Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755984Ab3DOWHU (ORCPT ); Mon, 15 Apr 2013 18:07:20 -0400 Received: from mail-oa0-f54.google.com ([209.85.219.54]:40532 "EHLO mail-oa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753787Ab3DOWHS (ORCPT ); Mon, 15 Apr 2013 18:07:18 -0400 MIME-Version: 1.0 In-Reply-To: References: <1365797627-20874-1-git-send-email-keescook@chromium.org> <1365797627-20874-7-git-send-email-keescook@chromium.org> <516A1D49.1050100@zytor.com> <516C702C.2030209@zytor.com> <516C751B.4020505@zytor.com> Date: Mon, 15 Apr 2013 15:07:17 -0700 X-Google-Sender-Auth: kd5YDH4Av85eJZe670nlntpPeeM Message-ID: Subject: Re: [PATCH 6/6] x86: kaslr: relocate base offset at boot From: Kees Cook To: Yinghai Lu Cc: "H. Peter Anvin" , Eric Northup , Linux Kernel Mailing List , "kernel-hardening@lists.openwall.com" , Thomas Gleixner , Ingo Molnar , "the arch/x86 maintainers" , Jarkko Sakkinen , Matthew Garrett , Matt Fleming , Dan Rosenberg , Julien Tinnes , Will Drewry Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1542 Lines: 43 On Mon, Apr 15, 2013 at 3:00 PM, Yinghai Lu wrote: > On Mon, Apr 15, 2013 at 2:46 PM, H. Peter Anvin wrote: >> On 04/15/2013 02:41 PM, Kees Cook wrote: > >> Please read what I wrote. >> >> The 2 GB limit is for the *virtual* mapping. >> >> The *physical* mapping, where it lands in RAM, is completely >> independent, and if you're going to randomize the latter, there is no >> reason it has to match the former. Instead, randomize it freely. >> >> That is different from the i386 kernel which runs at its >> physical-mapping address. >> >> Incidentally, for performance reasons please avoid locating the kernel >> below CONFIG_PHYSICAL_ADDRESS if possible. >> >> Also make sure your code works with more than 128 e820 entries. > > also do not overlap with boot_param, command_line, and initrd. > > and need to double check setup_header.init_size to make sure bss and > etc will not > fall into memory hole or reserved area in e820. > > also may need to setup page table for target position as bootloader may only > has ident mapping only for loaded bzImage 64 areas. > > looks you are trying redo the work for bootloader to pick loaded phys addr. aslr.S's select_aslr_address uses z_extract_offset as the upper bound. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/