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Date: Fri, 25 Nov 2011 13:06:47 +0000
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From: Peter Maydell <peter.maydell@linaro.org>
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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: Alexander Graf <agraf@suse.de>
Cc: riku.voipio@iki.fi, qemu-devel Developers <qemu-devel@nongnu.org>

On 24 November 2011 23:43, Alexander Graf <agraf@suse.de> wrote:
> ---
>
> v1 -> v2:
>
> =C2=A0- make prettier by just wrapping mmap in linux-user/mmap.c

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.

I'd prefer a

#if defined(MAP_32BIT) && defined(__x86_64__) && (TARGET_LONG_BITS =3D=3D 3=
2)
#define QEMU_MAP_32BIT MAP_32BIT
#else
#define QEMU_MAP_32BIT 0
#endif

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.)

-- PMM