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
13static DEFINE_RT_MUTEX(pmsg_lock);
14
15static 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
38static const struct file_operations pmsg_fops = {
39	.owner		= THIS_MODULE,
40	.llseek		= noop_llseek,
41	.write		= write_pmsg,
42};
43
44static struct class *pmsg_class;
45static int pmsg_major;
46#define PMSG_NAME "pmsg"
47#undef pr_fmt
48#define pr_fmt(fmt) PMSG_NAME ": " fmt
49
50static char *pmsg_devnode(const struct device *dev, umode_t *mode)
51{
52	if (mode)
53		*mode = 0220;
54	return NULL;
55}
56
57void 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
82err_device:
83	class_destroy(pmsg_class);
84err_class:
85	unregister_chrdev(pmsg_major, PMSG_NAME);
86err:
87	return;
88}
89
90void 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}