linux-kernel - Re: [PATCH] filldir write data missing size

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Date:	Mon, 21 Jul 2008 11:48:38 -0400
From:	Yoshinori Sato <ysato@...rs.sourceforge.jp>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] filldir write data missing size

At Sun, 20 Jul 2008 05:11:29 +0900,
OGAWA Hirofumi wrote:
> 
> Yoshinori Sato <ysato@...rs.sourceforge.jp> writes:
> 
> >> > -		if (__put_user(offset, &dirent->d_off))
> >> > +		if (__put_user((unsigned long)offset, &dirent->d_off))
> >> 
> >> Um.. __put_user() should be already doing it automatically..
> >
> > I'm mistake.
> >
> > I checked object, and found bad code.
> > This problem fix __put_user.
> 
> Um.. Could you explain the detail of problem? Is this a workaround or
> something for the bug of some compiler?  If so, shouldn't we fix
> __put_user() instead of caller?
> 
> E.g. the following or something fixes it? (btw, this is for x86)
> 
> #define __put_user(x, ptr) ({						\
>  	/* Since some compiler generates wrong code, we need __v.?? */	\
>         __typeof__(*(ptr)) __v = (x);					\
> 	__put_user_nocheck(__v, (ptr), sizeof(*(ptr)));			\
> })
> -- 
> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

This problem is sh-linux-gcc v4.1.2 and target sh2(a)-bigendian.

"__put_user(s64, u32_ptr)" compiled.

Correct code.
*u32_ptr = s64 & 0xffffffff;

Bad code.
*u32_ptr = s64 >> 32;

I'm add cast put_user 4byte case.

-- 
Yoshinori Sato
<ysato@...rs.sourceforge.jp>
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