linux-kernel - Re: [PATCH 02/15] arm: __NR

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Message-ID: <CAJfpegvZ-n4sT0ojj9iUg_R5gMZHT0caad6TpOdcmF=pdiXkqg@mail.gmail.com>
Date:	Fri, 11 Apr 2014 13:50:50 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arch <linux-arch@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>
Subject: Re: [PATCH 02/15] arm: __NR_syscalls fix

On Fri, Apr 11, 2014 at 12:33 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Fri, Apr 11, 2014 at 12:25:38PM +0200, Miklos Szeredi wrote:
>> From: Miklos Szeredi <mszeredi@...e.cz>
>>
>> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
>> Cc: Russell King <linux@....linux.org.uk>
>> ---
>
> This has me wondering...
>
> (a) what you think it fixes
> (b) whether you tried to build-test this
>
> The ARM instruction set supports 8-bit immediate constants with an even
> power of two shift.  384 fits that (0x180), 382 does not (0x17e), and
> in your following patch, 383 definitely doesn't (0x17f).
>
> Having this constant larger than necessary does not cause any problem
> for the syscall table: we explicitly pad it with calls to sys_ni_syscall
> to make up the difference.

Yes, and the padding will be of wrong length if NR_syscalls is
incorrect (which may be Oopsable?).  At least that is my impression
from a casual glance.

Thanks,
Miklos
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