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=-23.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 57671C433ED for ; Tue, 13 Apr 2021 22:35:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2F4CD611AD for ; Tue, 13 Apr 2021 22:35:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245471AbhDMWfW (ORCPT ); Tue, 13 Apr 2021 18:35:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242024AbhDMWfS (ORCPT ); Tue, 13 Apr 2021 18:35:18 -0400 Received: from mail-lj1-x231.google.com (mail-lj1-x231.google.com [IPv6:2a00:1450:4864:20::231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C1E5C061574 for ; Tue, 13 Apr 2021 15:34:57 -0700 (PDT) Received: by mail-lj1-x231.google.com with SMTP id c1so12895462ljd.7 for ; Tue, 13 Apr 2021 15:34:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=oJF6w+JMTuSZop9MJMz4VsonUaLscE7+OcJe1MsA8rs=; b=mrN0gs90E2s0BVMUOyeWeaGz1g8mVcNUJCd+5Gyy0lQB52oynNlljqHL5R0IE7XHID h76cr16sVfJzHCMoGA+Jfw2fTlcV8/MLikLzQ1WWExYh399Qat6jYXlaCd33GSg7LH82 EB5OMC81jUNotlwWuwD61uusbcT86UdE+5BsuI0y9sa1m/IcmUGy7SE8b7ZIHgdGDbP1 Y+kuQNl8IAgi853zsyiGp0Estdzgl6V1ewNNt2KMHPtfd9YklAtdDvBT6879mW3NoxVQ QFbOvpe3uiHTDMwKei2FppUZVbb4CxBCOWQGEL2GMQJzvUfHSkivgdO2Iu9bMwdnoAXn D/Xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=oJF6w+JMTuSZop9MJMz4VsonUaLscE7+OcJe1MsA8rs=; b=XCUa8N02JdxEH5RXcx09TvaDaTPhYyiZ0ZcJ+mPcF6ttdDL1sdPSdVfqPcImXnEVEW glQvWrXcU8872QRK8M0yTvWBYD4yuxJdnfoypA7bkgfXyQq3XjbOpsrvcPLiXH8iKkbh N4R3ZLa1cE+n+8FcraVM/9snEeQSB03NAmkFCLKxTc1hH9TtJaZxEzQsQ6B4aSQsk528 j2RD10KJ+nRqy3QDFD38nvBR87Df0EtEB7sSkzXv2mf4b7zX7/aY94+93E0msYitdkUj yYfNBGLsd0dom8D25hgeZ5Ky352fUy2n5gT9Err0gG0MxRCDQf1XIYWOgr4xqznKItrM 5kPg== X-Gm-Message-State: AOAM530ZdEoKyY7XX59b5frVpOP8kqnmVBhXD+vZ/UKMxjhKh/7bNFDZ cXYEfAaitaS9Kelo7bCINZXyWnwteLhKpL+O9FJqcw== X-Google-Smtp-Source: ABdhPJywJvJykScNB0Pa4H5oDn8OG/n14hS5yH9qaZ5p8dkYGYO69v0m2ikASEzrYT/xSTPFumMxKwkSLU1X4CJ+ZL0= X-Received: by 2002:a2e:b817:: with SMTP id u23mr4995069ljo.116.1618353295626; Tue, 13 Apr 2021 15:34:55 -0700 (PDT) MIME-Version: 1.0 References: <20210413153408.3027270-1-yhs@fb.com> <20210413153413.3027426-1-yhs@fb.com> In-Reply-To: From: Nick Desaulniers Date: Tue, 13 Apr 2021 15:34:44 -0700 Message-ID: Subject: Re: [PATCH bpf-next v3 1/5] selftests: set CC to clang in lib.mk if LLVM is set To: Yonghong Song Cc: Andrii Nakryiko , bpf , Andrii Nakryiko , Arnaldo Carvalho de Melo , Kernel Team , Sedat Dilek , Masahiro Yamada Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Apr 13, 2021 at 3:27 PM Yonghong Song wrote: > > > > On 4/13/21 3:13 PM, Nick Desaulniers wrote: > > On Tue, Apr 13, 2021 at 3:05 PM Andrii Nakryiko > > wrote: > >> > >> On Tue, Apr 13, 2021 at 8:34 AM Yonghong Song wrote: > >>> > >>> selftests/bpf/Makefile includes lib.mk. With the following command > >>> make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel > >>> make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1 V=1 > >>> some files are still compiled with gcc. This patch > >>> fixed lib.mk issue which sets CC to gcc in all cases. > >>> > >>> Cc: Sedat Dilek > >>> Signed-off-by: Yonghong Song > >>> --- > >>> tools/testing/selftests/lib.mk | 4 ++++ > >>> 1 file changed, 4 insertions(+) > >>> > >>> diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > >>> index a5ce26d548e4..9a41d8bb9ff1 100644 > >>> --- a/tools/testing/selftests/lib.mk > >>> +++ b/tools/testing/selftests/lib.mk > >>> @@ -1,6 +1,10 @@ > >>> # This mimics the top-level Makefile. We do it explicitly here so that this > >>> # Makefile can operate with or without the kbuild infrastructure. > >>> +ifneq ($(LLVM),) > >>> +CC := clang > >> > >> Does this mean that cross-compilation with Clang doesn't work at all > >> or is achieved in some other way? > > > > Right, this probably doesn't support cross compilation w/ Clang. > > Rather than invoke `$(CROSS_COMPILE) clang`, you'd do `clang > > --target=$(CROSS_COMPILE)`. Even then, cross linking executables is > > hairy. But at least this should enable native compilation, which is a > > start. > > See https://clang.llvm.org/docs/CrossCompilation.html. > As Nick said, clang prefers --target=$(CROSS_COMPILE) to > indicate cross compilation. User can pass additional > flags (CFLAGS) for cross compilation for the time being. > This is the same as main kernel Makefile. > > ifneq ($(LLVM),) > CC = clang > LD = ld.lld > AR = llvm-ar > NM = llvm-nm > OBJCOPY = llvm-objcopy > OBJDUMP = llvm-objdump > READELF = llvm-readelf > STRIP = llvm-strip > else > CC = $(CROSS_COMPILE)gcc > LD = $(CROSS_COMPILE)ld > AR = $(CROSS_COMPILE)ar > NM = $(CROSS_COMPILE)nm > OBJCOPY = $(CROSS_COMPILE)objcopy > OBJDUMP = $(CROSS_COMPILE)objdump > READELF = $(CROSS_COMPILE)readelf > STRIP = $(CROSS_COMPILE)strip > endif Right, then later in the top level Makefile to achieve cross compilation support 569 ifneq ($(CROSS_COMPILE),) 570 CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) ... The top level Makefile has this all wired up correctly; I wonder if tools/ could make use of the existing exports, rather than redoing all of that work? > > >> > >> > >>> +else > >>> CC := $(CROSS_COMPILE)gcc > >>> +endif > >>> > >>> ifeq (0,$(MAKELEVEL)) > >>> ifeq ($(OUTPUT),) > >>> -- > >>> 2.30.2 > >>> > > > > > > -- Thanks, ~Nick Desaulniers