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 }
145