1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2010 Werner Fink, Jiri Slaby
4 */
5
6#include <linux/console.h>
7#include <linux/kernel.h>
8#include <linux/proc_fs.h>
9#include <linux/seq_file.h>
10#include <linux/tty_driver.h>
11
12/*
13 * This is handler for /proc/consoles
14 */
15static int show_console_dev(struct seq_file *m, void *v)
16{
17 static const struct {
18 short flag;
19 char name;
20 } con_flags[] = {
21 { CON_ENABLED, 'E' },
22 { CON_CONSDEV, 'C' },
23 { CON_BOOT, 'B' },
24 { CON_NBCON, 'N' },
25 { CON_PRINTBUFFER, 'p' },
26 { CON_BRL, 'b' },
27 { CON_ANYTIME, 'a' },
28 };
29 char flags[ARRAY_SIZE(con_flags) + 1];
30 struct console *con = v;
31 unsigned int a;
32 dev_t dev = 0;
33
34 if (con->device) {
35 const struct tty_driver *driver;
36 int index;
37
38 /*
39 * Take console_lock to serialize device() callback with
40 * other console operations. For example, fg_console is
41 * modified under console_lock when switching vt.
42 */
43 console_lock();
44 driver = con->device(con, &index);
45 console_unlock();
46
47 if (driver) {
48 dev = MKDEV(driver->major, driver->minor_start);
49 dev += index;
50 }
51 }
52
53 for (a = 0; a < ARRAY_SIZE(con_flags); a++)
54 flags[a] = (con->flags & con_flags[a].flag) ?
55 con_flags[a].name : ' ';
56 flags[a] = 0;
57
58 seq_setwidth(m, size: 21 - 1);
59 seq_printf(m, fmt: "%s%d", con->name, con->index);
60 seq_pad(m, c: ' ');
61 seq_printf(m, fmt: "%c%c%c (%s)", con->read ? 'R' : '-',
62 ((con->flags & CON_NBCON) || con->write) ? 'W' : '-',
63 con->unblank ? 'U' : '-', flags);
64 if (dev)
65 seq_printf(m, fmt: " %4d:%d", MAJOR(dev), MINOR(dev));
66
67 seq_putc(m, c: '\n');
68 return 0;
69}
70
71static void *c_start(struct seq_file *m, loff_t *pos)
72 __acquires(&console_mutex)
73{
74 struct console *con;
75 loff_t off = 0;
76
77 /*
78 * Hold the console_list_lock to guarantee safe traversal of the
79 * console list. SRCU cannot be used because there is no
80 * place to store the SRCU cookie.
81 */
82 console_list_lock();
83 for_each_console(con)
84 if (off++ == *pos)
85 break;
86
87 return con;
88}
89
90static void *c_next(struct seq_file *m, void *v, loff_t *pos)
91{
92 struct console *con = v;
93
94 ++*pos;
95 return hlist_entry_safe(con->node.next, struct console, node);
96}
97
98static void c_stop(struct seq_file *m, void *v)
99 __releases(&console_mutex)
100{
101 console_list_unlock();
102}
103
104static const struct seq_operations consoles_op = {
105 .start = c_start,
106 .next = c_next,
107 .stop = c_stop,
108 .show = show_console_dev
109};
110
111static int __init proc_consoles_init(void)
112{
113 proc_create_seq("consoles", 0, NULL, &consoles_op);
114 return 0;
115}
116fs_initcall(proc_consoles_init);
117