From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755555AbbCRHav (ORCPT ); Wed, 18 Mar 2015 03:30:51 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:37069 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755414AbbCRH3Y (ORCPT ); Wed, 18 Mar 2015 03:29:24 -0400 From: Yinghai Lu To: Matt Fleming , "H. Peter Anvin" , Ingo Molnar , Jiri Kosina , Kees Cook , Borislav Petkov , Baoquan He Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org Subject: [PATCH v5 15/19] x86, kaslr: Introduce fetch_random_virt_offset to randomize the kernel text mapping address Date: Wed, 18 Mar 2015 00:28:22 -0700 Message-Id: <1426663706-23979-16-git-send-email-yinghai@kernel.org> X-Mailer: git-send-email 1.8.4.5 In-Reply-To: <1426663706-23979-1-git-send-email-yinghai@kernel.org> References: <1426663706-23979-1-git-send-email-yinghai@kernel.org> X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Baoquan He Kaslr extended kernel text mapping region size from 512M to 1G, namely CONFIG_RANDOMIZE_BASE_MAX_OFFSET. This means kernel text can be mapped to below region: [__START_KERNEL_map + LOAD_PHYSICAL_ADDR, __START_KERNEL_map + 1G] Introduce a function find_random_virt_offset() to get random value between LOAD_PHYSICAL_ADDR and CONFIG_RANDOMIZE_BASE_MAX_OFFSET. This random value will be added to __START_KERNEL_map to get the starting address which kernel text is mapped from. Since slot can be anywhere of this region, means it is an independent slot_area, it is simple to get a slot according to random value. Signed-off-by: Baoquan He --- arch/x86/boot/compressed/aslr.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c index 37dce4f..5114142 100644 --- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -369,6 +369,27 @@ static unsigned long find_random_addr(unsigned long minimum, return slots_fetch_random(); } +static unsigned long find_random_virt_offset(unsigned long minimum, + unsigned long image_size) +{ + unsigned long slot_num, random; + + /* Make sure minimum is aligned. */ + minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); + + if (image_size <= CONFIG_PHYSICAL_ALIGN) + slot_num = (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - minimum) / + CONFIG_PHYSICAL_ALIGN; + else + slot_num = (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - + minimum - image_size) / + CONFIG_PHYSICAL_ALIGN + 1; + + random = get_random_long() % slot_num; + + return random * CONFIG_PHYSICAL_ALIGN + minimum; +} + static void add_kaslr_setup_data(__u8 enabled) { struct setup_data *data; -- 1.8.4.5