fs/proc/kmsg.c

   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);