linux-kernel - Re: [PATCH 1/2] Add __compat_aligned_s64 and __compat_aligned

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Message-ID: <20131225181502.GA25627@gmail.com>
Date:	Wed, 25 Dec 2013 10:15:03 -0800
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	alan.cox@...el.com, Thomas Gleixner <tglx@...utronix.de>,
	tiwai@...e.de, perex@...ex.cz, alsa-devel@...a-project.org
Subject: Re: [PATCH 1/2] Add __compat_aligned_s64 and __compat_aligned_u64

On Wed, Dec 25, 2013 at 09:15:51AM -0800, H.J. Lu wrote:
> X32 uses the 32-bit compat layer for 32-bit kernel interface, which is
> also used by ia32.  But long long is 4-byte aligned for ia32 and 8-byte
> aligned for x32.  When the long long field in a system call struct has
> different offsets between ia32 and x32 due to alignment padding, like
> struct snd_ctl_elem_value in include/uapi/sound/asound.h, we need to
> either add a special case for x32 or we can use 4-byte aligned long
> long in the system call struct so that x32 can share the same compat
> system cal with ia32.  This patch adds __compat_aligned_s64 and
> __compat_aligned_u64 to include/uapi/asm-generic/int-ll64.h.  By
> default, they are the same as __s64/__u64.  It does the following
> things:
> 
> 1. Add default __compat_aligned_s64/__compat_aligned_u64 to
> include/uapi/asm-generic/int-ll64.h.
> 2. Add arch/x86/include/asm/types.h for kernel internal use, which is the
> same as before, i.e., <asm-generic/types.h>.
> 3. Change arch/x86/include/uapi/asm/types.h not to use the default
> include/uapi/asm-generic/int-ll64.h.  Instead, it has a modified copy
> of include/uapi/asm-generic/int-ll64.h with 4-byte aligned
> __compat_aligned_s64 and __compat_aligned_u64 for x32 and ia32.
> 
> When building x86 kernel, nothing is changed.  The difference is
> x32 can use 4-byte aligned long long for system calls so that it
> can share the same 32-bit compat system call with ia32.
> 
> Signed-off-by: H.J. Lu <hjl.tools@...il.com>
> ---
>  arch/x86/include/asm/types.h        |  6 ++++++
>  arch/x86/include/uapi/asm/types.h   | 35 ++++++++++++++++++++++++++++++++++-
>  include/uapi/asm-generic/int-ll64.h |  3 +++
>  3 files changed, 43 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/include/asm/types.h
...
> diff --git a/arch/x86/include/uapi/asm/types.h b/arch/x86/include/uapi/asm/types.h
> index 8e8c23f..7dac28b 100644
> --- a/arch/x86/include/uapi/asm/types.h
> +++ b/arch/x86/include/uapi/asm/types.h
...
> +#if defined(__i386__) || defined(__ILP32__)
> +typedef s64 __attribute__((aligned(4))) __compat_aligned_s64;
> +typedef u64 __attribute__((aligned(4))) __compat_aligned_u64;

Here are 2 typos. They should be __s64 and __u64.

> +#else
> +typedef __s64 __compat_aligned_s64;
> +typedef __u64 __compat_aligned_u64;
> +#endif

Here is the updated patch.

H.J.

View attachment "0001-Add-__compat_aligned_s64-and-__compat_aligned_u64.patch" of type "text/plain" (3818 bytes)