// SPDX-License-Identifier: GPL-2.0/* * proc_tty.c -- handles /proc/tty * * Copyright 1997, Theodore Ts'o */#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, '\n');} 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\n");		seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);		seq_puts(m, "system:console\n");#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\n");#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\n");#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);}