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=-6.8 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 17CBAC43143 for ; Mon, 1 Oct 2018 19:48:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC62C2146D for ; Mon, 1 Oct 2018 19:48:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=agner.ch header.i=@agner.ch header.b="wI2D8GAU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC62C2146D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=agner.ch 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 S1726313AbeJBC1f (ORCPT ); Mon, 1 Oct 2018 22:27:35 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:51606 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725994AbeJBC1f (ORCPT ); Mon, 1 Oct 2018 22:27:35 -0400 Received: from webmail.kmu-office.ch (unknown [IPv6:2a02:418:6a02::a3]) by mail.kmu-office.ch (Postfix) with ESMTPSA id E0D9F5C0172; Mon, 1 Oct 2018 21:48:10 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=agner.ch; s=dkim; t=1538423290; 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=HaUb5YWAAiWLBjmUatNG9APwicsr34uc4YX3x7sBRfs=; b=wI2D8GAUNtIlE3spT979Im1lSrURbD7jNYo3tkBHjwLgTcnccVa59NhsGBh/cKsGg61dBq HCAJq3cgjwOEjFvlHxt42KvJ1Esz5b7zA5fobncH3M2LNl1QeLrq5/BRv6USmrIBOceK64 mGfvqtfUMMUnBmI7kKVqTM+7LdT0HkE= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Mon, 01 Oct 2018 21:48:10 +0200 From: Stefan Agner To: Russell King - ARM Linux Cc: Joe Perches , arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ARM: disable ARMv6 for Clang older than 8.0 In-Reply-To: <20181001165342.GR30658@n2100.armlinux.org.uk> References: <20180930222230.24167-1-stefan@agner.ch> <20181001165342.GR30658@n2100.armlinux.org.uk> Message-ID: X-Sender: stefan@agner.ch User-Agent: Roundcube Webmail/1.3.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01.10.2018 18:53, Russell King - ARM Linux wrote: > On Sun, Sep 30, 2018 at 04:48:20PM -0700, Joe Perches wrote: >> On Mon, 2018-10-01 at 00:22 +0200, Stefan Agner wrote: >> > The kernel passes the ArmV6K architecture to the compiler when >> > using the multi platform selection and enabling ARMv6. Clang >> > older than version 8.0 emit assembly with an non-existing CPU, >> > which then makes the assembler fail. Prevent the user from >> > selecting ARMv6 when using Clang before 8.0. >> > >> > Signed-off-by: Stefan Agner >> > Link: https://github.com/ClangBuiltLinux/linux/issues/55 >> > --- >> > arch/arm/Kconfig | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig >> > index e8cd55a5b04c..8da160757381 100644 >> > --- a/arch/arm/Kconfig >> > +++ b/arch/arm/Kconfig >> > @@ -671,6 +671,7 @@ config ARCH_MULTI_V4_V5 >> > >> > config ARCH_MULTI_V6 >> > bool "ARMv6 based platforms (ARM11)" >> > + depends on !CC_IS_CLANG || CLANG_VERSION>=80000 >> > select ARCH_MULTI_V6_V7 >> > select CPU_V6K >> > >> >> Perhaps it'd be better to avoid this in selection >> criteria in Kconfig and instead add this to >> include/linux/compiler_clang.h >> --- >> include/linux/compiler-clang.h | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h >> index b1ce500fe8b3..90fd16c85359 100644 >> --- a/include/linux/compiler-clang.h >> +++ b/include/linux/compiler-clang.h >> @@ -3,6 +3,10 @@ >> #error "Please don't include directly, include instead." >> #endif >> >> +#if defined(CONFIG_ARCH_MULTI_V6) && CLANG_VERSION < 80000 >> +# error Sorry, your compiler is too old - please upgrade it. >> +#endif > > (a) does it makes sense to have arch CONFIG_* in linux/*.h? It could > instead go in arch/arm/kernel/asm-offsets.c, where we have the other > tests similar to this for GCC. > > (b) do we get far enough that the #error will be generated before the > reported assembler error happens? IOW, would the assembler error > mask this #error? > > I think it needs confirmation that a #error for this problem results > in the desired behaviour. Adding the above #error errors out before the assembler error happen in both cases. However, adding it to include/linux/compiler-clang.h leads to a bunch of warnings too: ... CC kernel/bounds.s In file included from :2: In file included from ././include/linux/compiler_types.h:59: ./include/linux/compiler-clang.h:7:2: error: "Sorry, your compiler is too old - please upgrade it." #error "Sorry, your compiler is too old - please upgrade it." ^ In file included from kernel/bounds.c:10: In file included from ./include/linux/page-flags.h:10: In file included from ./include/linux/bug.h:5: In file included from ./arch/arm/include/asm/bug.h:60: In file included from ./include/asm-generic/bug.h:18: In file included from ./include/linux/kernel.h:11: ./include/linux/bitops.h:53:41: warning: shift count >= width of type [-Wshift-count-overflow] return sizeof(w) == 4 ? hweight32(w) : hweight64(w); ^~~~~~~~~~~~ ./include/asm-generic/bitops/const_hweight.h:29:49: note: expanded from macro 'hweight64' #define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w)) ^~~~~~~~~~~~~~~~~~~~ ./include/asm-generic/bitops/const_hweight.h:21:76: note: expanded from macro '__const_hweight64' #define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32)) ^ ~~ ./include/asm-generic/bitops/const_hweight.h:20:49: note: expanded from macro '__const_hweight32' #define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16)) ^ ./include/asm-generic/bitops/const_hweight.h:19:48: note: expanded from macro '__const_hweight16' #define __const_hweight16(w) (__const_hweight8(w) + __const_hweight8((w) >> 8 )) ^ ./include/asm-generic/bitops/const_hweight.h:10:9: note: expanded from macro '__const_hweight8' ((!!((w) & (1ULL << 0))) + \ ^ Including it to arch/arm/kernel/asm-offsets.c does not lead to those warnings: ... CC kernel/bounds.s UPD include/generated/bounds.h CC arch/arm/kernel/asm-offsets.s arch/arm/kernel/asm-offsets.c:51:2: error: "Sorry, your compiler is too old - please upgrade it." #error "Sorry, your compiler is too old - please upgrade it." ^ 1 error generated. make[1]: *** [Kbuild:56: arch/arm/kernel/asm-offsets.s] Error 1 make: *** [Makefile:1100: prepare0] Error 2 -- Stefan