// SPDX-License-Identifier: GPL-2.0
/*
 * This module exports the functions:
 *
 *     'int set_selection(struct tiocl_selection __user *, struct tty_struct *)'
 *     'void clear_selection(void)'
 *     'int paste_selection(struct tty_struct *)'
 *     'int sel_loadlut(char __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/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>

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

extern void poke_blanked_console(void);

/* FIXME: all this needs locking */
/* Variables for selection control. */
/* Use a dynamic buffer, instead of static (Dec 1994) */
struct vc_data *sel_cons;               /* must not be deallocated */
static int use_unicode;
static volatile int sel_start = -1;     /* cleared by clear_selection */
static int sel_end;
static int sel_buffer_lth;
static char *sel_buffer;

/* 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(sel_cons, s, e-s+2, 1);
}

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

static u16
sel_pos(int n)
{
        return inverse_translate(sel_cons, screen_glyph(sel_cons, n),
                                use_unicode);
}

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

/*
 * 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 u16 c) {
        return c > 0x7f || (( inwordLut[c>>5] >> (c & 0x1F) ) & 1);
}

/**
 *      set loadlut             -       load the LUT table
 *      @p: user table
 *
 *      Load the LUT table from user space. The caller must hold the console
 *      lock. Make a temporary copy so a partial update doesn't make a mess.
 */
int sel_loadlut(char __user *p)
{
        u32 tmplut[ARRAY_SIZE(inwordLut)];
        if (copy_from_user(tmplut, (u32 __user *)(p+4), sizeof(inwordLut)))
                return -EFAULT;
        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));
}

/* constrain v such that v <= u */
static inline unsigned short limit(const unsigned short v, const unsigned short u)
{
        return (v > u) ? u : v;
}

/* stores the char in UTF8 and returns the number of bytes used (1-3) */
static int store_utf8(u16 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 {
                /* 1110**** 10****** 10****** */
                p[0] = 0xe0 | (c >> 12);
                p[1] = 0x80 | ((c >> 6) & 0x3f);
                p[2] = 0x80 | (c & 0x3f);
                return 3;
        }
}

/**
 *      set_selection           -       set the current selection.
 *      @sel: user selection info
 *      @tty: the console tty
 *
 *      Invoked by the ioctl handle for the vt layer.
 *
 *      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(const struct tiocl_selection __user *sel, struct tty_struct *tty)
{
        struct vc_data *vc = vc_cons[fg_console].d;
        int sel_mode, new_sel_start, new_sel_end, spc;
        char *bp, *obp;
        int i, ps, pe, multiplier;
        u16 c;
        int mode;

        poke_blanked_console();

        { unsigned short xs, ys, xe, ye;

          if (!access_ok(VERIFY_READ, sel, sizeof(*sel)))
                return -EFAULT;
          __get_user(xs, &sel->xs);
          __get_user(ys, &sel->ys);
          __get_user(xe, &sel->xe);
          __get_user(ye, &sel->ye);
          __get_user(sel_mode, &sel->sel_mode);
          xs--; ys--; xe--; ye--;
          xs = limit(xs, vc->vc_cols - 1);
          ys = limit(ys, vc->vc_rows - 1);
          xe = limit(xe, vc->vc_cols - 1);
          ye = limit(ye, vc->vc_rows - 1);
          ps = ys * vc->vc_size_row + (xs << 1);
          pe = ye * vc->vc_size_row + (xe << 1);

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

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

        if (ps > pe)    /* make sel_start <= sel_end */
        {
                int tmp = ps;
                ps = pe;
                pe = tmp;
        }

        if (sel_cons != vc_cons[fg_console].d) {
                clear_selection();
                sel_cons = vc_cons[fg_console].d;
        }
        mode = vt_do_kdgkbmode(fg_console);
        if (mode == K_UNICODE)
                use_unicode = 1;
        else
                use_unicode = 0;

        switch (sel_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 = isspace(sel_pos(ps));
                        for (new_sel_start = ps; ; ps -= 2)
                        {
                                if ((spc && !isspace(sel_pos(ps))) ||
                                    (!spc && !inword(sel_pos(ps))))
                                        break;
                                new_sel_start = ps;
                                if (!(ps % vc->vc_size_row))
                                        break;
                        }
                        spc = isspace(sel_pos(pe));
                        for (new_sel_end = pe; ; pe += 2)
                        {
                                if ((spc && !isspace(sel_pos(pe))) ||
                                    (!spc && !inword(sel_pos(pe))))
                                        break;
                                new_sel_end = pe;
                                if (!((pe + 2) % vc->vc_size_row))
                                        break;
                        }
                        break;
                case TIOCL_SELLINE:     /* line-by-line selection */
                        new_sel_start = ps - ps % vc->vc_size_row;
                        new_sel_end = pe + vc->vc_size_row
                                    - pe % 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) &&
                isspace(sel_pos(new_sel_end))) {
                for (pe = new_sel_end + 2; ; pe += 2)
                        if (!isspace(sel_pos(pe)) ||
                            atedge(pe, vc->vc_size_row))
                                break;
                if (isspace(sel_pos(pe)))
                        new_sel_end = pe;
        }
        if (sel_start == -1)    /* no current selection */
                highlight(new_sel_start, new_sel_end);
        else if (new_sel_start == sel_start)
        {
                if (new_sel_end == sel_end)     /* no action required */
                        return 0;
                else if (new_sel_end > sel_end) /* extend to right */
                        highlight(sel_end + 2, new_sel_end);
                else                            /* contract from right */
                        highlight(new_sel_end + 2, sel_end);
        }
        else if (new_sel_end == sel_end)
        {
                if (new_sel_start < sel_start)  /* extend to left */
                        highlight(new_sel_start, sel_start - 2);
                else                            /* contract from left */
                        highlight(sel_start, new_sel_start - 2);
        }
        else    /* some other case; start selection from scratch */
        {
                clear_selection();
                highlight(new_sel_start, new_sel_end);
        }
        sel_start = new_sel_start;
        sel_end = new_sel_end;

        /* Allocate a new buffer before freeing the old one ... */
        multiplier = use_unicode ? 3 : 1;  /* chars can take up to 3 bytes */
        bp = kmalloc(((sel_end-sel_start)/2+1)*multiplier, GFP_KERNEL);
        if (!bp) {
                printk(KERN_WARNING "selection: kmalloc() failed\n");
                clear_selection();
                return -ENOMEM;
        }
        kfree(sel_buffer);
        sel_buffer = bp;

        obp = bp;
        for (i = sel_start; i <= sel_end; i += 2) {
                c = sel_pos(i);
                if (use_unicode)
                        bp += store_utf8(c, bp);
                else
                        *bp++ = c;
                if (!isspace(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;
                }
        }
        sel_buffer_lth = bp - sel_buffer;
        return 0;
}

/* 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;
        unsigned int count;
        struct  tty_ldisc *ld;
        DECLARE_WAITQUEUE(wait, current);

        console_lock();
        poke_blanked_console();
        console_unlock();

        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);
        while (sel_buffer && sel_buffer_lth > pasted) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (tty_throttled(tty)) {
                        schedule();
                        continue;
                }
                __set_current_state(TASK_RUNNING);
                count = sel_buffer_lth - pasted;
                count = tty_ldisc_receive_buf(ld, sel_buffer + pasted, NULL,
                                              count);
                pasted += count;
        }
        remove_wait_queue(&vc->paste_wait, &wait);
        __set_current_state(TASK_RUNNING);

        tty_buffer_unlock_exclusive(&vc->port);
        tty_ldisc_deref(ld);
        return 0;
}