From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E37FC4646D for ; Sat, 11 Aug 2018 15:07:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E5C321C39 for ; Sat, 11 Aug 2018 15:07:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E5C321C39 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ZenIV.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727508AbeHKRmG (ORCPT ); Sat, 11 Aug 2018 13:42:06 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:41426 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727348AbeHKRmG (ORCPT ); Sat, 11 Aug 2018 13:42:06 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1foVUJ-0005VS-Bf; Sat, 11 Aug 2018 15:07:31 +0000 Date: Sat, 11 Aug 2018 16:07:31 +0100 From: Al Viro To: Richard Henderson Cc: Firoz Khan , linux-alpha@vger.kernel.org, ink@jurassic.park.msu.ru, mattst88@gmail.com, y2038@lists.linaro.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, arnd@arndb.de, deepa.kernel@gmail.com Subject: Re: [PATCH 3/6] alpha: Unify the not-implemented system call entry name Message-ID: <20180811150731.GG6515@ZenIV.linux.org.uk> References: <1531736638-15294-1-git-send-email-firoz.khan@linaro.org> <1531736638-15294-4-git-send-email-firoz.khan@linaro.org> <20180811000455.GC6515@ZenIV.linux.org.uk> <98937991-cefa-b7f3-11c3-12727b3159b1@twiddle.net> <20180811024553.GF6515@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 10, 2018 at 09:10:04PM -0700, Richard Henderson wrote: > On 08/10/2018 07:45 PM, Al Viro wrote: > > BTW, seeing that it's your code - why was unop used in > > alpha_ni_syscall? I don't remember the rules re pipeline > > stalls; is it that some earlier variants prefer unop to > > nop in such places? It's not that microoptimizing that > > one makes any difference, but just out of curiosity - > > would something like > > lda $0, -ENOSYS > > stq $sp, 0($sp) /* sp != 0 */ > > ret > > do just as well there? > > Oh that. Well, unop is a "load" and pairs with everything > on all cpus, where nop is an integer and doesn't always > pair. So I got into the habit of using unop for everything. > > The extra nop was so that lda + unop // stq + ret paired up > in in two cycles as opposed to lda /stall/ stq // ret in > three cycles on ev4+ev5. ev6 didn't care. FWIW. BTW, looking through old patches around entry.S, are you OK with this one? Same kind of macro as that for fork/vfork/clone glue... diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S index c64806a2daf5..828d641b4410 100644 --- a/arch/alpha/kernel/entry.S +++ b/arch/alpha/kernel/entry.S @@ -791,7 +791,7 @@ ret_from_kernel_thread: /* * Special system calls. Most of these are special in that they either - * have to play switch_stack games or in some way use the pt_regs struct. + * have to play switch_stack games. */ .macro fork_like name @@ -812,35 +812,25 @@ fork_like fork fork_like vfork fork_like clone +.macro sigreturn_like name .align 4 - .globl sys_sigreturn - .ent sys_sigreturn -sys_sigreturn: + .globl sys_\name + .ent sys_\name +sys_\name: .prologue 0 lda $9, ret_from_straced cmpult $26, $9, $9 lda $sp, -SWITCH_STACK_SIZE($sp) - jsr $26, do_sigreturn + jsr $26, do_\name bne $9, 1f jsr $26, syscall_trace_leave 1: br $1, undo_switch_stack br ret_from_sys_call -.end sys_sigreturn +.end sys_\name +.endm - .align 4 - .globl sys_rt_sigreturn - .ent sys_rt_sigreturn -sys_rt_sigreturn: - .prologue 0 - lda $9, ret_from_straced - cmpult $26, $9, $9 - lda $sp, -SWITCH_STACK_SIZE($sp) - jsr $26, do_rt_sigreturn - bne $9, 1f - jsr $26, syscall_trace_leave -1: br $1, undo_switch_stack - br ret_from_sys_call -.end sys_rt_sigreturn +sigreturn_like sigreturn +sigreturn_like rt_sigreturn .align 4 .globl alpha_ni_syscall