kernel/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 #define PMSG_MAX_BOUNCE_BUFFER_SIZE (2*PAGE_SIZE)
  23
  24 static ssize_t write_pmsg(struct file *file, const char __user *buf,
  25                           size_t count, loff_t *ppos)
  26 {
  27         size_t i, buffer_size;
  28         char *buffer;
  29
  30         if (!count)
  31                 return 0;
  32
  33         if (!access_ok(VERIFY_READ, buf, count))
  34                 return -EFAULT;
  35
  36         buffer_size = count;
  37         if (buffer_size > PMSG_MAX_BOUNCE_BUFFER_SIZE)
  38                 buffer_size = PMSG_MAX_BOUNCE_BUFFER_SIZE;
  39         buffer = vmalloc(buffer_size);
  40
  41         mutex_lock(&pmsg_lock);
  42         for (i = 0; i < count; ) {
  43                 size_t c = min(count - i, buffer_size);
  44                 u64 id;
  45                 long ret;
  46
  47                 ret = __copy_from_user(buffer, buf + i, c);
  48                 if (unlikely(ret != 0)) {
  49                         mutex_unlock(&pmsg_lock);
  50                         vfree(buffer);
  51                         return -EFAULT;
  52                 }
  53                 psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c,
  54                                   psinfo);
  55
  56                 i += c;
  57         }
  58
  59         mutex_unlock(&pmsg_lock);
  60         vfree(buffer);
  61         return count;
  62 }
  63
  64 static const struct file_operations pmsg_fops = {
  65         .owner          = THIS_MODULE,
  66         .llseek         = noop_llseek,
  67         .write          = write_pmsg,
  68 };
  69
  70 static struct class *pmsg_class;
  71 static int pmsg_major;
  72 #define PMSG_NAME "pmsg"
  73 #undef pr_fmt
  74 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  75
  76 static char *pmsg_devnode(struct device *dev, umode_t *mode)
  77 {
  78         if (mode)
  79                 *mode = 0220;
  80         return NULL;
  81 }
  82
  83 void pstore_register_pmsg(void)
  84 {
  85         struct device *pmsg_device;
  86
  87         pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
  88         if (pmsg_major < 0) {
  89                 pr_err("register_chrdev failed\n");
  90                 goto err;
  91         }
  92
  93         pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
  94         if (IS_ERR(pmsg_class)) {
  95                 pr_err("device class file already in use\n");
  96                 goto err_class;
  97         }
  98         pmsg_class->devnode = pmsg_devnode;
  99
 100         pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
 101                                         NULL, "%s%d", PMSG_NAME, 0);
 102         if (IS_ERR(pmsg_device)) {
 103                 pr_err("failed to create device\n");
 104                 goto err_device;
 105         }
 106         return;
 107
 108 err_device:
 109         class_destroy(pmsg_class);
 110 err_class:
 111         unregister_chrdev(pmsg_major, PMSG_NAME);
 112 err:
 113         return;
 114 }