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
18static struct sysrq_work ctrlchar_sysrq;
19
20static void
21ctrlchar_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
28void 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 */
47unsigned int
48ctrlchar_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}