// SPDX-License-Identifier: GPL-2.0
/*
 * This module exports the functions:
 *
 *     'int set_selection_user(struct tiocl_selection __user *,
 *                             struct tty_struct *)'
 *     'int set_selection_kernel(struct tiocl_selection *, struct tty_struct *)'
 *     'void clear_selection(void)'
 *     'int paste_selection(struct tty_struct *)'
 *     'int sel_loadlut(u32 __user *)'
 *
 * Now that /dev/vcs exists, most of this can disappear again.
 */

#include <linux/module.h>
#include <linux/tty.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/types.h>

#include <linux/uaccess.h>

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/consolemap.h>
#include <linux/selection.h>
#include <linux/tiocl.h>
#include <linux/console.h>
#include <linux/tty_flip.h>

#include <linux/sched/signal.h>

/* Don't take this from <ctype.h>: 011-015 on the screen aren't spaces */
#define is_space_on_vt(c)       ((c) == ' ')

/* FIXME: all this needs locking */
static struct vc_selection {
        struct mutex lock;
        struct vc_data *cons;                   /* must not be deallocated */
        char *buffer;
        unsigned int buf_len;
        volatile int start;                     /* cleared by clear_selection */
        int end;
} vc_sel = {
        .lock = __MUTEX_INITIALIZER(vc_sel.lock),
        .start = -1,
};

/* clear_selection, highlight and highlight_pointer can be called
   from interrupt (via scrollback/front) */

/* set reverse video on characters s-e of console with selection. */
static inline void highlight(const int s, const int e)
{
        invert_screen(vc_sel.cons, s, e-s+2, true);
}

/* use complementary color to show the pointer */
static inline void highlight_pointer(const int where)
{
        complement_pos(vc_sel.cons, where);
}

static u32
sel_pos(int n, bool unicode)
{
        if (unicode)
                return screen_glyph_unicode(vc_sel.cons, n / 2);
        return inverse_translate(vc_sel.cons, screen_glyph(vc_sel.cons, n),
                        false);
}

/**
 * clear_selection - remove current selection
 *
 * Remove the current selection highlight, if any from the console holding the
 * selection.
 *
 * Locking: The caller must hold the console lock.
 */
void clear_selection(void)
{
        highlight_pointer(-1); /* hide the pointer */
        if (vc_sel.start != -1) {
                highlight(vc_sel.start, vc_sel.end);
                vc_sel.start = -1;
        }
}
EXPORT_SYMBOL_GPL(clear_selection);

bool vc_is_sel(const struct vc_data *vc)
{
        return vc == vc_sel.cons;
}

/*
 * User settable table: what characters are to be considered alphabetic?
 * 128 bits. Locked by the console lock.
 */
static u32 inwordLut[]={
  0x00000000, /* control chars     */
  0x03FFE000, /* digits and "-./"  */
  0x87FFFFFE, /* uppercase and '_' */
  0x07FFFFFE, /* lowercase         */
};

static inline int inword(const u32 c)
{
        return c > 0x7f || (( inwordLut[c>>5] >> (c & 0x1F) ) & 1);
}

/**
 * sel_loadlut() - load the LUT table
 * @lut: user table
 *
 * Load the LUT table from user space. Make a temporary copy so a partial
 * update doesn't make a mess.
 *
 * Locking: The console lock is acquired.
 */
int sel_loadlut(u32 __user *lut)
{
        u32 tmplut[ARRAY_SIZE(inwordLut)];

        if (copy_from_user(tmplut, lut, sizeof(inwordLut)))
                return -EFAULT;

        guard(console_lock)();
        memcpy(inwordLut, tmplut, sizeof(inwordLut));

        return 0;
}

/* does screen address p correspond to character at LH/RH edge of screen? */
static inline int atedge(const int p, int size_row)
{
        return (!(p % size_row) || !((p + 2) % size_row));
}

/* stores the char in UTF8 and returns the number of bytes used (1-4) */
static int store_utf8(u32 c, char *p)
{
        if (c < 0x80) {
                /*  0******* */
                p[0] = c;
                return 1;
        } else if (c < 0x800) {
                /* 110***** 10****** */
                p[0] = 0xc0 | (c >> 6);
                p[1] = 0x80 | (c & 0x3f);
                return 2;
        } else if (c < 0x10000) {
                /* 1110**** 10****** 10****** */
                p[0] = 0xe0 | (c >> 12);
                p[1] = 0x80 | ((c >> 6) & 0x3f);
                p[2] = 0x80 | (c & 0x3f);
                return 3;
        } else if (c < 0x110000) {
                /* 11110*** 10****** 10****** 10****** */
                p[0] = 0xf0 | (c >> 18);
                p[1] = 0x80 | ((c >> 12) & 0x3f);
                p[2] = 0x80 | ((c >> 6) & 0x3f);
                p[3] = 0x80 | (c & 0x3f);
                return 4;
        } else {
                /* outside Unicode, replace with U+FFFD */
                p[0] = 0xef;
                p[1] = 0xbf;
                p[2] = 0xbd;
                return 3;
        }
}

/**
 * set_selection_user - set the current selection.
 * @sel: user selection info
 * @tty: the console tty
 *
 * Invoked by the ioctl handle for the vt layer.
 *
 * Locking: The entire selection process is managed under the console_lock.
 * It's a lot under the lock but its hardly a performance path.
 */
int set_selection_user(const struct tiocl_selection __user *sel,
                       struct tty_struct *tty)
{
        struct tiocl_selection v;

        if (copy_from_user(&v, sel, sizeof(*sel)))
                return -EFAULT;

        /*
         * TIOCL_SELCLEAR and TIOCL_SELPOINTER are OK to use without
         * CAP_SYS_ADMIN as they do not modify the selection.
         */
        switch (v.sel_mode) {
        case TIOCL_SELCLEAR:
        case TIOCL_SELPOINTER:
                break;
        default:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
        }

        return set_selection_kernel(&v, tty);
}

static int vc_selection_store_chars(struct vc_data *vc, bool unicode)
{
        char *bp, *obp;
        unsigned int i;

        /* Allocate a new buffer before freeing the old one ... */
        /* chars can take up to 4 bytes with unicode */
        bp = kmalloc_array((vc_sel.end - vc_sel.start) / 2 + 1, unicode ? 4 : 1,
                           GFP_KERNEL | __GFP_NOWARN);
        if (!bp) {
                printk(KERN_WARNING "selection: kmalloc() failed\n");
                clear_selection();
                return -ENOMEM;
        }
        kfree(vc_sel.buffer);
        vc_sel.buffer = bp;

        obp = bp;
        for (i = vc_sel.start; i <= vc_sel.end; i += 2) {
                u32 c = sel_pos(i, unicode);
                if (unicode)
                        bp += store_utf8(c, bp);
                else
                        *bp++ = c;
                if (!is_space_on_vt(c))
                        obp = bp;
                if (!((i + 2) % vc->vc_size_row)) {
                        /* strip trailing blanks from line and add newline,
                           unless non-space at end of line. */
                        if (obp != bp) {
                                bp = obp;
                                *bp++ = '\r';
                        }
                        obp = bp;
                }
        }
        vc_sel.buf_len = bp - vc_sel.buffer;

        return 0;
}

static int vc_do_selection(struct vc_data *vc, unsigned short mode, int ps,
                int pe)
{
        int new_sel_start, new_sel_end, spc;
        bool unicode = vt_do_kdgkbmode(fg_console) == K_UNICODE;

        switch (mode) {
        case TIOCL_SELCHAR:     /* character-by-character selection */
                new_sel_start = ps;
                new_sel_end = pe;
                break;
        case TIOCL_SELWORD:     /* word-by-word selection */
                spc = is_space_on_vt(sel_pos(ps, unicode));
                for (new_sel_start = ps; ; ps -= 2) {
                        if ((spc && !is_space_on_vt(sel_pos(ps, unicode))) ||
                            (!spc && !inword(sel_pos(ps, unicode))))
                                break;
                        new_sel_start = ps;
                        if (!(ps % vc->vc_size_row))
                                break;
                }

                spc = is_space_on_vt(sel_pos(pe, unicode));
                for (new_sel_end = pe; ; pe += 2) {
                        if ((spc && !is_space_on_vt(sel_pos(pe, unicode))) ||
                            (!spc && !inword(sel_pos(pe, unicode))))
                                break;
                        new_sel_end = pe;
                        if (!((pe + 2) % vc->vc_size_row))
                                break;
                }
                break;
        case TIOCL_SELLINE:     /* line-by-line selection */
                new_sel_start = rounddown(ps, vc->vc_size_row);
                new_sel_end = rounddown(pe, vc->vc_size_row) +
                        vc->vc_size_row - 2;
                break;
        case TIOCL_SELPOINTER:
                highlight_pointer(pe);
                return 0;
        default:
                return -EINVAL;
        }

        /* remove the pointer */
        highlight_pointer(-1);

        /* select to end of line if on trailing space */
        if (new_sel_end > new_sel_start &&
                !atedge(new_sel_end, vc->vc_size_row) &&
                is_space_on_vt(sel_pos(new_sel_end, unicode))) {
                for (pe = new_sel_end + 2; ; pe += 2)
                        if (!is_space_on_vt(sel_pos(pe, unicode)) ||
                            atedge(pe, vc->vc_size_row))
                                break;
                if (is_space_on_vt(sel_pos(pe, unicode)))
                        new_sel_end = pe;
        }
        if (vc_sel.start == -1) /* no current selection */
                highlight(new_sel_start, new_sel_end);
        else if (new_sel_start == vc_sel.start)
        {
                if (new_sel_end == vc_sel.end)  /* no action required */
                        return 0;
                else if (new_sel_end > vc_sel.end)      /* extend to right */
                        highlight(vc_sel.end + 2, new_sel_end);
                else                            /* contract from right */
                        highlight(new_sel_end + 2, vc_sel.end);
        }
        else if (new_sel_end == vc_sel.end)
        {
                if (new_sel_start < vc_sel.start) /* extend to left */
                        highlight(new_sel_start, vc_sel.start - 2);
                else                            /* contract from left */
                        highlight(vc_sel.start, new_sel_start - 2);
        }
        else    /* some other case; start selection from scratch */
        {
                clear_selection();
                highlight(new_sel_start, new_sel_end);
        }
        vc_sel.start = new_sel_start;
        vc_sel.end = new_sel_end;

        return vc_selection_store_chars(vc, unicode);
}

static int vc_selection(struct vc_data *vc, struct tiocl_selection *v,
                struct tty_struct *tty)
{
        int ps, pe;

        poke_blanked_console();

        if (v->sel_mode == TIOCL_SELCLEAR) {
                /* useful for screendump without selection highlights */
                clear_selection();
                return 0;
        }

        /* Historically 0 => max value */
        v->xs = umin(v->xs - 1, vc->vc_cols - 1);
        v->ys = umin(v->ys - 1, vc->vc_rows - 1);
        v->xe = umin(v->xe - 1, vc->vc_cols - 1);
        v->ye = umin(v->ye - 1, vc->vc_rows - 1);

        if (mouse_reporting() && (v->sel_mode & TIOCL_SELMOUSEREPORT)) {
                mouse_report(tty, v->sel_mode & TIOCL_SELBUTTONMASK, v->xs,
                             v->ys);
                return 0;
        }

        ps = v->ys * vc->vc_size_row + (v->xs << 1);
        pe = v->ye * vc->vc_size_row + (v->xe << 1);
        if (ps > pe)    /* make vc_sel.start <= vc_sel.end */
                swap(ps, pe);

        if (vc_sel.cons != vc) {
                clear_selection();
                vc_sel.cons = vc;
        }

        return vc_do_selection(vc, v->sel_mode, ps, pe);
}

int set_selection_kernel(struct tiocl_selection *v, struct tty_struct *tty)
{
        guard(mutex)(&vc_sel.lock);
        guard(console_lock)();
        return vc_selection(vc_cons[fg_console].d, v, tty);
}
EXPORT_SYMBOL_GPL(set_selection_kernel);

/* Insert the contents of the selection buffer into the
 * queue of the tty associated with the current console.
 * Invoked by ioctl().
 *
 * Locking: called without locks. Calls the ldisc wrongly with
 * unsafe methods,
 */
int paste_selection(struct tty_struct *tty)
{
        struct vc_data *vc = tty->driver_data;
        int     pasted = 0;
        size_t count;
        struct  tty_ldisc *ld;
        DECLARE_WAITQUEUE(wait, current);
        int ret = 0;

        bool bp = vc->vc_bracketed_paste;
        static const char bracketed_paste_start[] = "\033[200~";
        static const char bracketed_paste_end[]   = "\033[201~";
        const char *bps = bp ? bracketed_paste_start : NULL;
        const char *bpe = bp ? bracketed_paste_end : NULL;

        scoped_guard(console_lock)
                poke_blanked_console();

        ld = tty_ldisc_ref_wait(tty);
        if (!ld)
                return -EIO;    /* ldisc was hung up */
        tty_buffer_lock_exclusive(&vc->port);

        add_wait_queue(&vc->paste_wait, &wait);
        mutex_lock(&vc_sel.lock);
        while (vc_sel.buffer && (vc_sel.buf_len > pasted || bpe)) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (signal_pending(current)) {
                        ret = -EINTR;
                        break;
                }
                if (tty_throttled(tty)) {
                        mutex_unlock(&vc_sel.lock);
                        schedule();
                        mutex_lock(&vc_sel.lock);
                        continue;
                }
                __set_current_state(TASK_RUNNING);

                if (bps) {
                        bps += tty_ldisc_receive_buf(ld, bps, NULL, strlen(bps));
                        if (*bps != '\0')
                                continue;
                        bps = NULL;
                }

                count = vc_sel.buf_len - pasted;
                if (count) {
                        pasted += tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted,
                                                        NULL, count);
                        if (vc_sel.buf_len > pasted)
                                continue;
                }

                if (bpe) {
                        bpe += tty_ldisc_receive_buf(ld, bpe, NULL, strlen(bpe));
                        if (*bpe == '\0')
                                bpe = NULL;
                }
        }
        mutex_unlock(&vc_sel.lock);
        remove_wait_queue(&vc->paste_wait, &wait);
        __set_current_state(TASK_RUNNING);

        tty_buffer_unlock_exclusive(&vc->port);
        tty_ldisc_deref(ld);
        return ret;
}
EXPORT_SYMBOL_GPL(paste_selection);