LXR linux/drivers/accessibility/speakup/selection.c

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/slab.h> /* for kmalloc */
   3#include <linux/consolemap.h>
   4#include <linux/interrupt.h>
   5#include <linux/sched.h>
   6#include <linux/device.h> /* for dev_warn */
   7#include <linux/selection.h>
   8#include <linux/workqueue.h>
   9#include <linux/tty.h>
  10#include <linux/tty_flip.h>
  11#include <linux/atomic.h>
  12#include <linux/console.h>
  13
  14#include "speakup.h"
  15
  16unsigned short spk_xs, spk_ys, spk_xe, spk_ye; /* our region points */
  17struct vc_data *spk_sel_cons;
  18
  19struct speakup_selection_work {
  20        struct work_struct work;
  21        struct tiocl_selection sel;
  22        struct tty_struct *tty;
  23};
  24
  25static void __speakup_set_selection(struct work_struct *work)
  26{
  27        struct speakup_selection_work *ssw =
  28                container_of(work, struct speakup_selection_work, work);
  29
  30        struct tty_struct *tty;
  31        struct tiocl_selection sel;
  32
  33        sel = ssw->sel;
  34
  35        /* this ensures we copy sel before releasing the lock below */
  36        rmb();
  37
  38        /* release the lock by setting tty of the struct to NULL */
  39        tty = xchg(&ssw->tty, NULL);
  40
  41        if (spk_sel_cons != vc_cons[fg_console].d) {
  42                spk_sel_cons = vc_cons[fg_console].d;
  43                pr_warn("Selection: mark console not the same as cut\n");
  44                goto unref;
  45        }
  46
  47        console_lock();
  48        clear_selection();
  49        console_unlock();
  50
  51        set_selection_kernel(&sel, tty);
  52
  53unref:
  54        tty_kref_put(tty);
  55}
  56
  57static struct speakup_selection_work speakup_sel_work = {
  58        .work = __WORK_INITIALIZER(speakup_sel_work.work,
  59                                   __speakup_set_selection)
  60};
  61
  62int speakup_set_selection(struct tty_struct *tty)
  63{
  64        /* we get kref here first in order to avoid a subtle race when
  65         * cancelling selection work. getting kref first establishes the
  66         * invariant that if speakup_sel_work.tty is not NULL when
  67         * speakup_cancel_selection() is called, it must be the case that a put
  68         * kref is pending.
  69         */
  70        tty_kref_get(tty);
  71        if (cmpxchg(&speakup_sel_work.tty, NULL, tty)) {
  72                tty_kref_put(tty);
  73                return -EBUSY;
  74        }
  75        /* now we have the 'lock' by setting tty member of
  76         * speakup_selection_work. wmb() ensures that writes to
  77         * speakup_sel_work don't happen before cmpxchg() above.
  78         */
  79        wmb();
  80
  81        speakup_sel_work.sel.xs = spk_xs + 1;
  82        speakup_sel_work.sel.ys = spk_ys + 1;
  83        speakup_sel_work.sel.xe = spk_xe + 1;
  84        speakup_sel_work.sel.ye = spk_ye + 1;
  85        speakup_sel_work.sel.sel_mode = TIOCL_SELCHAR;
  86
  87        schedule_work_on(WORK_CPU_UNBOUND, &speakup_sel_work.work);
  88
  89        return 0;
  90}
  91
  92void speakup_cancel_selection(void)
  93{
  94        struct tty_struct *tty;
  95
  96        cancel_work_sync(&speakup_sel_work.work);
  97        /* setting to null so that if work fails to run and we cancel it,
  98         * we can run it again without getting EBUSY forever from there on.
  99         * we need to use xchg here to avoid race with speakup_set_selection()
 100         */
 101        tty = xchg(&speakup_sel_work.tty, NULL);
 102        if (tty)
 103                tty_kref_put(tty);
 104}
 105
 106static void __speakup_paste_selection(struct work_struct *work)
 107{
 108        struct speakup_selection_work *ssw =
 109                container_of(work, struct speakup_selection_work, work);
 110        struct tty_struct *tty = xchg(&ssw->tty, NULL);
 111
 112        paste_selection(tty);
 113        tty_kref_put(tty);
 114}
 115
 116static struct speakup_selection_work speakup_paste_work = {
 117        .work = __WORK_INITIALIZER(speakup_paste_work.work,
 118                                   __speakup_paste_selection)
 119};
 120
 121int speakup_paste_selection(struct tty_struct *tty)
 122{
 123        tty_kref_get(tty);
 124        if (cmpxchg(&speakup_paste_work.tty, NULL, tty)) {
 125                tty_kref_put(tty);
 126                return -EBUSY;
 127        }
 128
 129        schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
 130        return 0;
 131}
 132
 133void speakup_cancel_paste(void)
 134{
 135        struct tty_struct *tty;
 136
 137        cancel_work_sync(&speakup_paste_work.work);
 138        tty = xchg(&speakup_paste_work.tty, NULL);
 139        if (tty)
 140                tty_kref_put(tty);
 141}
 142