1// SPDX-License-Identifier: GPL-2.0
2/*
3 * proc_tty.c -- handles /proc/tty
4 *
5 * Copyright 1997, Theodore Ts'o
6 */
7#include <linux/module.h>
8#include <linux/init.h>
9#include <linux/errno.h>
10#include <linux/time.h>
11#include <linux/proc_fs.h>
12#include <linux/stat.h>
13#include <linux/tty.h>
14#include <linux/seq_file.h>
15#include <linux/bitops.h>
16#include "internal.h"
17
18/*
19 * The /proc/tty directory inodes...
20 */
21static struct proc_dir_entry *proc_tty_driver;
22
23/*
24 * This is the handler for /proc/tty/drivers
25 */
26static void show_tty_range(struct seq_file *m, struct tty_driver *p,
27	dev_t from, int num)
28{
29	seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
30	seq_printf(m, "/dev/%-8s ", p->name);
31	if (p->num > 1) {
32		seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
33			MINOR(from) + num - 1);
34	} else {
35		seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
36	}
37	switch (p->type) {
38	case TTY_DRIVER_TYPE_SYSTEM:
39		seq_puts(m, "system");
40		if (p->subtype == SYSTEM_TYPE_TTY)
41			seq_puts(m, ":/dev/tty");
42		else if (p->subtype == SYSTEM_TYPE_SYSCONS)
43			seq_puts(m, ":console");
44		else if (p->subtype == SYSTEM_TYPE_CONSOLE)
45			seq_puts(m, ":vtmaster");
46		break;
47	case TTY_DRIVER_TYPE_CONSOLE:
48		seq_puts(m, "console");
49		break;
50	case TTY_DRIVER_TYPE_SERIAL:
51		seq_puts(m, "serial");
52		break;
53	case TTY_DRIVER_TYPE_PTY:
54		if (p->subtype == PTY_TYPE_MASTER)
55			seq_puts(m, "pty:master");
56		else if (p->subtype == PTY_TYPE_SLAVE)
57			seq_puts(m, "pty:slave");
58		else
59			seq_puts(m, "pty");
60		break;
61	default:
62		seq_printf(m, "type:%d.%d", p->type, p->subtype);
63	}
64	seq_putc(m, '\n');
65}
66
67static int show_tty_driver(struct seq_file *m, void *v)
68{
69	struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
70	dev_t from = MKDEV(p->major, p->minor_start);
71	dev_t to = from + p->num;
72
73	if (&p->tty_drivers == tty_drivers.next) {
74		/* pseudo-drivers first */
75		seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
76		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
77		seq_puts(m, "system:/dev/tty\n");
78		seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
79		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
80		seq_puts(m, "system:console\n");
81#ifdef CONFIG_UNIX98_PTYS
82		seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
83		seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
84		seq_puts(m, "system\n");
85#endif
86#ifdef CONFIG_VT
87		seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
88		seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
89		seq_puts(m, "system:vtmaster\n");
90#endif
91	}
92
93	while (MAJOR(from) < MAJOR(to)) {
94		dev_t next = MKDEV(MAJOR(from)+1, 0);
95		show_tty_range(m, p, from, next - from);
96		from = next;
97	}
98	if (from != to)
99		show_tty_range(m, p, from, to - from);
100	return 0;
101}
102
103/* iterator */
104static void *t_start(struct seq_file *m, loff_t *pos)
105{
106	mutex_lock(&tty_mutex);
107	return seq_list_start(&tty_drivers, *pos);
108}
109
110static void *t_next(struct seq_file *m, void *v, loff_t *pos)
111{
112	return seq_list_next(v, &tty_drivers, pos);
113}
114
115static void t_stop(struct seq_file *m, void *v)
116{
117	mutex_unlock(&tty_mutex);
118}
119
120static const struct seq_operations tty_drivers_op = {
121	.start	= t_start,
122	.next	= t_next,
123	.stop	= t_stop,
124	.show	= show_tty_driver
125};
126
127/*
128 * This function is called by tty_register_driver() to handle
129 * registering the driver's /proc handler into /proc/tty/driver/<foo>
130 */
131void proc_tty_register_driver(struct tty_driver *driver)
132{
133	struct proc_dir_entry *ent;
134
135	if (!driver->driver_name || driver->proc_entry ||
136	    !driver->ops->proc_show)
137		return;
138
139	ent = proc_create_single_data(driver->driver_name, 0, proc_tty_driver,
140			       driver->ops->proc_show, driver);
141	driver->proc_entry = ent;
142}
143
144/*
145 * This function is called by tty_unregister_driver()
146 */
147void proc_tty_unregister_driver(struct tty_driver *driver)
148{
149	struct proc_dir_entry *ent;
150
151	ent = driver->proc_entry;
152	if (!ent)
153		return;
154
155	remove_proc_entry(ent->name, proc_tty_driver);
156
157	driver->proc_entry = NULL;
158}
159
160/*
161 * Called by proc_root_init() to initialize the /proc/tty subtree
162 */
163void __init proc_tty_init(void)
164{
165	if (!proc_mkdir("tty", NULL))
166		return;
167	proc_mkdir("tty/ldisc", NULL);	/* Preserved: it's userspace visible */
168	/*
169	 * /proc/tty/driver/serial reveals the exact character counts for
170	 * serial links which is just too easy to abuse for inferring
171	 * password lengths and inter-keystroke timings during password
172	 * entry.
173	 */
174	proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
175	proc_create_seq("tty/ldiscs", 0, NULL, &tty_ldiscs_seq_ops);
176	proc_create_seq("tty/drivers", 0, NULL, &tty_drivers_op);
177}
178