// SPDX-License-Identifier: GPL-2.0

  /*
   * proc_tty.c -- handles /proc/tty
   *
   * Copyright 1997, Theodore Ts'o
   */

  #include <linux/uaccess.h>

  #include <linux/module.h>

  #include <linux/init.h>
  #include <linux/errno.h>
  #include <linux/time.h>
  #include <linux/proc_fs.h>
  #include <linux/stat.h>
  #include <linux/tty.h>
  #include <linux/seq_file.h>
  #include <linux/bitops.h>

  #include "internal.h"

  /*
   * The /proc/tty directory inodes...
   */

  static struct proc_dir_entry *proc_tty_driver;

  
  /*
   * This is the handler for /proc/tty/drivers
   */
  static void show_tty_range(struct seq_file *m, struct tty_driver *p,
  	dev_t from, int num)
  {
  	seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
  	seq_printf(m, "/dev/%-8s ", p->name);
  	if (p->num > 1) {
  		seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
  			MINOR(from) + num - 1);
  	} else {
  		seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
  	}
  	switch (p->type) {
  	case TTY_DRIVER_TYPE_SYSTEM:

  		seq_puts(m, "system");

  		if (p->subtype == SYSTEM_TYPE_TTY)

  			seq_puts(m, ":/dev/tty");

  		else if (p->subtype == SYSTEM_TYPE_SYSCONS)

  			seq_puts(m, ":console");

  		else if (p->subtype == SYSTEM_TYPE_CONSOLE)

  			seq_puts(m, ":vtmaster");

  		break;
  	case TTY_DRIVER_TYPE_CONSOLE:

  		seq_puts(m, "console");

  		break;
  	case TTY_DRIVER_TYPE_SERIAL:

  		seq_puts(m, "serial");

  		break;
  	case TTY_DRIVER_TYPE_PTY:
  		if (p->subtype == PTY_TYPE_MASTER)

  			seq_puts(m, "pty:master");

  		else if (p->subtype == PTY_TYPE_SLAVE)

  			seq_puts(m, "pty:slave");

  		else

  			seq_puts(m, "pty");

  		break;
  	default:
  		seq_printf(m, "type:%d.%d", p->type, p->subtype);
  	}
  	seq_putc(m, '
  ');
  }
  
  static int show_tty_driver(struct seq_file *m, void *v)
  {

  	struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);

  	dev_t from = MKDEV(p->major, p->minor_start);
  	dev_t to = from + p->num;
  
  	if (&p->tty_drivers == tty_drivers.next) {
  		/* pseudo-drivers first */
  		seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
  		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);

  		seq_puts(m, "system:/dev/tty
  ");

  		seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
  		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);

  		seq_puts(m, "system:console
  ");

  #ifdef CONFIG_UNIX98_PTYS
  		seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
  		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);

  		seq_puts(m, "system
  ");

  #endif
  #ifdef CONFIG_VT
  		seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
  		seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);

  		seq_puts(m, "system:vtmaster
  ");

  #endif
  	}
  
  	while (MAJOR(from) < MAJOR(to)) {
  		dev_t next = MKDEV(MAJOR(from)+1, 0);
  		show_tty_range(m, p, from, next - from);
  		from = next;
  	}
  	if (from != to)
  		show_tty_range(m, p, from, to - from);
  	return 0;
  }
  
  /* iterator */
  static void *t_start(struct seq_file *m, loff_t *pos)
  {

  	mutex_lock(&tty_mutex);

  	return seq_list_start(&tty_drivers, *pos);

  }
  
  static void *t_next(struct seq_file *m, void *v, loff_t *pos)
  {

  	return seq_list_next(v, &tty_drivers, pos);

  }
  
  static void t_stop(struct seq_file *m, void *v)
  {

  	mutex_unlock(&tty_mutex);

  }

  static const struct seq_operations tty_drivers_op = {

  	.start	= t_start,
  	.next	= t_next,
  	.stop	= t_stop,
  	.show	= show_tty_driver
  };

  /*
   * This function is called by tty_register_driver() to handle
   * registering the driver's /proc handler into /proc/tty/driver/<foo>
   */
  void proc_tty_register_driver(struct tty_driver *driver)
  {
  	struct proc_dir_entry *ent;
  		

  	if (!driver->driver_name || driver->proc_entry ||

  	    !driver->ops->proc_show)

  		return;

  	ent = proc_create_single_data(driver->driver_name, 0, proc_tty_driver,
  			       driver->ops->proc_show, driver);

  	driver->proc_entry = ent;
  }
  
  /*
   * This function is called by tty_unregister_driver()
   */
  void proc_tty_unregister_driver(struct tty_driver *driver)
  {
  	struct proc_dir_entry *ent;
  
  	ent = driver->proc_entry;
  	if (!ent)
  		return;
  		

  	remove_proc_entry(ent->name, proc_tty_driver);

  	
  	driver->proc_entry = NULL;
  }
  
  /*
   * Called by proc_root_init() to initialize the /proc/tty subtree
   */
  void __init proc_tty_init(void)
  {

  	if (!proc_mkdir("tty", NULL))
  		return;

  	proc_mkdir("tty/ldisc", NULL);	/* Preserved: it's userspace visible */

  	/*
  	 * /proc/tty/driver/serial reveals the exact character counts for
  	 * serial links which is just too easy to abuse for inferring
  	 * password lengths and inter-keystroke timings during password
  	 * entry.
  	 */

  	proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);

  	proc_create_seq("tty/ldiscs", 0, NULL, &tty_ldiscs_seq_ops);
  	proc_create_seq("tty/drivers", 0, NULL, &tty_drivers_op);

  }