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 
write_pmsg(struct file * file,const char __user * buf,size_t count,loff_t * ppos)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 
pmsg_devnode(const struct device * dev,umode_t * mode)50 static char *pmsg_devnode(const struct device *dev, umode_t *mode)
51 {
52 	if (mode)
53 		*mode = 0220;
54 	return NULL;
55 }
56 
pstore_register_pmsg(void)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 
pstore_unregister_pmsg(void)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 }
96