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: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
index 1c0471d..0e307c9 100644
--- a/Documentation/sysrq.txt
+++ b/Documentation/sysrq.txt
@@ -11,11 +11,9 @@
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 @@
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