From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: X-Spam-Status: No, score=-1.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI,NICE_REPLY_A, RCVD_IN_DNSWL_MED,RCVD_IN_SBL_CSS,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=no autolearn_force=no version=3.4.6 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 986361F47C for ; Wed, 11 Jan 2023 01:23:04 +0000 (UTC) Authentication-Results: dcvr.yhbt.net; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.a=rsa-sha256 header.s=default header.b=QsprMoaa; dkim-atps=neutral Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 2D79B385843E for ; Wed, 11 Jan 2023 01:23:04 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2D79B385843E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1673400184; bh=hTL/z7TYLmenYRsL7oKxA3VtgR9zwFc2T1cHpmtPgHA=; h=Date:Subject:To:Cc:References:In-Reply-To:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From:Reply-To:From; b=QsprMoaaJNUnBT0a3XwRnXEkrW+y3HB3RgzIOfOgi3fX80/P24aulr91br75vk0W6 3Ev1NGmncsTt4sV0f0qESXRrop5JZAMW9ExUF4oWW8vfmxjDflsJbyDLncGtCtzltN JH8wsRnX8a0Rf+x7MocMQ08wh3CsdeTRF9KC87g4= Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by sourceware.org (Postfix) with ESMTPS id 3DA293858D33 for ; Wed, 11 Jan 2023 01:22:43 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 3DA293858D33 Received: by mail-pl1-x62e.google.com with SMTP id d15so15122017pls.6 for ; Tue, 10 Jan 2023 17:22:43 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=hTL/z7TYLmenYRsL7oKxA3VtgR9zwFc2T1cHpmtPgHA=; b=bPhvA/sV1HFMDaqZnXTY1GlxqzmUrNteT5VqVxnWk60BIWCGU2LwmExQMezsgdSjCU lr9out3X5zXvJPLhKu/NhLSqSTI1b/6M1jwsAEZUS/OVg0kqJumqrnE8boN2LZoaDQtQ bpKAW3Ty+mna7N5N6Md5OyL01oW0tnsgb5QOYrNCyJ4Qrcd2y9mq/S7CmF4d/La5/ebD 8OpLg/tsXVPtF9Em+urKwAZTEgGhkxXHO/I49F4BUXsWpVaFCe6JqqoP0sNnZlslkMHr 1r70gsqiVoTo7ciqTM3wIYRlIiMv6ZQpj4DgpOZh7QUzDVMkxReE2no+xF1XON+o3MxO X7lA== X-Gm-Message-State: AFqh2kqv0NgEyepC+NnbuWwRUE3fR4+wxI4Ic6HfhtFHqCvD7IUXOids 77357vB4cIm3gZip5cbiERdmpw== X-Google-Smtp-Source: AMrXdXvbL7c7Q6mjTqDlD18bK+d9ngDorZ7YFFQsEzv3N2nzE8B1b1qAziM2zmlBz2aZlWvRJN1vMA== X-Received: by 2002:a05:6a20:3955:b0:b5:ee36:59a8 with SMTP id r21-20020a056a20395500b000b5ee3659a8mr9571480pzg.2.1673400162098; Tue, 10 Jan 2023 17:22:42 -0800 (PST) Received: from [192.168.0.115] (63-157-97-90.dia.static.qwest.net. [63.157.97.90]) by smtp.gmail.com with ESMTPSA id ik9-20020a170902ab0900b00189743ed3b6sm8801912plb.64.2023.01.10.17.22.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jan 2023 17:22:41 -0800 (PST) Message-ID: <3923eeee-e4dc-0911-40bf-84c34aee962d@linaro.org> Date: Tue, 10 Jan 2023 17:22:37 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: Auto-enabling V unit and/or use of elf attributes (was Re: Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break) To: Vineet Gupta , Kito Cheng Cc: Philipp Tomsich , Andy Chiu , Vincent Chen , Florian Weimer , Rich Felker , Andrew Waterman , Palmer Dabbelt , =?UTF-8?Q?Christoph_M=c3=bcllner?= , davidlt@rivosinc.com, Arnd Bergmann , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Szabolcs Nagy , Greentime Hu , Aaron Durbin , Andrew de los Reyes , linux-riscv , GNU C Library References: <1631497278-29829-1-git-send-email-vincent.chen@sifive.com> <50c598a6-e3b3-3062-abe7-23a406067533@rivosinc.com> <7430f494-9b43-5e03-c1e9-6b83e2611a11@rivosinc.com> <91ef3c45-165f-d2b3-7c77-322c01802c41@rivosinc.com> <18465ca3-934f-5b3e-170c-1ff0edea3a89@rivosinc.com> <1f8f1d21-4a19-54fe-8b29-bf9e2a8501d7@rivosinc.com> <3a838afe-974b-60bb-a0e5-83e366ec652e@rivosinc.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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: , From: Richard Henderson via Libc-alpha Reply-To: Richard Henderson Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On 1/10/23 10:07, Vineet Gupta wrote: > Yes bulk of glibc might not have vector code, but those V ifunc routines do and IMO this > information needs to be recorded somewhere in the elf. Case in point being the current > issue with how to enable V unit. Community wants a per-process enable, using an explicit > prctl from userspace (since RV doesn't have fault-on-first use hardware mechanism unlike > some of the other arches). But how does the glibc loader know to invoke prctl. We can't > just rely on user env GLIBC_TUNABLE etc since that might not be accurate. It needs > somethign concrete which IMO can come from elf attributes. If not, do you have suggestions > on how to solve this issue ? Why not just fault on first use to enable? That's vastly less complicated than trying to plumb anything through elf resulting in a prctl. You might say "but the fault could fail to allocate memory", but honestly, the prctl isn't able to fail either -- if it doesn't work, the process must exit. And, surely, there's some minimal vector configuration for which the allocation must succeed. r~