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Commit 90397a41 authored by Thomas Garnier's avatar Thomas Garnier Committed by Ingo Molnar
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x86/mm: Add memory hotplug support for KASLR memory randomization 



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: default avatarThomas Garnier <thgarnie@google.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Alexander Popov <alpopov@ptsecurity.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lv Zheng <lv.zheng@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1466556426-32664-10-git-send-email-keescook@chromium.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a95ae27c

arch/x86/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -2010,6 +2010,21 @@ 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 terabytes 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

arch/x86/mm/kaslr.c

+6 −1
Original line number Diff line number Diff line
@@ -92,8 +92,13 @@ void __init kernel_randomize_memory(void) 
	if (!kaslr_memory_enabled())

		return;



	/*

	 * Update Physical memory mapping to available and

	 * add padding if needed (especially for memory hotplug support).

	 */

	BUG_ON(kaslr_regions[0].base != &page_offset_base);

	memory_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT);

	memory_tb = ((max_pfn << PAGE_SHIFT) >> TB_SHIFT) +

		CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;



	/* Adapt phyiscal memory region size based on available memory */

	if (memory_tb < kaslr_regions[0].size_tb)