GNU Linux-libre 4.19.211-gnu1
[releases.git] / 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 }