linux-kernel - Re: [PATCH] Kprobes i386 fix for mark ro data

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Message-ID: <5640c7e00706092324kd0ea8e0pef4a4cd764fce5d3@mail.gmail.com>
Date:	Sun, 10 Jun 2007 18:24:15 +1200
From:	"Ian McDonald" <ian.mcdonald@...di.co.nz>
To:	prasanna@...ibm.com
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Andi Kleen" <ak@...e.de>, "Jim Keniston" <jkenisto@...ibm.com>,
	"Chuck Ebbert" <cebbert@...hat.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	ananth@...ibm.com, anil.s.keshavamurthy@...el.com,
	"David S. Miller" <davem@...emloft.net>,
	"Patrick Andrieux" <patrick.andrieux@...il.com>,
	"DCCP Mailing List" <dccp@...r.kernel.org>, jbeulich@...ell.com,
	systemtap@...rces.redhat.com
Subject: Re: [PATCH] Kprobes i386 fix for mark ro data

On 6/7/07, S. P. Prasanna <prasanna@...ibm.com> wrote:
> > >It faulted when it tried to write the breakpoint instruction into the
> > >running kernel's executable code. Apparently the kernel code is now marked
> > >read-only?
> > >
> > >
> > Yes it would appear to be the case as user has CONFIG_DEBUG_RODATA
> > set. Patrick - can you turn this off and retest? It's under Kernel
> > Hacking, Write protect kernel read only data structures.
> >
>
> Ian,
>
> Please find the fix as suggested by Andi Kleen
> for the above stated problem.
>
> Thanks
> Prasanna
>
>
I went to test the fix and first of all went to replicate the problem.
My build has CONFIG_DEBUG_RODATA set but the problem does not occur
without the patch. Should I be concerned about this and raise a bug
for that as I would think that means there is a problem that the read
only protection isn't working (this is off Linus' tree synced
tonight).

Patrick - can you test whether this patch fixes your problem? You said
disabling CONFIG_DEBUG_RODATA fixed your problem but can you try
re-enabling and testing this patch?

Ian
-- 
Web: http://wand.net.nz/~iam4/
Blog: http://iansblog.jandi.co.nz
WAND Network Research Group
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