From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id LOtjCnHs1GQhFT0AWB0awg (envelope-from ) for ; Thu, 10 Aug 2023 09:56:01 -0400 Received: by simark.ca (Postfix, from userid 112) id 1CC5D1E0BB; Thu, 10 Aug 2023 09:56:01 -0400 (EDT) Received: from server2.sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id 0D7C91E028 for ; Thu, 10 Aug 2023 09:55:59 -0400 (EDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 701F13857736 for ; Thu, 10 Aug 2023 13:55:58 +0000 (GMT) Received: from angie.orcam.me.uk (angie.orcam.me.uk [IPv6:2001:4190:8020::34]) by sourceware.org (Postfix) with ESMTP id 95EB9385697D for ; Thu, 10 Aug 2023 13:55:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 95EB9385697D Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=orcam.me.uk Authentication-Results: sourceware.org; spf=none smtp.mailfrom=orcam.me.uk Received: by angie.orcam.me.uk (Postfix, from userid 500) id 287109200C1; Thu, 10 Aug 2023 15:55:44 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id 21F089200BF; Thu, 10 Aug 2023 14:55:44 +0100 (BST) Date: Thu, 10 Aug 2023 14:55:44 +0100 (BST) From: "Maciej W. Rozycki" To: Andy Chiu cc: Greg Savin , Greentime Hu , Oleg Nesterov , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-riscv@lists.infradead.org, gdb-patches@sourceware.org, Andrew Burgess Subject: Re: [PATCH] RISC-V: support for vector register accesses via ptrace() in RISC-V Linux native In-Reply-To: Message-ID: References: <20230803230110.904724-1-greg.savin@sifive.com> <20230810103510.GA2509@hsinchu26> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-3488.6 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, KAM_INFOUSMEBIZ, KAM_LAZY_DOMAIN_SECURITY, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" On Thu, 10 Aug 2023, Maciej W. Rozycki wrote: > > Does it make sense to you if we encapsulate this with a hwprobe syscall? > > e.g provide a hwprobe entry to get system's VLENB. We will have to > > increase and rearrange the buffer for NT_RISCV_VECTOR if we want to use > > ptrace as the entry point for this purpose. I am not very sure if it'd be > > too late to do though. > > No, how do you expect it to work with a core dump (that can be examined > on a different system, or with a cross-debugger)? You need to change the > API I'm afraid; it's unusable anyway. It's a pity the toolchain community > wasn't consulted if you weren't sure how to design the interface. Better > yet it would have been to implement the GDB side before the kernel part > has been committed. NB since this stuff went in with v6.5-rc1 and v6.5 hasn't been released you can still back out the problematic change as no one is expected to use RC stuff in production. Alternatively you can redefine NT_RISCV_VECTOR for a corrected ABI, but I think it shouldn't be necessary. You just need to act quickly as I guess there may be 1-2 further v6.5 RCs only and you have to get with that to Linus right away. We can have a release or two without NT_RISCV_VECTOR support for the otherwise included vector stuff, it shouldn't be a big deal. There just won't be support for the debug API. CC-ing Linux ptrace/RISC-V maintainers now to bring their attention. Maciej