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         if (!buffer)
  41                 return -ENOMEM;
  42
  43         mutex_lock(&pmsg_lock);
  44         for (i = 0; i < count; ) {
  45                 size_t c = min(count - i, buffer_size);
  46                 u64 id;
  47                 long ret;
  48
  49                 ret = __copy_from_user(buffer, buf + i, c);
  50                 if (unlikely(ret != 0)) {
  51                         mutex_unlock(&pmsg_lock);
  52                         vfree(buffer);
  53                         return -EFAULT;
  54                 }
  55                 psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c,
  56                                   psinfo);
  57
  58                 i += c;
  59         }
  60
  61         mutex_unlock(&pmsg_lock);
  62         vfree(buffer);
  63         return count;
  64 }
  65
  66 static const struct file_operations pmsg_fops = {
  67         .owner          = THIS_MODULE,
  68         .llseek         = noop_llseek,
  69         .write          = write_pmsg,
  70 };
  71
  72 static struct class *pmsg_class;
  73 static int pmsg_major;
  74 #define PMSG_NAME "pmsg"
  75 #undef pr_fmt
  76 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  77
  78 static char *pmsg_devnode(struct device *dev, umode_t *mode)
  79 {
  80         if (mode)
  81                 *mode = 0220;
  82         return NULL;
  83 }
  84
  85 void pstore_register_pmsg(void)
  86 {
  87         struct device *pmsg_device;
  88
  89         pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
  90         if (pmsg_major < 0) {
  91                 pr_err("register_chrdev failed\n");
  92                 goto err;
  93         }
  94
  95         pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
  96         if (IS_ERR(pmsg_class)) {
  97                 pr_err("device class file already in use\n");
  98                 goto err_class;
  99         }
 100         pmsg_class->devnode = pmsg_devnode;
 101
 102         pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
 103                                         NULL, "%s%d", PMSG_NAME, 0);
 104         if (IS_ERR(pmsg_device)) {
 105                 pr_err("failed to create device\n");
 106                 goto err_device;
 107         }
 108         return;
 109
 110 err_device:
 111         class_destroy(pmsg_class);
 112 err_class:
 113         unregister_chrdev(pmsg_major, PMSG_NAME);
 114 err:
 115         return;
 116 }
 117
 118 void pstore_unregister_pmsg(void)
 119 {
 120         device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
 121         class_destroy(pmsg_class);
 122         unregister_chrdev(pmsg_major, PMSG_NAME);
 123 }