From: Yuri Tikhonov <yur@emcraft•com>
To: Scott Wood <scottwood@freescale•com>
Cc: Wolfgang Denk <wd@denx•de>, Detlev Zundel <dzu@denx•de>,
linux-kernel@vger•kernel.org, Milton Miller <miltonm@bga•com>,
linuxppc-dev@ozlabs•org, Al Viro <viro@ZenIV•linux.org.uk>,
Geert Uytterhoeven <Geert.Uytterhoeven@sonycom•com>,
Ilya Yanok <yanok@emcraft•com>
Subject: Re[2]: [PATCH] fork_init: fix division by zero
Date: Wed, 10 Dec 2008 20:56:51 +0300 [thread overview]
Message-ID: <527599002.20081210205651@emcraft.com> (raw)
In-Reply-To: <20081210172512.GA19584@ld0162-tx32.am.freescale.net>
=0D=0AHello Scott,
On Wednesday, December 10, 2008 you wrote:
> On Wed, Dec 10, 2008 at 01:29:12PM +0300, Yuri Tikhonov wrote:
>> On Wednesday, December 10, 2008 you wrote:
>> > x * y / z is parsed as (x * y) / z, not x * (y / z).
>>=20
>> Here we believe in preprocessor: since all PAGE_SIZE, 8, and=20
>> THREAD_SIZE are the constants we expect it will calculate this.
>>=20
>> E.g. here is the result from this line as produced by cross-gcc=20
>> 4.2.2:
>>=20
>> lis r9,0
>> rlwinm r29,r29,2,16,29
>> stw r29,0(r9)
>>=20
>> As you see - only rotate-left, i.e. multiplication to the constant.
> Yes, and also note that it is masking the result by 0xfffc, to preserve
> the effect of any overflow in (x * y).
Right, such a mask was the result of missed brackets. Now (see=20
"[PATCH][v2] fork_init: fix division by zero" I've just posted) the=20
situation is better:
lis r9,0
rlwinm r29,r29,2,0,29
stw r29,0(r9)
I.e. the mask is 0xFFFFFFFC.
Regards, Yuri
--
Yuri Tikhonov, Senior Software Engineer
Emcraft Systems, www.emcraft.com
prev parent reply other threads:[~2008-12-10 17:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-09 17:44 [PATCH] fork_init: fix division by zero Yuri Tikhonov
2008-12-10 8:44 ` Geert Uytterhoeven
2008-12-10 10:01 ` Re[2]: " Yuri Tikhonov
2008-12-10 10:17 ` Al Viro
2008-12-10 10:29 ` Re[2]: " Yuri Tikhonov
2008-12-10 13:06 ` David Howells
2008-12-10 13:09 ` David Howells
2008-12-10 13:15 ` Geert Uytterhoeven
2008-12-10 13:25 ` Re[4]: " Yuri Tikhonov
2008-12-10 21:50 ` Re[2]: " Paul Mackerras
2008-12-10 17:25 ` Scott Wood
2008-12-10 17:56 ` Yuri Tikhonov [this message]
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