drivers/s390/char/ctrlchar.c

   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
  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
  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
  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 }