[PATCH] Configurable Magic Sysrq
From: Jan Kara
Date: Fri Oct 29 2004 - 04:44:43 EST
Hello,
I know about a few people who would like to use some functionality of
the Magic Sysrq but don't want to enable all the functions it provides.
So I wrote a patch which should allow them to do so. It allows to
configure available functions of Sysrq via /proc/sys/kernel/sysrq (the
interface is backward compatible). If you think it's useful then use it :)
Andrew, do you think it can go into mainline or it's just an overdesign?
Thanks in advance for comments, bugreports
Honza
--
Jan Kara <jack@xxxxxxx>
SuSE CR Labs
Enable configuration of sysrq functions via /proc/sys/kernel/sysrq.
Signed-off-by: Jan Kara <jack@xxxxxxx>
diff -ru linux-2.6.9/Documentation/sysrq.txt linux-2.6.9-sysrq/Documentation/sysrq.txt
--- linux-2.6.9/Documentation/sysrq.txt 2004-10-18 23:54:08.000000000 +0200
+++ linux-2.6.9-sysrq/Documentation/sysrq.txt 2004-10-22 18:58:07.924933784 +0200
@@ -10,13 +10,27 @@
* How do I enable the magic SysRq key?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when
-configuring the kernel. When running on a kernel with SysRq compiled in, it
-may be DISABLED at run-time using following command:
+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:
+ 0 - disable sysrq completely
+ 1 - enable all functions of sysrq
+ >1 - bitmask of allowed sysrq functions (see below for detailed function
+ description):
+ 2 - enable control of console logging level
+ 4 - enable control of keyboard (SAK, unraw)
+ 8 - enable debugging dumps of processes etc.
+ 16 - enable sync command
+ 32 - enable remount read-only
+ 64 - enable signalling of processes (term, kill)
+ 128 - allow reboot
- echo "0" > /proc/sys/kernel/sysrq
-
-Note that previous versions disabled sysrq by default, and you were required
-to specifically enable it at run-time. That is not the case any longer.
+You can set the value in the file by the following command:
+ echo "number" >/proc/sys/kernel/sysrq
* How do I use the magic SysRq key?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff -ru linux-2.6.9/drivers/char/sysrq.c linux-2.6.9-sysrq/drivers/char/sysrq.c
--- linux-2.6.9/drivers/char/sysrq.c 2004-10-18 23:55:06.000000000 +0200
+++ linux-2.6.9-sysrq/drivers/char/sysrq.c 2004-10-22 14:47:25.000000000 +0200
@@ -38,6 +38,15 @@
extern void reset_vc(unsigned int);
+/* 0x0001 is reserved for enable everything */
+#define SYSRQ_ENABLE_LOG 0x0002
+#define SYSRQ_ENABLE_KEYBOARD 0x0004
+#define SYSRQ_ENABLE_DUMP 0x0008
+#define SYSRQ_ENABLE_SYNC 0x0010
+#define SYSRQ_ENABLE_REMOUNT 0x0020
+#define SYSRQ_ENABLE_SIGNAL 0x0040
+#define SYSRQ_ENABLE_BOOT 0x0080
+
/* Whether we react on sysrq keys or just ignore them */
int sysrq_enabled = 1;
@@ -58,6 +67,7 @@
.handler = sysrq_handle_loglevel,
.help_msg = "loglevel0-8",
.action_msg = "Changing Loglevel",
+ .enable_mask = SYSRQ_ENABLE_LOG,
};
@@ -74,6 +84,7 @@
.handler = sysrq_handle_SAK,
.help_msg = "saK",
.action_msg = "SAK",
+ .enable_mask = SYSRQ_ENABLE_KEYBOARD,
};
#endif
@@ -91,6 +102,7 @@
.handler = sysrq_handle_unraw,
.help_msg = "unRaw",
.action_msg = "Keyboard mode set to XLATE",
+ .enable_mask = SYSRQ_ENABLE_KEYBOARD,
};
#endif /* CONFIG_VT */
@@ -105,6 +117,7 @@
.handler = sysrq_handle_reboot,
.help_msg = "reBoot",
.action_msg = "Resetting",
+ .enable_mask = SYSRQ_ENABLE_BOOT,
};
static void sysrq_handle_sync(int key, struct pt_regs *pt_regs,
@@ -117,6 +130,7 @@
.handler = sysrq_handle_sync,
.help_msg = "Sync",
.action_msg = "Emergency Sync",
+ .enable_mask = SYSRQ_ENABLE_SYNC,
};
static void sysrq_handle_mountro(int key, struct pt_regs *pt_regs,
@@ -129,6 +143,7 @@
.handler = sysrq_handle_mountro,
.help_msg = "Unmount",
.action_msg = "Emergency Remount R/O",
+ .enable_mask = SYSRQ_ENABLE_REMOUNT,
};
/* END SYNC SYSRQ HANDLERS BLOCK */
@@ -146,6 +161,7 @@
.handler = sysrq_handle_showregs,
.help_msg = "showPc",
.action_msg = "Show Regs",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
};
@@ -158,6 +174,7 @@
.handler = sysrq_handle_showstate,
.help_msg = "showTasks",
.action_msg = "Show State",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
};
@@ -170,6 +187,7 @@
.handler = sysrq_handle_showmem,
.help_msg = "showMem",
.action_msg = "Show Memory",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
};
/* SHOW SYSRQ HANDLERS BLOCK */
@@ -200,6 +218,7 @@
.handler = sysrq_handle_term,
.help_msg = "tErm",
.action_msg = "Terminate All Tasks",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
};
static void sysrq_handle_kill(int key, struct pt_regs *pt_regs,
@@ -212,6 +231,7 @@
.handler = sysrq_handle_kill,
.help_msg = "kIll",
.action_msg = "Kill All Tasks",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
};
/* END SIGNAL SYSRQ HANDLERS BLOCK */
@@ -331,9 +351,13 @@
op_p = __sysrq_get_key_op(key);
if (op_p) {
- printk ("%s\n", op_p->action_msg);
- console_loglevel = orig_log_level;
- op_p->handler(key, pt_regs, tty);
+ if (sysrq_enabled == 1 || sysrq_enabled & op_p->enable_mask) {
+ printk ("%s\n", op_p->action_msg);
+ console_loglevel = orig_log_level;
+ op_p->handler(key, pt_regs, tty);
+ }
+ else
+ printk("This sysrq operation is disabled.\n");
} else {
printk("HELP : ");
/* Only print the help msg once per handler */
diff -ru linux-2.6.9/include/linux/sysrq.h linux-2.6.9-sysrq/include/linux/sysrq.h
--- linux-2.6.9/include/linux/sysrq.h 2004-10-18 23:53:06.000000000 +0200
+++ linux-2.6.9-sysrq/include/linux/sysrq.h 2004-10-22 14:47:25.000000000 +0200
@@ -20,6 +20,7 @@
void (*handler)(int, struct pt_regs *, struct tty_struct *);
char *help_msg;
char *action_msg;
+ int enable_mask;
};
#ifdef CONFIG_MAGIC_SYSRQ