From owner-freebsd-arch  Mon Oct 29 21: 8: 9 2001
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Date: Mon, 29 Oct 2001 21:08:08 -0800
From: Marcel Moolenaar <marcel@xcllnt.net>
To: John Baldwin <jhb@FreeBSD.ORG>
Cc: arch@FreeBSD.ORG
Subject: Re: syscall() ABI questions
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References: <XFMail.011029021637.jhb@FreeBSD.org>
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On Mon, Oct 29, 2001 at 02:16:37AM -0800, John Baldwin wrote:
> I've got some questions about td->td_retval[1] and our syscall ABI.  On some
> archs (ia64, alpha) we preinitialie this value to 0.  On other archs (i386,
> sparc64, ppc) we set it to the value of the register it will be set to so that
> effectively this register's value is preserved across the syscall.  My question
> is do our syscall ABI's actually assume that for syscalls with only one return
> value that register isn't written to?  NetBSD recently changed their i386
> syscall code to preinitialize to 0 rather than %edx.  Anyone have the history
> on this?

I don't have the history, but I do know that Linux assumes %edx is
preserved. We may want to keep that in mind if for Linuxulator's
sake.

FYI,

-- 
 Marcel Moolenaar	  USPA: A-39004		 marcel@xcllnt.net

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