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Commit 5d6f647f authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
Browse files

[PATCH] debug: add sysrq_always_enabled boot option 



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: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e61c9018

Documentation/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -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.

drivers/char/sysrq.c

+31 −6
Original line number Diff line number Diff line
@@ -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);
@@ -414,8 +440,7 @@ 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;

	if (sysrq_on())

		__handle_sysrq(key, tty, 1);

}

EXPORT_SYMBOL(handle_sysrq);

drivers/char/viocons.c

+4 −6
Original line number Diff line number Diff line
@@ -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

include/linux/sysrq.h

+18 −4
Original line number Diff line number Diff line
@@ -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()

kernel/sysctl.c

+1 −2
Original line number Diff line number Diff line
@@ -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,