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_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 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 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 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 }; 110 111 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