From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 105540 invoked by alias); 14 Jan 2019 19:22:42 -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 105527 invoked by uid 89); 14 Jan 2019 19:22:42 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-11.9 required=5.0 tests=BAYES_00,GIT_PATCH_1,GIT_PATCH_2,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=H*UA:Zimbra, H*x:Zimbra, H*M:zimbra, clarification X-HELO: mail.efficios.com DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 005BCA3FDD DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1547493758; bh=DpFoyr4ZaxTw8xyYjUlySVIEAvWzDWa4seh1yWPRLek=; h=Date:From:To:Message-ID:MIME-Version; b=KXSeCyeVJT4UUYzNDp0gLmauP1j0a/v80b+vMEPqRGhiibHs2d4cpgWhgj0p0euwG CqV1AXEnQFJYB8G3Oqy5+CfMWlZTauzQUmxkS+NFvCAwEqYpYKPAxJDozhnLFiFAte mF1mcQC6MzDT0LhJ9jh5eCpoANkbKTcFVbO+oPeJVcx6dwL71m4qYTLhB3Pe+vc/r6 dlvq9F1kiWVnDqDYA5D/LduAn7ibJqHdyC1ZeNAVVXr7t4zLdp21KgHPrKw8Kw+r1N BaIKb2csTAtD679g1dsWzHMVCLUMDiUQHTDnr1vOWRSoNzjqZoFmtXNFiQO6ugdUNU Q0M5DR2t3rcJA== Date: Mon, 14 Jan 2019 19:22:00 -0000 From: Mathieu Desnoyers To: Florian Weimer Cc: carlos , Joseph Myers , Szabolcs Nagy , libc-alpha , Thomas Gleixner , Ben Maurer , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Will Deacon , Dave Watson , Paul Turner , Rich Felker , linux-kernel , linux-api Message-ID: <394676913.486.1547493757710.JavaMail.zimbra@efficios.com> In-Reply-To: <87fttv9iic.fsf@oldenburg2.str.redhat.com> References: <20181204192141.4684-1-mathieu.desnoyers@efficios.com> <87h8fkz6qx.fsf@oldenburg2.str.redhat.com> <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com> <87fttv9iic.fsf@oldenburg2.str.redhat.com> Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2019-01/txt/msg00302.txt.bz2 ----- On Jan 14, 2019, at 10:55 AM, Florian Weimer fweimer@redhat.com wrote: > * Mathieu Desnoyers: > >> Therefore, both symbols will end up in >> sysdeps/unix/sysv/linux/Versions. > > I'm not sure what you mean by that. The physical location in the > directory tree has little effect on which shared object the symbol is > placed in; that will need other changes. I'm currently moving the symbol definitions to csu/rseq-sym.c. On Linux, its content is overridden by a new sysdeps/unix/sysv/linux/rseq-sym.c which contains both __rseq_abi and __rseq_refcount symbols. On other platforms, it is a stub file. >>> By the way, you could avoid the need for unregistration if you allocated >>> the rseq areas persistently, index by TID. They are quite small, so >>> with the typical PID range, maybe the wasted memory due to changing TIDs >>> would be acceptable? >> >> Would we be able to access those __rseq_abi as normal TLS IE model >> variables ? The overhead of indexing an array matters for a >> fast-path. > > No, that wouldn't be possible in this case. You would need another > indirection. Thanks for the clarification! Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com