1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * proc_tty.c -- handles /proc/tty
4 *
5 * Copyright 1997, Theodore Ts'o
6 */
7
8 #include <linux/uaccess.h>
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/errno.h>
12 #include <linux/time.h>
13 #include <linux/proc_fs.h>
14 #include <linux/stat.h>
15 #include <linux/tty.h>
16 #include <linux/seq_file.h>
17 #include <linux/bitops.h>
18 #include "internal.h"
19
20 /*
21 * The /proc/tty directory inodes...
22 */
23 static struct proc_dir_entry *proc_tty_driver;
24
25 /*
26 * This is the handler for /proc/tty/drivers
27 */
show_tty_range(struct seq_file * m,struct tty_driver * p,dev_t from,int num)28 static void show_tty_range(struct seq_file *m, struct tty_driver *p,
29 dev_t from, int num)
30 {
31 seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
32 seq_printf(m, "/dev/%-8s ", p->name);
33 if (p->num > 1) {
34 seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
35 MINOR(from) + num - 1);
36 } else {
37 seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
38 }
39 switch (p->type) {
40 case TTY_DRIVER_TYPE_SYSTEM:
41 seq_puts(m, "system");
42 if (p->subtype == SYSTEM_TYPE_TTY)
43 seq_puts(m, ":/dev/tty");
44 else if (p->subtype == SYSTEM_TYPE_SYSCONS)
45 seq_puts(m, ":console");
46 else if (p->subtype == SYSTEM_TYPE_CONSOLE)
47 seq_puts(m, ":vtmaster");
48 break;
49 case TTY_DRIVER_TYPE_CONSOLE:
50 seq_puts(m, "console");
51 break;
52 case TTY_DRIVER_TYPE_SERIAL:
53 seq_puts(m, "serial");
54 break;
55 case TTY_DRIVER_TYPE_PTY:
56 if (p->subtype == PTY_TYPE_MASTER)
57 seq_puts(m, "pty:master");
58 else if (p->subtype == PTY_TYPE_SLAVE)
59 seq_puts(m, "pty:slave");
60 else
61 seq_puts(m, "pty");
62 break;
63 default:
64 seq_printf(m, "type:%d.%d", p->type, p->subtype);
65 }
66 seq_putc(m, '\n');
67 }
68
show_tty_driver(struct seq_file * m,void * v)69 static int show_tty_driver(struct seq_file *m, void *v)
70 {
71 struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
72 dev_t from = MKDEV(p->major, p->minor_start);
73 dev_t to = from + p->num;
74
75 if (&p->tty_drivers == tty_drivers.next) {
76 /* pseudo-drivers first */
77 seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
78 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
79 seq_puts(m, "system:/dev/tty\n");
80 seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
81 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
82 seq_puts(m, "system:console\n");
83 #ifdef CONFIG_UNIX98_PTYS
84 seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
85 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
86 seq_puts(m, "system\n");
87 #endif
88 #ifdef CONFIG_VT
89 seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
90 seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
91 seq_puts(m, "system:vtmaster\n");
92 #endif
93 }
94
95 while (MAJOR(from) < MAJOR(to)) {
96 dev_t next = MKDEV(MAJOR(from)+1, 0);
97 show_tty_range(m, p, from, next - from);
98 from = next;
99 }
100 if (from != to)
101 show_tty_range(m, p, from, to - from);
102 return 0;
103 }
104
105 /* iterator */
t_start(struct seq_file * m,loff_t * pos)106 static void *t_start(struct seq_file *m, loff_t *pos)
107 {
108 mutex_lock(&tty_mutex);
109 return seq_list_start(&tty_drivers, *pos);
110 }
111
t_next(struct seq_file * m,void * v,loff_t * pos)112 static void *t_next(struct seq_file *m, void *v, loff_t *pos)
113 {
114 return seq_list_next(v, &tty_drivers, pos);
115 }
116
t_stop(struct seq_file * m,void * v)117 static void t_stop(struct seq_file *m, void *v)
118 {
119 mutex_unlock(&tty_mutex);
120 }
121
122 static const struct seq_operations tty_drivers_op = {
123 .start = t_start,
124 .next = t_next,
125 .stop = t_stop,
126 .show = show_tty_driver
127 };
128
129 /*
130 * This function is called by tty_register_driver() to handle
131 * registering the driver's /proc handler into /proc/tty/driver/<foo>
132 */
proc_tty_register_driver(struct tty_driver * driver)133 void proc_tty_register_driver(struct tty_driver *driver)
134 {
135 struct proc_dir_entry *ent;
136
137 if (!driver->driver_name || driver->proc_entry ||
138 !driver->ops->proc_show)
139 return;
140
141 ent = proc_create_single_data(driver->driver_name, 0, proc_tty_driver,
142 driver->ops->proc_show, driver);
143 driver->proc_entry = ent;
144 }
145
146 /*
147 * This function is called by tty_unregister_driver()
148 */
proc_tty_unregister_driver(struct tty_driver * driver)149 void proc_tty_unregister_driver(struct tty_driver *driver)
150 {
151 struct proc_dir_entry *ent;
152
153 ent = driver->proc_entry;
154 if (!ent)
155 return;
156
157 remove_proc_entry(ent->name, proc_tty_driver);
158
159 driver->proc_entry = NULL;
160 }
161
162 /*
163 * Called by proc_root_init() to initialize the /proc/tty subtree
164 */
proc_tty_init(void)165 void __init proc_tty_init(void)
166 {
167 if (!proc_mkdir("tty", NULL))
168 return;
169 proc_mkdir("tty/ldisc", NULL); /* Preserved: it's userspace visible */
170 /*
171 * /proc/tty/driver/serial reveals the exact character counts for
172 * serial links which is just too easy to abuse for inferring
173 * password lengths and inter-keystroke timings during password
174 * entry.
175 */
176 proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
177 proc_create_seq("tty/ldiscs", 0, NULL, &tty_ldiscs_seq_ops);
178 proc_create_seq("tty/drivers", 0, NULL, &tty_drivers_op);
179 }
180