Re: [PATCH] man2 : syscall.2 : document syscall calling conventions

From: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>
To: Kyle McMartin <kyle-pfcGkIkfWfAsA/PxXw9srA@public.gmane.org>
Cc: "Michael Kerrisk (man-pages)"
	<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"linux-man" <linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Kyle McMartin <kyle-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Helge Deller <deller-Mmb7MZpHnFY@public.gmane.org>,
	"James E.J. Bottomley"
	<jejb-6jwH94ZQLHl74goWV3ctuw@public.gmane.org>,
	linux-parisc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] man2 : syscall.2 : document syscall calling conventions
Date: Sun, 7 Apr 2013 14:39:13 -0400	[thread overview]
Message-ID: <201304071439.15297.vapier@gentoo.org> (raw)
In-Reply-To: <20130407135514.GW12938-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>

[-- Attachment #1: Type: Text/Plain, Size: 884 bytes --]

On Sunday 07 April 2013 09:55:14 Kyle McMartin wrote:
> On Sun, Apr 07, 2013 at 12:00:50PM +0200, Michael Kerrisk (man-pages) wrote:
> > [Adding a few people to CC who may be able to help with Mike's doubts
> > on PA-RISC; folks, if any of you could have a quick look at the parisc
> > piece below, that would be helpful]
> 
> The syscall number is in %r20, everything else looks correct. The
> returned value is in %r28 and the args are %r26 through %r21.

just to be clear, the only insn you need is:
	ble 0x100(%sr2, %r0);

the kernel docs say sr2 holds the kernel gateway page (so i guess 0x100 is a 
known offset into that).  the docs don't mention r0 that i can see, so i'm 
guessing it's one of those "always 0" registers ?

the sysdep code has an ldi call in the branch delay slot (i think), but all 
that seems to do is load r20 with the syscall nr.
-mike

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 836 bytes --]