[deliverable/linux.git] / drivers / tty / vt / vt_ioctl.c

/*
 *  linux/drivers/char/vt_ioctl.c
 *
 *  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.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/smp_lock.h>
#include <linux/timex.h>

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

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

char vt_dont_switch;
extern struct tty_driver *console_driver;

#define VT_IS_IN_USE(i) (console_driver->ttys[i] && console_driver->ttys[i]->count)
#define VT_BUSY(i)      (VT_IS_IN_USE(i) || i == fg_console || vc_cons[i].d == sel_cons)

/*
 * 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 <linux/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);
}

/**
 *      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)
{
        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);
        /* Wait for it to pass */
        wait_event_interruptible_tty(vt_event_waitqueue, vw->done);
        /* Dequeue it */
        spin_lock_irqsave(&vt_event_lock, flags);
        list_del(&vw->list);
        spin_unlock_irqrestore(&vt_event_lock, flags);
}

/**
 *      vt_event_wait_ioctl     -       event ioctl handler
 *      @arg: argument to ioctl
 *
 *      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
 *      @event: event code
 *      @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 {
                if (n == fg_console + 1)
                        break;
                vw.event.event = VT_EVENT_SWITCH;
                vt_event_wait(&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)

#define i (tmp.kb_index)
#define s (tmp.kb_table)
#define v (tmp.kb_value)
static inline int
do_kdsk_ioctl(int cmd, struct kbentry __user *user_kbe, int perm, struct kbd_struct *kbd)
{
        struct kbentry tmp;
        ushort *key_map, val, ov;

        if (copy_from_user(&tmp, user_kbe, sizeof(struct kbentry)))
                return -EFAULT;

        if (!capable(CAP_SYS_TTY_CONFIG))
                perm = 0;

        switch (cmd) {
        case KDGKBENT:
                key_map = key_maps[s];
                if (key_map) {
                    val = U(key_map[i]);
                    if (kbd->kbdmode != VC_UNICODE && KTYP(val) >= NR_TYPES)
                        val = K_HOLE;
                } else
                    val = (i ? K_HOLE : K_NOSUCHMAP);
                return put_user(val, &user_kbe->kb_value);
        case KDSKBENT:
                if (!perm)
                        return -EPERM;
                if (!i && v == K_NOSUCHMAP) {
                        /* deallocate map */
                        key_map = key_maps[s];
                        if (s && key_map) {
                            key_maps[s] = NULL;
                            if (key_map[0] == U(K_ALLOCATED)) {
                                        kfree(key_map);
                                        keymap_count--;
                            }
                        }
                        break;
                }

                if (KTYP(v) < NR_TYPES) {
                    if (KVAL(v) > max_vals[KTYP(v)])
                                return -EINVAL;
                } else
                    if (kbd->kbdmode != VC_UNICODE)
                                return -EINVAL;

                /* ++Geert: non-PC keyboards may generate keycode zero */
#if !defined(__mc68000__) && !defined(__powerpc__)
                /* assignment to entry 0 only tests validity of args */
                if (!i)
                        break;
#endif

                if (!(key_map = key_maps[s])) {
                        int j;

                        if (keymap_count >= MAX_NR_OF_USER_KEYMAPS &&
                            !capable(CAP_SYS_RESOURCE))
                                return -EPERM;

                        key_map = kmalloc(sizeof(plain_map),
                                                     GFP_KERNEL);
                        if (!key_map)
                                return -ENOMEM;
                        key_maps[s] = key_map;
                        key_map[0] = U(K_ALLOCATED);
                        for (j = 1; j < NR_KEYS; j++)
                                key_map[j] = U(K_HOLE);
                        keymap_count++;
                }
                ov = U(key_map[i]);
                if (v == ov)
                        break;  /* nothing to do */
                /*
                 * Attention Key.
                 */
                if (((ov == K_SAK) || (v == K_SAK)) && !capable(CAP_SYS_ADMIN))
                        return -EPERM;
                key_map[i] = U(v);
                if (!s && (KTYP(ov) == KT_SHIFT || KTYP(v) == KT_SHIFT))
                        compute_shiftstate();
                break;
        }
        return 0;
}
#undef i
#undef s
#undef v

static inline int 
do_kbkeycode_ioctl(int cmd, struct kbkeycode __user *user_kbkc, int perm)
{
        struct kbkeycode tmp;
        int kc = 0;

        if (copy_from_user(&tmp, user_kbkc, sizeof(struct kbkeycode)))
                return -EFAULT;
        switch (cmd) {
        case KDGETKEYCODE:
                kc = getkeycode(tmp.scancode);
                if (kc >= 0)
                        kc = put_user(kc, &user_kbkc->keycode);
                break;
        case KDSETKEYCODE:
                if (!perm)
                        return -EPERM;
                kc = setkeycode(tmp.scancode, tmp.keycode);
                break;
        }
        return kc;
}

static inline int
do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
{
        struct kbsentry *kbs;
        char *p;
        u_char *q;
        u_char __user *up;
        int sz;
        int delta;
        char *first_free, *fj, *fnw;
        int i, j, k;
        int ret;

        if (!capable(CAP_SYS_TTY_CONFIG))
                perm = 0;

        kbs = kmalloc(sizeof(*kbs), GFP_KERNEL);
        if (!kbs) {
                ret = -ENOMEM;
                goto reterr;
        }

        /* we mostly copy too much here (512bytes), but who cares ;) */
        if (copy_from_user(kbs, user_kdgkb, sizeof(struct kbsentry))) {
                ret = -EFAULT;
                goto reterr;
        }
        kbs->kb_string[sizeof(kbs->kb_string)-1] = '\0';
        i = kbs->kb_func;

        switch (cmd) {
        case KDGKBSENT:
                sz = sizeof(kbs->kb_string) - 1; /* sz should have been
                                                  a struct member */
                up = user_kdgkb->kb_string;
                p = func_table[i];
                if(p)
                        for ( ; *p && sz; p++, sz--)
                                if (put_user(*p, up++)) {
                                        ret = -EFAULT;
                                        goto reterr;
                                }
                if (put_user('\0', up)) {
                        ret = -EFAULT;
                        goto reterr;
                }
                kfree(kbs);
                return ((p && *p) ? -EOVERFLOW : 0);
        case KDSKBSENT:
                if (!perm) {
                        ret = -EPERM;
                        goto reterr;
                }

                q = func_table[i];
                first_free = funcbufptr + (funcbufsize - funcbufleft);
                for (j = i+1; j < MAX_NR_FUNC && !func_table[j]; j++) 
                        ;
                if (j < MAX_NR_FUNC)
                        fj = func_table[j];
                else
                        fj = first_free;

                delta = (q ? -strlen(q) : 1) + strlen(kbs->kb_string);
                if (delta <= funcbufleft) {     /* it fits in current buf */
                    if (j < MAX_NR_FUNC) {
                        memmove(fj + delta, fj, first_free - fj);
                        for (k = j; k < MAX_NR_FUNC; k++)
                            if (func_table[k])
                                func_table[k] += delta;
                    }
                    if (!q)
                      func_table[i] = fj;
                    funcbufleft -= delta;
                } else {                        /* allocate a larger buffer */
                    sz = 256;
                    while (sz < funcbufsize - funcbufleft + delta)
                      sz <<= 1;
                    fnw = kmalloc(sz, GFP_KERNEL);
                    if(!fnw) {
                      ret = -ENOMEM;
                      goto reterr;
                    }

                    if (!q)
                      func_table[i] = fj;
                    if (fj > funcbufptr)
                        memmove(fnw, funcbufptr, fj - funcbufptr);
                    for (k = 0; k < j; k++)
                      if (func_table[k])
                        func_table[k] = fnw + (func_table[k] - funcbufptr);

                    if (first_free > fj) {
                        memmove(fnw + (fj - funcbufptr) + delta, fj, first_free - fj);
                        for (k = j; k < MAX_NR_FUNC; k++)
                          if (func_table[k])
                            func_table[k] = fnw + (func_table[k] - funcbufptr) + delta;
                    }
                    if (funcbufptr != func_buf)
                      kfree(funcbufptr);
                    funcbufptr = fnw;
                    funcbufleft = funcbufleft - delta + sz - funcbufsize;
                    funcbufsize = sz;
                }
                strcpy(func_table[i], kbs->kb_string);
                break;
        }
        ret = 0;
reterr:
        kfree(kbs);
        return ret;
}

static inline int 
do_fontx_ioctl(int cmd, struct consolefontdesc __user *user_cfd, int perm, struct console_font_op *op)
{
        struct consolefontdesc cfdarg;
        int i;

        if (copy_from_user(&cfdarg, user_cfd, sizeof(struct consolefontdesc))) 
                return -EFAULT;
        
        switch (cmd) {
        case PIO_FONTX:
                if (!perm)
                        return -EPERM;
                op->op = KD_FONT_OP_SET;
                op->flags = KD_FONT_FLAG_OLD;
                op->width = 8;
                op->height = cfdarg.charheight;
                op->charcount = cfdarg.charcount;
                op->data = cfdarg.chardata;
                return con_font_op(vc_cons[fg_console].d, op);
        case GIO_FONTX: {
                op->op = KD_FONT_OP_GET;
                op->flags = KD_FONT_FLAG_OLD;
                op->width = 8;
                op->height = cfdarg.charheight;
                op->charcount = cfdarg.charcount;
                op->data = cfdarg.chardata;
                i = con_font_op(vc_cons[fg_console].d, op);
                if (i)
                        return i;
                cfdarg.charheight = op->height;
                cfdarg.charcount = op->charcount;
                if (copy_to_user(user_cfd, &cfdarg, sizeof(struct consolefontdesc)))
                        return -EFAULT;
                return 0;
                }
        }
        return -EINVAL;
}

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

        if (copy_from_user(&tmp, user_ud, sizeof tmp))
                return -EFAULT;
        if (tmp.entries)
                if (!access_ok(VERIFY_WRITE, tmp.entries,
                                tmp.entry_ct*sizeof(struct unipair)))
                        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;
}



/*
 * 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, struct file * file,
             unsigned int cmd, unsigned long arg)
{
        struct vc_data *vc = tty->driver_data;
        struct console_font_op op;      /* used in multiple places here */
        struct kbd_struct * kbd;
        unsigned int console;
        unsigned char ucval;
        unsigned int uival;
        void __user *up = (void __user *)arg;
        int i, perm;
        int ret = 0;

        console = vc->vc_num;

        tty_lock();

        if (!vc_cons_allocated(console)) {      /* impossible? */
                ret = -ENOIOCTLCMD;
                goto out;
        }


        /*
         * 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;
 
        kbd = kbd_table + console;
        switch (cmd) {
        case TIOCLINUX:
                ret = tioclinux(tty, arg);
                break;
        case KIOCSOUND:
                if (!perm)
                        goto 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.
                 */
                if (arg)
                        arg = PIT_TICK_RATE / arg;
                kd_mksound(arg, 0);
                break;

        case KDMKTONE:
                if (!perm)
                        goto eperm;
        {
                unsigned int ticks, count;
                
                /*
                 * Generate the tone for the appropriate number of ticks.
                 * If the time is zero, turn off sound ourselves.
                 */
                ticks = HZ * ((arg >> 16) & 0xffff) / 1000;
                count = ticks ? (arg & 0xffff) : 0;
                if (count)
                        count = PIT_TICK_RATE / count;
                kd_mksound(count, ticks);
                break;
        }

        case KDGKBTYPE:
                /*
                 * this is naive.
                 */
                ucval = KB_101;
                goto setchar;

                /*
                 * 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...
                 */
                if (arg < GPFIRST || arg > GPLAST) {
                        ret = -EINVAL;
                        break;
                }
                ret = sys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
                break;

        case KDENABIO:
        case KDDISABIO:
                ret = sys_ioperm(GPFIRST, GPNUM,
                                  (cmd == KDENABIO)) ? -ENXIO : 0;
                break;
#endif

        /* Linux m68k/i386 interface for setting the keyboard delay/repeat rate */
                
        case KDKBDREP:
        {
                struct kbd_repeat kbrep;
                
                if (!capable(CAP_SYS_TTY_CONFIG))
                        goto eperm;

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

        case KDSETMODE:
                /*
                 * 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
                 */
                if (!perm)
                        goto eperm;
                switch (arg) {
                case KD_GRAPHICS:
                        break;
                case KD_TEXT0:
                case KD_TEXT1:
                        arg = KD_TEXT;
                case KD_TEXT:
                        break;
                default:
                        ret = -EINVAL;
                        goto out;
                }
                if (vc->vc_mode == (unsigned char) arg)
                        break;
                vc->vc_mode = (unsigned char) arg;
                if (console != fg_console)
                        break;
                /*
                 * explicitly blank/unblank the screen if switching modes
                 */
                console_lock();
                if (arg == KD_TEXT)
                        do_unblank_screen(1);
                else
                        do_blank_screen(1);
                console_unlock();
                break;

        case KDGETMODE:
                uival = vc->vc_mode;
                goto setint;

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

        case KDSKBMODE:
                if (!perm)
                        goto eperm;
                switch(arg) {
                  case K_RAW:
                        kbd->kbdmode = VC_RAW;
                        break;
                  case K_MEDIUMRAW:
                        kbd->kbdmode = VC_MEDIUMRAW;
                        break;
                  case K_XLATE:
                        kbd->kbdmode = VC_XLATE;
                        compute_shiftstate();
                        break;
                  case K_UNICODE:
                        kbd->kbdmode = VC_UNICODE;
                        compute_shiftstate();
                        break;
                  case K_OFF:
                        kbd->kbdmode = VC_OFF;
                        break;
                  default:
                        ret = -EINVAL;
                        goto out;
                }
                tty_ldisc_flush(tty);
                break;

        case KDGKBMODE:
                uival = ((kbd->kbdmode == VC_RAW) ? K_RAW :
                                 (kbd->kbdmode == VC_MEDIUMRAW) ? K_MEDIUMRAW :
                                 (kbd->kbdmode == VC_UNICODE) ? K_UNICODE :
                                 K_XLATE);
                goto setint;

        /* this could be folded into KDSKBMODE, but for compatibility
           reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
        case KDSKBMETA:
                switch(arg) {
                  case K_METABIT:
                        clr_vc_kbd_mode(kbd, VC_META);
                        break;
                  case K_ESCPREFIX:
                        set_vc_kbd_mode(kbd, VC_META);
                        break;
                  default:
                        ret = -EINVAL;
                }
                break;

        case KDGKBMETA:
                uival = (vc_kbd_mode(kbd, VC_META) ? K_ESCPREFIX : K_METABIT);
        setint:
                ret = put_user(uival, (int __user *)arg);
                break;

        case KDGETKEYCODE:
        case KDSETKEYCODE:
                if(!capable(CAP_SYS_TTY_CONFIG))
                        perm = 0;
                ret = do_kbkeycode_ioctl(cmd, up, perm);
                break;

        case KDGKBENT:
        case KDSKBENT:
                ret = do_kdsk_ioctl(cmd, up, perm, kbd);
                break;

        case KDGKBSENT:
        case KDSKBSENT:
                ret = do_kdgkb_ioctl(cmd, up, perm);
                break;

        case KDGKBDIACR:
        {
                struct kbdiacrs __user *a = up;
                struct kbdiacr diacr;
                int i;

                if (put_user(accent_table_size, &a->kb_cnt)) {
                        ret = -EFAULT;
                        break;
                }
                for (i = 0; i < accent_table_size; i++) {
                        diacr.diacr = conv_uni_to_8bit(accent_table[i].diacr);
                        diacr.base = conv_uni_to_8bit(accent_table[i].base);
                        diacr.result = conv_uni_to_8bit(accent_table[i].result);
                        if (copy_to_user(a->kbdiacr + i, &diacr, sizeof(struct kbdiacr))) {
                                ret = -EFAULT;
                                break;
                        }
                }
                break;
        }
        case KDGKBDIACRUC:
        {
                struct kbdiacrsuc __user *a = up;

                if (put_user(accent_table_size, &a->kb_cnt))
                        ret = -EFAULT;
                else if (copy_to_user(a->kbdiacruc, accent_table,
                                accent_table_size*sizeof(struct kbdiacruc)))
                        ret = -EFAULT;
                break;
        }

        case KDSKBDIACR:
        {
                struct kbdiacrs __user *a = up;
                struct kbdiacr diacr;
                unsigned int ct;
                int i;

                if (!perm)
                        goto eperm;
                if (get_user(ct,&a->kb_cnt)) {
                        ret = -EFAULT;
                        break;
                }
                if (ct >= MAX_DIACR) {
                        ret = -EINVAL;
                        break;
                }
                accent_table_size = ct;
                for (i = 0; i < ct; i++) {
                        if (copy_from_user(&diacr, a->kbdiacr + i, sizeof(struct kbdiacr))) {
                                ret = -EFAULT;
                                break;
                        }
                        accent_table[i].diacr = conv_8bit_to_uni(diacr.diacr);
                        accent_table[i].base = conv_8bit_to_uni(diacr.base);
                        accent_table[i].result = conv_8bit_to_uni(diacr.result);
                }
                break;
        }

        case KDSKBDIACRUC:
        {
                struct kbdiacrsuc __user *a = up;
                unsigned int ct;

                if (!perm)
                        goto eperm;
                if (get_user(ct,&a->kb_cnt)) {
                        ret = -EFAULT;
                        break;
                }
                if (ct >= MAX_DIACR) {
                        ret = -EINVAL;
                        break;
                }
                accent_table_size = ct;
                if (copy_from_user(accent_table, a->kbdiacruc, ct*sizeof(struct kbdiacruc)))
                        ret = -EFAULT;
                break;
        }

        /* the ioctls below read/set the flags usually shown in the leds */
        /* don't use them - they will go away without warning */
        case KDGKBLED:
                ucval = kbd->ledflagstate | (kbd->default_ledflagstate << 4);
                goto setchar;

        case KDSKBLED:
                if (!perm)
                        goto eperm;
                if (arg & ~0x77) {
                        ret = -EINVAL;
                        break;
                }
                kbd->ledflagstate = (arg & 7);
                kbd->default_ledflagstate = ((arg >> 4) & 7);
                set_leds();
                break;

        /* the ioctls below only set the lights, not the functions */
        /* for those, see KDGKBLED and KDSKBLED above */
        case KDGETLED:
                ucval = getledstate();
        setchar:
                ret = put_user(ucval, (char __user *)arg);
                break;

        case KDSETLED:
                if (!perm)
                        goto eperm;
                setledstate(kbd, arg);
                break;

        /*
         * 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))
                        goto eperm;
                if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
                        ret = -EINVAL;
                else {
                        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 VT_SETMODE:
        {
                struct vt_mode tmp;

                if (!perm)
                        goto eperm;
                if (copy_from_user(&tmp, up, sizeof(struct vt_mode))) {
                        ret = -EFAULT;
                        goto out;
                }
                if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS) {
                        ret = -EINVAL;
                        goto out;
                }
                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;
                console_unlock();
                break;
        }

        case VT_GETMODE:
        {
                struct vt_mode tmp;
                int rc;

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

                rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
                if (rc)
                        ret = -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))
                        ret = -EFAULT;
                else {
                        state = 1;      /* /dev/tty0 is always open */
                        for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask;
                                                        ++i, mask <<= 1)
                                if (VT_IS_IN_USE(i))
                                        state |= mask;
                        ret = put_user(state, &vtstat->v_state);
                }
                break;
        }

        /*
         * Returns the first available (non-opened) console.
         */
        case VT_OPENQRY:
                for (i = 0; i < MAX_NR_CONSOLES; ++i)
                        if (! VT_IS_IN_USE(i))
                                break;
                uival = i < MAX_NR_CONSOLES ? (i+1) : -1;
                goto setint;             

        /*
         * 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)
                        goto eperm;
                if (arg == 0 || arg > MAX_NR_CONSOLES)
                        ret =  -ENXIO;
                else {
                        arg--;
                        console_lock();
                        ret = vc_allocate(arg);
                        console_unlock();
                        if (ret)
                                break;
                        set_console(arg);
                }
                break;

        case VT_SETACTIVATE:
        {
                struct vt_setactivate vsa;

                if (!perm)
                        goto eperm;

                if (copy_from_user(&vsa, (struct vt_setactivate __user *)arg,
                                        sizeof(struct vt_setactivate))) {
                        ret = -EFAULT;
                        goto out;
                }
                if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
                        ret = -ENXIO;
                else {
                        vsa.console--;
                        console_lock();
                        ret = vc_allocate(vsa.console);
                        if (ret == 0) {
                                struct vc_data *nvc;
                                /* 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));
                        }
                        console_unlock();
                        if (ret)
                                break;
                        /* Commence switch and lock */
                        set_console(vsa.console);
                }
                break;
        }

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

        /*
         * 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)
                        goto eperm;

                if (vc->vt_mode.mode != VT_PROCESS) {
                        ret = -EINVAL;
                        break;
                }
                /*
                 * Switching-from response
                 */
                console_lock();
                if (vc->vt_newvt >= 0) {
                        if (arg == 0)
                                /*
                                 * Switch disallowed, so forget we were trying
                                 * to do it.
                                 */
                                vc->vt_newvt = -1;

                        else {
                                /*
                                 * The current vt has been released, so
                                 * complete the switch.
                                 */
                                int newvt;
                                newvt = vc->vt_newvt;
                                vc->vt_newvt = -1;
                                ret = vc_allocate(newvt);
                                if (ret) {
                                        console_unlock();
                                        break;
                                }
                                /*
                                 * 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);
                        }
                } else {
                        /*
                         * Switched-to response
                         */
                        /*
                         * If it's just an ACK, ignore it
                         */
                        if (arg != VT_ACKACQ)
                                ret = -EINVAL;
                }
                console_unlock();
                break;

         /*
          * Disallocate memory associated to VT (but leave VT1)
          */
         case VT_DISALLOCATE:
                if (arg > MAX_NR_CONSOLES) {
                        ret = -ENXIO;
                        break;
                }
                if (arg == 0) {
                    /* deallocate all unused consoles, but leave 0 */
                        console_lock();
                        for (i=1; i<MAX_NR_CONSOLES; i++)
                                if (! VT_BUSY(i))
                                        vc_deallocate(i);
                        console_unlock();
                } else {
                        /* deallocate a single console, if possible */
                        arg--;
                        if (VT_BUSY(arg))
                                ret = -EBUSY;
                        else if (arg) {                       /* leave 0 */
                                console_lock();
                                vc_deallocate(arg);
                                console_unlock();
                        }
                }
                break;

        case VT_RESIZE:
        {
                struct vt_sizes __user *vtsizes = up;
                struct vc_data *vc;

                ushort ll,cc;
                if (!perm)
                        goto eperm;
                if (get_user(ll, &vtsizes->v_rows) ||
                    get_user(cc, &vtsizes->v_cols))
                        ret = -EFAULT;
                else {
                        console_lock();
                        for (i = 0; i < MAX_NR_CONSOLES; i++) {
                                vc = vc_cons[i].d;

                                if (vc) {
                                        vc->vc_resize_user = 1;
                                        vc_resize(vc_cons[i].d, cc, ll);
                                }
                        }
                        console_unlock();
                }
                break;
        }

        case VT_RESIZEX:
        {
                struct vt_consize __user *vtconsize = up;
                ushort ll,cc,vlin,clin,vcol,ccol;
                if (!perm)
                        goto eperm;
                if (!access_ok(VERIFY_READ, vtconsize,
                                sizeof(struct vt_consize))) {
                        ret = -EFAULT;
                        break;
                }
                /* FIXME: Should check the copies properly */
                __get_user(ll, &vtconsize->v_rows);
                __get_user(cc, &vtconsize->v_cols);
                __get_user(vlin, &vtconsize->v_vlin);
                __get_user(clin, &vtconsize->v_clin);
                __get_user(vcol, &vtconsize->v_vcol);
                __get_user(ccol, &vtconsize->v_ccol);
                vlin = vlin ? vlin : vc->vc_scan_lines;
                if (clin) {
                        if (ll) {
                                if (ll != vlin/clin) {
                                        /* Parameters don't add up */
                                        ret = -EINVAL;
                                        break;
                                }
                        } else 
                                ll = vlin/clin;
                }
                if (vcol && ccol) {
                        if (cc) {
                                if (cc != vcol/ccol) {
                                        ret = -EINVAL;
                                        break;
                                }
                        } else
                                cc = vcol/ccol;
                }

                if (clin > 32) {
                        ret =  -EINVAL;
                        break;
                }
                    
                for (i = 0; i < MAX_NR_CONSOLES; i++) {
                        if (!vc_cons[i].d)
                                continue;
                        console_lock();
                        if (vlin)
                                vc_cons[i].d->vc_scan_lines = vlin;
                        if (clin)
                                vc_cons[i].d->vc_font.height = clin;
                        vc_cons[i].d->vc_resize_user = 1;
                        vc_resize(vc_cons[i].d, cc, ll);
                        console_unlock();
                }
                break;
        }

        case PIO_FONT: {
                if (!perm)
                        goto eperm;
                op.op = KD_FONT_OP_SET;
                op.flags = KD_FONT_FLAG_OLD | KD_FONT_FLAG_DONT_RECALC; /* Compatibility */
                op.width = 8;
                op.height = 0;
                op.charcount = 256;
                op.data = up;
                ret = con_font_op(vc_cons[fg_console].d, &op);
                break;
        }

        case GIO_FONT: {
                op.op = KD_FONT_OP_GET;
                op.flags = KD_FONT_FLAG_OLD;
                op.width = 8;
                op.height = 32;
                op.charcount = 256;
                op.data = up;
                ret = con_font_op(vc_cons[fg_console].d, &op);
                break;
        }

        case PIO_CMAP:
                if (!perm)
                        ret = -EPERM;
                else
                        ret = con_set_cmap(up);
                break;

        case GIO_CMAP:
                ret = con_get_cmap(up);
                break;

        case PIO_FONTX:
        case GIO_FONTX:
                ret = do_fontx_ioctl(cmd, up, perm, &op);
                break;

        case PIO_FONTRESET:
        {
                if (!perm)
                        goto eperm;

#ifdef BROKEN_GRAPHICS_PROGRAMS
                /* With BROKEN_GRAPHICS_PROGRAMS defined, the default
                   font is not saved. */
                ret = -ENOSYS;
                break;
#else
                {
                op.op = KD_FONT_OP_SET_DEFAULT;
                op.data = NULL;
                ret = con_font_op(vc_cons[fg_console].d, &op);
                if (ret)
                        break;
                con_set_default_unimap(vc_cons[fg_console].d);
                break;
                }
#endif
        }

        case KDFONTOP: {
                if (copy_from_user(&op, up, sizeof(op))) {
                        ret = -EFAULT;
                        break;
                }
                if (!perm && op.op != KD_FONT_OP_GET)
                        goto eperm;
                ret = con_font_op(vc, &op);
                if (ret)
                        break;
                if (copy_to_user(up, &op, sizeof(op)))
                        ret = -EFAULT;
                break;
        }

        case PIO_SCRNMAP:
                if (!perm)
                        ret = -EPERM;
                else
                        ret = con_set_trans_old(up);
                break;

        case GIO_SCRNMAP:
                ret = con_get_trans_old(up);
                break;

        case PIO_UNISCRNMAP:
                if (!perm)
                        ret = -EPERM;
                else
                        ret = con_set_trans_new(up);
                break;

        case GIO_UNISCRNMAP:
                ret = con_get_trans_new(up);
                break;

        case PIO_UNIMAPCLR:
              { struct unimapinit ui;
                if (!perm)
                        goto eperm;
                ret = copy_from_user(&ui, up, sizeof(struct unimapinit));
                if (ret)
                        ret = -EFAULT;
                else
                        con_clear_unimap(vc, &ui);
                break;
              }

        case PIO_UNIMAP:
        case GIO_UNIMAP:
                ret = do_unimap_ioctl(cmd, up, perm, vc);
                break;

        case VT_LOCKSWITCH:
                if (!capable(CAP_SYS_TTY_CONFIG))
                        goto eperm;
                vt_dont_switch = 1;
                break;
        case VT_UNLOCKSWITCH:
                if (!capable(CAP_SYS_TTY_CONFIG))
                        goto eperm;
                vt_dont_switch = 0;
                break;
        case VT_GETHIFONTMASK:
                ret = put_user(vc->vc_hi_font_mask,
                                        (unsigned short __user *)arg);
                break;
        case VT_WAITEVENT:
                ret = vt_event_wait_ioctl((struct vt_event __user *)arg);
                break;
        default:
                ret = -ENOIOCTLCMD;
        }
out:
        tty_unlock();
        return ret;
eperm:
        ret = -EPERM;
        goto out;
}

void reset_vc(struct vc_data *vc)
{
        vc->vc_mode = KD_TEXT;
        kbd_table[vc->vc_num].kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
        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;
        if (!in_interrupt())    /* Via keyboard.c:SAK() - akpm */
                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;

        console_lock();
        vc = vc_con->d;
        if (vc) {
                tty = vc->port.tty;
                /*
                 * SAK should also work in all raw modes and reset
                 * them properly.
                 */
                if (tty)
                        __do_SAK(tty);
                reset_vc(vc);
        }
        console_unlock();
}

#ifdef CONFIG_COMPAT

struct compat_consolefontdesc {
        unsigned short charcount;       /* characters in font (256 or 512) */
        unsigned short charheight;      /* scan lines per character (1-32) */
        compat_caddr_t chardata;        /* font data in expanded form */
};

static inline int
compat_fontx_ioctl(int cmd, struct compat_consolefontdesc __user *user_cfd,
                         int perm, struct console_font_op *op)
{
        struct compat_consolefontdesc cfdarg;
        int i;

        if (copy_from_user(&cfdarg, user_cfd, sizeof(struct compat_consolefontdesc)))
                return -EFAULT;

        switch (cmd) {
        case PIO_FONTX:
                if (!perm)
                        return -EPERM;
                op->op = KD_FONT_OP_SET;
                op->flags = KD_FONT_FLAG_OLD;
                op->width = 8;
                op->height = cfdarg.charheight;
                op->charcount = cfdarg.charcount;
                op->data = compat_ptr(cfdarg.chardata);
                return con_font_op(vc_cons[fg_console].d, op);
        case GIO_FONTX:
                op->op = KD_FONT_OP_GET;
                op->flags = KD_FONT_FLAG_OLD;
                op->width = 8;
                op->height = cfdarg.charheight;
                op->charcount = cfdarg.charcount;
                op->data = compat_ptr(cfdarg.chardata);
                i = con_font_op(vc_cons[fg_console].d, op);
                if (i)
                        return i;
                cfdarg.charheight = op->height;
                cfdarg.charcount = op->charcount;
                if (copy_to_user(user_cfd, &cfdarg, sizeof(struct compat_consolefontdesc)))
                        return -EFAULT;
                return 0;
        }
        return -EINVAL;
}

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);
        op->flags |= KD_FONT_FLAG_OLD;
        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);
        if (tmp_entries)
                if (!access_ok(VERIFY_WRITE, tmp_entries,
                                tmp.entry_ct*sizeof(struct unipair)))
                        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;
}

long vt_compat_ioctl(struct tty_struct *tty, struct file * file,
             unsigned int cmd, unsigned long arg)
{
        struct vc_data *vc = tty->driver_data;
        struct console_font_op op;      /* used in multiple places here */
        struct kbd_struct *kbd;
        unsigned int console;
        void __user *up = (void __user *)arg;
        int perm;
        int ret = 0;

        console = vc->vc_num;

        tty_lock();

        if (!vc_cons_allocated(console)) {      /* impossible? */
                ret = -ENOIOCTLCMD;
                goto out;
        }

        /*
         * 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;

        kbd = kbd_table + console;
        switch (cmd) {
        /*
         * these need special handlers for incompatible data structures
         */
        case PIO_FONTX:
        case GIO_FONTX:
                ret = compat_fontx_ioctl(cmd, up, perm, &op);
                break;

        case KDFONTOP:
                ret = compat_kdfontop_ioctl(up, perm, &op, vc);
                break;

        case PIO_UNIMAP:
        case GIO_UNIMAP:
                ret = compat_unimap_ioctl(cmd, up, perm, vc);
                break;

        /*
         * 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:
        case VT_RESIZE:
        case VT_RESIZEX:
                goto fallback;

        /*
         * the rest has a compatible data structure behind arg,
         * but we have to convert it to a proper 64 bit pointer.
         */
        default:
                arg = (unsigned long)compat_ptr(arg);
                goto fallback;
        }
out:
        tty_unlock();
        return ret;

fallback:
        tty_unlock();
        return vt_ioctl(tty, file, cmd, arg);
}


#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;

        console_lock();
        /* Graphics mode - up to X */
        if (disable_vt_switch) {
                console_unlock();
                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. */
                console_unlock();
                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.
                 */
                console_unlock();
                return -EIO;
        }
        console_unlock();
        tty_lock();
        if (vt_waitactive(vt + 1)) {
                pr_debug("Suspend: Can't switch VCs.");
                tty_unlock();
                return -EINTR;
        }
        tty_unlock();
        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)
{
        console_lock();
        disable_vt_switch = !do_switch;
        console_unlock();
}
EXPORT_SYMBOL(pm_set_vt_switch);