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 "internal.h"
  19
  20 static DEFINE_MUTEX(pmsg_lock);
  21
  22 static ssize_t write_pmsg(struct file *file, const char __user *buf,
  23                           size_t count, loff_t *ppos)
  24 {
  25         struct pstore_record record;
  26         int ret;
  27
  28         if (!count)
  29                 return 0;
  30
  31         pstore_record_init(&record, psinfo);
  32         record.type = PSTORE_TYPE_PMSG;
  33         record.size = count;
  34
  35         /* check outside lock, page in any data. write_user also checks */
  36         if (!access_ok(VERIFY_READ, buf, count))
  37                 return -EFAULT;
  38
  39         mutex_lock(&pmsg_lock);
  40         ret = psinfo->write_user(&record, buf);
  41         mutex_unlock(&pmsg_lock);
  42         return ret ? ret : count;
  43 }
  44
  45 static const struct file_operations pmsg_fops = {
  46         .owner          = THIS_MODULE,
  47         .llseek         = noop_llseek,
  48         .write          = write_pmsg,
  49 };
  50
  51 static struct class *pmsg_class;
  52 static int pmsg_major;
  53 #define PMSG_NAME "pmsg"
  54 #undef pr_fmt
  55 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  56
  57 static char *pmsg_devnode(struct device *dev, umode_t *mode)
  58 {
  59         if (mode)
  60                 *mode = 0220;
  61         return NULL;
  62 }
  63
  64 void pstore_register_pmsg(void)
  65 {
  66         struct device *pmsg_device;
  67
  68         pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
  69         if (pmsg_major < 0) {
  70                 pr_err("register_chrdev failed\n");
  71                 goto err;
  72         }
  73
  74         pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
  75         if (IS_ERR(pmsg_class)) {
  76                 pr_err("device class file already in use\n");
  77                 goto err_class;
  78         }
  79         pmsg_class->devnode = pmsg_devnode;
  80
  81         pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
  82                                         NULL, "%s%d", PMSG_NAME, 0);
  83         if (IS_ERR(pmsg_device)) {
  84                 pr_err("failed to create device\n");
  85                 goto err_device;
  86         }
  87         return;
  88
  89 err_device:
  90         class_destroy(pmsg_class);
  91 err_class:
  92         unregister_chrdev(pmsg_major, PMSG_NAME);
  93 err:
  94         return;
  95 }
  96
  97 void pstore_unregister_pmsg(void)
  98 {
  99         device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
 100         class_destroy(pmsg_class);
 101         unregister_chrdev(pmsg_major, PMSG_NAME);
 102 }