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Re: 64-bit and N32 kernel interfaces

To: Jun Sun <jsun@mvista.com>
Subject: Re: 64-bit and N32 kernel interfaces
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 4 Sep 2002 20:40:38 +0200
Cc: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, linux-mips@linux-mips.org
In-reply-to: <3D7643BA.6090807@mvista.com>; from jsun@mvista.com on Wed, Sep 04, 2002 at 10:32:42AM -0700
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On Wed, Sep 04, 2002 at 10:32:42AM -0700, Jun Sun wrote:

> > The primary problem is the differnet calling sequence for o32 and N64.
> > As it looks we'll be able to use either the o32 function or the native
> > syscall to implement all of the necessary N32 syscalls.
> 
> For 64bit kernel, do we intend to have one syscall table that support o32,
> n32 and n64 altogether?  Or we will have multiple tables for them?

Several approach to solve that problem.  Adding another 1000 entries - which
will cost 8000 bytes of memory that will be mostly zeros.  Having wrappers
for each function that do the appropriate argument and result convertion
is another.  etc.

> > The question is if we want to reserve another 1000 entries in our already
> > huge syscall table for N32 or if we got a better solution ...
> 
> It seems n32 can be naturally implemented through n64 syscalls, although I am 
> sure there are some nasty details to work out.

Unfortunately there are ...

> Where can I find n32/n64 spec?

mipsabi.org which is no longer online.  Anyway, I don't think there is a
formal published N32 spec.  And this whole thread is about the syscall
interface.  That isn't part of any ABI spec.

  Ralf

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