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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79711C433FE for ; Tue, 5 Oct 2021 12:12:44 +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 4305061166 for ; Tue, 5 Oct 2021 12:12:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 4305061166 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; 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Tue, 05 Oct 2021 05:10:36 -0700 (PDT) X-Gm-Message-State: AOAM532KKN/L49/kBmlB3Ac+ncWsJuc5AU2p445M73IupQtgirkU3vS0 7eQq9AXs9ExnHlV0IOFXuf0qYpog+83Ig4JIEtw= X-Google-Smtp-Source: ABdhPJwLYSA8nY+bqlyeSIuMrUxgclh1swXRPcyLQDJayAHGygGHVAtDIUAeFbkNTA5KF7XnNd+4klHssmyqTVPNVIQ= X-Received: by 2002:a1c:2358:: with SMTP id j85mr3004262wmj.1.1633435835810; Tue, 05 Oct 2021 05:10:35 -0700 (PDT) MIME-Version: 1.0 References: <20211005071542.3127341-1-ardb@kernel.org> <20211005071542.3127341-3-ardb@kernel.org> In-Reply-To: <20211005071542.3127341-3-ardb@kernel.org> From: Arnd Bergmann Date: Tue, 5 Oct 2021 14:10:19 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 2/9] ARM: assembler: introduce bl_r and bl_m macros To: Ard Biesheuvel Cc: Linux ARM , Russell King - ARM Linux , Arnd Bergmann , Kees Cook , Keith Packard , Linus Walleij X-Provags-ID: V03:K1:3XjxOa3aNqQCMkpCMJOrETk1yF2UydeI558SbXa9jAdjVOJGPok VOnmLiLxWfEE6C67U8nidVpxPLKZ8okOy5Dd7Co/D5acFSsb9osowp/yYNOEM2a/AxQTUV1 sdsgd569tGk9pLoEglQ7/LN4tb5Ord69fgxW4EgpgCz16lZ2D+4OTyxAreWPX9zmgMV5adI apEnERs77pI+fLJVnsuZA== X-UI-Out-Filterresults: notjunk:1;V03:K0:YFu28s02/J4=:EOtAwVJtCTXGrBZ9dP/Q35 6wuPOH9dQk9ZGOWQhjbmRvfGcBU2un8vx+vOC6Kmt7wK5TTZA2HVgfo3+vvqM7sNqta4Bujm9 h3B84HD6sJJiPDl7RClk3+o5KWmRB4erVmmYHlH6Dq/EY1lqarMRFnwL4GHXIAm/mJgVK982X Sj1GZ6c/ag2VKHZPr6nZRDblA4HS/uO4x1HHMEYR//Rbl6kG3Lf/xmYFQiSL6Aoiu/XurQvWa uS1Rsod++wARAy+fObja1BkYenlb3p81T1kGs0v9CBk5AxpO4A65Cw8U4mzccMqvkeG2nAWkr EJWLa77PJJDE7erslKc5h8ph3pdWi9RljRHez0bpfBwC1/P0EcOcpFk5QOhAo3TagsK7t80Ot IIjU1qkf7ulYcCqfVqakOXFJSOaEmfBOChns8mQet05sEWHTiPACOkT8gV3WN8sy9mCQUWF9N RYnZQV54FtGYYr7GRTzKkR2kXVfkQ/5iUd2c7db4n6yj7wrdWr4oEqwApQG6RkTeQc3URofKL +VynnsBdvW7lUlyEPXAslZz6iUTVGO8cOMatu/FcX90Xw10uTrEYMUK5/kveqgZA4MXnN4s15 kNCk/W8F4iLnMqkcWsaxihfDgT0k3pVOWhKJFRSU8AOCSRw6f+G+MgpVJMyPWAs33GofYcRm8 8Mgg/GZyuap4kansae9oCVW+j32H+oZbREd0fVHIkESHA/3FzxbmP9mmR6gSK78g1z4tsg7yN 6w/6NPYlr/VKcqh2J06mIvvyiUswj4Koz+LfHBAAT3WIj8YCIgprFMtH4vP08n+0rlAUwg/1D t1koFfpgJ7XVEQiYONBFKcF0Dhw2z8FOHj2pbGfQP3Iup5vV6tRPySrRLToVwexRCztYVo6DK pYf7CneKIK1u+/R4GD8g== X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211005_051039_685636_6410266B X-CRM114-Status: GOOD ( 15.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 5, 2021 at 9:15 AM Ard Biesheuvel wrote: > > Add some macros that abstract the difference between the ways indirect > calls are performed on older and newer ARM architecture revisions. > > The main difference is to prefer blx instructions over explicit LR > assignments when possible, as these tend to confuse the prediction logic > in out-of-order cores when speculating across a function return. > > Signed-off-by: Ard Biesheuvel Reviewed-by: Arnd Bergmann > + .macro bl_r, dst:req, c > + .if __LINUX_ARM_ARCH__ < 6 > + mov\c lr, pc > + mov\c pc, \dst > + .else > + blx\c \dst > + .endif > + .endm I suppose we could use blx on ARMv5 as well, but it wouldn't make a difference there, right? Arnd _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel