// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1992 obz under the linux copyright
 *
 *  Dynamic diacritical handling - aeb@cwi.nl - Dec 1993
 *  Dynamic keymap and string allocation - aeb@cwi.nl - May 1994
 *  Restrict VT switching via ioctl() - grif@cs.ucr.edu - Dec 1995
 *  Some code moved for less code duplication - Andi Kleen - Mar 1997
 *  Check put/get_user, cleanups - acme@conectiva.com.br - Jun 2001
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/sched/signal.h>
#include <linux/tty.h>
#include <linux/timer.h>
#include <linux/kernel.h>
#include <linux/compat.h>
#include <linux/module.h>
#include <linux/kd.h>
#include <linux/vt.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/console.h>
#include <linux/consolemap.h>
#include <linux/signal.h>
#include <linux/suspend.h>
#include <linux/timex.h>

#include <asm/io.h>
#include <linux/uaccess.h>

#include <linux/nospec.h>

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/kbd_diacr.h>
#include <linux/selection.h>

bool vt_dont_switch;

static inline bool vt_in_use(unsigned int i)
{
        const struct vc_data *vc = vc_cons[i].d;

        /*
         * console_lock must be held to prevent the vc from being deallocated
         * while we're checking whether it's in-use.
         */
        WARN_CONSOLE_UNLOCKED();

        return vc && kref_read(&vc->port.kref) > 1;
}

static inline bool vt_busy(int i)
{
        if (vt_in_use(i))
                return true;
        if (i == fg_console)
                return true;
        if (vc_is_sel(vc_cons[i].d))
                return true;

        return false;
}

/*
 * Console (vt and kd) routines, as defined by USL SVR4 manual, and by
 * experimentation and study of X386 SYSV handling.
 *
 * One point of difference: SYSV vt's are /dev/vtX, which X >= 0, and
 * /dev/console is a separate ttyp. Under Linux, /dev/tty0 is /dev/console,
 * and the vc start at /dev/ttyX, X >= 1. We maintain that here, so we will
 * always treat our set of vt as numbered 1..MAX_NR_CONSOLES (corresponding to
 * ttys 0..MAX_NR_CONSOLES-1). Explicitly naming VT 0 is illegal, but using
 * /dev/tty0 (fg_console) as a target is legal, since an implicit aliasing
 * to the current console is done by the main ioctl code.
 */

#ifdef CONFIG_X86
#include <asm/syscalls.h>
#endif

static void complete_change_console(struct vc_data *vc);

/*
 *      User space VT_EVENT handlers
 */

struct vt_event_wait {
        struct list_head list;
        struct vt_event event;
        int done;
};

static LIST_HEAD(vt_events);
static DEFINE_SPINLOCK(vt_event_lock);
static DECLARE_WAIT_QUEUE_HEAD(vt_event_waitqueue);

/**
 *      vt_event_post
 *      @event: the event that occurred
 *      @old: old console
 *      @new: new console
 *
 *      Post an VT event to interested VT handlers
 */

void vt_event_post(unsigned int event, unsigned int old, unsigned int new)
{
        struct list_head *pos, *head;
        unsigned long flags;
        int wake = 0;

        spin_lock_irqsave(&vt_event_lock, flags);
        head = &vt_events;

        list_for_each(pos, head) {
                struct vt_event_wait *ve = list_entry(pos,
                                                struct vt_event_wait, list);
                if (!(ve->event.event & event))
                        continue;
                ve->event.event = event;
                /* kernel view is consoles 0..n-1, user space view is
                   console 1..n with 0 meaning current, so we must bias */
                ve->event.oldev = old + 1;
                ve->event.newev = new + 1;
                wake = 1;
                ve->done = 1;
        }
        spin_unlock_irqrestore(&vt_event_lock, flags);
        if (wake)
                wake_up_interruptible(&vt_event_waitqueue);
}

static void __vt_event_queue(struct vt_event_wait *vw)
{
        unsigned long flags;
        /* Prepare the event */
        INIT_LIST_HEAD(&vw->list);
        vw->done = 0;
        /* Queue our event */
        spin_lock_irqsave(&vt_event_lock, flags);
        list_add(&vw->list, &vt_events);
        spin_unlock_irqrestore(&vt_event_lock, flags);
}

static void __vt_event_wait(struct vt_event_wait *vw)
{
        /* Wait for it to pass */
        wait_event_interruptible(vt_event_waitqueue, vw->done);
}

static void __vt_event_dequeue(struct vt_event_wait *vw)
{
        unsigned long flags;

        /* Dequeue it */
        spin_lock_irqsave(&vt_event_lock, flags);
        list_del(&vw->list);
        spin_unlock_irqrestore(&vt_event_lock, flags);
}

/**
 *      vt_event_wait           -       wait for an event
 *      @vw: our event
 *
 *      Waits for an event to occur which completes our vt_event_wait
 *      structure. On return the structure has wv->done set to 1 for success
 *      or 0 if some event such as a signal ended the wait.
 */

static void vt_event_wait(struct vt_event_wait *vw)
{
        __vt_event_queue(vw);
        __vt_event_wait(vw);
        __vt_event_dequeue(vw);
}

/**
 *      vt_event_wait_ioctl     -       event ioctl handler
 *      @event: argument to ioctl (the event)
 *
 *      Implement the VT_WAITEVENT ioctl using the VT event interface
 */

static int vt_event_wait_ioctl(struct vt_event __user *event)
{
        struct vt_event_wait vw;

        if (copy_from_user(&vw.event, event, sizeof(struct vt_event)))
                return -EFAULT;
        /* Highest supported event for now */
        if (vw.event.event & ~VT_MAX_EVENT)
                return -EINVAL;

        vt_event_wait(&vw);
        /* If it occurred report it */
        if (vw.done) {
                if (copy_to_user(event, &vw.event, sizeof(struct vt_event)))
                        return -EFAULT;
                return 0;
        }
        return -EINTR;
}

/**
 *      vt_waitactive   -       active console wait
 *      @n: new console
 *
 *      Helper for event waits. Used to implement the legacy
 *      event waiting ioctls in terms of events
 */

int vt_waitactive(int n)
{
        struct vt_event_wait vw;
        do {
                vw.event.event = VT_EVENT_SWITCH;
                __vt_event_queue(&vw);
                if (n == fg_console + 1) {
                        __vt_event_dequeue(&vw);
                        break;
                }
                __vt_event_wait(&vw);
                __vt_event_dequeue(&vw);
                if (vw.done == 0)
                        return -EINTR;
        } while (vw.event.newev != n);
        return 0;
}

/*
 * these are the valid i/o ports we're allowed to change. they map all the
 * video ports
 */
#define GPFIRST 0x3b4
#define GPLAST 0x3df
#define GPNUM (GPLAST - GPFIRST + 1)

/*
 * currently, setting the mode from KD_TEXT to KD_GRAPHICS doesn't do a whole
 * lot. i'm not sure if it should do any restoration of modes or what...
 *
 * XXX It should at least call into the driver, fbdev's definitely need to
 * restore their engine state. --BenH
 *
 * Called with the console lock held.
 */
static int vt_kdsetmode(struct vc_data *vc, unsigned long mode)
{
        switch (mode) {
        case KD_GRAPHICS:
                break;
        case KD_TEXT0:
        case KD_TEXT1:
                mode = KD_TEXT;
                fallthrough;
        case KD_TEXT:
                break;
        default:
                return -EINVAL;
        }

        if (vc->vc_mode == mode)
                return 0;

        vc->vc_mode = mode;
        if (vc->vc_num != fg_console)
                return 0;

        /* explicitly blank/unblank the screen if switching modes */
        if (mode == KD_TEXT)
                do_unblank_screen(1);
        else
                do_blank_screen(1);

        return 0;
}

static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
                unsigned long arg, bool perm)
{
        struct vc_data *vc = tty->driver_data;
        void __user *up = (void __user *)arg;
        unsigned int console = vc->vc_num;
        int ret;

        switch (cmd) {
        case KIOCSOUND:
                if (!perm)
                        return -EPERM;
                /*
                 * The use of PIT_TICK_RATE is historic, it used to be
                 * the platform-dependent CLOCK_TICK_RATE between 2.6.12
                 * and 2.6.36, which was a minor but unfortunate ABI
                 * change. kd_mksound is locked by the input layer.
                 */
                if (arg)
                        arg = PIT_TICK_RATE / arg;
                kd_mksound(arg, 0);
                break;

        case KDMKTONE:
                if (!perm)
                        return -EPERM;
        {
                unsigned int ticks, count;

                /*
                 * Generate the tone for the appropriate number of ticks.
                 * If the time is zero, turn off sound ourselves.
                 */
                ticks = msecs_to_jiffies((arg >> 16) & 0xffff);
                count = ticks ? (arg & 0xffff) : 0;
                if (count)
                        count = PIT_TICK_RATE / count;
                kd_mksound(count, ticks);
                break;
        }

        case KDGKBTYPE:
                /*
                 * this is naïve.
                 */
                return put_user(KB_101, (char __user *)arg);

                /*
                 * These cannot be implemented on any machine that implements
                 * ioperm() in user level (such as Alpha PCs) or not at all.
                 *
                 * XXX: you should never use these, just call ioperm directly..
                 */
#ifdef CONFIG_X86
        case KDADDIO:
        case KDDELIO:
                /*
                 * KDADDIO and KDDELIO may be able to add ports beyond what
                 * we reject here, but to be safe...
                 *
                 * These are locked internally via sys_ioperm
                 */
                if (arg < GPFIRST || arg > GPLAST)
                        return -EINVAL;

                return ksys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;

        case KDENABIO:
        case KDDISABIO:
                return ksys_ioperm(GPFIRST, GPNUM,
                                  (cmd == KDENABIO)) ? -ENXIO : 0;
#endif

        /* Linux m68k/i386 interface for setting the keyboard delay/repeat rate */

        case KDKBDREP:
        {
                struct kbd_repeat kbrep;

                if (!capable(CAP_SYS_TTY_CONFIG))
                        return -EPERM;

                if (copy_from_user(&kbrep, up, sizeof(struct kbd_repeat)))
                        return -EFAULT;

                ret = kbd_rate(&kbrep);
                if (ret)
                        return ret;
                if (copy_to_user(up, &kbrep, sizeof(struct kbd_repeat)))
                        return -EFAULT;
                break;
        }

        case KDSETMODE: {
                if (!perm)
                        return -EPERM;

                guard(console_lock)();
                return vt_kdsetmode(vc, arg);
        }
        case KDGETMODE:
                return put_user(vc->vc_mode, (int __user *)arg);

        case KDMAPDISP:
        case KDUNMAPDISP:
                /*
                 * these work like a combination of mmap and KDENABIO.
                 * this could be easily finished.
                 */
                return -EINVAL;

        case KDSKBMODE:
                if (!perm)
                        return -EPERM;
                ret = vt_do_kdskbmode(console, arg);
                if (ret)
                        return ret;
                tty_ldisc_flush(tty);
                break;

        case KDGKBMODE:
                return put_user(vt_do_kdgkbmode(console), (int __user *)arg);

        /* this could be folded into KDSKBMODE, but for compatibility
           reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
        case KDSKBMETA:
                return vt_do_kdskbmeta(console, arg);

        case KDGKBMETA:
                /* FIXME: should review whether this is worth locking */
                return put_user(vt_do_kdgkbmeta(console), (int __user *)arg);

        case KDGETKEYCODE:
        case KDSETKEYCODE:
                if(!capable(CAP_SYS_TTY_CONFIG))
                        perm = 0;
                return vt_do_kbkeycode_ioctl(cmd, up, perm);

        case KDGKBENT:
        case KDSKBENT:
                return vt_do_kdsk_ioctl(cmd, up, perm, console);

        case KDGKBSENT:
        case KDSKBSENT:
                return vt_do_kdgkb_ioctl(cmd, up, perm);

        /* Diacritical processing. Handled in keyboard.c as it has
           to operate on the keyboard locks and structures */
        case KDGKBDIACR:
        case KDGKBDIACRUC:
        case KDSKBDIACR:
        case KDSKBDIACRUC:
                return vt_do_diacrit(cmd, up, perm);

        /* the ioctls below read/set the flags usually shown in the leds */
        /* don't use them - they will go away without warning */
        case KDGKBLED:
        case KDSKBLED:
        case KDGETLED:
        case KDSETLED:
                return vt_do_kdskled(console, cmd, arg, perm);

        /*
         * A process can indicate its willingness to accept signals
         * generated by pressing an appropriate key combination.
         * Thus, one can have a daemon that e.g. spawns a new console
         * upon a keypress and then changes to it.
         * See also the kbrequest field of inittab(5).
         */
        case KDSIGACCEPT:
                if (!perm || !capable(CAP_KILL))
                        return -EPERM;
                if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
                        return -EINVAL;

                spin_lock_irq(&vt_spawn_con.lock);
                put_pid(vt_spawn_con.pid);
                vt_spawn_con.pid = get_pid(task_pid(current));
                vt_spawn_con.sig = arg;
                spin_unlock_irq(&vt_spawn_con.lock);
                break;

        case KDFONTOP: {
                struct console_font_op op;

                if (copy_from_user(&op, up, sizeof(op)))
                        return -EFAULT;
                if (!perm && op.op != KD_FONT_OP_GET)
                        return -EPERM;
                ret = con_font_op(vc, &op);
                if (ret)
                        return ret;
                if (copy_to_user(up, &op, sizeof(op)))
                        return -EFAULT;
                break;
        }

        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

static inline int do_unimap_ioctl(int cmd, struct unimapdesc __user *user_ud,
                bool perm, struct vc_data *vc)
{
        struct unimapdesc tmp;

        if (copy_from_user(&tmp, user_ud, sizeof tmp))
                return -EFAULT;
        switch (cmd) {
        case PIO_UNIMAP:
                if (!perm)
                        return -EPERM;
                return con_set_unimap(vc, tmp.entry_ct, tmp.entries);
        case GIO_UNIMAP:
                if (!perm && fg_console != vc->vc_num)
                        return -EPERM;
                return con_get_unimap(vc, tmp.entry_ct, &(user_ud->entry_ct),
                                tmp.entries);
        }
        return 0;
}

static int vt_io_ioctl(struct vc_data *vc, unsigned int cmd, void __user *up,
                bool perm)
{
        switch (cmd) {
        case PIO_CMAP:
                if (!perm)
                        return -EPERM;
                return con_set_cmap(up);

        case GIO_CMAP:
                return con_get_cmap(up);

        case PIO_SCRNMAP:
                if (!perm)
                        return -EPERM;
                return con_set_trans_old(up);

        case GIO_SCRNMAP:
                return con_get_trans_old(up);

        case PIO_UNISCRNMAP:
                if (!perm)
                        return -EPERM;
                return con_set_trans_new(up);

        case GIO_UNISCRNMAP:
                return con_get_trans_new(up);

        case PIO_UNIMAPCLR:
                if (!perm)
                        return -EPERM;
                con_clear_unimap(vc);
                break;

        case PIO_UNIMAP:
        case GIO_UNIMAP:
                return do_unimap_ioctl(cmd, up, perm, vc);

        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

static int vt_reldisp(struct vc_data *vc, unsigned int swtch)
{
        int newvt, ret;

        if (vc->vt_mode.mode != VT_PROCESS)
                return -EINVAL;

        /* Switched-to response */
        if (vc->vt_newvt < 0) {
                 /* If it's just an ACK, ignore it */
                return swtch == VT_ACKACQ ? 0 : -EINVAL;
        }

        /* Switching-from response */
        if (swtch == 0) {
                /* Switch disallowed, so forget we were trying to do it. */
                vc->vt_newvt = -1;
                return 0;
        }

        /* The current vt has been released, so complete the switch. */
        newvt = vc->vt_newvt;
        vc->vt_newvt = -1;
        ret = vc_allocate(newvt);
        if (ret)
                return ret;

        /*
         * When we actually do the console switch, make sure we are atomic with
         * respect to other console switches..
         */
        complete_change_console(vc_cons[newvt].d);

        return 0;
}

static int vt_setactivate(struct vt_setactivate __user *sa)
{
        struct vt_setactivate vsa;
        struct vc_data *nvc;
        int ret;

        if (copy_from_user(&vsa, sa, sizeof(vsa)))
                return -EFAULT;
        if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
                return -ENXIO;

        vsa.console--;
        vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES);
        scoped_guard(console_lock) {
                ret = vc_allocate(vsa.console);
                if (ret)
                        return ret;

                /*
                 * This is safe providing we don't drop the console sem between
                 * vc_allocate and finishing referencing nvc.
                 */
                nvc = vc_cons[vsa.console].d;
                nvc->vt_mode = vsa.mode;
                nvc->vt_mode.frsig = 0;
                put_pid(nvc->vt_pid);
                nvc->vt_pid = get_pid(task_pid(current));
        }

        /* Commence switch and lock */
        /* Review set_console locks */
        set_console(vsa.console);

        return 0;
}

/* deallocate a single console, if possible (leave 0) */
static int vt_disallocate(unsigned int vc_num)
{
        struct vc_data *vc = NULL;

        scoped_guard(console_lock) {
                if (vt_busy(vc_num))
                        return -EBUSY;
                if (vc_num)
                        vc = vc_deallocate(vc_num);
        }

        if (vc && vc_num >= MIN_NR_CONSOLES)
                tty_port_put(&vc->port);

        return 0;
}

/* deallocate all unused consoles, but leave 0 */
static void vt_disallocate_all(void)
{
        struct vc_data *vc[MAX_NR_CONSOLES];
        int i;

        scoped_guard(console_lock)
                for (i = 1; i < MAX_NR_CONSOLES; i++)
                        if (!vt_busy(i))
                                vc[i] = vc_deallocate(i);
                        else
                                vc[i] = NULL;

        for (i = 1; i < MAX_NR_CONSOLES; i++) {
                if (vc[i] && i >= MIN_NR_CONSOLES)
                        tty_port_put(&vc[i]->port);
        }
}

static int vt_resizex(struct vc_data *vc, struct vt_consize __user *cs)
{
        struct vt_consize v;
        int i;

        if (copy_from_user(&v, cs, sizeof(struct vt_consize)))
                return -EFAULT;

        /* FIXME: Should check the copies properly */
        if (!v.v_vlin)
                v.v_vlin = vc->vc_scan_lines;

        if (v.v_clin) {
                int rows = v.v_vlin / v.v_clin;
                if (v.v_rows != rows) {
                        if (v.v_rows) /* Parameters don't add up */
                                return -EINVAL;
                        v.v_rows = rows;
                }
        }

        if (v.v_vcol && v.v_ccol) {
                int cols = v.v_vcol / v.v_ccol;
                if (v.v_cols != cols) {
                        if (v.v_cols)
                                return -EINVAL;
                        v.v_cols = cols;
                }
        }

        if (v.v_clin > 32)
                return -EINVAL;

        for (i = 0; i < MAX_NR_CONSOLES; i++) {
                struct vc_data *vcp;

                if (!vc_cons[i].d)
                        continue;
                guard(console_lock)();
                vcp = vc_cons[i].d;
                if (vcp) {
                        int ret;
                        int save_scan_lines = vcp->vc_scan_lines;
                        int save_cell_height = vcp->vc_cell_height;

                        if (v.v_vlin)
                                vcp->vc_scan_lines = v.v_vlin;
                        if (v.v_clin)
                                vcp->vc_cell_height = v.v_clin;
                        ret = __vc_resize(vcp, v.v_cols, v.v_rows, true);
                        if (ret) {
                                vcp->vc_scan_lines = save_scan_lines;
                                vcp->vc_cell_height = save_cell_height;
                                return ret;
                        }
                }
        }

        return 0;
}

/*
 * We handle the console-specific ioctl's here.  We allow the
 * capability to modify any console, not just the fg_console.
 */
int vt_ioctl(struct tty_struct *tty,
             unsigned int cmd, unsigned long arg)
{
        struct vc_data *vc = tty->driver_data;
        void __user *up = (void __user *)arg;
        int i, perm;
        int ret;

        /*
         * To have permissions to do most of the vt ioctls, we either have
         * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
         */
        perm = 0;
        if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
                perm = 1;

        ret = vt_k_ioctl(tty, cmd, arg, perm);
        if (ret != -ENOIOCTLCMD)
                return ret;

        ret = vt_io_ioctl(vc, cmd, up, perm);
        if (ret != -ENOIOCTLCMD)
                return ret;

        switch (cmd) {
        case TIOCLINUX:
                return tioclinux(tty, arg);
        case VT_SETMODE:
        {
                struct vt_mode tmp;

                if (!perm)
                        return -EPERM;
                if (copy_from_user(&tmp, up, sizeof(struct vt_mode)))
                        return -EFAULT;
                if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS)
                        return -EINVAL;

                guard(console_lock)();
                vc->vt_mode = tmp;
                /* the frsig is ignored, so we set it to 0 */
                vc->vt_mode.frsig = 0;
                put_pid(vc->vt_pid);
                vc->vt_pid = get_pid(task_pid(current));
                /* no switch is required -- saw@shade.msu.ru */
                vc->vt_newvt = -1;
                break;
        }

        case VT_GETMODE:
        {
                struct vt_mode tmp;
                int rc;

                scoped_guard(console_lock)
                        memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));

                rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
                if (rc)
                        return -EFAULT;
                break;
        }

        /*
         * Returns global vt state. Note that VT 0 is always open, since
         * it's an alias for the current VT, and people can't use it here.
         * We cannot return state for more than 16 VTs, since v_state is short.
         */
        case VT_GETSTATE:
        {
                struct vt_stat __user *vtstat = up;
                unsigned short state, mask;

                if (put_user(fg_console + 1, &vtstat->v_active))
                        return -EFAULT;

                state = 1;      /* /dev/tty0 is always open */
                scoped_guard(console_lock) /* required by vt_in_use() */
                        for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask; ++i, mask <<= 1)
                                if (vt_in_use(i))
                                        state |= mask;
                return put_user(state, &vtstat->v_state);
        }

        /*
         * Returns the first available (non-opened) console.
         */
        case VT_OPENQRY:
                scoped_guard(console_lock) /* required by vt_in_use() */
                        for (i = 0; i < MAX_NR_CONSOLES; ++i)
                                if (!vt_in_use(i))
                                        break;
                i = i < MAX_NR_CONSOLES ? (i+1) : -1;
                return put_user(i, (int __user *)arg);

        /*
         * ioctl(fd, VT_ACTIVATE, num) will cause us to switch to vt # num,
         * with num >= 1 (switches to vt 0, our console, are not allowed, just
         * to preserve sanity).
         */
        case VT_ACTIVATE:
                if (!perm)
                        return -EPERM;
                if (arg == 0 || arg > MAX_NR_CONSOLES)
                        return -ENXIO;

                arg--;
                arg = array_index_nospec(arg, MAX_NR_CONSOLES);
                scoped_guard(console_lock) {
                        ret = vc_allocate(arg);
                        if (ret)
                                return ret;
                }
                set_console(arg);
                break;

        case VT_SETACTIVATE:
                if (!perm)
                        return -EPERM;

                return vt_setactivate(up);

        /*
         * wait until the specified VT has been activated
         */
        case VT_WAITACTIVE:
                if (!perm)
                        return -EPERM;
                if (arg == 0 || arg > MAX_NR_CONSOLES)
                        return -ENXIO;
                return vt_waitactive(arg);

        /*
         * If a vt is under process control, the kernel will not switch to it
         * immediately, but postpone the operation until the process calls this
         * ioctl, allowing the switch to complete.
         *
         * According to the X sources this is the behavior:
         *      0:      pending switch-from not OK
         *      1:      pending switch-from OK
         *      2:      completed switch-to OK
         */
        case VT_RELDISP:
        {
                if (!perm)
                        return -EPERM;

                guard(console_lock)();
                return vt_reldisp(vc, arg);
        }

         /*
          * Disallocate memory associated to VT (but leave VT1)
          */
         case VT_DISALLOCATE:
                if (arg > MAX_NR_CONSOLES)
                        return -ENXIO;

                if (arg == 0) {
                        vt_disallocate_all();
                        break;
                }

                arg = array_index_nospec(arg - 1, MAX_NR_CONSOLES);
                return vt_disallocate(arg);

        case VT_RESIZE:
        {
                struct vt_sizes __user *vtsizes = up;
                struct vc_data *vc;
                ushort ll,cc;

                if (!perm)
                        return -EPERM;
                if (get_user(ll, &vtsizes->v_rows) ||
                    get_user(cc, &vtsizes->v_cols))
                        return -EFAULT;

                guard(console_lock)();
                for (i = 0; i < MAX_NR_CONSOLES; i++) {
                        vc = vc_cons[i].d;

                        if (vc) {
                                /* FIXME: review v tty lock */
                                ret = __vc_resize(vc_cons[i].d, cc, ll, true);
                                if (ret)
                                        return ret;
                        }
                }
                break;
        }

        case VT_RESIZEX:
                if (!perm)
                        return -EPERM;

                return vt_resizex(vc, up);

        case VT_LOCKSWITCH:
                if (!capable(CAP_SYS_TTY_CONFIG))
                        return -EPERM;
                vt_dont_switch = true;
                break;
        case VT_UNLOCKSWITCH:
                if (!capable(CAP_SYS_TTY_CONFIG))
                        return -EPERM;
                vt_dont_switch = false;
                break;
        case VT_GETHIFONTMASK:
                return put_user(vc->vc_hi_font_mask,
                                        (unsigned short __user *)arg);
        case VT_WAITEVENT:
                return vt_event_wait_ioctl((struct vt_event __user *)arg);

        case VT_GETCONSIZECSRPOS:
        {
                struct vt_consizecsrpos concsr;

                console_lock();
                concsr.con_cols = vc->vc_cols;
                concsr.con_rows = vc->vc_rows;
                concsr.csr_col = vc->state.x;
                concsr.csr_row = vc->state.y;
                console_unlock();
                if (copy_to_user(up, &concsr, sizeof(concsr)))
                        return -EFAULT;
                return 0;
        }

        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

void reset_vc(struct vc_data *vc)
{
        vc->vc_mode = KD_TEXT;
        vt_reset_unicode(vc->vc_num);
        vc->vt_mode.mode = VT_AUTO;
        vc->vt_mode.waitv = 0;
        vc->vt_mode.relsig = 0;
        vc->vt_mode.acqsig = 0;
        vc->vt_mode.frsig = 0;
        put_pid(vc->vt_pid);
        vc->vt_pid = NULL;
        vc->vt_newvt = -1;
        reset_palette(vc);
}

void vc_SAK(struct work_struct *work)
{
        struct vc *vc_con =
                container_of(work, struct vc, SAK_work);
        struct vc_data *vc;
        struct tty_struct *tty;

        guard(console_lock)();
        vc = vc_con->d;
        if (!vc)
                return;

        /* FIXME: review tty ref counting */
        tty = vc->port.tty;
        /* SAK should also work in all raw modes and reset them properly. */
        if (tty)
                __do_SAK(tty);
        reset_vc(vc);
}

#ifdef CONFIG_COMPAT

struct compat_console_font_op {
        compat_uint_t op;        /* operation code KD_FONT_OP_* */
        compat_uint_t flags;     /* KD_FONT_FLAG_* */
        compat_uint_t width, height;     /* font size */
        compat_uint_t charcount;
        compat_caddr_t data;    /* font data with height fixed to 32 */
};

static inline int
compat_kdfontop_ioctl(struct compat_console_font_op __user *fontop,
                         int perm, struct console_font_op *op, struct vc_data *vc)
{
        int i;

        if (copy_from_user(op, fontop, sizeof(struct compat_console_font_op)))
                return -EFAULT;
        if (!perm && op->op != KD_FONT_OP_GET)
                return -EPERM;
        op->data = compat_ptr(((struct compat_console_font_op *)op)->data);
        i = con_font_op(vc, op);
        if (i)
                return i;
        ((struct compat_console_font_op *)op)->data = (unsigned long)op->data;
        if (copy_to_user(fontop, op, sizeof(struct compat_console_font_op)))
                return -EFAULT;
        return 0;
}

struct compat_unimapdesc {
        unsigned short entry_ct;
        compat_caddr_t entries;
};

static inline int
compat_unimap_ioctl(unsigned int cmd, struct compat_unimapdesc __user *user_ud,
                         int perm, struct vc_data *vc)
{
        struct compat_unimapdesc tmp;
        struct unipair __user *tmp_entries;

        if (copy_from_user(&tmp, user_ud, sizeof tmp))
                return -EFAULT;
        tmp_entries = compat_ptr(tmp.entries);
        switch (cmd) {
        case PIO_UNIMAP:
                if (!perm)
                        return -EPERM;
                return con_set_unimap(vc, tmp.entry_ct, tmp_entries);
        case GIO_UNIMAP:
                if (!perm && fg_console != vc->vc_num)
                        return -EPERM;
                return con_get_unimap(vc, tmp.entry_ct, &(user_ud->entry_ct), tmp_entries);
        }
        return 0;
}

long vt_compat_ioctl(struct tty_struct *tty,
             unsigned int cmd, unsigned long arg)
{
        struct vc_data *vc = tty->driver_data;
        struct console_font_op op;      /* used in multiple places here */
        void __user *up = compat_ptr(arg);
        int perm;

        /*
         * To have permissions to do most of the vt ioctls, we either have
         * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
         */
        perm = 0;
        if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
                perm = 1;

        switch (cmd) {
        /*
         * these need special handlers for incompatible data structures
         */

        case KDFONTOP:
                return compat_kdfontop_ioctl(up, perm, &op, vc);

        case PIO_UNIMAP:
        case GIO_UNIMAP:
                return compat_unimap_ioctl(cmd, up, perm, vc);

        /*
         * all these treat 'arg' as an integer
         */
        case KIOCSOUND:
        case KDMKTONE:
#ifdef CONFIG_X86
        case KDADDIO:
        case KDDELIO:
#endif
        case KDSETMODE:
        case KDMAPDISP:
        case KDUNMAPDISP:
        case KDSKBMODE:
        case KDSKBMETA:
        case KDSKBLED:
        case KDSETLED:
        case KDSIGACCEPT:
        case VT_ACTIVATE:
        case VT_WAITACTIVE:
        case VT_RELDISP:
        case VT_DISALLOCATE:
                return vt_ioctl(tty, cmd, arg);

        /*
         * the rest has a compatible data structure behind arg,
         * but we have to convert it to a proper 64 bit pointer.
         */
        default:
                return vt_ioctl(tty, cmd, (unsigned long)up);
        }
}


#endif /* CONFIG_COMPAT */


/*
 * Performs the back end of a vt switch. Called under the console
 * semaphore.
 */
static void complete_change_console(struct vc_data *vc)
{
        unsigned char old_vc_mode;
        int old = fg_console;

        last_console = fg_console;

        /*
         * If we're switching, we could be going from KD_GRAPHICS to
         * KD_TEXT mode or vice versa, which means we need to blank or
         * unblank the screen later.
         */
        old_vc_mode = vc_cons[fg_console].d->vc_mode;
        switch_screen(vc);

        /*
         * This can't appear below a successful kill_pid().  If it did,
         * then the *blank_screen operation could occur while X, having
         * received acqsig, is waking up on another processor.  This
         * condition can lead to overlapping accesses to the VGA range
         * and the framebuffer (causing system lockups).
         *
         * To account for this we duplicate this code below only if the
         * controlling process is gone and we've called reset_vc.
         */
        if (old_vc_mode != vc->vc_mode) {
                if (vc->vc_mode == KD_TEXT)
                        do_unblank_screen(1);
                else
                        do_blank_screen(1);
        }

        /*
         * If this new console is under process control, send it a signal
         * telling it that it has acquired. Also check if it has died and
         * clean up (similar to logic employed in change_console())
         */
        if (vc->vt_mode.mode == VT_PROCESS) {
                /*
                 * Send the signal as privileged - kill_pid() will
                 * tell us if the process has gone or something else
                 * is awry
                 */
                if (kill_pid(vc->vt_pid, vc->vt_mode.acqsig, 1) != 0) {
                /*
                 * The controlling process has died, so we revert back to
                 * normal operation. In this case, we'll also change back
                 * to KD_TEXT mode. I'm not sure if this is strictly correct
                 * but it saves the agony when the X server dies and the screen
                 * remains blanked due to KD_GRAPHICS! It would be nice to do
                 * this outside of VT_PROCESS but there is no single process
                 * to account for and tracking tty count may be undesirable.
                 */
                        reset_vc(vc);

                        if (old_vc_mode != vc->vc_mode) {
                                if (vc->vc_mode == KD_TEXT)
                                        do_unblank_screen(1);
                                else
                                        do_blank_screen(1);
                        }
                }
        }

        /*
         * Wake anyone waiting for their VT to activate
         */
        vt_event_post(VT_EVENT_SWITCH, old, vc->vc_num);
        return;
}

/*
 * Performs the front-end of a vt switch
 */
void change_console(struct vc_data *new_vc)
{
        struct vc_data *vc;

        if (!new_vc || new_vc->vc_num == fg_console || vt_dont_switch)
                return;

        /*
         * If this vt is in process mode, then we need to handshake with
         * that process before switching. Essentially, we store where that
         * vt wants to switch to and wait for it to tell us when it's done
         * (via VT_RELDISP ioctl).
         *
         * We also check to see if the controlling process still exists.
         * If it doesn't, we reset this vt to auto mode and continue.
         * This is a cheap way to track process control. The worst thing
         * that can happen is: we send a signal to a process, it dies, and
         * the switch gets "lost" waiting for a response; hopefully, the
         * user will try again, we'll detect the process is gone (unless
         * the user waits just the right amount of time :-) and revert the
         * vt to auto control.
         */
        vc = vc_cons[fg_console].d;
        if (vc->vt_mode.mode == VT_PROCESS) {
                /*
                 * Send the signal as privileged - kill_pid() will
                 * tell us if the process has gone or something else
                 * is awry.
                 *
                 * We need to set vt_newvt *before* sending the signal or we
                 * have a race.
                 */
                vc->vt_newvt = new_vc->vc_num;
                if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
                        /*
                         * It worked. Mark the vt to switch to and
                         * return. The process needs to send us a
                         * VT_RELDISP ioctl to complete the switch.
                         */
                        return;
                }

                /*
                 * The controlling process has died, so we revert back to
                 * normal operation. In this case, we'll also change back
                 * to KD_TEXT mode. I'm not sure if this is strictly correct
                 * but it saves the agony when the X server dies and the screen
                 * remains blanked due to KD_GRAPHICS! It would be nice to do
                 * this outside of VT_PROCESS but there is no single process
                 * to account for and tracking tty count may be undesirable.
                 */
                reset_vc(vc);

                /*
                 * Fall through to normal (VT_AUTO) handling of the switch...
                 */
        }

        /*
         * Ignore all switches in KD_GRAPHICS+VT_AUTO mode
         */
        if (vc->vc_mode == KD_GRAPHICS)
                return;

        complete_change_console(new_vc);
}

/* Perform a kernel triggered VT switch for suspend/resume */

static int disable_vt_switch;

int vt_move_to_console(unsigned int vt, int alloc)
{
        int prev;

        scoped_guard(console_lock) {
                /* Graphics mode - up to X */
                if (disable_vt_switch)
                        return 0;

                prev = fg_console;

                if (alloc && vc_allocate(vt)) {
                        /*
                         * We can't have a free VC for now. Too bad, we don't want to mess the
                         * screen for now.
                         */
                        return -ENOSPC;
                }

                if (set_console(vt)) {
                        /*
                         * We're unable to switch to the SUSPEND_CONSOLE. Let the calling function
                         * know so it can decide what to do.
                         */
                        return -EIO;
                }
        }
        if (vt_waitactive(vt + 1)) {
                pr_debug("Suspend: Can't switch VCs.");
                return -EINTR;
        }
        return prev;
}

/*
 * Normally during a suspend, we allocate a new console and switch to it.
 * When we resume, we switch back to the original console.  This switch
 * can be slow, so on systems where the framebuffer can handle restoration
 * of video registers anyways, there's little point in doing the console
 * switch.  This function allows you to disable it by passing it '0'.
 */
void pm_set_vt_switch(int do_switch)
{
        guard(console_lock)();
        disable_vt_switch = !do_switch;
}
EXPORT_SYMBOL(pm_set_vt_switch);