fs/proc/proc_tty.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * proc_tty.c -- handles /proc/tty
0004  *
0005  * Copyright 1997, Theodore Ts'o
0006  */
0007 #include <linux/module.h>
0008 #include <linux/init.h>
0009 #include <linux/errno.h>
0010 #include <linux/time.h>
0011 #include <linux/proc_fs.h>
0012 #include <linux/stat.h>
0013 #include <linux/tty.h>
0014 #include <linux/seq_file.h>
0015 #include <linux/bitops.h>
0016 #include "internal.h"
0017
0018 /*
0019  * The /proc/tty directory inodes...
0020  */
0021 static struct proc_dir_entry *proc_tty_driver;
0022
0023 /*
0024  * This is the handler for /proc/tty/drivers
0025  */
0026 static void show_tty_range(struct seq_file *m, struct tty_driver *p,
0027     dev_t from, int num)
0028 {
0029     seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
0030     seq_printf(m, "/dev/%-8s ", p->name);
0031     if (p->num > 1) {
0032         seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
0033             MINOR(from) + num - 1);
0034     } else {
0035         seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
0036     }
0037     switch (p->type) {
0038     case TTY_DRIVER_TYPE_SYSTEM:
0039         seq_puts(m, "system");
0040         if (p->subtype == SYSTEM_TYPE_TTY)
0041             seq_puts(m, ":/dev/tty");
0042         else if (p->subtype == SYSTEM_TYPE_SYSCONS)
0043             seq_puts(m, ":console");
0044         else if (p->subtype == SYSTEM_TYPE_CONSOLE)
0045             seq_puts(m, ":vtmaster");
0046         break;
0047     case TTY_DRIVER_TYPE_CONSOLE:
0048         seq_puts(m, "console");
0049         break;
0050     case TTY_DRIVER_TYPE_SERIAL:
0051         seq_puts(m, "serial");
0052         break;
0053     case TTY_DRIVER_TYPE_PTY:
0054         if (p->subtype == PTY_TYPE_MASTER)
0055             seq_puts(m, "pty:master");
0056         else if (p->subtype == PTY_TYPE_SLAVE)
0057             seq_puts(m, "pty:slave");
0058         else
0059             seq_puts(m, "pty");
0060         break;
0061     default:
0062         seq_printf(m, "type:%d.%d", p->type, p->subtype);
0063     }
0064     seq_putc(m, '\n');
0065 }
0066
0067 static int show_tty_driver(struct seq_file *m, void *v)
0068 {
0069     struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
0070     dev_t from = MKDEV(p->major, p->minor_start);
0071     dev_t to = from + p->num;
0072
0073     if (&p->tty_drivers == tty_drivers.next) {
0074         /* pseudo-drivers first */
0075         seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
0076         seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
0077         seq_puts(m, "system:/dev/tty\n");
0078         seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
0079         seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
0080         seq_puts(m, "system:console\n");
0081 #ifdef CONFIG_UNIX98_PTYS
0082         seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
0083         seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
0084         seq_puts(m, "system\n");
0085 #endif
0086 #ifdef CONFIG_VT
0087         seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
0088         seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
0089         seq_puts(m, "system:vtmaster\n");
0090 #endif
0091     }
0092
0093     while (MAJOR(from) < MAJOR(to)) {
0094         dev_t next = MKDEV(MAJOR(from)+1, 0);
0095         show_tty_range(m, p, from, next - from);
0096         from = next;
0097     }
0098     if (from != to)
0099         show_tty_range(m, p, from, to - from);
0100     return 0;
0101 }
0102
0103 /* iterator */
0104 static void *t_start(struct seq_file *m, loff_t *pos)
0105 {
0106     mutex_lock(&tty_mutex);
0107     return seq_list_start(&tty_drivers, *pos);
0108 }
0109
0110 static void *t_next(struct seq_file *m, void *v, loff_t *pos)
0111 {
0112     return seq_list_next(v, &tty_drivers, pos);
0113 }
0114
0115 static void t_stop(struct seq_file *m, void *v)
0116 {
0117     mutex_unlock(&tty_mutex);
0118 }
0119
0120 static const struct seq_operations tty_drivers_op = {
0121     .start  = t_start,
0122     .next   = t_next,
0123     .stop   = t_stop,
0124     .show   = show_tty_driver
0125 };
0126
0127 /*
0128  * This function is called by tty_register_driver() to handle
0129  * registering the driver's /proc handler into /proc/tty/driver/<foo>
0130  */
0131 void proc_tty_register_driver(struct tty_driver *driver)
0132 {
0133     struct proc_dir_entry *ent;
0134
0135     if (!driver->driver_name || driver->proc_entry ||
0136         !driver->ops->proc_show)
0137         return;
0138
0139     ent = proc_create_single_data(driver->driver_name, 0, proc_tty_driver,
0140                    driver->ops->proc_show, driver);
0141     driver->proc_entry = ent;
0142 }
0143
0144 /*
0145  * This function is called by tty_unregister_driver()
0146  */
0147 void proc_tty_unregister_driver(struct tty_driver *driver)
0148 {
0149     struct proc_dir_entry *ent;
0150
0151     ent = driver->proc_entry;
0152     if (!ent)
0153         return;
0154
0155     remove_proc_entry(ent->name, proc_tty_driver);
0156
0157     driver->proc_entry = NULL;
0158 }
0159
0160 /*
0161  * Called by proc_root_init() to initialize the /proc/tty subtree
0162  */
0163 void __init proc_tty_init(void)
0164 {
0165     if (!proc_mkdir("tty", NULL))
0166         return;
0167     proc_mkdir("tty/ldisc", NULL);  /* Preserved: it's userspace visible */
0168     /*
0169      * /proc/tty/driver/serial reveals the exact character counts for
0170      * serial links which is just too easy to abuse for inferring
0171      * password lengths and inter-keystroke timings during password
0172      * entry.
0173      */
0174     proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
0175     proc_create_seq("tty/ldiscs", 0, NULL, &tty_ldiscs_seq_ops);
0176     proc_create_seq("tty/drivers", 0, NULL, &tty_drivers_op);
0177 }