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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 35E93C4338F for ; Fri, 20 Aug 2021 17:24:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E35B61154 for ; Fri, 20 Aug 2021 17:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234564AbhHTRZB (ORCPT ); Fri, 20 Aug 2021 13:25:01 -0400 Received: from gate.crashing.org ([63.228.1.57]:47018 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233256AbhHTRZA (ORCPT ); Fri, 20 Aug 2021 13:25:00 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 17KHIkfB024178; Fri, 20 Aug 2021 12:18:46 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 17KHIjOe024175; Fri, 20 Aug 2021 12:18:45 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 20 Aug 2021 12:18:45 -0500 From: Segher Boessenkool To: Michael Ellerman Cc: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread Message-ID: <20210820171845.GS1583@gate.crashing.org> References: <91b1d242525307ceceec7ef6e832bfbacdd4501b.1629436472.git.christophe.leroy@csgroup.eu> <871r6oe2i8.fsf@mpe.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <871r6oe2i8.fsf@mpe.ellerman.id.au> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 20, 2021 at 10:15:11PM +1000, Michael Ellerman wrote: > Christophe Leroy writes: > > Copied from commit 89bbe4c798bc ("powerpc/64: indirect function call > > use bctrl rather than blrl in ret_from_kernel_thread") > > > > blrl is not recommended to use as an indirect function call, as it may > > corrupt the link stack predictor. > > Do we know if any 32-bit CPUs have a link stack predictor or similar? 74xx do. Segher