/*      $NetBSD: cons.c,v 1.96 2025/12/20 10:51:05 skrll Exp $  */

/*
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * from: Utah $Hdr: cons.c 1.7 92/01/21$
 *
 *      @(#)cons.c      8.2 (Berkeley) 1/12/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: cons.c,v 1.96 2025/12/20 10:51:05 skrll Exp $");

#include <sys/param.h>

#include <sys/atomic.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/heartbeat.h>
#include <sys/ioctl.h>
#include <sys/kauth.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/poll.h>
#include <sys/proc.h>
#include <sys/pserialize.h>
#include <sys/systm.h>
#include <sys/tty.h>
#include <sys/vnode.h>

#include <dev/cons.h>

#include "nullcons.h"

dev_type_open(cnopen);
dev_type_close(cnclose);
dev_type_read(cnread);
dev_type_write(cnwrite);
dev_type_ioctl(cnioctl);
dev_type_poll(cnpoll);
dev_type_kqfilter(cnkqfilter);

static bool cn_redirect(dev_t *, int, int *, struct tty **);
static void cn_release(struct tty *);

const struct cdevsw cons_cdevsw = {
        .d_open = cnopen,
        .d_close = cnclose,
        .d_read = cnread,
        .d_write = cnwrite,
        .d_ioctl = cnioctl,
        .d_stop = nostop,
        .d_tty = notty,
        .d_poll = cnpoll,
        .d_mmap = nommap,
        .d_kqfilter = cnkqfilter,
        .d_discard = nodiscard,
        .d_flag = D_TTY|D_MPSAFE,
};

static struct kmutex cn_lock;

struct  tty *volatile constty;  /* virtual console output device */
struct  consdev *cn_tab;        /* physical console device info */
struct  vnode *cn_devvp[2];     /* vnode for underlying device. */

void
cn_set_tab(struct consdev *tab)
{

        /*
         * This is a point that we should have KASSERT(cold) or add
         * synchronization in case this can happen after cold boot.
         * However, cn_tab initialization is so critical to any
         * diagnostics or debugging that we need to tread carefully
         * about introducing new ways to crash.  So let's put the
         * assertion in only after we've audited most or all of the
         * cn_tab updates.
         */
        cn_tab = tab;
}

int
cnopen(dev_t dev, int flag, int mode, struct lwp *l)
{
        dev_t cndev;
        int unit, error;

        unit = minor(dev);
        if (unit > 1)
                return ENODEV;

        mutex_enter(&cn_lock);

        if (cn_tab == NULL) {
                error = 0;
                goto out;
        }

        /*
         * always open the 'real' console device, so we don't get nailed
         * later.  This follows normal device semantics; they always get
         * open() calls.
         */
        cndev = cn_tab->cn_dev;
#if NNULLCONS > 0
        if (cndev == NODEV) {
                nullconsattach(0);
        }
#else /* NNULLCONS > 0 */
        if (cndev == NODEV) {
                /*
                 * This is most likely an error in the console attach
                 * code. Panicking looks better than jumping into nowhere
                 * through cdevsw below....
                 */
                panic("cnopen: no console device");
        }
#endif /* NNULLCONS > 0 */
        if (dev == cndev) {
                /*
                 * This causes cnopen() to be called recursively, which
                 * is generally a bad thing.  It is often caused when
                 * dev == 0 and cn_dev has not been set, but was probably
                 * initialised to 0.
                 */
                panic("cnopen: cn_tab->cn_dev == dev");
        }
        if (cn_devvp[unit] != NULLVP) {
                error = 0;
                goto out;
        }
        if ((error = cdevvp(cndev, &cn_devvp[unit])) != 0) {
                printf("cnopen: unable to get vnode reference\n");
                goto out;
        }
        vn_lock(cn_devvp[unit], LK_EXCLUSIVE | LK_RETRY);
        error = VOP_OPEN(cn_devvp[unit], flag, kauth_cred_get());
        VOP_UNLOCK(cn_devvp[unit]);

out:    mutex_exit(&cn_lock);
        return error;
}

int
cnclose(dev_t dev, int flag, int mode, struct lwp *l)
{
        struct vnode *vp;
        int unit, error;

        unit = minor(dev);
        if (unit > 1)
                return ENODEV;

        mutex_enter(&cn_lock);

        if (cn_tab == NULL) {
                error = 0;
                goto out;
        }

        vp = cn_devvp[unit];
        cn_devvp[unit] = NULL;
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        error = VOP_CLOSE(vp, flag, kauth_cred_get());
        VOP_UNLOCK(vp);
        vrele(vp);

out:    mutex_exit(&cn_lock);
        return error;
}

int
cnread(dev_t dev, struct uio *uio, int flag)
{
        struct tty *ctp = NULL;
        int error;

        /*
         * If we would redirect input, punt.  This will keep strange
         * things from happening to people who are using the real
         * console.  Nothing should be using /dev/console for
         * input (except a shell in single-user mode, but then,
         * one wouldn't TIOCCONS then).
         */
        if (!cn_redirect(&dev, 1, &error, &ctp))
                return error;
        error = cdev_read(dev, uio, flag);
        cn_release(ctp);
        return error;
}

int
cnwrite(dev_t dev, struct uio *uio, int flag)
{
        struct tty *ctp = NULL;
        int error;

        /* Redirect output, if that's appropriate. */
        if (!cn_redirect(&dev, 0, &error, &ctp))
                return error;
        error = cdev_write(dev, uio, flag);
        cn_release(ctp);
        return error;
}

int
cnioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
{
        struct tty *ctp = NULL;
        int error;

        error = 0;

        /*
         * Superuser can always use this to wrest control of console
         * output from the "virtual" console.
         */
        if (cmd == TIOCCONS) {
                struct tty *tp;

                mutex_enter(&constty_lock);
                tp = atomic_load_relaxed(&constty);
                if (tp == NULL) {
                        mutex_exit(&constty_lock);
                        goto passthrough; /* XXX ??? */
                }
                error = kauth_authorize_device_tty(l->l_cred,
                    KAUTH_DEVICE_TTY_VIRTUAL, tp);
                if (!error)
                        atomic_store_relaxed(&constty, NULL);
                mutex_exit(&constty_lock);
                return error;
        }
passthrough:
        /*
         * Redirect the ioctl, if that's appropriate.
         * Note that strange things can happen, if a program does
         * ioctls on /dev/console, then the console is redirected
         * out from under it.
         */
        if (!cn_redirect(&dev, 0, &error, &ctp))
                return error;
        error = cdev_ioctl(dev, cmd, data, flag, l);
        cn_release(ctp);
        return error;
}

/*ARGSUSED*/
int
cnpoll(dev_t dev, int events, struct lwp *l)
{
        struct tty *ctp = NULL;
        int error;

        /*
         * Redirect the poll, if that's appropriate.
         * I don't want to think of the possible side effects
         * of console redirection here.
         */
        if (!cn_redirect(&dev, 0, &error, &ctp))
                return POLLHUP;
        error = cdev_poll(dev, events, l);
        cn_release(ctp);
        return error;
}

/*ARGSUSED*/
int
cnkqfilter(dev_t dev, struct knote *kn)
{
        struct tty *ctp = NULL;
        int error;

        /*
         * Redirect the kqfilter, if that's appropriate.
         * I don't want to think of the possible side effects
         * of console redirection here.
         */
        if (!cn_redirect(&dev, 0, &error, &ctp))
                return error;
        error = cdev_kqfilter(dev, kn);
        cn_release(ctp);
        return error;
}

int
cngetc(void)
{
        if (cn_tab == NULL)
                return (0);
        int s = splhigh();
        for (;;) {
                const int rv = (*cn_tab->cn_getc)(cn_tab->cn_dev);
                if (rv >= 0) {
                        splx(s);
                        return rv;
                }
                docritpollhooks();
        }
}

int
cngetsn(char *cp, int size)
{
        char *lp;
        int c, len;

        cnpollc(true);

        lp = cp;
        len = 0;
        for (;;) {
                c = cngetc();
                switch (c) {
                case '\n':
                case '\r':
                        printf("\n");
                        *lp++ = '\0';
                        cnpollc(false);
                        return (len);
                case '\b':
                case '\177':
                case '#':
                        if (len) {
                                --len;
                                --lp;
                                printf("\b \b");
                        }
                        continue;
                case '@':
                case 'u'&037:   /* CTRL-u */
                        len = 0;
                        lp = cp;
                        printf("\n");
                        continue;
                default:
                        if (len + 1 >= size || c < ' ') {
                                printf("\007");
                                continue;
                        }
                        printf("%c", c);
                        ++len;
                        *lp++ = c;
                }
        }
}

void
cnputc(int c)
{

        if (cn_tab == NULL)
                return;

/*
 * XXX
 * for some reason this causes ARCS firmware to output an endless stream of
 * whitespaces with n32 kernels, so use the pre-1.74 code for now until I can
 * figure out why this happens
 */
#ifndef sgimips
        if (c) {
                if (c == '\n') {
                        (*cn_tab->cn_putc)(cn_tab->cn_dev, '\r');
                        docritpollhooks();
                }
                (*cn_tab->cn_putc)(cn_tab->cn_dev, c);
        }
#else
        if (c) {
                (*cn_tab->cn_putc)(cn_tab->cn_dev, c);
                if (c == '\n') {
                        docritpollhooks();
                        (*cn_tab->cn_putc)(cn_tab->cn_dev, '\r');
                }
        }
#endif
}

void
cnpollc(int on)
{
        static int refcount = 0;

        if (cn_tab == NULL)
                return;
        if (!on)
                --refcount;
        if (refcount == 0) {
                if (on) {
                        /*
                         * Bind to the current CPU by disabling
                         * preemption (more convenient than finding a
                         * place to store a stack to unwind for
                         * curlwp_bind/bindx, and preemption wouldn't
                         * happen anyway while spinning at high IPL in
                         * cngetc) so that curcpu() is stable so that
                         * we can suspend heartbeat checks for it.
                         */
                        kpreempt_disable();
                        heartbeat_suspend();
                }
                (*cn_tab->cn_pollc)(cn_tab->cn_dev, on);
                if (!on) {
                        heartbeat_resume();
                        kpreempt_enable();
                }
        }
        if (on)
                ++refcount;
}

void
nullcnpollc(dev_t dev, int on)
{

}

void
cnbell(u_int pitch, u_int period, u_int volume)
{

        if (cn_tab == NULL || cn_tab->cn_bell == NULL)
                return;
        (*cn_tab->cn_bell)(cn_tab->cn_dev, pitch, period, volume);
}

void
cnflush(void)
{
        if (cn_tab == NULL || cn_tab->cn_flush == NULL)
                return;
        (*cn_tab->cn_flush)(cn_tab->cn_dev);
}

void
cnhalt(void)
{
        if (cn_tab == NULL || cn_tab->cn_halt == NULL)
                return;
        (*cn_tab->cn_halt)(cn_tab->cn_dev);
}

/*
 * Redirect output, if that's appropriate.  If there's no real console,
 * return ENXIO.
 */
static bool
cn_redirect(dev_t *devp, int is_read, int *error, struct tty **ctpp)
{
        dev_t dev = *devp;
        struct tty *ctp;
        int s;
        bool ok = false;

        *error = ENXIO;
        *ctpp = NULL;
        s = pserialize_read_enter();
        if ((ctp = atomic_load_consume(&constty)) != NULL && minor(dev) == 0 &&
            (cn_tab == NULL || (cn_tab->cn_pri != CN_REMOTE))) {
                if (is_read) {
                        *error = 0;
                        goto out;
                }
                tty_acquire(ctp);
                *ctpp = ctp;
                dev = ctp->t_dev;
        } else if (cn_tab == NULL)
                goto out;
        else
                dev = cn_tab->cn_dev;
        ok = true;
        *devp = dev;
out:    pserialize_read_exit(s);
        return ok;
}

static void
cn_release(struct tty *ctp)
{

        if (ctp == NULL)
                return;
        tty_release(ctp);
}

MODULE(MODULE_CLASS_DRIVER, cons, NULL);

static int
cons_modcmd(modcmd_t cmd, void *arg)
{

        switch (cmd) {
        case MODULE_CMD_INIT:
                mutex_init(&cn_lock, MUTEX_DEFAULT, IPL_NONE);
                return 0;
        case MODULE_CMD_FINI:
                mutex_destroy(&cn_lock);
                return 0;
        default:
                return ENOTTY;
        }
}