proc_tty.c

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/*
 * proc_tty.c -- handles /proc/tty
 *
 * Copyright 1997, Theodore Ts'o
 */

#include <asm/uaccess.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/seq_file.h>
#include <linux/bitops.h>

/*
 * The /proc/tty directory inodes...
 */
static struct proc_dir_entry *proc_tty_ldisc, *proc_tty_driver;

/*
 * This is the handler for /proc/tty/drivers
 */
static void show_tty_range(struct seq_file *m, struct tty_driver *p,
    dev_t from, int num)
{
    seq_printf(m, "%-20s ", p->driver_name ? p->driver_name : "unknown");
    seq_printf(m, "/dev/%-8s ", p->name);
    if (p->num > 1) {
        seq_printf(m, "%3d %d-%d ", MAJOR(from), MINOR(from),
            MINOR(from) + num - 1);
    } else {
        seq_printf(m, "%3d %7d ", MAJOR(from), MINOR(from));
    }
    switch (p->type) {
    case TTY_DRIVER_TYPE_SYSTEM:
        seq_puts(m, "system");
        if (p->subtype == SYSTEM_TYPE_TTY)
            seq_puts(m, ":/dev/tty");
        else if (p->subtype == SYSTEM_TYPE_SYSCONS)
            seq_puts(m, ":console");
        else if (p->subtype == SYSTEM_TYPE_CONSOLE)
            seq_puts(m, ":vtmaster");
        break;
    case TTY_DRIVER_TYPE_CONSOLE:
        seq_puts(m, "console");
        break;
    case TTY_DRIVER_TYPE_SERIAL:
        seq_puts(m, "serial");
        break;
    case TTY_DRIVER_TYPE_PTY:
        if (p->subtype == PTY_TYPE_MASTER)
            seq_puts(m, "pty:master");
        else if (p->subtype == PTY_TYPE_SLAVE)
            seq_puts(m, "pty:slave");
        else
            seq_puts(m, "pty");
        break;
    default:
        seq_printf(m, "type:%d.%d", p->type, p->subtype);
    }
    seq_putc(m, '\n');
}

static int show_tty_driver(struct seq_file *m, void *v)
{
    struct tty_driver *p = list_entry(v, struct tty_driver, tty_drivers);
    dev_t from = MKDEV(p->major, p->minor_start);
    dev_t to = from + p->num;

    if (&p->tty_drivers == tty_drivers.next) {
        /* pseudo-drivers first */
        seq_printf(m, "%-20s /dev/%-8s ", "/dev/tty", "tty");
        seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 0);
        seq_puts(m, "system:/dev/tty\n");
        seq_printf(m, "%-20s /dev/%-8s ", "/dev/console", "console");
        seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 1);
        seq_puts(m, "system:console\n");
#ifdef CONFIG_UNIX98_PTYS
        seq_printf(m, "%-20s /dev/%-8s ", "/dev/ptmx", "ptmx");
        seq_printf(m, "%3d %7d ", TTYAUX_MAJOR, 2);
        seq_puts(m, "system\n");
#endif
#ifdef CONFIG_VT
        seq_printf(m, "%-20s /dev/%-8s ", "/dev/vc/0", "vc/0");
        seq_printf(m, "%3d %7d ", TTY_MAJOR, 0);
        seq_puts(m, "system:vtmaster\n");
#endif
    }

    while (MAJOR(from) < MAJOR(to)) {
        dev_t next = MKDEV(MAJOR(from)+1, 0);
        show_tty_range(m, p, from, next - from);
        from = next;
    }
    if (from != to)
        show_tty_range(m, p, from, to - from);
    return 0;
}

/* iterator */
static void *t_start(struct seq_file *m, loff_t *pos)
{
    mutex_lock(&tty_mutex);
    return seq_list_start(&tty_drivers, *pos);
}

static void *t_next(struct seq_file *m, void *v, loff_t *pos)
{
    return seq_list_next(v, &tty_drivers, pos);
}

static void t_stop(struct seq_file *m, void *v)
{
    mutex_unlock(&tty_mutex);
}

static const struct seq_operations tty_drivers_op = {
    .start  = t_start,
    .next   = t_next,
    .stop   = t_stop,
    .show   = show_tty_driver
};

static int tty_drivers_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &tty_drivers_op);
}

static const struct file_operations proc_tty_drivers_operations = {
    .open       = tty_drivers_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

/*
 * This function is called by tty_register_driver() to handle
 * registering the driver's /proc handler into /proc/tty/driver/<foo>
 */
void proc_tty_register_driver(struct tty_driver *driver)
{
    struct proc_dir_entry *ent;
        
    if (!driver->driver_name || driver->proc_entry ||
        !driver->ops->proc_fops)
        return;

    ent = proc_create_data(driver->driver_name, 0, proc_tty_driver,
                   driver->ops->proc_fops, driver);
    driver->proc_entry = ent;
}

/*
 * This function is called by tty_unregister_driver()
 */
void proc_tty_unregister_driver(struct tty_driver *driver)
{
    struct proc_dir_entry *ent;

    ent = driver->proc_entry;
    if (!ent)
        return;
        
    remove_proc_entry(driver->driver_name, proc_tty_driver);
    
    driver->proc_entry = NULL;
}

/*
 * Called by proc_root_init() to initialize the /proc/tty subtree
 */
void __init proc_tty_init(void)
{
    if (!proc_mkdir("tty", NULL))
        return;
    proc_tty_ldisc = proc_mkdir("tty/ldisc", NULL);
    /*
     * /proc/tty/driver/serial reveals the exact character counts for
     * serial links which is just too easy to abuse for inferring
     * password lengths and inter-keystroke timings during password
     * entry.
     */
    proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
    proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
    proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
}