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 * ctrlchar_handle - check for special chars at start of input
38 *
39 * @buf: console input buffer
40 * @len: length of valid data in buffer
41 * @tty: the tty struct for this console
42 *
43 * Return: CTRLCHAR_NONE, if nothing matched,
44 *         CTRLCHAR_SYSRQ, if sysrq was encountered
45 *         otherwise char to be inserted logically or'ed
46 *         with CTRLCHAR_CTRL
47 */
48unsigned int
49ctrlchar_handle(const unsigned char *buf, int len, struct tty_struct *tty)
50{
51	if ((len < 2) || (len > 3))
52		return CTRLCHAR_NONE;
53
54	/* hat is 0xb1 in codepage 037 (US etc.) and thus */
55	/* converted to 0x5e in ascii ('^') */
56	if ((buf[0] != '^') && (buf[0] != '\252'))
57		return CTRLCHAR_NONE;
58
59#ifdef CONFIG_MAGIC_SYSRQ
60	/* racy */
61	if (len == 3 && buf[1] == '-') {
62		ctrlchar_sysrq.key = buf[2];
63		schedule_sysrq_work(&ctrlchar_sysrq);
64		return CTRLCHAR_SYSRQ;
65	}
66#endif
67
68	if (len != 2)
69		return CTRLCHAR_NONE;
70
71	switch (tolower(buf[1])) {
72	case 'c':
73		return INTR_CHAR(tty) | CTRLCHAR_CTRL;
74	case 'd':
75		return EOF_CHAR(tty)  | CTRLCHAR_CTRL;
76	case 'z':
77		return SUSP_CHAR(tty) | CTRLCHAR_CTRL;
78	}
79	return CTRLCHAR_NONE;
80}
81