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 <linux/uaccess.h> 19 #include <asm/io.h> 20 21 extern wait_queue_head_t log_wait; 22 23 static int kmsg_open(struct inode * inode, struct file * file) 24 { 25 return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC); 26 } 27 28 static int kmsg_release(struct inode * inode, struct file * file) 29 { 30 (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC); 31 return 0; 32 } 33 34 static ssize_t kmsg_read(struct file *file, char __user *buf, 35 size_t count, loff_t *ppos) 36 { 37 if ((file->f_flags & O_NONBLOCK) && 38 !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) 39 return -EAGAIN; 40 return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC); 41 } 42 43 static __poll_t kmsg_poll(struct file *file, poll_table *wait) 44 { 45 poll_wait(file, &log_wait, wait); 46 if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) 47 return EPOLLIN | EPOLLRDNORM; 48 return 0; 49 } 50 51 52 static const struct proc_ops kmsg_proc_ops = { 53 .proc_flags = PROC_ENTRY_PERMANENT, 54 .proc_read = kmsg_read, 55 .proc_poll = kmsg_poll, 56 .proc_open = kmsg_open, 57 .proc_release = kmsg_release, 58 .proc_lseek = generic_file_llseek, 59 }; 60 61 static int __init proc_kmsg_init(void) 62 { 63 proc_create("kmsg", S_IRUSR, NULL, &kmsg_proc_ops); 64 return 0; 65 } 66 fs_initcall(proc_kmsg_init); 67