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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 B82F1C48BD5 for ; Tue, 25 Jun 2019 17:00:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96B662064A for ; Tue, 25 Jun 2019 17:00:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729409AbfFYRAb (ORCPT ); Tue, 25 Jun 2019 13:00:31 -0400 Received: from foss.arm.com ([217.140.110.172]:45714 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728506AbfFYRAa (ORCPT ); Tue, 25 Jun 2019 13:00:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E699F360; Tue, 25 Jun 2019 10:00:29 -0700 (PDT) Received: from [10.1.196.72] (e119884-lin.cambridge.arm.com [10.1.196.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BEB0F3F718; Tue, 25 Jun 2019 10:00:28 -0700 (PDT) Subject: Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build To: Nick Desaulniers Cc: Qian Cai , Thomas Gleixner , Will Deacon , Catalin Marinas , Linux ARM , "linux-kernel@vger.kernel.org" , Nathan Chancellor References: <1561464964.5154.63.camel@lca.pw> <1561467369.5154.67.camel@lca.pw> <00a78980-6b9c-5d5b-ed01-b28bb34be022@arm.com> <1561470705.5154.68.camel@lca.pw> <5113362e-1256-6712-6ce8-9599b1806cf1@arm.com> <1561472887.5154.72.camel@lca.pw> <668bbe72-b32b-8cee-ccad-d1f6110c6728@arm.com> From: Vincenzo Frascino Message-ID: <193c179e-16ca-4b4e-2584-75e8f6c1819f@arm.com> Date: Tue, 25 Jun 2019 18:00:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------C25D41F534D1DAA79714818A" Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------C25D41F534D1DAA79714818A Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Hi Nick, On 25/06/2019 17:26, Nick Desaulniers wrote: > On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino > wrote: >> >> Hi Qian, >> >> ... >> >>> >>> but clang 7.0 is still use in many distros by default, so maybe this commit can >>> be fixed by adding a conditional check to use "small" if clang version < 8.0. >>> >> >> Could you please verify that the patch below works for you? > > Should it be checking against CONFIG_CLANG_VERSION, or better yet be > using cc-option macro? > This is what I did in my proposed patch, but I was surprised that clang-7 generates relocations that clang-8 does not. LD arch/arm64/kernel/vdso/vdso.so.dbg VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg 00000000000009d0 R_AARCH64_JUMP_SLOT _mcount arch/arm64/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported make[1]: *** [arch/arm64/kernel/vdso/Makefile:59: arch/arm64/kernel/vdso/vdso.so.dbg] Error 1 make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2 This is the the result of the macro I introduced in lib/vdso/Makefile. And I just found out why. I forgot to add a "+" in the patch provided :) @Qian: Could you please retry with the one provided below? -- Regards, Vincenzo --->8---- --------------C25D41F534D1DAA79714818A Content-Type: text/x-patch; name="0001-arm64-vdso-Fix-compilation-with-clang-8.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-arm64-vdso-Fix-compilation-with-clang-8.patch" >From eed9ea23cf999d31b87db4b98a8e9de209706132 Mon Sep 17 00:00:00 2001 From: Vincenzo Frascino Date: Tue, 25 Jun 2019 15:49:37 +0100 Subject: [PATCH] arm64: vdso: Fix compilation with clang < 8 clang versions previous to 8 do not support -mcmodel=tiny. Add a check to the vDSO Makefile for arm64 to remove the flag when these versions of the compiler are detected. Reported-by: Qian Cai Signed-off-by: Vincenzo Frascino --- arch/arm64/kernel/vdso/Makefile | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile index ec81d28aeb5d..5154f50aff2d 100644 --- a/arch/arm64/kernel/vdso/Makefile +++ b/arch/arm64/kernel/vdso/Makefile @@ -38,6 +38,11 @@ else CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -include $(c-gettimeofday-y) endif +# Clang versions less than 8 do not support -mcmodel=tiny +ifeq ($(shell test $(CONFIG_CLANG_VERSION) -lt 80000; echo $$?),0) +CFLAGS_REMOVE_vgettimeofday.o += -mcmodel=tiny +endif + # Disable gcov profiling for VDSO code GCOV_PROFILE := n -- 2.22.0 --------------C25D41F534D1DAA79714818A--