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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 C5C92C43381 for ; Mon, 18 Feb 2019 03:17:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 95AA7208E4 for ; Mon, 18 Feb 2019 03:17:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728480AbfBRDRf (ORCPT ); Sun, 17 Feb 2019 22:17:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45924 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728052AbfBRDRe (ORCPT ); Sun, 17 Feb 2019 22:17:34 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 76F69C03DFE1; Mon, 18 Feb 2019 03:17:33 +0000 (UTC) Received: from localhost (ovpn-12-45.pek2.redhat.com [10.72.12.45]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 792491024965; Mon, 18 Feb 2019 03:17:32 +0000 (UTC) Date: Mon, 18 Feb 2019 11:17:29 +0800 From: Baoquan He To: Kees Cook Cc: LKML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Dave Hansen , Andy Lutomirski , Peter Zijlstra , X86 ML , Mike Travis , Thomas Garnier , Andrew Morton , Masahiro Yamada , "Kirill A. Shutemov" Subject: Re: [PATCH v3 1/6] x86/mm/KASLR: Improve code comments about struct kaslr_memory_region Message-ID: <20190218031729.GG14858@MiWiFi-R3L-srv> References: <20190216140008.28671-1-bhe@redhat.com> <20190216140008.28671-2-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 18 Feb 2019 03:17:33 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/17/19 at 09:07am, Kees Cook wrote: > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index 3f452ffed7e9..d7c6e4e8e48e 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -42,10 +42,59 @@ > > static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE; > > > > /* > > - * Memory regions randomized by KASLR (except modules that use a separate logic > > - * earlier during boot). The list is ordered based on virtual addresses. This > > - * order is kept after randomization. > > + * 'struct kasl_memory_region' entries represent continuous chunks of > > Typo: struct kaslr_memory_region Will change. Thanks for reviewing this patchset and great suggestions. > > Also, while you're rewriting this, how about putting it in full > kern-doc format? (You're already using the "@field" style...) I think > you just need the "/**" header... Sure, will update. > > /** > * struct name.... - short description... > > > + * kernel virtual memory regions, to be randomized by KASLR. > > + * > > + * ( The exception is the module space virtual memory window which > > + * uses separate logic earlier during bootup. ) > > + * > > + * Currently there are three such regions: the physical memory mapping, > > + * vmalloc and vmemmap regions. > > + * > > + * The array below has the entries ordered based on virtual addresses. > > + * The order is kept after randomization, i.e. the randomized > > + * virtual addresses of these regions are still ascending. > > + * > > + * Here are the fields: > > + * > > + * @base: points to a global variable used by the MM to get the > > + * virtual base address of any of the above regions. This allows the > > + * early KASLR code to modify these base addresses early during bootup, > > + * on a per bootup basis, without the MM code even being aware of whether > > + * it got changed and to what value. > > + * > > + * When KASLR is active then the MM code makes sure that for each region > > + * there's such a single, dynamic, global base address 'unsigned long' > > + * variable available for the KASLR code to point to and modify directly: > > + * > > + * { &page_offset_base, 0 }, > > + * { &vmalloc_base, 0 }, > > + * { &vmemmap_base, 1 }, > > + * > > + * @size_tb: size in TB of each memory region. Thereinto, the size of > > nit: "Thereinto" is odd. I'd say "Therefore". Will replace it with 'Therefore'. > > > + * the physical memory mapping region is variable, calculated according > > + * to the actual size of system RAM in order to save more space for > > + * randomization. The rest are fixed values related to paging mode. > > + * > > + * @size_tb: is the size of each memory region after randomization, and > > + * its unit is TB. > > Redundant lines? I added it on purpose to stress these regions and their sizes, can remove this line. Or edit it like: * @size_tb: is the size of each memory region after randomization, and * its unit is TB: * Physical memory mapping: (actual RAM size + 10 TB padding) * Vmalloc: 32 TB * Vmemmap: 1 TB > > > + * > > + * Physical memory mapping: (actual RAM size + 10 TB padding) > > + * Vmalloc: 32 TB > > + * Vmemmap: 1 TB > > + * > > + * When randomize the layout, their order are kept, still the physical > > + * memory mapping region is handled fistly, next vmalloc and vmemmap. > > typo: "first" Will change. > > > + * E.g the physical memory region, we limit the starting address to be > > + * taken from the 1st 1/3 part of the whole available virtual address > > + * space which is from 0xffff880000000000 to 0xfffffe0000000000, namely > > + * the original starting address of the physical memory mapping region > > + * to the starting address of cpu_entry_area mapping region. Once a random > > + * address is chosen for the physical memory mapping, we jump over the > > + * region and add 1G to begin the next region handling with the remaining > > + * available space. > > Should the "operation" comments (rather than the struct field > comments) be moved to the start of the kernel_randomize_memory() > function instead? This paragraph is used to describe the order in which regions are handled, incidentally give an example to detail it. Since struct kasl_memory_region is the core and only data KASLR handled, put it here. > > -Kees > > > */ > > + > > static __initdata struct kaslr_memory_region { > > unsigned long *base; > > unsigned long size_tb; > > -- > > 2.17.2 > > > > > -- > Kees Cook