// SPDX-License-Identifier: GPL-2.0
/*
 * proc_tty.c -- handles /proc/tty
 *
 * Copyright 1997, Theodore Ts'o
 */

#include <linux/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_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_mkdir("tty/ldisc", NULL);  /* Preserved: it's userspace visible */
        /*
         * /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);
}