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 */
15 static 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
70 static 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
88 static 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
96 static void c_stop(struct seq_file *m, void *v)
97 {
98 console_list_unlock();
99 }
100
101 static 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
108 static int __init proc_consoles_init(void)
109 {
110 proc_create_seq("consoles", 0, NULL, &consoles_op);
111 return 0;
112 }
113 fs_initcall(proc_consoles_init);
114
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