Date: Wed, 3 Sep 2014 17:30:01 -0400 (EDT) From: Benjamin Kaduk <bjk@freebsd.org> To: Steven Stewart-Gallus <sstewartgallus00@mylangara.bc.ca> Cc: freebsd-hackers@freebsd.org Subject: Re: Can anyone help clarify details about the FreeBSD system call interface? Message-ID: <alpine.GSO.1.10.1409031725380.21571@multics.mit.edu> In-Reply-To: <fc15f845287.53ffbbde@langara.bc.ca> References: <fb4bf68f53c5.53ff77ee@langara.bc.ca> <alpine.GSO.1.10.1408281618310.21571@multics.mit.edu> <fc15f845287.53ffbbde@langara.bc.ca>
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On Thu, 28 Aug 2014, Steven Stewart-Gallus wrote:
> > svn blame says that the whole implementation dates from r1541.
> > Looks like
> > it was never implemented. Some googling indicates that it was a
> > plannedroutine to set the stack size, which was never implemented,
> > anywhere.
>
> > The locking comments were added in r79224, but the implementation is
> > otherwise from r1541, i.e., it was never implemented.
>
> Alright, so sys/kern/syscalls.master can be patched somewhat like so
> and I won't need to document them?
>
> -72 AUE_O_VADVISE STD { int ovadvise(int anom); } vadvise \
> - ovadvise_args int
> +72 AUE_NULL OBSOL ovadvise
>
> -70 AUE_SSTK STD { int sstk(int incr); }
> +70 AUE_SSTK OBSOL sstk
I don't think so; I think that would be a regression.
We do currently provide implementations for these syscalls, that just
happen to always return failure. I think that the OBSOL annotation
corresponds to a complete lack of implementation. Perhaps it would be
acceptable at a major release boundary, but this is not my area of
expertise.
> Okay, Linux has similar reserved system calls such as tuxcall. Linux
> deals with these by having an unimplemented.2 manpage which lists
> obsolete or reserved system calls. So we can just add to the manpage
> stuff like: afs3_syscall is a system call reserved for the use of the
> OpenAFS people.
I don't have any particular objection to such a thing existing, but I
wonder whether the developer time to create it could be better used on
other things. I guess it comes down to what value it is seen as
providing.
-Ben
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