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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B9B7C433F5 for ; Wed, 11 May 2022 07:27:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 143A36B0073; Wed, 11 May 2022 03:27:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0CD2D6B0075; Wed, 11 May 2022 03:27:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E87486B0078; Wed, 11 May 2022 03:26:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id D63AC6B0073 for ; Wed, 11 May 2022 03:26:59 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 9F583121F0A for ; Wed, 11 May 2022 07:26:59 +0000 (UTC) X-FDA: 79452630558.18.D992529 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf28.hostedemail.com (Postfix) with ESMTP id 6A1B7C009B for ; Wed, 11 May 2022 07:26:39 +0000 (UTC) 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=WqQvvzTawsUra3llaTMtecCGxHMoJa0AaVmr+uqshgk=; b=rXYulYiOCSxQOkz21USvuZ8PMZ TFMOCQktj/apPUevOQxpan2cX+AhwEDOr7WXdUVoA21F/MINzQLqplcr3DnEtIkCuBFQzIYGlVpcz iwTSzsGhevzamCUouHqSkWI3AzTOR7KDHHraSFvv9iCDUougczpM5iSCjchEwHWyrEx8seEsjAFp8 I0Q2NoC2U43NCqaZFejkQApFweQvaB9ecj+xvMJMinXynwM/qFm1Xl0IRWUgf+OLAUoz4Phf3g5fo URRiGJ+HUn/aRnclAPxEz8gn39NHtp0w1CftST7ng5oE4E/lV+ya7UHoIaI3XcAW0iJTYXP22RTgA LdIbpmEg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nogkG-005ENO-GQ; Wed, 11 May 2022 07:26:52 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 0CFF0980E3A; Wed, 11 May 2022 09:26:52 +0200 (CEST) Date: Wed, 11 May 2022 09:26:51 +0200 From: Peter Zijlstra To: "Kirill A. Shutemov" Cc: Dave Hansen , Andy Lutomirski , x86@kernel.org, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFCv2 09/10] x86/mm: Add userspace API to enable Linear Address Masking Message-ID: <20220511072651.GV76023@worktop.programming.kicks-ass.net> References: <20220511022751.65540-1-kirill.shutemov@linux.intel.com> <20220511022751.65540-11-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220511022751.65540-11-kirill.shutemov@linux.intel.com> X-Stat-Signature: fxg8m9nfefqrkw45r5zywut5fm34m8h9 Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=rXYulYiO; spf=none (imf28.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 6A1B7C009B X-HE-Tag: 1652253999-376414 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 11, 2022 at 05:27:50AM +0300, Kirill A. Shutemov wrote: > @@ -1013,8 +1017,23 @@ static long thread_feature_prctl(struct task_struct *task, int option, > > /* Handle ARCH_THREAD_FEATURE_ENABLE */ > > + if (features & (X86_THREAD_LAM_U48 | X86_THREAD_LAM_U57)) { > + long ret; > + > + /* LAM is only available in long mode */ > + if (in_32bit_syscall()) > + return -EINVAL; So what happens if userspace sets up a 32bit code entry in the LDT and does the LAM thing as a 64bit syscamm but then goes run 32bit code? > + > + ret = enable_lam(task, features); > + if (ret) > + return ret; > + } > + > task->thread.features |= features; > out: > + /* Update CR3 to get LAM active */ > + switch_mm(task->mm, task->mm, task); > + > return task->thread.features; > } >