Subject: Re: [PATCH 6/7] remove all remaining _syscallX macros
From: David Woodhouse <dwmw2@infradead.org>
To: Andi Kleen <ak@suse.de>
Cc: David Miller <davem@davemloft.net>, arnd@arndb.de,
       linux-arch@vger.kernel.org, jdike@addtoit.com, B.Steinbrink@gmx.de,
       arjan@infradead.org, chase.venters@clientec.com, akpm@osdl.org,
       rmk+lkml@arm.linux.org.uk, rusty@rustcorp.com.au,
       linux-kernel@vger.kernel.org
In-Reply-To: <200608281028.13652.ak@suse.de>
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	 <20060828.011929.66059812.davem@davemloft.net>
	 <200608281028.13652.ak@suse.de>
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Date: Mon, 28 Aug 2006 09:40:36 +0100
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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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