From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 92631 invoked by alias); 9 Oct 2019 11:04:07 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 92623 invoked by uid 89); 9 Oct 2019 11:04:07 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-6.0 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS autolearn=ham version=3.3.1 spammy=HX-Languages-Length:1081 X-HELO: mx1.redhat.com From: Florian Weimer To: Christian Brauner Cc: Adhemerval Zanella , libc-alpha@sourceware.org Subject: Re: [PATCH] [GLIBC RFC] clone3: add CLONE3_RESET_SIGHAND References: <20191008134417.16113-1-christian.brauner@ubuntu.com> <5cab2cbb-e72b-4eb0-5271-1a90c4e8de95@linaro.org> <20191009104830.w2fkr4m3lrkfowxq@wittgenstein> Date: Wed, 09 Oct 2019 11:04:00 -0000 In-Reply-To: <20191009104830.w2fkr4m3lrkfowxq@wittgenstein> (Christian Brauner's message of "Wed, 9 Oct 2019 12:48:31 +0200") Message-ID: <87bluq18po.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-SW-Source: 2019-10/txt/msg00243.txt.bz2 * Christian Brauner: > I've been thinking about two things how to do this: > - mask the flags that the kernel does not support That doesn't look fully backwards-compatible to me. The argument isn't currently read/write, is it? It would work for us though. > - add another argument to struct clone_args that is "known_flags" > when the syscall returns it'll be set to all the flags this kernel > knows about This needs some sort of protocol to detect whether the argument was updated. I suppose we could define CLONE3_INITIALLY_SUPPORTED_FLAGS with all the flag bits currently supported and tell developers to initialize struct clone_args with: .known_flags = CLONE3_INITIALLY_SUPPORTED_FLAGS, Then the result would be correct whether or not known_flags is supported by the kernel or not. This too would work fine for glibc internal use. By theway, I don't think we have a good userspace API story for extensible *output* arguments yet. Every system call does things a little bit differently there. Thanks, Florian