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, fmt: "%-20s ", p->driver_name ? p->driver_name : "unknown");
30 seq_printf(m, fmt: "/dev/%-8s ", p->name);
31 if (p->num > 1) {
32 seq_printf(m, fmt: "%3d %d-%d ", MAJOR(from), MINOR(from),
33 MINOR(from) + num - 1);
34 } else {
35 seq_printf(m, fmt: "%3d %7d ", MAJOR(from), MINOR(from));
36 }
37 switch (p->type) {
38 case TTY_DRIVER_TYPE_SYSTEM:
39 seq_puts(m, s: "system");
40 if (p->subtype == SYSTEM_TYPE_TTY)
41 seq_puts(m, s: ":/dev/tty");
42 else if (p->subtype == SYSTEM_TYPE_SYSCONS)
43 seq_puts(m, s: ":console");
44 else if (p->subtype == SYSTEM_TYPE_CONSOLE)
45 seq_puts(m, s: ":vtmaster");
46 break;
47 case TTY_DRIVER_TYPE_CONSOLE:
48 seq_puts(m, s: "console");
49 break;
50 case TTY_DRIVER_TYPE_SERIAL:
51 seq_puts(m, s: "serial");
52 break;
53 case TTY_DRIVER_TYPE_PTY:
54 if (p->subtype == PTY_TYPE_MASTER)
55 seq_puts(m, s: "pty:master");
56 else if (p->subtype == PTY_TYPE_SLAVE)
57 seq_puts(m, s: "pty:slave");
58 else
59 seq_puts(m, s: "pty");
60 break;
61 default:
62 seq_printf(m, fmt: "type:%d.%d", p->type, p->subtype);
63 }
64 seq_putc(m, c: '\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, fmt: "%-20s /dev/%-8s ", "/dev/tty", "tty");
76 seq_printf(m, fmt: "%3d %7d ", TTYAUX_MAJOR, 0);
77 seq_puts(m, s: "system:/dev/tty\n");
78 seq_printf(m, fmt: "%-20s /dev/%-8s ", "/dev/console", "console");
79 seq_printf(m, fmt: "%3d %7d ", TTYAUX_MAJOR, 1);
80 seq_puts(m, s: "system:console\n");
81#ifdef CONFIG_UNIX98_PTYS
82 seq_printf(m, fmt: "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
83 seq_printf(m, fmt: "%3d %7d ", TTYAUX_MAJOR, 2);
84 seq_puts(m, s: "system\n");
85#endif
86#ifdef CONFIG_VT
87 seq_printf(m, fmt: "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
88 seq_printf(m, fmt: "%3d %7d ", TTY_MAJOR, 0);
89 seq_puts(m, s: "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, num: next - from);
96 from = next;
97 }
98 if (from != to)
99 show_tty_range(m, p, from, num: to - from);
100 return 0;
101}
102
103/* iterator */
104static void *t_start(struct seq_file *m, loff_t *pos)
105{
106 mutex_lock(lock: &tty_mutex);
107 return seq_list_start(head: &tty_drivers, pos: *pos);
108}
109
110static void *t_next(struct seq_file *m, void *v, loff_t *pos)
111{
112 return seq_list_next(v, head: &tty_drivers, ppos: pos);
113}
114
115static void t_stop(struct seq_file *m, void *v)
116{
117 mutex_unlock(lock: &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(name: driver->driver_name, mode: 0, parent: proc_tty_driver,
140 show: driver->ops->proc_show, data: 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