RE: Customising the NMI handler

[Simon Egerton <segerton@cct.co.uk>]

Hi John,

Thanks for your reply, I'll have a look into the oprofile software.  I agree
that it would be easier to patch the kernel.  I was thinking of the
situation where the system is already up and running, but the user prefers
not to bring the system down, for whatever reason, they could simply load
the module to update their system with the hot swap features.  But maybe
this is a case of trying to cater for a very small minority of cases...

Thanks again,

Simon.

	-----Original Message-----
	From:	John Levon [SMTP:movement@marcelothewonderpenguin.com]
	Sent:	10 July 2002 03:34
	To:	kernelnewbies@nl.linux.org
	Subject:	Re: Customising the NMI handler

	> I am using Linux on a Compact PCI system with a System Controller
and
	> a set
	> of Peripheral boards.  Each time one of these peripheral boards is
hot
	> swapped a NMI interrupt is generated on the System Controller
board.
	> I have
	> in mind to write a driver that handles these NMI interrupts.  I
don't
	> really
	> want to start hacking the kernel source, but would rather like to
	> build a
	> module that can be loaded at some point.
	 
	Why ? Modify the kernel source, it's not difficult and is almost
	definitely the best solution.
	 
	> My idea is to get the module to
	> replace the NMI vector to the existing NMI handler function (in
	> linux/arch/i386/kernel/entry.S that is set from the trap_init
function
	> in
	> /linux/arch/i386/kernel/traps.c) with my own handler function,
calling
	> the
	> previous handler if necessary after my handler has done its bit.
A
	> pretty
	> standard idea.  Now, in terms of swimming, I still have my
inflatable
	> armbands on here! So I was wondering if this were possible?
	 
	It's possible, but is horrifically ugly. If you really really want
to do
	this, check out oprofile.sf.net source code, particularly the code
that
	calls _set_gate().
	 
	> module? Looking through the traps.c file I see that there is a
	> function
	> trap_init_f00f_bug which makes the IDT read only?

	It makes a copy read only iirc 

	john

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