/*
 * APEI Error Record Serialization Table debug support
 *
 * ERST is a way provided by APEI to save and retrieve hardware error
 * information to and from a persistent store. This file provide the
 * debugging/testing support for ERST kernel support and firmware
 * implementation.
 *
 * Copyright 2010 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <acpi/apei.h>
#include <linux/miscdevice.h>

#include "apei-internal.h"

#define ERST_DBG_PFX                    "ERST DBG: "

#define ERST_DBG_RECORD_LEN_MAX         0x4000

static void *erst_dbg_buf;
static unsigned int erst_dbg_buf_len;

/* Prevent erst_dbg_read/write from being invoked concurrently */
static DEFINE_MUTEX(erst_dbg_mutex);

static int erst_dbg_open(struct inode *inode, struct file *file)
{
        int rc, *pos;

        if (erst_disable)
                return -ENODEV;

        pos = (int *)&file->private_data;

        rc = erst_get_record_id_begin(pos);
        if (rc)
                return rc;

        return nonseekable_open(inode, file);
}

static int erst_dbg_release(struct inode *inode, struct file *file)
{
        erst_get_record_id_end();

        return 0;
}

static long erst_dbg_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
        int rc;
        u64 record_id;
        u32 record_count;

        switch (cmd) {
        case APEI_ERST_CLEAR_RECORD:
                rc = copy_from_user(&record_id, (void __user *)arg,
                                    sizeof(record_id));
                if (rc)
                        return -EFAULT;
                return erst_clear(record_id);
        case APEI_ERST_GET_RECORD_COUNT:
                rc = erst_get_record_count();
                if (rc < 0)
                        return rc;
                record_count = rc;
                rc = put_user(record_count, (u32 __user *)arg);
                if (rc)
                        return rc;
                return 0;
        default:
                return -ENOTTY;
        }
}

static ssize_t erst_dbg_read(struct file *filp, char __user *ubuf,
                             size_t usize, loff_t *off)
{
        int rc, *pos;
        ssize_t len = 0;
        u64 id;

        if (*off)
                return -EINVAL;

        if (mutex_lock_interruptible(&erst_dbg_mutex) != 0)
                return -EINTR;

        pos = (int *)&filp->private_data;

retry_next:
        rc = erst_get_record_id_next(pos, &id);
        if (rc)
                goto out;
        /* no more record */
        if (id == APEI_ERST_INVALID_RECORD_ID) {
                /*
                 * If the persistent store is empty initially, the function
                 * 'erst_read' below will return "-ENOENT" value. This causes
                 * 'retry_next' label is entered again. The returned value
                 * should be zero indicating the read operation is EOF.
                 */
                len = 0;

                goto out;
        }
retry:
        rc = len = erst_read(id, erst_dbg_buf, erst_dbg_buf_len);
        /* The record may be cleared by others, try read next record */
        if (rc == -ENOENT)
                goto retry_next;
        if (rc < 0)
                goto out;
        if (len > ERST_DBG_RECORD_LEN_MAX) {
                pr_warning(ERST_DBG_PFX
                           "Record (ID: 0x%llx) length is too long: %zd\n",
                           id, len);
                rc = -EIO;
                goto out;
        }
        if (len > erst_dbg_buf_len) {
                void *p;
                rc = -ENOMEM;
                p = kmalloc(len, GFP_KERNEL);
                if (!p)
                        goto out;
                kfree(erst_dbg_buf);
                erst_dbg_buf = p;
                erst_dbg_buf_len = len;
                goto retry;
        }

        rc = -EINVAL;
        if (len > usize)
                goto out;

        rc = -EFAULT;
        if (copy_to_user(ubuf, erst_dbg_buf, len))
                goto out;
        rc = 0;
out:
        mutex_unlock(&erst_dbg_mutex);
        return rc ? rc : len;
}

static ssize_t erst_dbg_write(struct file *filp, const char __user *ubuf,
                              size_t usize, loff_t *off)
{
        int rc;
        struct cper_record_header *rcd;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        if (usize > ERST_DBG_RECORD_LEN_MAX) {
                pr_err(ERST_DBG_PFX "Too long record to be written\n");
                return -EINVAL;
        }

        if (mutex_lock_interruptible(&erst_dbg_mutex))
                return -EINTR;
        if (usize > erst_dbg_buf_len) {
                void *p;
                rc = -ENOMEM;
                p = kmalloc(usize, GFP_KERNEL);
                if (!p)
                        goto out;
                kfree(erst_dbg_buf);
                erst_dbg_buf = p;
                erst_dbg_buf_len = usize;
        }
        rc = copy_from_user(erst_dbg_buf, ubuf, usize);
        if (rc) {
                rc = -EFAULT;
                goto out;
        }
        rcd = erst_dbg_buf;
        rc = -EINVAL;
        if (rcd->record_length != usize)
                goto out;

        rc = erst_write(erst_dbg_buf);

out:
        mutex_unlock(&erst_dbg_mutex);
        return rc < 0 ? rc : usize;
}

static const struct file_operations erst_dbg_ops = {
        .owner          = THIS_MODULE,
        .open           = erst_dbg_open,
        .release        = erst_dbg_release,
        .read           = erst_dbg_read,
        .write          = erst_dbg_write,
        .unlocked_ioctl = erst_dbg_ioctl,
        .llseek         = no_llseek,
};

static struct miscdevice erst_dbg_dev = {
        .minor  = MISC_DYNAMIC_MINOR,
        .name   = "erst_dbg",
        .fops   = &erst_dbg_ops,
};

static __init int erst_dbg_init(void)
{
        if (erst_disable) {
                pr_info(ERST_DBG_PFX "ERST support is disabled.\n");
                return -ENODEV;
        }
        return misc_register(&erst_dbg_dev);
}

static __exit void erst_dbg_exit(void)
{
        misc_deregister(&erst_dbg_dev);
        kfree(erst_dbg_buf);
}

module_init(erst_dbg_init);
module_exit(erst_dbg_exit);

MODULE_AUTHOR("Huang Ying");
MODULE_DESCRIPTION("APEI Error Record Serialization Table debug support");
MODULE_LICENSE("GPL");