fs/pstore/pmsg.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2014  Google, Inc.
   4  */
   5
   6 #include <linux/cdev.h>
   7 #include <linux/device.h>
   8 #include <linux/fs.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/rtmutex.h>
  11 #include "internal.h"
  12
  13 static DEFINE_RT_MUTEX(pmsg_lock);
  14
  15 static ssize_t write_pmsg(struct file *file, const char __user *buf,
  16                           size_t count, loff_t *ppos)
  17 {
  18         struct pstore_record record;
  19         int ret;
  20
  21         if (!count)
  22                 return 0;
  23
  24         pstore_record_init(&record, psinfo);
  25         record.type = PSTORE_TYPE_PMSG;
  26         record.size = count;
  27
  28         /* check outside lock, page in any data. write_user also checks */
  29         if (!access_ok(buf, count))
  30                 return -EFAULT;
  31
  32         rt_mutex_lock(&pmsg_lock);
  33         ret = psinfo->write_user(&record, buf);
  34         rt_mutex_unlock(&pmsg_lock);
  35         return ret ? ret : count;
  36 }
  37
  38 static const struct file_operations pmsg_fops = {
  39         .owner          = THIS_MODULE,
  40         .llseek         = noop_llseek,
  41         .write          = write_pmsg,
  42 };
  43
  44 static struct class *pmsg_class;
  45 static int pmsg_major;
  46 #define PMSG_NAME "pmsg"
  47 #undef pr_fmt
  48 #define pr_fmt(fmt) PMSG_NAME ": " fmt
  49
  50 static char *pmsg_devnode(const struct device *dev, umode_t *mode)
  51 {
  52         if (mode)
  53                 *mode = 0220;
  54         return NULL;
  55 }
  56
  57 void pstore_register_pmsg(void)
  58 {
  59         struct device *pmsg_device;
  60
  61         pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
  62         if (pmsg_major < 0) {
  63                 pr_err("register_chrdev failed\n");
  64                 goto err;
  65         }
  66
  67         pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
  68         if (IS_ERR(pmsg_class)) {
  69                 pr_err("device class file already in use\n");
  70                 goto err_class;
  71         }
  72         pmsg_class->devnode = pmsg_devnode;
  73
  74         pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
  75                                         NULL, "%s%d", PMSG_NAME, 0);
  76         if (IS_ERR(pmsg_device)) {
  77                 pr_err("failed to create device\n");
  78                 goto err_device;
  79         }
  80         return;
  81
  82 err_device:
  83         class_destroy(pmsg_class);
  84 err_class:
  85         unregister_chrdev(pmsg_major, PMSG_NAME);
  86 err:
  87         return;
  88 }
  89
  90 void pstore_unregister_pmsg(void)
  91 {
  92         device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
  93         class_destroy(pmsg_class);
  94         unregister_chrdev(pmsg_major, PMSG_NAME);
  95 }