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 20 extern wait_queue_head_t log_wait; 21 22 static int kmsg_open(struct inode * inode, struct file * file) 23 { 24 return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC); 25 } 26 27 static int kmsg_release(struct inode * inode, struct file * file) 28 { 29 (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC); 30 return 0; 31 } 32 33 static ssize_t kmsg_read(struct file *file, char __user *buf, 34 size_t count, loff_t *ppos) 35 { 36 if ((file->f_flags & O_NONBLOCK) && 37 !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) 38 return -EAGAIN; 39 return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC); 40 } 41 42 static __poll_t kmsg_poll(struct file *file, poll_table *wait) 43 { 44 poll_wait(file, &log_wait, wait); 45 if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) 46 return EPOLLIN | EPOLLRDNORM; 47 return 0; 48 } 49 50 51 static const struct proc_ops kmsg_proc_ops = { 52 .proc_flags = PROC_ENTRY_PERMANENT, 53 .proc_read = kmsg_read, 54 .proc_poll = kmsg_poll, 55 .proc_open = kmsg_open, 56 .proc_release = kmsg_release, 57 .proc_lseek = generic_file_llseek, 58 }; 59 60 static int __init proc_kmsg_init(void) 61 { 62 proc_create("kmsg", S_IRUSR, NULL, &kmsg_proc_ops); 63 return 0; 64 } 65 fs_initcall(proc_kmsg_init); 66