linux-kernel - Re: [PATCH 08/10] Use __kernel_ulong_t in struct msqid64

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Message-ID: <4FB58EFD.7010302@zytor.com>
Date:	Thu, 17 May 2012 16:51:25 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"H.J. Lu" <hjl.tools@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	torvalds@...ux-foundation.org, mingo@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH 08/10] Use __kernel_ulong_t in struct msqid64_ds

On 05/17/2012 03:13 PM, H.J. Lu wrote:
> From: "H.J. Lu" <hjl.tools@...il.com>
> 
> Replace unsigned long with __kernel_ulong_t in struct msqid64_ds for
> user space.  Don't change unsigned long when __BITS_PER_LONG != 64
> since __kernel_ulong_t == unsigned long in this case.
> 
> Signed-off-by: H.J. Lu <hjl.tools@...il.com>

This patch and the one before it seems to have another problem: we
currently define __BITS_PER_LONG as:

#ifdef __x86_64__
# define __BITS_PER_LONG 64
#else
# define __BITS_PER_LONG 32
#endif

... which means __BITS_PER_LONG == 64 on x86-64.  This seems wrong.  The
result would seem to be that the padding members around __kernel_time_t
in struct shmid64_ds (not visible in patch 07/10 but existing in the
same structure) work by accident (I also wonder how the heck they're
currently supposed to work on bigendian architectures!!)

However, whereas struct shmid64_ds seems to work okay, this patch would
now seem to be wrong.

The sane thing would seem to be to change __BITS_PER_LONG to 32 on x32
and fix the padding hacks in struct shmid64_ds; H.J., would you agree?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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