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