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Commit 8eaede49 authored by Ben Hutchings's avatar Ben Hutchings Committed by Greg Kroah-Hartman
Browse files

sysrq: Allow magic SysRq key functions to be disabled through Kconfig 



Turn the initial value of sysctl kernel.sysrq (SYSRQ_DEFAULT_ENABLE)
into a Kconfig variable.

Original version by Bastian Blank <waldi@debian.org>.

Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e8b5cbb0

Documentation/sysrq.txt

+6 −7
Original line number Diff line number Diff line
@@ -11,11 +11,9 @@ regardless of whatever else it is doing, unless it is completely locked up. 
You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when

configuring the kernel. When running a kernel with SysRq compiled in,

/proc/sys/kernel/sysrq controls the functions allowed to be invoked via

the SysRq key. By default the file contains 1 which means that every

possible SysRq request is allowed (in older versions SysRq was disabled

by default, and you were required to specifically enable it at run-time

but this is not the case any more). Here is the list of possible values

in /proc/sys/kernel/sysrq:

the SysRq key. The default value in this file is set by the

CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE config symbol, which itself defaults

to 1. Here is the list of possible values in /proc/sys/kernel/sysrq:

   0 - disable sysrq completely

   1 - enable all functions of sysrq

  >1 - bitmask of allowed sysrq functions (see below for detailed function
@@ -32,8 +30,9 @@ in /proc/sys/kernel/sysrq: 
You can set the value in the file by the following command:

    echo "number" >/proc/sys/kernel/sysrq



The number may be written either as decimal or as hexadecimal with the

0x prefix.

The number may be written here either as decimal or as hexadecimal

with the 0x prefix. CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE must always be

written in hexadecimal.



Note that the value of /proc/sys/kernel/sysrq influences only the invocation

via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always

drivers/tty/sysrq.c

+1 −1
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ 
#include <asm/irq_regs.h>



/* Whether we react on sysrq keys or just ignore them */

static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;

static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;

static bool __read_mostly sysrq_always_enabled;



unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };

include/linux/sysrq.h

+0 −3
Original line number Diff line number Diff line
@@ -17,9 +17,6 @@ 
#include <linux/errno.h>

#include <linux/types.h>



/* Enable/disable SYSRQ support by default (0==no, 1==yes). */

#define SYSRQ_DEFAULT_ENABLE	1



/* Possible values of bitmask for enabling sysrq functions */

/* 0x0001 is reserved for enable everything */

#define SYSRQ_ENABLE_LOG	0x0002

kernel/sysctl.c

+1 −1
Original line number Diff line number Diff line
@@ -190,7 +190,7 @@ static int proc_dostring_coredump(struct ctl_table *table, int write, 


#ifdef CONFIG_MAGIC_SYSRQ

/* Note: sysrq code uses it's own private copy */

static int __sysrq_enabled = SYSRQ_DEFAULT_ENABLE;

static int __sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;



static int sysrq_sysctl_handler(ctl_table *table, int write,

				void __user *buffer, size_t *lenp,

lib/Kconfig.debug

+9 −0
Original line number Diff line number Diff line
@@ -312,6 +312,15 @@ config MAGIC_SYSRQ 
	  keys are documented in <file:Documentation/sysrq.txt>. Don't say Y

	  unless you really know what this hack does.



config MAGIC_SYSRQ_DEFAULT_ENABLE

	hex "Enable magic SysRq key functions by default"

	depends on MAGIC_SYSRQ

	default 0x1

	help

	  Specifies which SysRq key functions are enabled by default.

	  This may be set to 1 or 0 to enable or disable them all, or

	  to a bitmask as described in Documentation/sysrq.txt.



config DEBUG_KERNEL

	bool "Kernel debugging"

	help