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From: Alexander Graf <agraf@suse.de>
In-Reply-To: <CAFEAcA_qSML2F_c1w+OGxGJuYFa7Ok_Jb-36-BWpiSV6=tc77w@mail.gmail.com>
Date: Mon, 19 Dec 2011 14:09:44 +0100
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Subject: Re: [Qemu-devel] [PATCH v2] linux-user: Fix 32-on-64 mmap for x86_64
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: riku.voipio@iki.fi, qemu-devel Developers <qemu-devel@nongnu.org>


On 25.11.2011, at 14:06, Peter Maydell wrote:

> On 24 November 2011 23:43, Alexander Graf <agraf@suse.de> wrote:
>> ---
>>=20
>> v1 -> v2:
>>=20
>>  - make prettier by just wrapping mmap in linux-user/mmap.c
>=20
> Hmm. I prefer the non-wrapped version :-)
> In particular, qemu_mmap() implies that (like other qemu_foo
> wrappers) this is a portability wrapper that should be used for
> all mmap calls. But actually we only want to apply MAP_32BIT
> for those mmap()s which are mmapping guest memory requests.
> So just having an extra flag in the cases where we need the
> flag seems more straightforward.
>=20
> I'd prefer a
>=20
> #if defined(MAP_32BIT) && defined(__x86_64__) && (TARGET_LONG_BITS =3D=3D=
 32)
> #define QEMU_MAP_32BIT MAP_32BIT
> #else
> #define QEMU_MAP_32BIT 0
> #endif
>=20
> and then use QEMU_MAP_32BIT. (That way it's obvious when you're
> looking at the mmap() calls that they're not using the host's
> MAP_32BIT but something that might be different.)

This patch is actually wrong and we should rather make proper -R values =
the default instead of relying on MAP_32BIT.


Alex