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Date: Sat, 22 Jan 2011 06:41:15 +0800
Message-ID: <AANLkTimH2PVYSsJWj4KMeE8wDPfUqT95iWOJyC9v=Vbk@mail.gmail.com>
Subject: Re: [Qemu-devel] Changing the content of target cpu registers
From: =?ISO-8859-1?Q?Rapha=EBl_Lef=E8vre?= <taylor.lefevre@gmail.com>
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Cc: Blue Swirl <blauwirbel@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>

On Wed, Jan 19, 2011 at 2:13 AM, Stefano Bonifazi
<stefboombastic@gmail.com> wrote:
> On 01/18/2011 06:17 PM, Blue Swirl wrote:
>>
>> On Tue, Jan 18, 2011 at 9:29 AM, Stefano Bonifazi
>> <stefboombastic@gmail.com> =A0wrote:
>>>
>>> Hi all!
>>> =A0I am working on qemu-user (qemu-ppc).
>>> I'd like to edit the values of target registers during the execution. C=
an
>>> I
>>> do that by simply changing the content of env->gpr[] or do these only
>>> contain a copy of the values of the registers?
>>> In this last case, where are the real values of the target registers
>>> stored
>>> so that by modifying them I can alter the behavior of the target code
>>> execution?
>>
>> env->gpr is the canonical location, but the translator assigns TCG
>> variables to them (cpu_gpr[] in translate.c), so GPR contents may be
>> cached to these. But when helpers are called or the TB finishes,
>> env->gpr should be valid again.
>
> Hi!
> =A0Thank you for your answer!
> So if I understand well if I set env->gpr in a code section where there i=
s
> no TCG translation on progress, I can edit directly the target CPU regist=
er
> right?
> Best Regards!
> Stefano B.
>
>

In fact, I need to apologize for my poor comprehension to your
questions even after digesting the explinations from Blue Swirl. By
tracing code of qemu, "env->gpr" should be able to be modified any
place directly(or indirectly) whether the TCG involved or not.