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