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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6EC9CC63697 for ; Thu, 19 Nov 2020 16:15:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03A2D246CE for ; Thu, 19 Nov 2020 16:15:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YJwUoJv4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727356AbgKSQPD (ORCPT ); Thu, 19 Nov 2020 11:15:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727741AbgKSQPD (ORCPT ); Thu, 19 Nov 2020 11:15:03 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15943C0613CF; Thu, 19 Nov 2020 08:15:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=d5rQ16w64peZRzRHWzAxkB2LwT7DS/SXDMY8OqFuQNY=; b=YJwUoJv45W97ErJVfazec+sHxs hq51UV+/nTAfEiPVZEwD9mrusLQ/nV3TnwhRIHICcchcHbPvnr44cSBqaidFOm52WsqmnykhIZ9n+ BvHt1pvgQS/fEAKZ3pBlHYKl7j1s/Kbdn0ykKIYiBsOWDOOfs58Cwn1eLBoVpcBtpxoBygPKwYXrM SL/XpGqevieEZW8Npvo62E+aE8sjYa0Zlr8cETEMJAEIowdw0kKU/uDtKnLwtieWmb6y9GcHGpgPW L2gNFgTO1vuLoabvLfZe0rCzqU4jgiXWbqPW4rR5bf1uASwPIOoMYbk4lyjD5XkQzB03NF1V6ZpP1 wNQCVqKw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfmaA-0006zX-SH; Thu, 19 Nov 2020 16:14:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id ABB5F3019CE; Thu, 19 Nov 2020 17:14:48 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8703A203C45DF; Thu, 19 Nov 2020 17:14:48 +0100 (CET) Date: Thu, 19 Nov 2020 17:14:48 +0100 From: Peter Zijlstra To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , kernel-team@android.com Subject: Re: [PATCH v3 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Message-ID: <20201119161448.GR3121392@hirez.programming.kicks-ass.net> References: <20201113093720.21106-1-will@kernel.org> <20201113093720.21106-9-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201113093720.21106-9-will@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, Nov 13, 2020 at 09:37:13AM +0000, Will Deacon wrote: > When exec'ing a 32-bit task on a system with mismatched support for > 32-bit EL0, try to ensure that it starts life on a CPU that can actually > run it. > > Signed-off-by: Will Deacon > --- > arch/arm64/kernel/process.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 1540ab0fbf23..17b94007fed4 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -625,6 +625,16 @@ unsigned long arch_align_stack(unsigned long sp) > return sp & ~0xf; > } > > +static void adjust_compat_task_affinity(struct task_struct *p) > +{ > + const struct cpumask *mask = system_32bit_el0_cpumask(); > + > + if (restrict_cpus_allowed_ptr(p, mask)) > + set_cpus_allowed_ptr(p, mask); This silently destroys user state, at the very least that ought to go with a WARN or something. Ideally SIGKILL though. What's to stop someone from doing a sched_setaffinity() right after the execve, same problem. So why bother.. > + > + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); > +} > + > /* > * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY. > */ > @@ -635,7 +645,7 @@ void arch_setup_new_exec(void) > if (is_compat_task()) { > mmflags = MMCF_AARCH32; > if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) > - set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); > + adjust_compat_task_affinity(current); > } > > current->mm->context.flags = mmflags; > -- > 2.29.2.299.gdc1121823c-goog >