODs: */
#ifdef  CONFIG_MEMORY_FAILURE
        MCESEV(
                KEEP, "Action required but unaffected thread is continuable",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR, MCI_UC_SAR|MCI_ADDR),
                MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, MCG_STATUS_RIPV)
                ),
        MCESEV(
                AR, "Action required: data load error in a user process",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
                USER
                ),
        MCESEV(
                AR, "Action required: instruction fetch error in a user process",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_INSTR),
                USER
                ),
#endif
        MCESEV(
                PANIC, "Action required: unknown MCACOD",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_UC_SAR)
                ),

        /* known AO MCACODs: */
        MCESEV(
                AO, "Action optional: memory scrubbing error",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCACOD_SCRUBMSK, MCI_UC_S|MCACOD_SCRUB)
                ),
        MCESEV(
                AO, "Action optional: last level cache writeback error",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCACOD, MCI_UC_S|MCACOD_L3WB)
                ),
        MCESEV(
                SOME, "Action optional: unknown MCACOD",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_UC_S)
                ),
        MCESEV(
                SOME, "Action optional with lost events",
                SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_STATUS_OVER|MCI_UC_S)
                ),

        MCESEV(
                PANIC, "Overflowed uncorrected",
                BITSET(MCI_STATUS_OVER|MCI_STATUS_UC)
                ),
        MCESEV(
                UC, "Uncorrected",
                BITSET(MCI_STATUS_UC)
                ),
        MCESEV(
                SOME, "No match",
                BITSET(0)
                )       /* always matches. keep at end */
};

/*
 * If mcgstatus indicated that ip/cs on the stack were
 * no good, then "m->cs" will be zero and we will have
 * to assume the worst case (IN_KERNEL) as we actually
 * have no idea what we were executing when the machine
 * check hit.
 * If we do have a good "m->cs" (or a faked one in the
 * case we were executing in VM86 mode) we can use it to
 * distinguish an exception taken in user from from one
 * taken in the kernel.
 */
static int error_context(struct mce *m)
{
        return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
}

int mce_severity(struct mce *m, int tolerant, char **msg)
{
        enum context ctx = error_context(m);
        struct severity *s;

        for (s = severities;; s++) {
                if ((m->status & s->mask) != s->result)
                        continue;
                if ((m->mcgstatus & s->mcgmask) != s->mcgres)
                        continue;
                if (s->ser == SER_REQUIRED && !mca_cfg.ser)
                        continue;
                if (s->ser == NO_SER && mca_cfg.ser)
                        continue;
                if (s->context && ctx != s->context)
                        continue;
                if (msg)
                        *msg = s->msg;
                s->covered = 1;
                if (s->sev >= MCE_UC_SEVERITY && ctx == IN_KERNEL) {
                        if (panic_on_oops || tolerant < 1)
                                return MCE_PANIC_SEVERITY;
                }
                return s->sev;
        }
}

#ifdef CONFIG_DEBUG_FS
static void *s_start(struct seq_file *f, loff_t *pos)
{
        if (*pos >= ARRAY_SIZE(severities))
                return NULL;
        return &severities[*pos];
}

static void *s_next(struct seq_file *f, void *data, loff_t *pos)
{
        if (++(*pos) >= ARRAY_SIZE(severities))
                return NULL;
        return &severities[*pos];
}

static void s_stop(struct seq_file *f, void *data)
{
}

static int s_show(struct seq_file *f, void *data)
{
        struct severity *ser = data;
        seq_printf(f, "%d\t%s\n", ser->covered, ser->msg);
        return 0;
}

static const struct seq_operations severities_seq_ops = {
        .start  = s_start,
        .next   = s_next,
        .stop   = s_stop,
        .show   = s_show,
};

static int severities_coverage_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &severities_seq_ops);
}

static ssize_t severities_coverage_write(struct file *file,
                                         const char __user *ubuf,
                                         size_t count, loff_t *ppos)
{
        int i;
        for (i = 0; i < ARRAY_SIZE(severities); i++)
                severities[i].covered = 0;
        return count;
}

static const struct file_operations severities_coverage_fops = {
        .open           = severities_coverage_open,
        .release        = seq_release,
        .read           = seq_read,
        .write          = severities_coverage_write,
        .llseek         = seq_lseek,
};

static int __init severities_debugfs_init(void)
{
        struct dentry *dmce, *fsev;

        dmce = mce_get_debugfs_dir();
        if (!dmce)
                goto err_out;

        fsev = debugfs_create_file("severities-coverage", 0444, dmce, NULL,
                                   &severities_coverage_fops);
        if (!fsev)
                goto err_out;

        return 0;

err_out:
        return -ENOMEM;
}
late_initcall(severities_debugfs_init);
#endif /* CONFIG_DEBUG_FS */