1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/fs/proc/kmsg.c
4  *
5  *  Copyright (C) 1992  by Linus Torvalds
6  *
7  */
8 
9 #include <linux/types.h>
10 #include <linux/errno.h>
11 #include <linux/time.h>
12 #include <linux/kernel.h>
13 #include <linux/poll.h>
14 #include <linux/proc_fs.h>
15 #include <linux/fs.h>
16 #include <linux/syslog.h>
17 
18 #include <asm/io.h>
19 
kmsg_open(struct inode * inode,struct file * file)20 static int kmsg_open(struct inode * inode, struct file * file)
21 {
22 	return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC);
23 }
24 
kmsg_release(struct inode * inode,struct file * file)25 static int kmsg_release(struct inode * inode, struct file * file)
26 {
27 	(void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC);
28 	return 0;
29 }
30 
kmsg_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)31 static ssize_t kmsg_read(struct file *file, char __user *buf,
32 			 size_t count, loff_t *ppos)
33 {
34 	if ((file->f_flags & O_NONBLOCK) &&
35 	    !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))
36 		return -EAGAIN;
37 	return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC);
38 }
39 
kmsg_poll(struct file * file,poll_table * wait)40 static __poll_t kmsg_poll(struct file *file, poll_table *wait)
41 {
42 	poll_wait(file, &log_wait, wait);
43 	if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))
44 		return EPOLLIN | EPOLLRDNORM;
45 	return 0;
46 }
47 
48 
49 static const struct proc_ops kmsg_proc_ops = {
50 	.proc_flags	= PROC_ENTRY_PERMANENT,
51 	.proc_read	= kmsg_read,
52 	.proc_poll	= kmsg_poll,
53 	.proc_open	= kmsg_open,
54 	.proc_release	= kmsg_release,
55 	.proc_lseek	= generic_file_llseek,
56 };
57 
proc_kmsg_init(void)58 static int __init proc_kmsg_init(void)
59 {
60 	proc_create("kmsg", S_IRUSR, NULL, &kmsg_proc_ops);
61 	return 0;
62 }
63 fs_initcall(proc_kmsg_init);
64