linux-kernel - Re: [DISCUSS] Making system calls more portable.

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Message-ID: <Pine.LNX.4.61.0701071156430.4365@yvahk01.tjqt.qr>
Date:	Sun, 7 Jan 2007 12:03:58 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Amit Choudhary <amit2030@...oo.com>
cc:	Rene Herman <rene.herman@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [DISCUSS] Making system calls more portable.

On Jan 7 2007 01:07, Amit Choudhary wrote:
>
>I will come to the main issue later but I just wanted to point out
>that we maintain information at two separate places - mapping
>between the name and the number in user space and kernel space.
>Shouldn't this duplication be removed.

For example? Do you plan on using "syscall strings" instead of
syscall numbers? I would not go for it. Comparing strings takes much
longer than comparing a register-size integer.

>Now, let's say a vendor has linux_kernel_version_1 that has 300
>system calls. The vendor needs to give some extra functionality to
>its customers and the way chosen is to implement new system call.
>The new system call number is 301. [...]

Umm, like with Internet addresses, you can't just reserve yourself
one you like. Including MACs on the local ethernet segment. Though
the MAC space is large with 2^48 or more, you can ARP spoof and
hinder the net.
In other words, if the vendor, or you, are going to use a
non-standard 301, you are supposed to run into problems, sooner or
later [Murphy's Law or Finagle's Corollary].
What you probably want is a syscall number range marked for private
use, much like there is for majors in /dev or 10.0.0.0/8 on inet.

	-`J'
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