1/*
  2 * Copyright 2014  Google, Inc.
  3 *
  4 * This software is licensed under the terms of the GNU General Public
  5 * License version 2, as published by the Free Software Foundation, and
  6 * may be copied, distributed, and modified under those terms.
  7 *
  8 * This program is distributed in the hope that it will be useful,
  9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11 * GNU General Public License for more details.
 12 */
 13
 14#include <linux/cdev.h>
 15#include <linux/device.h>
 16#include <linux/fs.h>
 17#include <linux/uaccess.h>
 18#include <linux/vmalloc.h>
 19#include "internal.h"
 20
 21static DEFINE_MUTEX(pmsg_lock);
 22
 23static ssize_t write_pmsg(struct file *file, const char __user *buf,
 24			  size_t count, loff_t *ppos)
 25{
 26	u64 id;
 27	int ret;
 28
 29	if (!count)
 30		return 0;
 31
 32	/* check outside lock, page in any data. write_buf_user also checks */
 33	if (!access_ok(VERIFY_READ, buf, count))
 34		return -EFAULT;
 35
 36	mutex_lock(&pmsg_lock);
 37	ret = psinfo->write_buf_user(PSTORE_TYPE_PMSG, 0, &id, 0, buf, 0, count,
 38				     psinfo);
 39	mutex_unlock(&pmsg_lock);
 40	return ret ? ret : count;
 41}
 42
 43static const struct file_operations pmsg_fops = {
 44	.owner		= THIS_MODULE,
 45	.llseek		= noop_llseek,
 46	.write		= write_pmsg,
 47};
 48
 49static struct class *pmsg_class;
 50static int pmsg_major;
 51#define PMSG_NAME "pmsg"
 52#undef pr_fmt
 53#define pr_fmt(fmt) PMSG_NAME ": " fmt
 54
 55static char *pmsg_devnode(struct device *dev, umode_t *mode)
 56{
 57	if (mode)
 58		*mode = 0220;
 59	return NULL;
 60}
 61
 62void pstore_register_pmsg(void)
 63{
 64	struct device *pmsg_device;
 65
 66	pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
 67	if (pmsg_major < 0) {
 68		pr_err("register_chrdev failed\n");
 69		goto err;
 70	}
 71
 72	pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
 73	if (IS_ERR(pmsg_class)) {
 74		pr_err("device class file already in use\n");
 75		goto err_class;
 76	}
 77	pmsg_class->devnode = pmsg_devnode;
 78
 79	pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
 80					NULL, "%s%d", PMSG_NAME, 0);
 81	if (IS_ERR(pmsg_device)) {
 82		pr_err("failed to create device\n");
 83		goto err_device;
 84	}
 85	return;
 86
 87err_device:
 88	class_destroy(pmsg_class);
 89err_class:
 90	unregister_chrdev(pmsg_major, PMSG_NAME);
 91err:
 92	return;
 93}
 94
 95void pstore_unregister_pmsg(void)
 96{
 97	device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
 98	class_destroy(pmsg_class);
 99	unregister_chrdev(pmsg_major, PMSG_NAME);
100}