From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Wed, 04 Mar 2009 15:44:37 +0000 (GMT) Received: from localhost.localdomain ([127.0.0.1]:7066 "EHLO h5.dl5rb.org.uk") by ftp.linux-mips.org with ESMTP id S21365601AbZCDPof (ORCPT ); Wed, 4 Mar 2009 15:44:35 +0000 Received: from h5.dl5rb.org.uk (localhost.localdomain [127.0.0.1]) by h5.dl5rb.org.uk (8.14.3/8.14.3) with ESMTP id n24FiQlo019538; Wed, 4 Mar 2009 15:44:26 GMT Received: (from ralf@localhost) by h5.dl5rb.org.uk (8.14.3/8.14.3/Submit) id n24FiIYL019535; Wed, 4 Mar 2009 15:44:18 GMT Date: Wed, 4 Mar 2009 15:44:18 +0000 From: Ralf Baechle To: Brian Foster Cc: David Daney , "Maciej W. Rozycki" , linux-mips@linux-mips.org, libc-ports@sourceware.org, "Maciej W. Rozycki" Subject: Re: [PATCH, RFC] MIPS: Implement the getcontext API Message-ID: <20090304154418.GA13464@linux-mips.org> References: <49AD6139.60209@caviumnetworks.com> <200903040919.29294.brian.foster@innova-card.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200903040919.29294.brian.foster@innova-card.com> User-Agent: Mutt/1.5.18 (2008-05-17) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 22000 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Wed, Mar 04, 2009 at 09:19:28AM +0100, Brian Foster wrote: > On Tuesday 03 March 2009 17:56:25 David Daney wrote: > >[ ... ] > > When (and if) we move the sigreturn trampoline to a vdso we should be > > able to maintain the ABI. > > it's more a matter of “when” rather than “if”. > there is still an intention here to use XI (we > have SmartMIPS), which requires not using the > signal (or FP) trampoline on the stack. > > moving the signal trampoline to a vdso (which > is(? was?) called, maybe misleadingly, ‘vsyscall’, > on other architectures) is the obvious solution to > that part of the puzzle. and yes, it is possible > to maintain the ABI; the signal trampoline is still > also put on the stack, and modulo XI, would work if > used — the trampoline-on-stack is simply not used > if there is a vdso with the signal trampoline. We generally want to get rid of stack trampolines. Trampolines require cacheflushing which especially on SMP systems can be a rather expensive operation. Ralf