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 void speakup_clear_selection(void)
  26 {
  27         console_lock();
  28         clear_selection();
  29         console_unlock();
  30 }
  31
  32 static void __speakup_set_selection(struct work_struct *work)
  33 {
  34         struct speakup_selection_work *ssw =
  35                 container_of(work, struct speakup_selection_work, work);
  36
  37         struct tty_struct *tty;
  38         struct tiocl_selection sel;
  39
  40         sel = ssw->sel;
  41
  42         /* this ensures we copy sel before releasing the lock below */
  43         rmb();
  44
  45         /* release the lock by setting tty of the struct to NULL */
  46         tty = xchg(&ssw->tty, NULL);
  47
  48         if (spk_sel_cons != vc_cons[fg_console].d) {
  49                 spk_sel_cons = vc_cons[fg_console].d;
  50                 pr_warn("Selection: mark console not the same as cut\n");
  51                 goto unref;
  52         }
  53
  54         set_selection_kernel(&sel, tty);
  55
  56 unref:
  57         tty_kref_put(tty);
  58 }
  59
  60 static struct speakup_selection_work speakup_sel_work = {
  61         .work = __WORK_INITIALIZER(speakup_sel_work.work,
  62                                    __speakup_set_selection)
  63 };
  64
  65 int speakup_set_selection(struct tty_struct *tty)
  66 {
  67         /* we get kref here first in order to avoid a subtle race when
  68          * cancelling selection work. getting kref first establishes the
  69          * invariant that if speakup_sel_work.tty is not NULL when
  70          * speakup_cancel_selection() is called, it must be the case that a put
  71          * kref is pending.
  72          */
  73         tty_kref_get(tty);
  74         if (cmpxchg(&speakup_sel_work.tty, NULL, tty)) {
  75                 tty_kref_put(tty);
  76                 return -EBUSY;
  77         }
  78         /* now we have the 'lock' by setting tty member of
  79          * speakup_selection_work. wmb() ensures that writes to
  80          * speakup_sel_work don't happen before cmpxchg() above.
  81          */
  82         wmb();
  83
  84         speakup_sel_work.sel.xs = spk_xs + 1;
  85         speakup_sel_work.sel.ys = spk_ys + 1;
  86         speakup_sel_work.sel.xe = spk_xe + 1;
  87         speakup_sel_work.sel.ye = spk_ye + 1;
  88         speakup_sel_work.sel.sel_mode = TIOCL_SELCHAR;
  89
  90         schedule_work_on(WORK_CPU_UNBOUND, &speakup_sel_work.work);
  91
  92         return 0;
  93 }
  94
  95 void speakup_cancel_selection(void)
  96 {
  97         struct tty_struct *tty;
  98
  99         cancel_work_sync(&speakup_sel_work.work);
 100         /* setting to null so that if work fails to run and we cancel it,
 101          * we can run it again without getting EBUSY forever from there on.
 102          * we need to use xchg here to avoid race with speakup_set_selection()
 103          */
 104         tty = xchg(&speakup_sel_work.tty, NULL);
 105         if (tty)
 106                 tty_kref_put(tty);
 107 }
 108
 109 static void __speakup_paste_selection(struct work_struct *work)
 110 {
 111         struct speakup_selection_work *ssw =
 112                 container_of(work, struct speakup_selection_work, work);
 113         struct tty_struct *tty = xchg(&ssw->tty, NULL);
 114
 115         paste_selection(tty);
 116         tty_kref_put(tty);
 117 }
 118
 119 static struct speakup_selection_work speakup_paste_work = {
 120         .work = __WORK_INITIALIZER(speakup_paste_work.work,
 121                                    __speakup_paste_selection)
 122 };
 123
 124 int speakup_paste_selection(struct tty_struct *tty)
 125 {
 126         tty_kref_get(tty);
 127         if (cmpxchg(&speakup_paste_work.tty, NULL, tty)) {
 128                 tty_kref_put(tty);
 129                 return -EBUSY;
 130         }
 131
 132         schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
 133         return 0;
 134 }
 135
 136 void speakup_cancel_paste(void)
 137 {
 138         struct tty_struct *tty;
 139
 140         cancel_work_sync(&speakup_paste_work.work);
 141         tty = xchg(&speakup_paste_work.tty, NULL);
 142         if (tty)
 143                 tty_kref_put(tty);
 144 }