From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Schwab Subject: Re: Add private syscalls to support NPTL Date: Wed, 19 Aug 2009 10:35:39 +0200 Message-ID: References: <4A89D037.7090807@codesourcery.com> <20090818022850.GA17279@cynthia.pants.nu> <4A8A532E.6060709@codesourcery.com> <20090818234017.GA32464@cynthia.pants.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx2.redhat.com ([66.187.237.31]:57442 "EHLO mx2.redhat.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750923AbZHSIh5 (ORCPT ); Wed, 19 Aug 2009 04:37:57 -0400 In-Reply-To: <20090818234017.GA32464@cynthia.pants.nu> (Brad Boyer's message of "Tue, 18 Aug 2009 16:40:17 -0700") Sender: linux-m68k-owner@vger.kernel.org List-Id: linux-m68k@vger.kernel.org To: Brad Boyer Cc: Maxim Kuvyrkov , Geert Uytterhoeven , linux-m68k@vger.kernel.org Brad Boyer writes: > On Tue, Aug 18, 2009 at 11:07:26AM +0400, Maxim Kuvyrkov wrote: >> The reason for this calling convention is to minimize difference in >> invokation of the vDSO helper and the syscall. The helper gets its >> arguments in a0 (mem), d0 (oldval) and d1 (newval); in a stub, which is >> used when vDSO is not available, one then can do: >> >> movel %d0,%a1 >> movel #NR,%d0 >> trap #0 > > Then wouldn't it make sense to use %d2 instead of %a1? d2 is a callee-saved register, a1 isn't. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."