/*
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #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
  ",
  			   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
  ");
  		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.
  ");
  		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");