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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9D04C4332F for ; Fri, 9 Dec 2022 10:04:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229714AbiLIKEI (ORCPT ); Fri, 9 Dec 2022 05:04:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229605AbiLIKEG (ORCPT ); Fri, 9 Dec 2022 05:04:06 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A0DB196 for ; Fri, 9 Dec 2022 02:03:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670580189; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Unpex6/NiCsmNu3cvjnAB1nJqSua03CVH4d0B3gW9To=; b=R/qb9HTGrWxiUwnlqOK2SK9+8Bj5w/YMBedXExcwxGHYK+HYgzqx5Gg7L90MWVqgm2Kgnn I/KxHqE+IxgY+N/phNwCiQT9r0q0wThJ2KTi1CrFWhPexfgTDLAvTMA8RoXDP2cjo2v9fo iabsE131t7lhnwwx62XIcyoy27ZNG+w= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-418-2rh5rKxzNzO0sMjpvC5Luw-1; Fri, 09 Dec 2022 05:03:07 -0500 X-MC-Unique: 2rh5rKxzNzO0sMjpvC5Luw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 328088582B9; Fri, 9 Dec 2022 10:03:06 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.193.168]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 886292166B26; Fri, 9 Dec 2022 10:03:01 +0000 (UTC) From: Florian Weimer To: Andrew Waterman Cc: Palmer Dabbelt , Vineet Gupta , stillson@rivosinc.com, Paul Walmsley , anup@brainfault.org, atishp@atishpatra.org, guoren@kernel.org, Conor Dooley , greentime.hu@sifive.com, vincent.chen@sifive.com, andy.chiu@sifive.com, Darius Rad , arnd@kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, bjorn@kernel.org, libc-alpha@sourceware.org, christoph.muellner@vrull.eu, Aaron Durbin , linux@rivosinc.com Subject: Re: RISCV Vector unit disabled by default for new task (was Re: [PATCH v12 17/17] riscv: prctl to enable vector commands) References: Date: Fri, 09 Dec 2022 11:02:57 +0100 In-Reply-To: (Andrew Waterman's message of "Thu, 8 Dec 2022 21:42:34 -1000") Message-ID: <877cz0nbce.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Waterman: > This suggests that ld.so, early-stage libc, or possibly both will need > to make this prctl() call, perhaps by parsing the ELF headers of the > binary and each library to determine if the V extension is used. If the string functions use the V extension, it will be enabled unconditionally. So I don't see why it's okay for libc to trigger this alleged UAPI change, when the kernel can't do it by default. Thanks, Florian