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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 38AD0C282C4 for ; Tue, 12 Feb 2019 19:26:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EED7E222C6 for ; Tue, 12 Feb 2019 19:26:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=agner.ch header.i=@agner.ch header.b="OFoUjrv+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732339AbfBLT0j (ORCPT ); Tue, 12 Feb 2019 14:26:39 -0500 Received: from mail.kmu-office.ch ([178.209.48.109]:43232 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729500AbfBLT0i (ORCPT ); Tue, 12 Feb 2019 14:26:38 -0500 Received: from webmail.kmu-office.ch (unknown [IPv6:2a02:418:6a02::a3]) by mail.kmu-office.ch (Postfix) with ESMTPSA id 012025C08D0; Tue, 12 Feb 2019 20:26:36 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=agner.ch; s=dkim; t=1549999596; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vMAsB1iZFN1YlAUlS1QoRPtJAL//cY9F2EkH1ZgpbxQ=; b=OFoUjrv+26oYRTa6vjpk2jFsvuaxdACurbDjQXyvlQ3O+WC+SwFgAazXGvEeNaStYK/yrL 9q/W9tn0lGUDILBNx+CEP7m2fd8I+sYdgWl/AbLcYMBsEYMqJ/p16PRSDrK9PCpuYV76nS YDGPDKuIrIqF8V7JSy61tTMMDjYEelA= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Tue, 12 Feb 2019 20:26:35 +0100 From: Stefan Agner To: Nick Desaulniers Cc: Russell King , Nathan Chancellor , Arnd Bergmann , Ard Biesheuvel , Nicolas Pitre , Thierry Reding , Will Deacon , julien.thierry@arm.com, Mark Rutland , LKML , Linux ARM Subject: Re: [PATCH 4/5] ARM: use unified assembler in c files In-Reply-To: References: Message-ID: X-Sender: stefan@agner.ch User-Agent: Roundcube Webmail/1.3.7 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11.02.2019 19:17, Nick Desaulniers wrote: > On Sat, Feb 9, 2019 at 9:28 AM Stefan Agner wrote: >> >> Thanks for the reviews so far. >> >> During some more testing I stumbled upon another issue: >> >> On 07.02.2019 10:48, Stefan Agner wrote: >> > Use unified assembler syntax (UAL) in inline assembler. Divided >> > syntax is considered depricated. This will also allow to build >> > the kernel using LLVM's integrated assembler. >> > >> > Signed-off-by: Stefan Agner >> > --- >> > arch/arm/mm/copypage-v4mc.c | 2 +- >> > arch/arm/mm/copypage-v4wb.c | 2 +- >> > arch/arm/mm/copypage-v4wt.c | 2 +- >> > 3 files changed, 3 insertions(+), 3 deletions(-) >> > >> > diff --git a/arch/arm/mm/copypage-v4mc.c b/arch/arm/mm/copypage-v4mc.c >> > index b03202cddddb..b19c7ad1a6de 100644 >> > --- a/arch/arm/mm/copypage-v4mc.c >> > +++ b/arch/arm/mm/copypage-v4mc.c >> > @@ -56,7 +56,7 @@ static void mc_copy_user_page(void *from, void *to) >> > ldmia %0!, {r2, r3, ip, lr} @ 4\n\ >> > subs %2, %2, #1 @ 1\n\ >> > stmia %1!, {r2, r3, ip, lr} @ 4\n\ >> > - ldmneia %0!, {r2, r3, ip, lr} @ 4\n\ >> > + ldmiane %0!, {r2, r3, ip, lr} @ 4\n\ >> > bne 1b @ " >> > : "+&r" (from), "+&r" (to), "=&r" (tmp) >> > : "2" (PAGE_SIZE / 64) >> > diff --git a/arch/arm/mm/copypage-v4wb.c b/arch/arm/mm/copypage-v4wb.c >> > index cd3e165afeed..6e3c9b69dd25 100644 >> > --- a/arch/arm/mm/copypage-v4wb.c >> > +++ b/arch/arm/mm/copypage-v4wb.c >> > @@ -38,7 +38,7 @@ static void v4wb_copy_user_page(void *kto, const void *kfrom) >> > ldmia %1!, {r3, r4, ip, lr} @ 4\n\ >> > subs %2, %2, #1 @ 1\n\ >> > stmia %0!, {r3, r4, ip, lr} @ 4\n\ >> > - ldmneia %1!, {r3, r4, ip, lr} @ 4\n\ >> > + ldmiane %1!, {r3, r4, ip, lr} @ 4\n\ >> > bne 1b @ 1\n\ >> > mcr p15, 0, %1, c7, c10, 4 @ 1 drain WB" >> > : "+&r" (kto), "+&r" (kfrom), "=&r" (tmp) >> > diff --git a/arch/arm/mm/copypage-v4wt.c b/arch/arm/mm/copypage-v4wt.c >> > index 8614572e1296..4a40fa1cbc2a 100644 >> > --- a/arch/arm/mm/copypage-v4wt.c >> > +++ b/arch/arm/mm/copypage-v4wt.c >> > @@ -34,7 +34,7 @@ static void v4wt_copy_user_page(void *kto, const void *kfrom) >> > ldmia %1!, {r3, r4, ip, lr} @ 4\n\ >> > subs %2, %2, #1 @ 1\n\ >> > stmia %0!, {r3, r4, ip, lr} @ 4\n\ >> > - ldmneia %1!, {r3, r4, ip, lr} @ 4\n\ >> > + ldmiane %1!, {r3, r4, ip, lr} @ 4\n\ >> > bne 1b @ 1\n\ >> > mcr p15, 0, %2, c7, c7, 0 @ flush ID cache" >> > : "+&r" (kto), "+&r" (kfrom), "=&r" (tmp) >> >> When compiling with gcc, this leads to: >> >> /tmp/ccrvA1wy.s: Assembler messages: >> /tmp/ccrvA1wy.s:180: Error: bad instruction `ldmiane r0!,{r3,r4,ip,lr}' >> make[1]: *** [scripts/Makefile.build:277: arch/arm/mm/copypage-v4wb.o] >> Error 1 >> make: *** [Makefile:1042: arch/arm/mm] Error 2 >> >> Unfortunately, the gcc option -masm-syntax-unified which allows unified >> syntax in inline assembly is broken (see also >> https://lkml.org/lkml/2019/1/7/1320). >> >> So this requires to sprinkle those inline assembly with ".syntax >> unified" strings, similar to how I've done it in uaccess.h. > > Not sure if this is purely a bug in GCC; Clang treats inline asm > statements as unique, so asm directives do not carry over from one > inline asm statement to another. This has caused issues in other > arch's inline assembly, where we need to repeat asm directives > repeatedly for each inline asm statement. > https://bugs.llvm.org/show_bug.cgi?id=19749 I don't think that this Clang bug is related. GCC always emits a ".syntax xxx". The -masm-syntax-unified flag allows to select unified syntax, but it is broken in current GCC releases. I reported the bug and sent a fix to the GCC community, the upcoming GCC 9, as well as 7 and 8 bugfix releases, will have it fixed. See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88648 -- Stefan