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/rtmutex.h>
  19 #include "internal.h"
  20
  21 static DEFINE_RT_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         struct pstore_record record;
  27         int ret;
  28
  29         if (!count)
  30                 return 0;
  31
  32         pstore_record_init(&record, psinfo);
  33         record.type = PSTORE_TYPE_PMSG;
  34         record.size = count;
  35
  36         /* check outside lock, page in any data. write_user also checks */
  37         if (!access_ok(VERIFY_READ, buf, count))
  38                 return -EFAULT;
  39
  40         rt_mutex_lock(&pmsg_lock);
  41         ret = psinfo->write_user(&record, buf);
  42         rt_mutex_unlock(&pmsg_lock);
  43         return ret ? ret : count;
  44 }
  45
  46 static const struct file_operations pmsg_fops = {
  47         .owner          = THIS_MODULE,
  48         .llseek         = noop_llseek,
  49         .write          = write_pmsg,
  50 };
  51
  52 static struct class *pmsg_class;
  53 static int pmsg_major;
  54 #define PMSG_NAME "pmsg"
  55 #undef pr_fmt
  56 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  57
  58 static char *pmsg_devnode(struct device *dev, umode_t *mode)
  59 {
  60         if (mode)
  61                 *mode = 0220;
  62         return NULL;
  63 }
  64
  65 void pstore_register_pmsg(void)
  66 {
  67         struct device *pmsg_device;
  68
  69         pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
  70         if (pmsg_major < 0) {
  71                 pr_err("register_chrdev failed\n");
  72                 goto err;
  73         }
  74
  75         pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
  76         if (IS_ERR(pmsg_class)) {
  77                 pr_err("device class file already in use\n");
  78                 goto err_class;
  79         }
  80         pmsg_class->devnode = pmsg_devnode;
  81
  82         pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
  83                                         NULL, "%s%d", PMSG_NAME, 0);
  84         if (IS_ERR(pmsg_device)) {
  85                 pr_err("failed to create device\n");
  86                 goto err_device;
  87         }
  88         return;
  89
  90 err_device:
  91         class_destroy(pmsg_class);
  92 err_class:
  93         unregister_chrdev(pmsg_major, PMSG_NAME);
  94 err:
  95         return;
  96 }
  97
  98 void pstore_unregister_pmsg(void)
  99 {
 100         device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
 101         class_destroy(pmsg_class);
 102         unregister_chrdev(pmsg_major, PMSG_NAME);
 103 }