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Subject[PATCH] Sticky/Key-Setable SysRq (resubmit)
Attached is the patch from last week which provides the sysrq system
with the following:

a toggleable 'sticky' flag in /proc, which makes the sysrq key work on bad
keyboards, and through bad KVMs.

the ability to set which key in /proc, which makes the sysrq key work on
system _without_ a 'sysrq' key; like bad KVMs.

I've gotten no tracktion on this in a week, so I'm resubmitting it.

--
Crutcher <crutcher@datastacks.com>
GCS d--- s+:>+:- a-- C++++$ UL++++$ L+++$>++++ !E PS+++ PE Y+ PGP+>++++
R-(+++) !tv(+++) b+(++++) G+ e>++++ h+>++ r* y+>*$
diff -ur linux-2.4.11-pre2/drivers/char/keyboard.c linux-2.4.11-pre2-stateful_sysrq/drivers/char/keyboard.c
--- linux-2.4.11-pre2/drivers/char/keyboard.c Tue Sep 18 16:39:51 2001
+++ linux-2.4.11-pre2-stateful_sysrq/drivers/char/keyboard.c Wed Oct 3 00:15:08 2001
@@ -21,6 +21,12 @@
*
* 27-05-97: Added support for the Magic SysRq Key (Martin Mares)
* 30-07-98: Dead keys redone, aeb@cwi.nl.
+ *
+ * 28-09-2001: Crutcher Dunnavant <crutcher+kernel@datastacks.com>
+ * Add stateful sysrq features, based upon work from:
+ * Mathew Mills <mmills@amazon.com>
+ * Norman Murray <nmurray@redhat.com>
+ *
*/

#include <linux/config.h>
@@ -157,7 +163,14 @@
struct pt_regs * kbd_pt_regs;

#ifdef CONFIG_MAGIC_SYSRQ
-static int sysrq_pressed;
+static enum {
+ UP_AND_CLEAR,
+ DOWN_AND_WAITING,
+ DOWN_AND_DONE,
+ UP_AND_WAITING,
+ DOWN_AND_PASS
+} sysrq_state;
+extern struct sysrq_ctls_struct sysrq_ctls;
#endif

static struct pm_dev *pm_kbd;
@@ -246,15 +259,76 @@
} else
rep = test_and_set_bit(keycode, key_down);

-#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */
- if (keycode == SYSRQ_KEY) {
- sysrq_pressed = !up_flag;
- goto out;
- } else if (sysrq_pressed) {
- if (!up_flag) {
- handle_sysrq(kbd_sysrq_xlate[keycode], kbd_pt_regs, kbd, tty);
- goto out;
+#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */
+ /*
+ Pressing magic + command key acts as a chorded command.
+ Pressing and releasing magic without a command key acts sticky,
+ using the next non-magic key as a command key
+ Pressing magic twice without a command key passes the magic key
+ through.
+ */
+
+ if (sysrq_ctls.enabled) {
+ if (keycode == sysrq_ctls.keycode) switch(sysrq_state) {
+ case UP_AND_CLEAR:
+ sysrq_state = up_flag ? UP_AND_CLEAR :
+ DOWN_AND_WAITING;
+ /* consume the key event */
+ goto out;
+
+ case DOWN_AND_WAITING:
+ if (up_flag) {
+ if (sysrq_ctls.sticky) {
+ sysrq_state = UP_AND_WAITING;
+ } else {
+ sysrq_state = UP_AND_CLEAR;
+ }
+ } else {
+ sysrq_state = DOWN_AND_WAITING;
+ }
+ /* consume the key event */
+ goto out;
+
+ case DOWN_AND_DONE:
+ sysrq_state = up_flag ? UP_AND_CLEAR :
+ DOWN_AND_DONE;
+ /* consume the key event */
+ goto out;
+
+ case DOWN_AND_PASS:
+ case UP_AND_WAITING:
+ sysrq_state = up_flag ? UP_AND_CLEAR :
+ DOWN_AND_PASS;
+ /* pass the key event through */
+ break;
+
+ } else switch(sysrq_state) {
+ case UP_AND_WAITING:
+ case DOWN_AND_WAITING:
+ case DOWN_AND_DONE:
+ if (!up_flag) {
+ handle_sysrq(kbd_sysrq_xlate[keycode],
+ kbd_pt_regs, kbd, tty);
+ }
+
+ if (sysrq_state == UP_AND_WAITING) {
+ sysrq_state = UP_AND_CLEAR;
+ } else {
+ sysrq_state = DOWN_AND_DONE;
+ }
+
+ /* consume the key event */
+ goto out;
+
+
+ case DOWN_AND_PASS:
+ case UP_AND_CLEAR:
+ /* pass the key event through */
+ break;
+
}
+ } else {
+ sysrq_state = UP_AND_CLEAR;
}
#endif

diff -ur linux-2.4.11-pre2/drivers/char/sysrq.c linux-2.4.11-pre2-stateful_sysrq/drivers/char/sysrq.c
--- linux-2.4.11-pre2/drivers/char/sysrq.c Mon Oct 1 23:13:36 2001
+++ linux-2.4.11-pre2-stateful_sysrq/drivers/char/sysrq.c Wed Oct 3 09:55:42 2001
@@ -32,12 +32,24 @@

#include <asm/ptrace.h>

+/* for the SYSRQ_KEY definition */
+#include <asm/keyboard.h>
+
extern void reset_vc(unsigned int);
extern struct list_head super_blocks;

/* Whether we react on sysrq keys or just ignore them */
-int sysrq_enabled = 1;
+struct sysrq_ctls_struct sysrq_ctls = {
+ /* Whether we react on sysrq keys or just ignore them */
+ enabled: 1,
+
+ /* The keycode for the magic key, referred to as sysrq */
+ keycode: SYSRQ_KEY,

+ /* is the sysrq key 'sticky'? */
+ sticky: 0,
+};
+
/* Machine specific power off function */
void (*sysrq_power_off)(void);

@@ -231,7 +243,7 @@
static void sysrq_handle_mountro(int key, struct pt_regs *pt_regs,
struct kbd_struct *kbd, struct tty_struct *tty) {
emergency_sync_scheduled = EMERG_REMOUNT;
- wakeup_bdflush(0);
+ wakeup_bdflush();
}
static struct sysrq_key_op sysrq_mountro_op = {
handler: sysrq_handle_mountro,
@@ -433,7 +445,7 @@

void handle_sysrq(int key, struct pt_regs *pt_regs,
struct kbd_struct *kbd, struct tty_struct *tty) {
- if (!sysrq_enabled)
+ if (!sysrq_ctls.enabled)
return;

__sysrq_lock_table();
@@ -453,7 +465,7 @@
int orig_log_level;
int i, j;

- if (!sysrq_enabled)
+ if (!sysrq_ctls.enabled)
return;

orig_log_level = console_loglevel;
diff -ur linux-2.4.11-pre2/include/linux/sysctl.h linux-2.4.11-pre2-stateful_sysrq/include/linux/sysctl.h
--- linux-2.4.11-pre2/include/linux/sysctl.h Mon Oct 1 23:13:44 2001
+++ linux-2.4.11-pre2-stateful_sysrq/include/linux/sysctl.h Wed Oct 3 00:17:13 2001
@@ -106,7 +106,7 @@
KERN_MSGMAX=35, /* int: Maximum size of a messege */
KERN_MSGMNB=36, /* int: Maximum message queue size */
KERN_MSGPOOL=37, /* int: Maximum system message pool size */
- KERN_SYSRQ=38, /* int: Sysreq enable */
+ KERN_SYSRQ=38, /* struct: Sysreq enable, keycode, sticky */
KERN_MAX_THREADS=39, /* int: Maximum nr of threads in the system */
KERN_RANDOM=40, /* Random driver */
KERN_SHMALL=41, /* int: Maximum size of shared memory */
diff -ur linux-2.4.11-pre2/include/linux/sysrq.h linux-2.4.11-pre2-stateful_sysrq/include/linux/sysrq.h
--- linux-2.4.11-pre2/include/linux/sysrq.h Mon Oct 1 23:13:44 2001
+++ linux-2.4.11-pre2-stateful_sysrq/include/linux/sysrq.h Wed Oct 3 00:15:26 2001
@@ -26,6 +26,13 @@

#ifdef CONFIG_MAGIC_SYSRQ

+/* sysrq_ctls - controls aspects of the SYSRQ magic key hack*/
+struct sysrq_ctls_struct {
+ int enabled;
+ int keycode;
+ int sticky;
+};
+
/* Generic SysRq interface -- you may call it from any device driver, supplying
* ASCII code of the key, pointer to registers and kbd/tty structs (if they
* are available -- else NULL's).
diff -ur linux-2.4.11-pre2/kernel/sysctl.c linux-2.4.11-pre2-stateful_sysrq/kernel/sysctl.c
--- linux-2.4.11-pre2/kernel/sysctl.c Mon Oct 1 23:13:44 2001
+++ linux-2.4.11-pre2-stateful_sysrq/kernel/sysctl.c Wed Oct 3 00:18:43 2001
@@ -46,7 +46,7 @@
extern int sysctl_overcommit_memory;
extern int max_threads;
extern int nr_queued_signals, max_queued_signals;
-extern int sysrq_enabled;
+extern struct sysrq_ctls_struct sysrq_ctls;
extern int core_uses_pid;
extern int cad_pid;

@@ -233,7 +233,11 @@
0644, NULL, &proc_dointvec},
#endif
#ifdef CONFIG_MAGIC_SYSRQ
- {KERN_SYSRQ, "sysrq", &sysrq_enabled, sizeof (int),
+ {KERN_SYSRQ, "sysrq", &sysrq_ctls.enabled, sizeof (int),
+ 0644, NULL, &proc_dointvec},
+ {KERN_SYSRQ, "sysrq-key", &sysrq_ctls.keycode, sizeof (sysrq_ctls.keycode),
+ 0644, NULL, &proc_dointvec},
+ {KERN_SYSRQ, "sysrq-sticky", &sysrq_ctls.sticky, sizeof (sysrq_ctls.sticky),
0644, NULL, &proc_dointvec},
#endif
{KERN_CADPID, "cad_pid", &cad_pid, sizeof (int),
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