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 6C422C433FE for ; Wed, 2 Feb 2022 23:36:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A51BE8D011D; Wed, 2 Feb 2022 18:36:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A01768D0119; Wed, 2 Feb 2022 18:36:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C9F18D011D; Wed, 2 Feb 2022 18:36:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0227.hostedemail.com [216.40.44.227]) by kanga.kvack.org (Postfix) with ESMTP id 7CD478D0119 for ; Wed, 2 Feb 2022 18:36:44 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 36025944D8 for ; Wed, 2 Feb 2022 23:36:44 +0000 (UTC) X-FDA: 79099451928.11.BFEFACE Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf03.hostedemail.com (Postfix) with ESMTP id D603C20009 for ; Wed, 2 Feb 2022 23:36:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=sKMSro+nqi3+TRaInDh/r5jt9h3R6I+1JvbqLUuQ9zw=; b=EQFB7AmHjcEOog2AgXpabrhNbq eb+nIuW++r278MsQm+yo6BJLgWEi7DgA0z/LlXygv3QszEhUFbTZTYEd7tnQF95I9q+HDvddpS0dr ZT4oOJqpMyq2CEFRDI9sNR/0008KH9VEFO6SEXb/UlghtmM1nhzbpJM/5gNt8d05BRv4D8tQ5GrZW fpzQ8SgxsTS6vdNOuRec1F/wQ5pWQ0g4+NAL2ajplTSo5BZ+1fnALWGrFPMSPAfHFWRnsxJ/WmIg1 N3Sh1ZVZn6t5DVK/fZ6Xax5LywKa/tBa8o8JoZbW2WIGkbbwfyxz0e9MK78JgVYWCcygyNJY3ImiP uQFa5xkw==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nFPAz-00H4rN-PB; Wed, 02 Feb 2022 23:36:37 +0000 Date: Wed, 2 Feb 2022 15:36:37 -0800 From: Luis Chamberlain To: Christophe Leroy Cc: Jessica Yu , "linux-kernel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "kgdb-bugreport@lists.sourceforge.net" , "linux-mm@kvack.org" , "linux-arch@vger.kernel.org" , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras Subject: Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: nil X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D603C20009 X-Stat-Signature: gb4sma6rwsj7zzarp7gficwaoi5fkb6k Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=EQFB7AmH; spf=none (imf03.hostedemail.com: domain of mcgrof@infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=mcgrof@infradead.org; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-HE-Tag: 1643845003-966744 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 Thu, Jan 27, 2022 at 11:28:12AM +0000, Christophe Leroy wrote: > book3s/32 and 8xx have a separate area for allocating modules, > defined by MODULES_VADDR / MODULES_END. > > On book3s/32, it is not possible to protect against execution > on a page basis. A full 256M segment is either Exec or NoExec. > The module area is in an Exec segment while vmalloc area is > in a NoExec segment. > > In order to protect module data against execution, select > ARCH_WANTS_MODULES_DATA_IN_VMALLOC. > > For the 8xx (and possibly other 32 bits platform in the future), > there is no such constraint on Exec/NoExec protection, however > there is a critical distance between kernel functions and callers > that needs to remain below 32Mbytes in order to avoid costly > trampolines. By allocating data outside of module area, we > increase the chance for module text to remain within acceptable > distance from kernel core text. > > So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well. > > Signed-off-by: Christophe Leroy > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Paul Mackerras Cc list first and then the SOB. Luis