linux-kernel - Re: [RFC][3/11][MANUX] Kernel compatibility : syscall numbers

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Date:	Wed, 16 Apr 2014 12:23:12 +0200
From:	Emmanuel Colbus <ecolbus@...ux.info>
To:	Clemens Ladisch <clemens@...isch.de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][3/11][MANUX] Kernel compatibility : syscall numbers

Le 16/04/2014 09:03, Clemens Ladisch a écrit :
> Emmanuel Colbus wrote:
>> I have a question regarding vector 0x80.
>>
>> As I mentionned earlier, my OS's internals are very different from
>> Linux's, thus I have had a need for a few new syscalls. Since I wanted
>> to avoid any collision with Linux
> 
> ... you could just use another vector, such as 0x81.
> 
>> but I also wanted to keep the ability to put the syscall table in
>> a single 4096-byte page on 64-bit computers (on which I hope to run
>> one day), I chose to start taking syscall number 511, and to progress
>> downwards - currently, I'm using numbers 511 through 501 included
> 
> These implementation details do not need to show up in the interface:
> 
> int syscall_0x81(int nr, ...)
> {
>     if (nr in range)
>         return table[511 - nr](...);
> }
> 
> 
> Regards,
> Clemens
> 

This would stop working as soon as I implemented any syscall/sysret or
sysenter/sysexit-like thing, as this technique has no notion of a
syscall vector.

Regards,

Emmanuel
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