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=-2.3 required=3.0 tests=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 1F47CC83000 for ; Tue, 28 Apr 2020 23:43:08 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AC5902070B for ; Tue, 28 Apr 2020 23:43:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC5902070B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49BdVv2W7FzDqvx for ; Wed, 29 Apr 2020 09:43:03 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 49BdSN436dzDqtt for ; Wed, 29 Apr 2020 09:40:52 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 03SNelvK008990; Tue, 28 Apr 2020 18:40:47 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 03SNel35008989; Tue, 28 Apr 2020 18:40:47 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 28 Apr 2020 18:40:46 -0500 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: [PATCH v2] powerpc/64: BE option to use ELFv2 ABI for big endian kernels Message-ID: <20200428234046.GP17645@gate.crashing.org> References: <20200428112517.1402927-1-npiggin@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200428112517.1402927-1-npiggin@gmail.com> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi! On Tue, Apr 28, 2020 at 09:25:17PM +1000, Nicholas Piggin wrote: > +config BUILD_BIG_ENDIAN_ELF_V2 > + bool "Build big-endian kernel using ELFv2 ABI (EXPERIMENTAL)" > + depends on PPC64 && CPU_BIG_ENDIAN && EXPERT > + default n > + select BUILD_ELF_V2 > + help > + This builds the kernel image using the ELFv2 ABI, which has a > + reduced stack overhead and faster function calls. This does not > + affect the userspace ABIs. > + > + ELFv2 is the standard ABI for little-endian, but for big-endian > + this is an experimental option that is less tested (kernel and > + toolchain). This requires gcc 4.9 or newer and binutils 2.24 or > + newer. Is it clear that this is only for 64-bit? Maybe this text should fit that in somewhere? It's not obvious to people who do not already know that ELFv2 is just the (nick-)name of a particular ABI, not a new kind of ELF (it is just version 1 ELF in fact), and that ABI is for 64-bit Power only. Segher