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Date: Wed, 26 Aug 2009 16:40:43 +0300
From: Riku Voipio <riku.voipio@iki.fi>
Subject: Re: [Qemu-devel] [Patch] linux-user/syscall.c - don't add
	GUEST_BASE to NULL pointer
Message-ID: <20090826134043.GB7862@kos.to>
References: <200908260002.03066.dl9pf@gmx.de> <200908260137.48781.dl9pf@gmx.de>
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To: Jan-Simon =?utf-8?Q?M=C3=B6ller?= <dl9pf@gmx.de>
Cc: qemu-devel@nongnu.org

On Wed, Aug 26, 2009 at 01:37:48AM +0200, Jan-Simon M=C3=B6ller wrote:
> Thinking a bit more about this, I wonder if g2h(x) shouldn't itself alw=
ays=20
> return NULL on x =3D NULL ?=20

I agree this seems like a a better idea than modifying the users of g2h.

> Something like:
>=20
> Signed-off-by:  Jan-Simon M=C3=B6ller  <dl9pf@gmx.de>
>=20
> diff --git a/cpu-all.h b/cpu-all.h
> index 1a6a812..631f678 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -633,7 +633,7 @@ extern int have_guest_base;
>  #endif
>=20
>  /* All direct uses of g2h and h2g need to go away for usermode softmmu=
.  */
> -#define g2h(x) ((void *)((unsigned long)(x) + GUEST_BASE))
> +#define g2h(x) ( !x ? NULL:((void *)((unsigned long)(x) + GUEST_BASE))=
)
>  #define h2g(x) ({ \
>      unsigned long __ret =3D (unsigned long)(x) - GUEST_BASE; \
>      /* Check if given address fits target address space */ \
>=20
>=20
> I read the comment above, but before replacing it in user-mode (if poss=
ible),=20
> we should fix it ;) .
>=20
>=20
> Best,
> Jan-Simon
>=20
>=20
>=20