Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752722AbcDOWEH (ORCPT ); Fri, 15 Apr 2016 18:04:07 -0400 Received: from mail-pf0-f176.google.com ([209.85.192.176]:35180 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752521AbcDOWEE (ORCPT ); Fri, 15 Apr 2016 18:04:04 -0400 From: Thomas Garnier To: "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Thomas Garnier , Dmitry Vyukov , Paolo Bonzini , Dan Williams , Kees Cook , Stephen Smalley , Seth Jennings , Kefeng Wang , Jonathan Corbet , Matt Fleming , Toshi Kani , Alexander Kuleshov , Alexander Popov , Joerg Roedel , Dave Young , Baoquan He , Dave Hansen , Mark Salter , Boris Ostrovsky Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, gthelen@google.com, kernel-hardening@lists.openwall.com Subject: [RFC v1 4/4] x86, boot: Memory hotplug support for KASLR memory randomization Date: Fri, 15 Apr 2016 15:03:13 -0700 Message-Id: <1460757793-59020-5-git-send-email-thgarnie@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1460757793-59020-1-git-send-email-thgarnie@google.com> References: <1460757793-59020-1-git-send-email-thgarnie@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2532 Lines: 76 Add a new option (CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING) to define the padding used for the physical memory mapping section when KASLR memory is enabled. It ensures there is enough virtual address space when CONFIG_MEMORY_HOTPLUG is used. The default value is 10 terabytes. If CONFIG_MEMORY_HOTPLUG is not used, no space is reserved increasing the entropy available. Signed-off-by: Thomas Garnier --- Based on next-20160413 --- arch/x86/Kconfig | 15 +++++++++++++++ arch/x86/mm/kaslr.c | 14 ++++++++++++-- 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 7c786d4..cc01b69 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2018,6 +2018,21 @@ config RANDOMIZE_MEMORY If unsure, say N. +config RANDOMIZE_MEMORY_PHYSICAL_PADDING + hex "Physical memory mapping padding" if EXPERT + depends on RANDOMIZE_MEMORY + default "0xa" if MEMORY_HOTPLUG + default "0x0" + range 0x1 0x40 if MEMORY_HOTPLUG + range 0x0 0x40 + ---help--- + Define the padding in terabyte added to the existing physical memory + size during kernel memory randomization. It is useful for memory + hotplug support but reduces the entropy available for address + randomization. + + If unsure, leave at the default value. + config HOTPLUG_CPU bool "Support for hot-pluggable CPUs" depends on SMP diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 9de807d..f7dc477 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -63,7 +63,7 @@ void __init kernel_randomize_memory(void) { size_t i; unsigned long addr = memory_rand_start; - unsigned long padding, rand, mem_tb; + unsigned long padding, rand, mem_tb, page_offset_padding; struct rnd_state rnd_st; unsigned long remain_padding = memory_rand_end - memory_rand_start; @@ -74,8 +74,18 @@ void __init kernel_randomize_memory(void) if (!xen_domain()) page_offset_base -= __XEN_SPACE; + /* + * Update Physical memory mapping to available and + * add padding if needed (especially for memory hotplug support). + */ + page_offset_padding = CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; + +#ifdef CONFIG_MEMORY_HOTPLUG + page_offset_padding = max(1UL, page_offset_padding); +#endif + BUG_ON(kaslr_regions[0].base != &page_offset_base); - mem_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT); + mem_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT) + page_offset_padding; if (mem_tb < kaslr_regions[0].size_tb) kaslr_regions[0].size_tb = mem_tb; -- 2.8.0.rc3.226.g39d4020