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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 133A9C43381 for ; Mon, 1 Apr 2019 08:14:35 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D46BF2084B for ; Mon, 1 Apr 2019 08:14:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ndeUMX8d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D46BF2084B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=KwIgW5ft2v7b6v35kBwgsnMBG27IoIh95yKODRsvA5E=; b=ndeUMX8dChLyha tAN7J9bie8N8jCU+16PEhS58gj2CplsZfL8bOl1MxbllbQ0mpvDS3Bg6MAW9/I24Rj1cUqQa59c8v PCTJfhCve0Ncyk8fycyixvh8xs8W/hfvobQ6PAdL6UTu+PEUXA6f/AWzcMgQ0WTV/ZEWlgvCsXt+D nUdlHdXz5iPAG6zkWwczC+0qfdvgt7c7/sKBk3/fcyuB3vZTDGHcQ9UIJtxa8VZb9st1a6oM6aZ3E zk/KED2QXAO2CEgV1D4KbDUuqnDgh5Cpng+oKh7INPQ3EscIpwxQLXxKWBxJvxBzB5Hnu7QTmxGjJ KoNnlG8kiEqdB/sOphhg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hAs5O-0003FA-Jr; Mon, 01 Apr 2019 08:14:30 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hAs5K-0003Bd-MW for linux-arm-kernel@lists.infradead.org; Mon, 01 Apr 2019 08:14:28 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A82CD374; Mon, 1 Apr 2019 01:14:24 -0700 (PDT) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 113EB3F690; Mon, 1 Apr 2019 01:14:23 -0700 (PDT) Date: Mon, 1 Apr 2019 09:14:22 +0100 From: Andrew Murray To: Phil Blundell Subject: Re: [PATCH v2 2/6] arm64: HWCAP: add support for AT_HWCAP2 Message-ID: <20190401081421.GB53702@e119886-lin.cambridge.arm.com> References: <1550751657-30252-1-git-send-email-andrew.murray@arm.com> <1550751657-30252-3-git-send-email-andrew.murray@arm.com> <20190221184500.GO16031@e103592.cambridge.arm.com> <20190327150224.GE43527@e119886-lin.cambridge.arm.com> <20190327152414.GF43527@e119886-lin.cambridge.arm.com> <20190328112734.GZ3567@e103592.cambridge.arm.com> <83b59b0f-cee7-92d5-2ed2-5300f92d7329@arm.com> <212459f27da12ec266fa1fa970356559a509f76d.camel@pbcl.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <212459f27da12ec266fa1fa970356559a509f76d.camel@pbcl.net> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190401_011426_767754_7C690BC0 X-CRM114-Status: GOOD ( 19.54 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: GNU C Library , Szabolcs Nagy , Catalin Marinas , Will Deacon , nd , Dave P Martin , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Mar 29, 2019 at 04:57:46PM +0000, Phil Blundell wrote: > On Fri, 2019-03-29 at 16:44 +0000, Szabolcs Nagy wrote: > > i think hwcap bit 63 is already reserved by glibc > > internally for tls support, it is not clear to me > > if that's still relevant (aarch64 post-dates tls > > support, so this might be historical cruft that can > > be cleaned up), i only see one comment about it: > > At the time that bit was invented, it was only set when glibc was built > with TLS support enabled (i.e. USE_TLS defined). It would cause the > dynamic linker to add "tls" as a hwcap subdirectory in its search path, which I guess was useful in the days when TLS-enabled and non-TLS-enabled versions of the same DSO needed to be able to co-exist. > > At some later date, I forget when, TLS became mandatory and the USE_TLS > condition went away. The comment seems to be saying that it was > thought necessary to keep the pseudo-hwcap bit set so that any DSOs in > a "tls" subdirectory would still be found. That seems like a debatable proposition even at the time, and even more so today, but I guess it was hard to prove the negative. > > Even if aarch64 has always had TLS, in principle there might be some > ancient DSOs lurking in "tls" subdirectories which would no longer be > loaded if you were to stop setting that bit. I'm sure that would be manageable, but equally it doesn't seem that these bits are so scarce that it's worth going to any effort to scavenge old ones. > > > i think it's better to use a different bit > > for aarch64 ifunc abi hacks (e.g. 1ULL << 62) > > I agree. OK, I'll respin and reserve bit 1ULL << 62. Thanks, Andrew Murray > > p. > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel