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_PRINTBUFFER,	'p' },
25		{ CON_BRL,		'b' },
26		{ CON_ANYTIME,		'a' },
27	};
28	char flags[ARRAY_SIZE(con_flags) + 1];
29	struct console *con = v;
30	unsigned int a;
31	dev_t dev = 0;
32
33	if (con->device) {
34		const struct tty_driver *driver;
35		int index;
36
37		/*
38		 * Take console_lock to serialize device() callback with
39		 * other console operations. For example, fg_console is
40		 * modified under console_lock when switching vt.
41		 */
42		console_lock();
43		driver = con->device(con, &index);
44		console_unlock();
45
46		if (driver) {
47			dev = MKDEV(driver->major, driver->minor_start);
48			dev += index;
49		}
50	}
51
52	for (a = 0; a < ARRAY_SIZE(con_flags); a++)
53		flags[a] = (con->flags & con_flags[a].flag) ?
54			con_flags[a].name : ' ';
55	flags[a] = 0;
56
57	seq_setwidth(m, 21 - 1);
58	seq_printf(m, "%s%d", con->name, con->index);
59	seq_pad(m, ' ');
60	seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-',
61			con->write ? 'W' : '-', con->unblank ? 'U' : '-',
62			flags);
63	if (dev)
64		seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev));
65
66	seq_putc(m, '\n');
67	return 0;
68}
69
70static void *c_start(struct seq_file *m, loff_t *pos)
71{
72	struct console *con;
73	loff_t off = 0;
74
75	/*
76	 * Hold the console_list_lock to guarantee safe traversal of the
77	 * console list. SRCU cannot be used because there is no
78	 * place to store the SRCU cookie.
79	 */
80	console_list_lock();
81	for_each_console(con)
82		if (off++ == *pos)
83			break;
84
85	return con;
86}
87
88static void *c_next(struct seq_file *m, void *v, loff_t *pos)
89{
90	struct console *con = v;
91
92	++*pos;
93	return hlist_entry_safe(con->node.next, struct console, node);
94}
95
96static void c_stop(struct seq_file *m, void *v)
97{
98	console_list_unlock();
99}
100
101static const struct seq_operations consoles_op = {
102	.start	= c_start,
103	.next	= c_next,
104	.stop	= c_stop,
105	.show	= show_console_dev
106};
107
108static int __init proc_consoles_init(void)
109{
110	proc_create_seq("consoles", 0, NULL, &consoles_op);
111	return 0;
112}
113fs_initcall(proc_consoles_init);
114