fs/proc/proc_tty.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * proc_tty.c -- handles /proc/tty
   4  *
   5  * Copyright 1997, Theodore Ts'o
   6  */
   7 #include <linux/module.h>
   8 #include <linux/init.h>
   9 #include <linux/errno.h>
  10 #include <linux/time.h>
  11 #include <linux/proc_fs.h>
  12 #include <linux/stat.h>
  13 #include <linux/tty.h>
  14 #include <linux/seq_file.h>
  15 #include <linux/bitops.h>
  16 #include "internal.h"
  17
  18 /*
  19  * The /proc/tty directory inodes...
  20  */
  21 static struct proc_dir_entry *proc_tty_driver;
  22
  23 /*
  24  * This is the handler for /proc/tty/drivers
  25  */
  26 static void show_tty_range(struct seq_file *m, struct tty_driver *p,
  27         dev_t from, int num)
  28 {
  29         seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
  30         seq_printf(m, "/dev/%-8s ", p->name);
  31         if (p->num > 1) {
  32                 seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
  33                         MINOR(from) + num - 1);
  34         } else {
  35                 seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
  36         }
  37         switch (p->type) {
  38         case TTY_DRIVER_TYPE_SYSTEM:
  39                 seq_puts(m, "system");
  40                 if (p->subtype == SYSTEM_TYPE_TTY)
  41                         seq_puts(m, ":/dev/tty");
  42                 else if (p->subtype == SYSTEM_TYPE_SYSCONS)
  43                         seq_puts(m, ":console");
  44                 else if (p->subtype == SYSTEM_TYPE_CONSOLE)
  45                         seq_puts(m, ":vtmaster");
  46                 break;
  47         case TTY_DRIVER_TYPE_CONSOLE:
  48                 seq_puts(m, "console");
  49                 break;
  50         case TTY_DRIVER_TYPE_SERIAL:
  51                 seq_puts(m, "serial");
  52                 break;
  53         case TTY_DRIVER_TYPE_PTY:
  54                 if (p->subtype == PTY_TYPE_MASTER)
  55                         seq_puts(m, "pty:master");
  56                 else if (p->subtype == PTY_TYPE_SLAVE)
  57                         seq_puts(m, "pty:slave");
  58                 else
  59                         seq_puts(m, "pty");
  60                 break;
  61         default:
  62                 seq_printf(m, "type:%d.%d", p->type, p->subtype);
  63         }
  64         seq_putc(m, '\n');
  65 }
  66
  67 static int show_tty_driver(struct seq_file *m, void *v)
  68 {
  69         struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
  70         dev_t from = MKDEV(p->major, p->minor_start);
  71         dev_t to = from + p->num;
  72
  73         if (&p->tty_drivers == tty_drivers.next) {
  74                 /* pseudo-drivers first */
  75                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
  76                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
  77                 seq_puts(m, "system:/dev/tty\n");
  78                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
  79                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
  80                 seq_puts(m, "system:console\n");
  81 #ifdef CONFIG_UNIX98_PTYS
  82                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
  83                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
  84                 seq_puts(m, "system\n");
  85 #endif
  86 #ifdef CONFIG_VT
  87                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
  88                 seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
  89                 seq_puts(m, "system:vtmaster\n");
  90 #endif
  91         }
  92
  93         while (MAJOR(from) < MAJOR(to)) {
  94                 dev_t next = MKDEV(MAJOR(from)+1, 0);
  95                 show_tty_range(m, p, from, next - from);
  96                 from = next;
  97         }
  98         if (from != to)
  99                 show_tty_range(m, p, from, to - from);
 100         return 0;
 101 }
 102
 103 /* iterator */
 104 static void *t_start(struct seq_file *m, loff_t *pos)
 105 {
 106         mutex_lock(&tty_mutex);
 107         return seq_list_start(&tty_drivers, *pos);
 108 }
 109
 110 static void *t_next(struct seq_file *m, void *v, loff_t *pos)
 111 {
 112         return seq_list_next(v, &tty_drivers, pos);
 113 }
 114
 115 static void t_stop(struct seq_file *m, void *v)
 116 {
 117         mutex_unlock(&tty_mutex);
 118 }
 119
 120 static const struct seq_operations tty_drivers_op = {
 121         .start  = t_start,
 122         .next   = t_next,
 123         .stop   = t_stop,
 124         .show   = show_tty_driver
 125 };
 126
 127 /*
 128  * This function is called by tty_register_driver() to handle
 129  * registering the driver's /proc handler into /proc/tty/driver/<foo>
 130  */
 131 void proc_tty_register_driver(struct tty_driver *driver)
 132 {
 133         struct proc_dir_entry *ent;
 134
 135         if (!driver->driver_name || driver->proc_entry ||
 136             !driver->ops->proc_show)
 137                 return;
 138
 139         ent = proc_create_single_data(driver->driver_name, 0, proc_tty_driver,
 140                                driver->ops->proc_show, driver);
 141         driver->proc_entry = ent;
 142 }
 143
 144 /*
 145  * This function is called by tty_unregister_driver()
 146  */
 147 void proc_tty_unregister_driver(struct tty_driver *driver)
 148 {
 149         struct proc_dir_entry *ent;
 150
 151         ent = driver->proc_entry;
 152         if (!ent)
 153                 return;
 154
 155         remove_proc_entry(ent->name, proc_tty_driver);
 156
 157         driver->proc_entry = NULL;
 158 }
 159
 160 /*
 161  * Called by proc_root_init() to initialize the /proc/tty subtree
 162  */
 163 void __init proc_tty_init(void)
 164 {
 165         if (!proc_mkdir("tty", NULL))
 166                 return;
 167         proc_mkdir("tty/ldisc", NULL);  /* Preserved: it's userspace visible */
 168         /*
 169          * /proc/tty/driver/serial reveals the exact character counts for
 170          * serial links which is just too easy to abuse for inferring
 171          * password lengths and inter-keystroke timings during password
 172          * entry.
 173          */
 174         proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
 175         proc_create_seq("tty/ldiscs", 0, NULL, &tty_ldiscs_seq_ops);
 176         proc_create_seq("tty/drivers", 0, NULL, &tty_drivers_op);
 177 }