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[PATCH] debug: add sysrq_always_enabled boot option

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Most distributions enable sysrq support but set it to 0 by default.  Add a
sysrq_always_enabled boot option to always-enable sysrq keys.  Useful for
debugging - without having to modify the disribution's config files (which
might not be possible if the kernel is on a live CD, etc.).

Also, while at it, clean up the sysrq interfaces.

[bunk@stusta.de: make sysrq_always_enabled_setup() static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ingo Molnar 2006-12-13 00:34:36 -08:00 committed by Linus Torvalds
parent e61c90188b
commit 5d6f647fc6
5 changed files with 60 additions and 18 deletions
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6
Documentation/kernel-parameters.txt
View file

@ -1656,6 +1656,12 @@ and is between 256 and 4096 characters. It is defined in the file
sym53c416= [HW,SCSI]
See header of drivers/scsi/sym53c416.c.
sysrq_always_enabled
[KNL]
Ignore sysrq setting - this boot parameter will
neutralize any effect of /proc/sys/kernel/sysrq.
Useful for debugging.
t128= [HW,SCSI]
See header of drivers/scsi/t128.c.

37
drivers/char/sysrq.c
View file

@ -41,7 +41,34 @@
#include <asm/irq_regs.h>
/* Whether we react on sysrq keys or just ignore them */
int sysrq_enabled = 1;
int __read_mostly __sysrq_enabled = 1;
static int __read_mostly sysrq_always_enabled;
int sysrq_on(void)
{
return __sysrq_enabled || sysrq_always_enabled;
}
/*
* A value of 1 means 'all', other nonzero values are an op mask:
*/
static inline int sysrq_on_mask(int mask)
{
return sysrq_always_enabled || __sysrq_enabled == 1 ||
(__sysrq_enabled & mask);
}
static int __init sysrq_always_enabled_setup(char *str)
{
sysrq_always_enabled = 1;
printk(KERN_INFO "debug: sysrq always enabled.\n");
return 1;
}
__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
{
@ -379,8 +406,7 @@ void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
* Should we check for enabled operations (/proc/sysrq-trigger
* should not) and is the invoked operation enabled?
*/
if (!check_mask || sysrq_enabled == 1 ||
(sysrq_enabled & op_p->enable_mask)) {
if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
printk("%s\n", op_p->action_msg);
console_loglevel = orig_log_level;
op_p->handler(key, tty);
@ -414,9 +440,8 @@ void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
*/
void handle_sysrq(int key, struct tty_struct *tty)
{
if (!sysrq_enabled)
return;
__handle_sysrq(key, tty, 1);
if (sysrq_on())
__handle_sysrq(key, tty, 1);
}
EXPORT_SYMBOL(handle_sysrq);

10
drivers/char/viocons.c
View file

@ -61,10 +61,7 @@
static DEFINE_SPINLOCK(consolelock);
static DEFINE_SPINLOCK(consoleloglock);
#ifdef CONFIG_MAGIC_SYSRQ
static int vio_sysrq_pressed;
extern int sysrq_enabled;
#endif
#define VIOCHAR_NUM_BUF 16
@ -936,8 +933,10 @@ static void vioHandleData(struct HvLpEvent *event)
*/
num_pushed = 0;
for (index = 0; index < cevent->len; index++) {
#ifdef CONFIG_MAGIC_SYSRQ
if (sysrq_enabled) {
/*
* Will be optimized away if !CONFIG_MAGIC_SYSRQ:
*/
if (sysrq_on()) {
/* 0x0f is the ascii character for ^O */
if (cevent->data[index] == '\x0f') {
vio_sysrq_pressed = 1;
@ -956,7 +955,6 @@ static void vioHandleData(struct HvLpEvent *event)
continue;
}
}
#endif
/*
* The sysrq sequence isn't included in this check if
* sysrq is enabled and compiled into the kernel because

22
include/linux/sysrq.h
View file

@ -37,23 +37,37 @@ struct sysrq_key_op {
#ifdef CONFIG_MAGIC_SYSRQ
extern int sysrq_on(void);
/*
* Do not use this one directly:
*/
extern int __sysrq_enabled;
/* 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).
*/
void handle_sysrq(int, struct tty_struct *);
void __handle_sysrq(int, struct tty_struct *, int check_mask);
int register_sysrq_key(int, struct sysrq_key_op *);
int unregister_sysrq_key(int, struct sysrq_key_op *);
void handle_sysrq(int key, struct tty_struct *tty);
void __handle_sysrq(int key, struct tty_struct *tty, int check_mask);
int register_sysrq_key(int key, struct sysrq_key_op *op);
int unregister_sysrq_key(int key, struct sysrq_key_op *op);
struct sysrq_key_op *__sysrq_get_key_op(int key);
#else
static inline int sysrq_on(void)
{
return 0;
}
static inline int __reterr(void)
{
return -EINVAL;
}
static inline void handle_sysrq(int key, struct tty_struct *tty)
{
}
#define register_sysrq_key(ig,nore) __reterr()
#define unregister_sysrq_key(ig,nore) __reterr()

3
kernel/sysctl.c
View file

@ -65,7 +65,6 @@ extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
extern int sysctl_panic_on_oom;
extern int max_threads;
extern int sysrq_enabled;
extern int core_uses_pid;
extern int suid_dumpable;
extern char core_pattern[];
@ -543,7 +542,7 @@ static ctl_table kern_table[] = {
{
.ctl_name = KERN_SYSRQ,
.procname = "sysrq",
.data = &sysrq_enabled,
.data = &__sysrq_enabled,
.maxlen = sizeof (int),
.mode = 0644,
.proc_handler = &proc_dointvec,