linux-kernel - Re: [patch 06/11] Text Edit Lock

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Message-ID: <20071206144431.GA11846@Krystal>
Date:	Thu, 6 Dec 2007 09:44:32 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	pageexec@...email.hu
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch 06/11] Text Edit Lock - Alternative code for x86

* pageexec@...email.hu (pageexec@...email.hu) wrote:
> On 5 Dec 2007 at 21:02, Mathieu Desnoyers wrote:
> 
> > Fix a memcpy that should be a text_poke (in apply_alternatives).
> > 
> > Use kernel_wp_save/kernel_wp_restore in text_poke to support DEBUG_RODATA
> > correctly and so the CPU HOTPLUG special case can be removed.
> > 
> > Add text_poke_early, for alternatives and paravirt boot-time and module load
> > time patching.
> > 
> > Notes:
> > - we use a macro for kernel_wp_save/restore to mimic local_irq_save/restore: the
> >   argument is passed without &.
> 
> sorry to chime in again, but lately i've been thinking that the
> cr0 argument is not really needed if one can ensure that calls
> to the kernel open/close macros won't nest (i checked and even
> in the PaX case it's easy to ensure, even desirable in fact).
> 
> in your case it's also true for now and i can't think of a situation
> where you'd really want to nest in the future (that'd mean opening
> up the kernel while some complex piece of code runs, more complex
> than a mere memset at least ;-). what do you think?
> 

It is correct to assume that the WP bit will always be activated, in
every configuration, even though we don't use the DEBUG_RODATA ?

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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