Toshiharu Harada
harad****@gmail*****
2007年 11月 6日 (火) 07:17:51 JST
TOMOYO
ForkLKMLのsmack v10のスレッドで、「カーネル内の文字列パーサーは
良くない」というどこかで聞いたようなコメントに対して
Linusがこんなレスをつけています。
筋の通った良い、そして影響力のあるコメントです。
---------- Forwarded message ----------
From: Linus Torvalds <torvalds>
Date: 2007/11/06 1:21
Subject: Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser
On Mon, 5 Nov 2007, Ahmed S. Darwish wrote:
> On Sun, Nov 04, 2007 at 12:28:48PM +0000, Pavel Machek wrote:
> >
> > Can we avoid string parsers in the kernel?
> >
>
> Ok, Could someone suggest a better idea please ?.
I personally think string parsers are *much* better than the alternatives
(which basically boil down to nasty binary interfaces)
> I thought about packing the rules in a structure and sending
> it over an ioctl() command. Is this applicable ?
That's *MUCH* worse.
Strings are nice. They aren't that complex, and as long as it's not a
performance-critical area, there are basically no downsides.
Binary structures and ioctl's are *much* worse. They are totally
undebuggable with generic tools (think "echo" or "strace"), and they are a
total nightmare to parse across architectures and pointer sizes.
So the rule should be: always use strings if at all possible and relevant.
If the data is fundamentally binary, it shouldn't be re-coded to ascii (no
real advantage), but if the data is "stringish", and there aren't big
performance issues, then keep it as strings.
Linus
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