// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/fs/proc/kmsg.c
   *
   *  Copyright (C) 1992  by Linus Torvalds
   *
   */
  
  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/time.h>
  #include <linux/kernel.h>
  #include <linux/poll.h>

  #include <linux/proc_fs.h>

  #include <linux/fs.h>

  #include <linux/syslog.h>

  #include <linux/uaccess.h>

  #include <asm/io.h>
  
  extern wait_queue_head_t log_wait;

  static int kmsg_open(struct inode * inode, struct file * file)
  {

  	return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC);

  }
  
  static int kmsg_release(struct inode * inode, struct file * file)
  {

  	(void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC);

  	return 0;
  }
  
  static ssize_t kmsg_read(struct file *file, char __user *buf,
  			 size_t count, loff_t *ppos)
  {

  	if ((file->f_flags & O_NONBLOCK) &&

  	    !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))

  		return -EAGAIN;

  	return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC);

  }

  static __poll_t kmsg_poll(struct file *file, poll_table *wait)

  {
  	poll_wait(file, &log_wait, wait);

  	if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))

  		return EPOLLIN | EPOLLRDNORM;

  	return 0;
  }

  static const struct proc_ops kmsg_proc_ops = {

  	.proc_flags	= PROC_ENTRY_PERMANENT,

  	.proc_read	= kmsg_read,
  	.proc_poll	= kmsg_poll,
  	.proc_open	= kmsg_open,
  	.proc_release	= kmsg_release,
  	.proc_lseek	= generic_file_llseek,

  };

  
  static int __init proc_kmsg_init(void)
  {

  	proc_create("kmsg", S_IRUSR, NULL, &kmsg_proc_ops);

  	return 0;
  }

  fs_initcall(proc_kmsg_init);