Re: [PATCH 6/7] remove all remaining _syscallX macros

David Woodhouse
2006-08-28T08:40:45Z

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