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
  16 unsigned short spk_xs, spk_ys, spk_xe, spk_ye; /* our region points */
  17 struct vc_data *spk_sel_cons;
  18
  19 struct speakup_selection_work {
  20         struct work_struct work;
  21         struct tiocl_selection sel;
  22         struct tty_struct *tty;
  23 };
  24
  25 static 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
  53 unref:
  54         tty_kref_put(tty);
  55 }
  56
  57 static struct speakup_selection_work speakup_sel_work = {
  58         .work = __WORK_INITIALIZER(speakup_sel_work.work,
  59                                    __speakup_set_selection)
  60 };
  61
  62 int 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
  92 void 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
 106 static 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
 116 static struct speakup_selection_work speakup_paste_work = {
 117         .work = __WORK_INITIALIZER(speakup_paste_work.work,
 118                                    __speakup_paste_selection)
 119 };
 120
 121 int 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
 133 void 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 }