From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id CE4B31F55B for ; Tue, 2 Jun 2020 01:43:08 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 1A564383E806; Tue, 2 Jun 2020 01:43:03 +0000 (GMT) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by sourceware.org (Postfix) with ESMTP id B9A7D38708F9; Tue, 2 Jun 2020 01:42:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org B9A7D38708F9 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=segher@kernel.crashing.org Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 0521gSr7013590; Mon, 1 Jun 2020 20:42:29 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 0521gSOw013589; Mon, 1 Jun 2020 20:42:28 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 1 Jun 2020 20:42:27 -0500 From: Segher Boessenkool To: Joseph Myers Subject: Re: ppc64le and 32-bit LE userland compatibility Message-ID: <20200602014227.GM31009@gate.crashing.org> References: <2047231.C4sosBPzcN@sheen> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: libc-alpha@sourceware.org, eery@paperfox.es, daniel@octaforge.org, musl@lists.openwall.com, Will Springer , binutils@sourceware.org, libc-dev@lists.llvm.org, linuxppc-dev@lists.ozlabs.org Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Hi Joseph, On Mon, Jun 01, 2020 at 09:28:25PM +0000, Joseph Myers wrote: > On Fri, 29 May 2020, Will Springer via Binutils wrote: > > > Hey all, a couple of us over in #talos-workstation on freenode have been > > working on an effort to bring up a Linux PowerPC userland that runs in 32-bit > > little-endian mode, aka ppcle. As far as we can tell, no ABI has ever been > > designated for this (unless you count the patchset from a decade ago [1]), so > > it's pretty much uncharted territory as far as Linux is concerned. We want to > > sync up with libc and the relevant kernel folks to establish the best path > > forward. > > As a general comment on the glibc side of things, if this is considered > like a new port, and it probably is, the same principles that apply to new > ports apply here. > > There's a general discussion at > , although much of that is > only applicable when adding new CPU architecture support. More specific > points include that new 32-bit ports should default to 64-bit time and > file offsets from the start, with no support for 32-bit time or offsets > (meaning that if you want to use this with some kind of library call > translation, the library call translation will need to deal with > corresponding type size conversions). Either that, or use the same as BE 32-bit PowerPC Linux, I'd say (it won't make things worse, and if it is easier?) But preferably the newer, better, thing of course :-) > And a new port should not be added > that uses the IBM long double format. You can use IEEE binary128 long > double, possibly with an ABI similar to that used on powerpc64le, or can > use long double = double, but should not support IBM long double, and > preferably should only have one long double format rather than using the > glibc support for building with different options resulting in functions > for different long double formats being called. You cannot use IEEE QP float ("binary128") here, but more on that in a later post. (I so very much agree about the problems having more than one long double format -- on the other hand, you'll just share it with BE, and with the existing powerpcle-linux (sup)port). Segher