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   */
show_console_dev(struct seq_file * m,void * v)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_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, 21 - 1);
59  	seq_printf(m, "%s%d", con->name, con->index);
60  	seq_pad(m, ' ');
61  	seq_printf(m, "%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, " %4d:%d", MAJOR(dev), MINOR(dev));
66  
67  	seq_putc(m, '\n');
68  	return 0;
69  }
70  
c_start(struct seq_file * m,loff_t * pos)71  static 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  
c_next(struct seq_file * m,void * v,loff_t * pos)90  static 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  
c_stop(struct seq_file * m,void * v)98  static void c_stop(struct seq_file *m, void *v)
99  	__releases(&console_mutex)
100  {
101  	console_list_unlock();
102  }
103  
104  static 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  
proc_consoles_init(void)111  static int __init proc_consoles_init(void)
112  {
113  	proc_create_seq("consoles", 0, NULL, &consoles_op);
114  	return 0;
115  }
116  fs_initcall(proc_consoles_init);
117