Quelle  selection.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h> /* for kmalloc */
#include <linux/consolemap.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/device.h> /* for dev_warn */
#include <linux/selection.h>
#include <linux/workqueue.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/atomic.h>
#include <linux/console.h>

#include "speakup.h"

unsigned short spk_xs, spk_ys, spk_xe, spk_ye; /* our region points */
struct vc_data *spk_sel_cons;

struct speakup_selection_work {
 struct work_struct work;
 struct tiocl_selection sel;
 struct tty_struct *tty;
};

static void __speakup_set_selection(struct work_struct *work)
{
 struct speakup_selection_work *ssw =
  container_of(work, struct speakup_selection_work, work);

 struct tty_struct *tty;
 struct tiocl_selection sel;

 sel = ssw->sel;

 /* this ensures we copy sel before releasing the lock below */
 rmb();

 /* release the lock by setting tty of the struct to NULL */
 tty = xchg(&ssw->tty, NULL);

 if (spk_sel_cons != vc_cons[fg_console].d) {
  spk_sel_cons = vc_cons[fg_console].d;
  pr_warn("Selection: mark console not the same as cut\n");
  goto unref;
 }

 console_lock();
 clear_selection();
 console_unlock();

 set_selection_kernel(&sel, tty);

unref:
 tty_kref_put(tty);
}

static struct speakup_selection_work speakup_sel_work = {
 .work = __WORK_INITIALIZER(speakup_sel_work.work,
       __speakup_set_selection)
};

int speakup_set_selection(struct tty_struct *tty)
{
 /* we get kref here first in order to avoid a subtle race when
 * cancelling selection work. getting kref first establishes the
 * invariant that if speakup_sel_work.tty is not NULL when
 * speakup_cancel_selection() is called, it must be the case that a put
 * kref is pending.
 */
 tty_kref_get(tty);
 if (cmpxchg(&speakup_sel_work.tty, NULL, tty)) {
  tty_kref_put(tty);
  return -EBUSY;
 }
 /* now we have the 'lock' by setting tty member of
 * speakup_selection_work. wmb() ensures that writes to
 * speakup_sel_work don't happen before cmpxchg() above.
 */
 wmb();

 speakup_sel_work.sel.xs = spk_xs + 1;
 speakup_sel_work.sel.ys = spk_ys + 1;
 speakup_sel_work.sel.xe = spk_xe + 1;
 speakup_sel_work.sel.ye = spk_ye + 1;
 speakup_sel_work.sel.sel_mode = TIOCL_SELCHAR;

 schedule_work_on(WORK_CPU_UNBOUND, &speakup_sel_work.work);

 return 0;
}

void speakup_cancel_selection(void)
{
 struct tty_struct *tty;

 cancel_work_sync(&speakup_sel_work.work);
 /* setting to null so that if work fails to run and we cancel it,
 * we can run it again without getting EBUSY forever from there on.
 * we need to use xchg here to avoid race with speakup_set_selection()
 */
 tty = xchg(&speakup_sel_work.tty, NULL);
 if (tty)
  tty_kref_put(tty);
}

static void __speakup_paste_selection(struct work_struct *work)
{
 struct speakup_selection_work *ssw =
  container_of(work, struct speakup_selection_work, work);
 struct tty_struct *tty = xchg(&ssw->tty, NULL);

 paste_selection(tty);
 tty_kref_put(tty);
}

static struct speakup_selection_work speakup_paste_work = {
 .work = __WORK_INITIALIZER(speakup_paste_work.work,
       __speakup_paste_selection)
};

int speakup_paste_selection(struct tty_struct *tty)
{
 tty_kref_get(tty);
 if (cmpxchg(&speakup_paste_work.tty, NULL, tty)) {
  tty_kref_put(tty);
  return -EBUSY;
 }

 schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
 return 0;
}

void speakup_cancel_paste(void)
{
 struct tty_struct *tty;

 cancel_work_sync(&speakup_paste_work.work);
 tty = xchg(&speakup_paste_work.tty, NULL);
 if (tty)
  tty_kref_put(tty);
}