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Message-ID: <38e10823-8916-66d0-7fe9-1fe465a9c5e0@infradead.org>
Date: Mon, 25 Jun 2018 16:41:09 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Thomas Garnier <thgarnie@...gle.com>, kernel-hardening@...ts.openwall.com
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Matthias Kaehlcke <mka@...omium.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Tom Lendacky <thomas.lendacky@....com>, Cao jin <caoj.fnst@...fujitsu.com>,
Kees Cook <keescook@...omium.org>, Baoquan He <bhe@...hat.com>,
"H.J. Lu" <hjl.tools@...il.com>, Jan H. Schönherr
<jschoenh@...zon.de>, Kate Stewart <kstewart@...uxfoundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...e.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 27/27] x86/kaslr: Add option to extend KASLR range from
1GB to 3GB
On 06/25/18 15:39, Thomas Garnier wrote:
> Add a new CONFIG_RANDOMIZE_BASE_LARGE option to benefit from PIE
> support. It increases the KASLR range from 1GB to 3GB. The new range
> stars at 0xffffffff00000000 just above the EFI memory region. This
> option is off by default.
>
> The boot code is adapted to create the appropriate page table spanning
> three PUD pages.
>
> The relocation table uses 64-bit integers generated with the updated
> relocation tool with the large-reloc option.
>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
> arch/x86/Kconfig | 21 +++++++++++++++++++++
> arch/x86/boot/compressed/Makefile | 5 +++++
> arch/x86/boot/compressed/misc.c | 10 +++++++++-
> arch/x86/include/asm/page_64_types.h | 9 +++++++++
> arch/x86/kernel/head64.c | 15 ++++++++++++---
> arch/x86/kernel/head_64.S | 11 ++++++++++-
> 6 files changed, 66 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 42f77aff5df1..f6cb20a66e8a 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2236,6 +2236,27 @@ config X86_PIE
> select DYNAMIC_MODULE_BASE
> select MODULE_REL_CRCS if MODVERSIONS
>
> +config RANDOMIZE_BASE_LARGE
> + bool "Increase the randomization range of the kernel image"
> + depends on X86_64 && RANDOMIZE_BASE
> + select X86_PIE
> + select X86_MODULE_PLTS if MODULES
> + default n
> + ---help---
> + Build the kernel as a Position Independent Executable (PIE) and
> + increase the available randomization range from 1GB to 3GB.
> +
> + This option impacts performance on kernel CPU intensive workloads up
> + to 10% due to PIE generated code. Impact on user-mode processes and
> + typical usage would be significantly less (0.50% when you build the
how about:
(0.5% during a kernel build).
> + kernel).
> +
> + The kernel and modules will generate slightly more assembly (1 to 2%
> + increase on the .text sections). The vmlinux binary will be
> + significantly smaller due to less relocations.
preferably s/less/fewer/
> +
> + If unsure say N
> +
> config HOTPLUG_CPU
> bool "Support for hot-pluggable CPUs"
> depends on SMP
--
~Randy
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