fs/pstore/pmsg.c

   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
  21 static DEFINE_MUTEX(pmsg_lock);
  22
  23 static 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
  43 static const struct file_operations pmsg_fops = {
  44         .owner          = THIS_MODULE,
  45         .llseek         = noop_llseek,
  46         .write          = write_pmsg,
  47 };
  48
  49 static struct class *pmsg_class;
  50 static int pmsg_major;
  51 #define PMSG_NAME "pmsg"
  52 #undef pr_fmt
  53 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  54
  55 static char *pmsg_devnode(struct device *dev, umode_t *mode)
  56 {
  57         if (mode)
  58                 *mode = 0220;
  59         return NULL;
  60 }
  61
  62 void 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
  87 err_device:
  88         class_destroy(pmsg_class);
  89 err_class:
  90         unregister_chrdev(pmsg_major, PMSG_NAME);
  91 err:
  92         return;
  93 }
  94
  95 void 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 }