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* proc_tty.c -- handles /proc/tty
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* Copyright 1997, Theodore Ts'o
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#include <asm/uaccess.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/errno.h>
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#include <linux/time.h>
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#include <linux/proc_fs.h>
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#include <linux/stat.h>
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#include <linux/tty.h>
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#include <linux/seq_file.h>
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#include <linux/bitops.h>
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* The /proc/tty directory inodes...
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static struct proc_dir_entry *proc_tty_ldisc, *proc_tty_driver;
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* This is the handler for /proc/tty/drivers
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static void show_tty_range(struct seq_file *m, struct tty_driver *p,
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seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
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seq_printf(m, "/dev/%-8s ", p->name);
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seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
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MINOR(from) + num - 1);
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seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
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case TTY_DRIVER_TYPE_SYSTEM:
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seq_puts(m, "system");
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if (p->subtype == SYSTEM_TYPE_TTY)
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seq_puts(m, ":/dev/tty");
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else if (p->subtype == SYSTEM_TYPE_SYSCONS)
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seq_puts(m, ":console");
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else if (p->subtype == SYSTEM_TYPE_CONSOLE)
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seq_puts(m, ":vtmaster");
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case TTY_DRIVER_TYPE_CONSOLE:
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seq_puts(m, "console");
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case TTY_DRIVER_TYPE_SERIAL:
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seq_puts(m, "serial");
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case TTY_DRIVER_TYPE_PTY:
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if (p->subtype == PTY_TYPE_MASTER)
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seq_puts(m, "pty:master");
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else if (p->subtype == PTY_TYPE_SLAVE)
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seq_puts(m, "pty:slave");
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seq_printf(m, "type:%d.%d", p->type, p->subtype);
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static int show_tty_driver(struct seq_file *m, void *v)
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struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
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dev_t from = MKDEV(p->major, p->minor_start);
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dev_t to = from + p->num;
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if (&p->tty_drivers == tty_drivers.next) {
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/* pseudo-drivers first */
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seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
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seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
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seq_puts(m, "system:/dev/tty\n");
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seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
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seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
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seq_puts(m, "system:console\n");
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#ifdef CONFIG_UNIX98_PTYS
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seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
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seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
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seq_puts(m, "system\n");
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seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
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seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
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seq_puts(m, "system:vtmaster\n");
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while (MAJOR(from) < MAJOR(to)) {
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dev_t next = MKDEV(MAJOR(from)+1, 0);
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show_tty_range(m, p, from, next - from);
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show_tty_range(m, p, from, to - from);
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static void *t_start(struct seq_file *m, loff_t *pos)
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mutex_lock(&tty_mutex);
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return seq_list_start(&tty_drivers, *pos);
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static void *t_next(struct seq_file *m, void *v, loff_t *pos)
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return seq_list_next(v, &tty_drivers, pos);
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static void t_stop(struct seq_file *m, void *v)
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mutex_unlock(&tty_mutex);
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static const struct seq_operations tty_drivers_op = {
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.show = show_tty_driver
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static int tty_drivers_open(struct inode *inode, struct file *file)
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return seq_open(file, &tty_drivers_op);
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static const struct file_operations proc_tty_drivers_operations = {
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.open = tty_drivers_open,
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.release = seq_release,
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* This function is called by tty_register_driver() to handle
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* registering the driver's /proc handler into /proc/tty/driver/<foo>
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void proc_tty_register_driver(struct tty_driver *driver)
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struct proc_dir_entry *ent;
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if (!driver->driver_name || driver->proc_entry ||
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!driver->ops->proc_fops)
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ent = proc_create_data(driver->driver_name, 0, proc_tty_driver,
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driver->ops->proc_fops, driver);
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driver->proc_entry = ent;
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* This function is called by tty_unregister_driver()
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void proc_tty_unregister_driver(struct tty_driver *driver)
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struct proc_dir_entry *ent;
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ent = driver->proc_entry;
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remove_proc_entry(driver->driver_name, proc_tty_driver);
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driver->proc_entry = NULL;
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* Called by proc_root_init() to initialize the /proc/tty subtree
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void __init proc_tty_init(void)
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if (!proc_mkdir("tty", NULL))
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proc_tty_ldisc = proc_mkdir("tty/ldisc", NULL);
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* /proc/tty/driver/serial reveals the exact character counts for
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* serial links which is just too easy to abuse for inferring
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* password lengths and inter-keystroke timings during password
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proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
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proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
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proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);