linux-kernel - Re: Need help with register_page_fault

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Message-ID: <20071118141741.28738bee@laptopd505.fenrus.org>
Date:	Sun, 18 Nov 2007 14:17:41 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Pavel Roskin <proski@....org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Need help with register_page_fault_notifier() replacement in
 2.6.24

On Sun, 18 Nov 2007 12:40:16 -0500
Pavel Roskin <proski@....org> wrote:

> Hello!
> 
> I'm trying to update a special tracing version of madwifi (driver for
> Atheros wireless cards) for Linux 2.6.24.  This version was created to
> help reverse engineering the non-free part of the driver (also known
> as HAL, hardware abstraction layer).
> 
> The problem is that functions register_page_fault_notifier() and
> unregister_page_fault_notifier() are gone in the current kernel git
> repository.
> 
> They are needed to intercept access to the card by causing page fault
> and intercepting it.
> 
> Those functions were removed on i386 platform because kprobes now
> registers the flat handler directly.  The log says that other callers
> are supposed to use kprobes now.
> 
> But what would be the right way to do it?  I can intercept
> do_page_fault() with kprobes, but that looks unsafe, since
> do_page_fault() is used by kprobes internally.
> 
> Or maybe I should install a fault handler with register_kprobe()?  The
> problem is, it is only called for faults in kp->pre_handler and
> kp->post_handler and for single-stepping.  I don't want to single-step
> anything, and moving all driver functionality in kp->pre_handler would
> be strange.
> 
> Perhaps I'm missing something obvious.  Any help will be appreciated.
> 

if it's just for a custom case (as it sounds like).. a simple small
change to the pagefault handler sounds like the easiest thing to do...
(eg just a direct function call to what would have been your notifier)

-- 
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