xref: /openbmc/linux/fs/pstore/pmsg.c (revision b78412b8)
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 }
103