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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 581B9C43460 for ; Fri, 14 May 2021 08:53:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EC3C613DF for ; Fri, 14 May 2021 08:53:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233687AbhENIys (ORCPT ); Fri, 14 May 2021 04:54:48 -0400 Received: from gate.crashing.org ([63.228.1.57]:60419 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231145AbhENIyl (ORCPT ); Fri, 14 May 2021 04:54:41 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 14E8kuAV007787; Fri, 14 May 2021 03:46:56 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 14E8koYF007785; Fri, 14 May 2021 03:46:50 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 14 May 2021 03:46:49 -0500 From: Segher Boessenkool To: Masahiro Yamada Cc: Nathan Chancellor , Alexey Kardashevskiy , linuxppc-dev , Linux Kernel Mailing List , Linux Kbuild mailing list , clang-built-linux , Nick Desaulniers , Michal Marek , Michael Ellerman Subject: Re: [PATCH kernel v3] powerpc/makefile: Do not redefine $(CPP) for preprocessor Message-ID: <20210514084649.GI10366@gate.crashing.org> References: <20210513115904.519912-1-aik@ozlabs.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! On Fri, May 14, 2021 at 11:42:32AM +0900, Masahiro Yamada wrote: > In my best guess, the reason why powerpc adding the endian flag to CPP > is this line in arch/powerpc/kernel/vdso64/vdso64.lds.S > > #ifdef __LITTLE_ENDIAN__ > OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle") > #else > OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc") > #endif Which is equivalent to #ifdef __LITTLE_ENDIAN__ OUTPUT_FORMAT("elf64-powerpcle") #else OUTPUT_FORMAT("elf64-powerpc") #endif so please change that at the same time if you touch this :-) > __LITTLE_ENDIAN__ is defined by powerpc gcc and clang. This predefined macro is required by the newer ABIs, but all older compilers have it as well. _LITTLE_ENDIAN is not supported on all platforms (but it is if your compiler targets Linux, which you cannot necessarily rely on). These macros are PowerPC-specific. For GCC, for all targets, you can say #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ You do not need any of the other *ORDER__ macros in most cases. See "info cpp" for the sordid details. > [2] powerpc-linux-gnu-gcc + -mlittle-endian -> __LITTLE_ENDIAN__ is defined You can just write -mbig and -mlittle btw. Those aren't available on all targets, but neither are the long-winded -m{big,little}-endian option names. Pet peeve, I know :-) HtH, Segher