linux-kernel - CONFIG_DEBUG_RODATA prevents kprobes from working on 2.6.22-rc2

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Message-ID: <46545EA5.3020201@redhat.com>
Date:	Wed, 23 May 2007 11:32:53 -0400
From:	William Cohen <wcohen@...hat.com>
To:	linux-kernel@...r.kernel.org
Subject: CONFIG_DEBUG_RODATA prevents kprobes from working on 2.6.22-rc2

The recent changes in the 2.6.22-rc2 kernel to the write protection of read only 
data enable by CONFIG_DEBUG_RODATA prevents kprobes from working. At least on 
the on i386 and x86_64 machine the mark_rodata_ro() function marks memory 
starting from _text as read only. Thus, when kprobes attempts to write a break 
point into a location in the kernel it faults.

There is a description of the problem at:

http://sources.redhat.com/bugzilla/show_bug.cgi?id=4531

Shouldn't mark_rodata_ro be less agressive when CONFIG_KPROBES is enabled? Or 
should kprobes temporarily change the page to be writeable, set the break point, 
and then return the page to read only?

-Will
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