linux-kernel - Re: [tip:x86/x32] x32: Fix alignment fail in struct compat

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Message-ID: <4F61278A.4000908@zytor.com>
Date:	Wed, 14 Mar 2012 16:19:38 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"H.J. Lu" <hjl.tools@...il.com>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/x32] x32: Fix alignment fail in struct compat_siginfo

On 03/14/2012 04:17 PM, H.J. Lu wrote:
> 
> Just for the record, although the offsets of _utime and _stime are
> multiple of 8 bytes, struct siginfo is only aligned at 4 bytes.  So
> the addresses of  _utime and _stime may not be 8byte aligned.
> But misaligned int64 load/store are OK for x86-64.
> 

Yes; the real question I guess is where struct siginfo appears and if it
is misaligned by construction.  It obviously appears in the signal stack
frame but also in a couple of system calls.  It might be possible to put
an __attribute__((aligned(8))) on the whole structure in the x32 case?

	-hpa
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