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 <asm/io.h>
  19
  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
  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
  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
  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
  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);