1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Unified handling of special chars.
4  *
5  *    Copyright IBM Corp. 2001
6  *    Author(s): Fritz Elfert <felfert@millenux.com> <elfert@de.ibm.com>
7  *
8  */
9 
10 #include <linux/stddef.h>
11 #include <asm/errno.h>
12 #include <linux/sysrq.h>
13 #include <linux/ctype.h>
14 
15 #include "ctrlchar.h"
16 
17 #ifdef CONFIG_MAGIC_SYSRQ
18 static struct sysrq_work ctrlchar_sysrq;
19 
20 static void
ctrlchar_handle_sysrq(struct work_struct * work)21 ctrlchar_handle_sysrq(struct work_struct *work)
22 {
23 	struct sysrq_work *sysrq = container_of(work, struct sysrq_work, work);
24 
25 	handle_sysrq(sysrq->key);
26 }
27 
schedule_sysrq_work(struct sysrq_work * sw)28 void schedule_sysrq_work(struct sysrq_work *sw)
29 {
30 	INIT_WORK(&sw->work, ctrlchar_handle_sysrq);
31 	schedule_work(&sw->work);
32 }
33 #endif
34 
35 
36 /**
37  * Check for special chars at start of input.
38  *
39  * @param buf Console input buffer.
40  * @param len Length of valid data in buffer.
41  * @param tty The tty struct for this console.
42  * @return CTRLCHAR_NONE, if nothing matched,
43  *         CTRLCHAR_SYSRQ, if sysrq was encountered
44  *         otherwise char to be inserted logically or'ed
45  *         with CTRLCHAR_CTRL
46  */
47 unsigned int
ctrlchar_handle(const unsigned char * buf,int len,struct tty_struct * tty)48 ctrlchar_handle(const unsigned char *buf, int len, struct tty_struct *tty)
49 {
50 	if ((len < 2) || (len > 3))
51 		return CTRLCHAR_NONE;
52 
53 	/* hat is 0xb1 in codepage 037 (US etc.) and thus */
54 	/* converted to 0x5e in ascii ('^') */
55 	if ((buf[0] != '^') && (buf[0] != '\252'))
56 		return CTRLCHAR_NONE;
57 
58 #ifdef CONFIG_MAGIC_SYSRQ
59 	/* racy */
60 	if (len == 3 && buf[1] == '-') {
61 		ctrlchar_sysrq.key = buf[2];
62 		schedule_sysrq_work(&ctrlchar_sysrq);
63 		return CTRLCHAR_SYSRQ;
64 	}
65 #endif
66 
67 	if (len != 2)
68 		return CTRLCHAR_NONE;
69 
70 	switch (tolower(buf[1])) {
71 	case 'c':
72 		return INTR_CHAR(tty) | CTRLCHAR_CTRL;
73 	case 'd':
74 		return EOF_CHAR(tty)  | CTRLCHAR_CTRL;
75 	case 'z':
76 		return SUSP_CHAR(tty) | CTRLCHAR_CTRL;
77 	}
78 	return CTRLCHAR_NONE;
79 }
80