drivers/staging/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         console_lock();
  55         set_selection_kernel(&sel, tty);
  56         console_unlock();
  57
  58 unref:
  59         tty_kref_put(tty);
  60 }
  61
  62 static struct speakup_selection_work speakup_sel_work = {
  63         .work = __WORK_INITIALIZER(speakup_sel_work.work,
  64                                    __speakup_set_selection)
  65 };
  66
  67 int speakup_set_selection(struct tty_struct *tty)
  68 {
  69         /* we get kref here first in order to avoid a subtle race when
  70          * cancelling selection work. getting kref first establishes the
  71          * invariant that if speakup_sel_work.tty is not NULL when
  72          * speakup_cancel_selection() is called, it must be the case that a put
  73          * kref is pending.
  74          */
  75         tty_kref_get(tty);
  76         if (cmpxchg(&speakup_sel_work.tty, NULL, tty)) {
  77                 tty_kref_put(tty);
  78                 return -EBUSY;
  79         }
  80         /* now we have the 'lock' by setting tty member of
  81          * speakup_selection_work. wmb() ensures that writes to
  82          * speakup_sel_work don't happen before cmpxchg() above.
  83          */
  84         wmb();
  85
  86         speakup_sel_work.sel.xs = spk_xs + 1;
  87         speakup_sel_work.sel.ys = spk_ys + 1;
  88         speakup_sel_work.sel.xe = spk_xe + 1;
  89         speakup_sel_work.sel.ye = spk_ye + 1;
  90         speakup_sel_work.sel.sel_mode = TIOCL_SELCHAR;
  91
  92         schedule_work_on(WORK_CPU_UNBOUND, &speakup_sel_work.work);
  93
  94         return 0;
  95 }
  96
  97 void speakup_cancel_selection(void)
  98 {
  99         struct tty_struct *tty;
 100
 101         cancel_work_sync(&speakup_sel_work.work);
 102         /* setting to null so that if work fails to run and we cancel it,
 103          * we can run it again without getting EBUSY forever from there on.
 104          * we need to use xchg here to avoid race with speakup_set_selection()
 105          */
 106         tty = xchg(&speakup_sel_work.tty, NULL);
 107         if (tty)
 108                 tty_kref_put(tty);
 109 }
 110
 111 static void __speakup_paste_selection(struct work_struct *work)
 112 {
 113         struct speakup_selection_work *ssw =
 114                 container_of(work, struct speakup_selection_work, work);
 115         struct tty_struct *tty = xchg(&ssw->tty, NULL);
 116
 117         paste_selection(tty);
 118         tty_kref_put(tty);
 119 }
 120
 121 static struct speakup_selection_work speakup_paste_work = {
 122         .work = __WORK_INITIALIZER(speakup_paste_work.work,
 123                                    __speakup_paste_selection)
 124 };
 125
 126 int speakup_paste_selection(struct tty_struct *tty)
 127 {
 128         tty_kref_get(tty);
 129         if (cmpxchg(&speakup_paste_work.tty, NULL, tty)) {
 130                 tty_kref_put(tty);
 131                 return -EBUSY;
 132         }
 133
 134         schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
 135         return 0;
 136 }
 137
 138 void speakup_cancel_paste(void)
 139 {
 140         struct tty_struct *tty;
 141
 142         cancel_work_sync(&speakup_paste_work.work);
 143         tty = xchg(&speakup_paste_work.tty, NULL);
 144         if (tty)
 145                 tty_kref_put(tty);
 146 }