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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 795D1C43381 for ; Fri, 29 Mar 2019 16:58:03 +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 4993A21773 for ; Fri, 29 Mar 2019 16:58:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="F6nDN1GU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4993A21773 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pbcl.net 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:MIME-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nHvYO6Ubs7vsEJFeR3XskhCC8X8SV36TCgxd/Qsw1vc=; b=F6nDN1GUOiYA2J Jn9b+b5lqfecHdF2jToUUVHjVSfyUpWBt5ZeiBiwt+n4lc1/ClHzF38SGratJsJA7AC/Xs/kKTrlD iJT5O2TNNfHFUp23GZuy1vr4fN4zMPOOBjmknBtnn99AEsqTFKa6TN3/BACDtiSr45frdPaM1Liyh MoGL3N6bzoNvTzHrHkJgEMH+K65tNqGky76RxvefA5cANjlD5J+9JKwlD26M3+eoproIuUfQzKV5z glvsNkvvIoN62z9wCIwaIY8ekFIqprOT866U4Qjrwg/A3O0in+Sv1X229cKiJG0PSlu5qrfckEv3W lwqajZNUnBQcPwZNHIdA==; 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 1h9upJ-00057P-Vi; Fri, 29 Mar 2019 16:57:57 +0000 Received: from mail.pbcl.net ([2a01:4f8:d12:ec2::2]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h9upG-000573-2E for linux-arm-kernel@lists.infradead.org; Fri, 29 Mar 2019 16:57:55 +0000 Received: from [2a00:c60:0:cb01:e23f:49ff:fe47:b7fd] (helo=phil-desktop) by mail.pbcl.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1h9up9-0003c5-Pe; Fri, 29 Mar 2019 17:57:49 +0100 Message-ID: <212459f27da12ec266fa1fa970356559a509f76d.camel@pbcl.net> Subject: Re: [PATCH v2 2/6] arm64: HWCAP: add support for AT_HWCAP2 From: Phil Blundell To: Szabolcs Nagy , Dave P Martin , Andrew Murray Date: Fri, 29 Mar 2019 16:57:46 +0000 In-Reply-To: <83b59b0f-cee7-92d5-2ed2-5300f92d7329@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> User-Agent: Evolution 3.30.5-1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190329_095754_256036_29D7C17C X-CRM114-Status: GOOD ( 13.05 ) 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: Catalin Marinas , nd , Will Deacon , GNU C Library , "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, 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. p. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel