linux-kernel - Re: [PATCH] x86_64: make traps on 'iret' be debuggable in user space

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Message-ID: <47AB9416.2030508@redhat.com>
Date:	Thu, 07 Feb 2008 18:28:22 -0500
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Roland McGrath <roland@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	Glauber de Oliveira Costa <gcosta@...hat.com>
Subject: Re: [PATCH] x86_64: make traps on 'iret' be debuggable in user	space

On 02/07/2008 03:30 PM, Roland McGrath wrote:
>> Did you test without CONFIG_PARAVIRT, and CONFIG_PARAVIRT booted both with and
>> without the "noreplace-paravirt" parameter?
> 
> I did not test CONFIG_PARAVIRT at all.  I just fixed what its introduction
> had done to break generic x86-64.
> 
> 

It looks you may have broken paravirt (if even that case worked) because
the iret is actually at the iret_label you removed (after the instruction
is patched.) And most likely neither version worked with "noreplace-paravirt',
because then the iret instruction is out-of-line and the INTERRUPT_RETURN
jumps to it.


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