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

From: "Patrick Andrieux" <patrick dot andrieux at gmail dot com>
To: "Ian McDonald" <ian dot mcdonald at jandi dot co dot nz>
Cc: prasanna at in dot ibm dot com, "Andrew Morton" <akpm at linux-foundation dot org>, "Andi Kleen" <ak at suse dot de>, "Jim Keniston" <jkenisto at us dot ibm dot com>, "Chuck Ebbert" <cebbert at redhat dot com>, "Linux Kernel Mailing List" <linux-kernel at vger dot kernel dot org>, ananth at in dot ibm dot com, anil dot s dot keshavamurthy at intel dot com, "David S. Miller" <davem at davemloft dot net>, "DCCP Mailing List" <dccp at vger dot kernel dot org>, jbeulich at novell dot com, systemtap at sources dot redhat dot com
Date: Mon, 11 Jun 2007 19:36:41 +0100
Subject: Re: [PATCH] Kprobes i386 fix for mark ro data
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References: <5640c7e00706061347v42c9ecbahb5354f6687a70a78@mail.gmail.com> <46673B76.2090508@redhat.com> <5640c7e00706061612h62074699wdbd2725654a164@mail.gmail.com> <20070607042229.GA9350@in.ibm.com> <5640c7e00706092324kd0ea8e0pef4a4cd764fce5d3@mail.gmail.com>

Hi,

This patch fixed my problem. I re-enabled CONFIG_DEBUG_RODATA and I
don't have seg fault with or without your DCCP patches. Inserting
`dccp_probe` or `tcp_probe`module doesn't cause any troubles.

Patrick.

On 10/06/07, Ian McDonald <ian.mcdonald@jandi.co.nz> wrote:

On 6/7/07, S. P. Prasanna <prasanna@in.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

References:
- Re: [PATCH] Kprobes i386 fix for mark ro data
  - From: S. P. Prasanna
- Re: [PATCH] Kprobes i386 fix for mark ro data
  - From: Ian McDonald

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