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Subjectupdate to SysRQ patch
Oops, the second example module I posted did bad things on 
SMP based machines, so here is a respin of it:


#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sysrq.h>

/*
* This is a example of some of the more complex things that
* the SysRQ registration patch makes possible
*/

void dumpfake_handler (int key, struct pt_regs *pt_regs,
struct kbd_struct *kbd, struct tty_struct *tty) {
int i = key - '0';
printk("<1>Dump fake-device %d\n00 A2 F4 9C 8D 01 34 42\n", i);
}

struct sysrq_key_op dumpfake_op = {
handler: dumpfake_handler,
help_msg: "dump-fake0-9",
action_msg: "Dumping Fake Device\n"
};

struct sysrq_key_op *op_stash[10];
int overloaded = 0;

void overload_handler (int, struct pt_regs *,
struct kbd_struct *, struct tty_struct *);
struct sysrq_key_op overload_op = {
handler: overload_handler,
help_msg: "Fakemenu",
action_msg: "Loading Fake Meni\n"
};

/*
* keep in mind that this functions is called (ultimately) by
* handle_sysrq, and as such, is already inside of the table
* lock. (I forgot this the first time I wrote it, and tried
* to lock here :)
* Which works on non-SMP machines :(
*/
void overload_handler (int key, struct pt_regs *pt_regs,
struct kbd_struct *kbd, struct tty_struct *tty) {
int i;
if (overloaded) {
overload_op.help_msg = "Fakemenu";
overload_op.action_msg = "Loading Fake Menu\n";
for (i=0;i<10;i++) __sysrq_put_key_op(i + '0', op_stash[i]);
overloaded = 0;
} else {
overload_op.help_msg = "unloadFakemenu";
overload_op.action_msg = "Unloading Fake Menu\n";
for (i=0;i<10;i++) __sysrq_put_key_op(i + '0', &dumpfake_op);
overloaded = 1;
}
}

int init_module (void) {
int i;
__sysrq_table_lock();
for (i=0;i<10;i++) op_stash[i] = __sysrq_get_key_op(i + '0');
__sysrq_table_unlock();

REGISTER_SYSRQ_KEY('f', &overload_op);
printk("<1>overload example loaded\n");
return 0;
}

void cleanup_module (void) {
int i;
if (overloaded) {
__sysrq_table_lock();
for (i=0;i<10;i++) __sysrq_put_key_op(i + '0', op_stash[i]);
__sysrq_table_unlock();
}

UNREGISTER_SYSRQ_KEY('f', &overload_op);
printk("<1>overload example unloaded\n");
}


--
"I may be a monkey, Crutcher Dunnavant
but I'm a monkey <crutcher@redhat.com>
with ambition!" Red Hat OS Development

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