Date: Tue, 30 Oct 2001 04:07:56 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: John Baldwin <jhb@FreeBSD.ORG> Cc: <arch@FreeBSD.ORG> Subject: Re: syscall() ABI questions Message-ID: <20011030035059.L12873-100000@delplex.bde.org> In-Reply-To: <XFMail.011029021637.jhb@FreeBSD.org>
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On Mon, 29 Oct 2001, 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? Not me. It's older than FreeBSD-1.1. It seems to be just a pessimization to preinitialize retval[1]. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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