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
   8 #include <linux/uaccess.h>
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/errno.h>
  12 #include <linux/time.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/stat.h>
  15 #include <linux/tty.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/bitops.h>
  18
  19 /*
  20  * The /proc/tty directory inodes...
  21  */
  22 static struct proc_dir_entry *proc_tty_driver;
  23
  24 /*
  25  * This is the handler for /proc/tty/drivers
  26  */
  27 static void show_tty_range(struct seq_file *m, struct tty_driver *p,
  28         dev_t from, int num)
  29 {
  30         seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
  31         seq_printf(m, "/dev/%-8s ", p->name);
  32         if (p->num > 1) {
  33                 seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
  34                         MINOR(from) + num - 1);
  35         } else {
  36                 seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
  37         }
  38         switch (p->type) {
  39         case TTY_DRIVER_TYPE_SYSTEM:
  40                 seq_puts(m, "system");
  41                 if (p->subtype == SYSTEM_TYPE_TTY)
  42                         seq_puts(m, ":/dev/tty");
  43                 else if (p->subtype == SYSTEM_TYPE_SYSCONS)
  44                         seq_puts(m, ":console");
  45                 else if (p->subtype == SYSTEM_TYPE_CONSOLE)
  46                         seq_puts(m, ":vtmaster");
  47                 break;
  48         case TTY_DRIVER_TYPE_CONSOLE:
  49                 seq_puts(m, "console");
  50                 break;
  51         case TTY_DRIVER_TYPE_SERIAL:
  52                 seq_puts(m, "serial");
  53                 break;
  54         case TTY_DRIVER_TYPE_PTY:
  55                 if (p->subtype == PTY_TYPE_MASTER)
  56                         seq_puts(m, "pty:master");
  57                 else if (p->subtype == PTY_TYPE_SLAVE)
  58                         seq_puts(m, "pty:slave");
  59                 else
  60                         seq_puts(m, "pty");
  61                 break;
  62         default:
  63                 seq_printf(m, "type:%d.%d", p->type, p->subtype);
  64         }
  65         seq_putc(m, '\n');
  66 }
  67
  68 static int show_tty_driver(struct seq_file *m, void *v)
  69 {
  70         struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
  71         dev_t from = MKDEV(p->major, p->minor_start);
  72         dev_t to = from + p->num;
  73
  74         if (&p->tty_drivers == tty_drivers.next) {
  75                 /* pseudo-drivers first */
  76                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
  77                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
  78                 seq_puts(m, "system:/dev/tty\n");
  79                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
  80                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
  81                 seq_puts(m, "system:console\n");
  82 #ifdef CONFIG_UNIX98_PTYS
  83                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
  84                 seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
  85                 seq_puts(m, "system\n");
  86 #endif
  87 #ifdef CONFIG_VT
  88                 seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
  89                 seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
  90                 seq_puts(m, "system:vtmaster\n");
  91 #endif
  92         }
  93
  94         while (MAJOR(from) < MAJOR(to)) {
  95                 dev_t next = MKDEV(MAJOR(from)+1, 0);
  96                 show_tty_range(m, p, from, next - from);
  97                 from = next;
  98         }
  99         if (from != to)
 100                 show_tty_range(m, p, from, to - from);
 101         return 0;
 102 }
 103
 104 /* iterator */
 105 static void *t_start(struct seq_file *m, loff_t *pos)
 106 {
 107         mutex_lock(&tty_mutex);
 108         return seq_list_start(&tty_drivers, *pos);
 109 }
 110
 111 static void *t_next(struct seq_file *m, void *v, loff_t *pos)
 112 {
 113         return seq_list_next(v, &tty_drivers, pos);
 114 }
 115
 116 static void t_stop(struct seq_file *m, void *v)
 117 {
 118         mutex_unlock(&tty_mutex);
 119 }
 120
 121 static const struct seq_operations tty_drivers_op = {
 122         .start  = t_start,
 123         .next   = t_next,
 124         .stop   = t_stop,
 125         .show   = show_tty_driver
 126 };
 127
 128 static int tty_drivers_open(struct inode *inode, struct file *file)
 129 {
 130         return seq_open(file, &tty_drivers_op);
 131 }
 132
 133 static const struct file_operations proc_tty_drivers_operations = {
 134         .open           = tty_drivers_open,
 135         .read           = seq_read,
 136         .llseek         = seq_lseek,
 137         .release        = seq_release,
 138 };
 139
 140 /*
 141  * This function is called by tty_register_driver() to handle
 142  * registering the driver's /proc handler into /proc/tty/driver/<foo>
 143  */
 144 void proc_tty_register_driver(struct tty_driver *driver)
 145 {
 146         struct proc_dir_entry *ent;
 147
 148         if (!driver->driver_name || driver->proc_entry ||
 149             !driver->ops->proc_fops)
 150                 return;
 151
 152         ent = proc_create_data(driver->driver_name, 0, proc_tty_driver,
 153                                driver->ops->proc_fops, driver);
 154         driver->proc_entry = ent;
 155 }
 156
 157 /*
 158  * This function is called by tty_unregister_driver()
 159  */
 160 void proc_tty_unregister_driver(struct tty_driver *driver)
 161 {
 162         struct proc_dir_entry *ent;
 163
 164         ent = driver->proc_entry;
 165         if (!ent)
 166                 return;
 167
 168         remove_proc_entry(driver->driver_name, proc_tty_driver);
 169
 170         driver->proc_entry = NULL;
 171 }
 172
 173 /*
 174  * Called by proc_root_init() to initialize the /proc/tty subtree
 175  */
 176 void __init proc_tty_init(void)
 177 {
 178         if (!proc_mkdir("tty", NULL))
 179                 return;
 180         proc_mkdir("tty/ldisc", NULL);  /* Preserved: it's userspace visible */
 181         /*
 182          * /proc/tty/driver/serial reveals the exact character counts for
 183          * serial links which is just too easy to abuse for inferring
 184          * password lengths and inter-keystroke timings during password
 185          * entry.
 186          */
 187         proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
 188         proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
 189         proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
 190 }