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 
__speakup_set_selection(struct work_struct * work)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 
speakup_set_selection(struct tty_struct * tty)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 
speakup_cancel_selection(void)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 
__speakup_paste_selection(struct work_struct * work)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 
speakup_paste_selection(struct tty_struct * tty)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 
speakup_cancel_paste(void)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 }
142