linux-kernel - Re: [PATCH 6/7] remove all remaining

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Date:	Mon, 28 Aug 2006 09:40:36 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Andi Kleen <ak@...e.de>
Cc:	David Miller <davem@...emloft.net>, arnd@...db.de,
	linux-arch@...r.kernel.org, jdike@...toit.com, B.Steinbrink@....de,
	arjan@...radead.org, chase.venters@...entec.com, akpm@...l.org,
	rmk+lkml@....linux.org.uk, rusty@...tcorp.com.au,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] remove all remaining _syscallX macros

On Mon, 2006-08-28 at 10:28 +0200, Andi Kleen wrote:
> On Monday 28 August 2006 10:19, David Miller wrote:
> 
> > I see it as duplication because the person who writes the
> > kernel is the one who ends up writing the libc syscall
> > bits or explains to the libc person for that arch how
> > things work.  
> 
> And the way to explain it is to write the reference code.

That's a new and interesting thing to add to the list of things
that /usr/include/linux is _not_:

/usr/include/linux is _not_ a place to dump "reference code" in lieu of
documentation on using kernel interfaces.

Besides, the _syscallX implementations in the kernel were generally
unsuitable for use in that way anyway -- I'd be much more inclined to
rely on the libc version. The kernel version would do strange things
like break with PIC code by using an unavailable register (i386),
misalign 64-bit syscall arguments on 32-bit machines (MIPS), etc. 

> > And once one libc implmenetation of this 
> > exists, it can be used as a reference for other libc
> > variants.
> 
> At least on x86-64 various glibc versions had quite buggy
> syscall()s, that is why I never trusted it very much.

I assume these were very _early_ glibc in when the port was new? 

> > Finally, once it's done, it's done, and that's it.
> 
> Except if you still have to deal with old user land.

The limited subset of old userland which elected to use _syscallX()
instead of libc's syscall(), and which can be fixed fairly easily.

-- 
dwmw2

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