From: "H. Peter Anvin" <hpa@zytor.com>
To: Kees Cook <keescook@chromium.org>
Cc: Eric Northup <digitaleric@google.com>,
Yinghai Lu <yinghai@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
the arch/x86 maintainers <x86@kernel.org>,
Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
Matthew Garrett <mjg@redhat.com>,
Matt Fleming <matt.fleming@intel.com>,
Dan Rosenberg <drosenberg@vsecurity.com>,
Julien Tinnes <jln@google.com>, Will Drewry <wad@chromium.org>
Subject: Re: [PATCH 6/6] x86: kaslr: relocate base offset at boot
Date: Mon, 15 Apr 2013 14:46:03 -0700 [thread overview]
Message-ID: <516C751B.4020505@zytor.com> (raw)
In-Reply-To: <CAGXu5jJkA0y+5-or4vxUHE5GyNODSoefrYJO7scM1Jh56FoUuA@mail.gmail.com>
On 04/15/2013 02:41 PM, Kees Cook wrote:
>>
>> You seem to be missing something here...
>>
>> There are *two* mappings in 64-bit mode. Physically, if you're going to
>> randomize you might as well randomize over the entire range... except
>> not too far down (on either 32 or 64 bit mode)... in particular, you
>> don't want to drop below 16 MiB if you can avoid it.
>>
>> On 64 bits, there is no reason the virtual address has to be randomized
>> the same way.
>
> Aren't we bound by the negative 2GB addressing due to -mcmodel=kernel?
>
Guys,
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.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2013-04-15 21:46 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-12 20:13 [PATCH v2 0/6] kernel ASLR Kees Cook
2013-04-12 20:13 ` [PATCH 1/6] x86: relocs: generalize Elf structure names Kees Cook
2013-04-16 23:17 ` [tip:x86/kaslr] x86, relocs: Generalize ELF " tip-bot for Kees Cook
2013-04-12 20:13 ` [PATCH 2/6] x86: relocs: consolidate processing logic Kees Cook
2013-04-16 23:18 ` [tip:x86/kaslr] x86, relocs: Consolidate " tip-bot for Kees Cook
2013-04-12 20:13 ` [PATCH 3/6] x86: relocs: add 64-bit ELF support to relocs tool Kees Cook
2013-04-16 23:19 ` [tip:x86/kaslr] x86, relocs: Add " tip-bot for Kees Cook
2013-04-12 20:13 ` [PATCH 4/6] x86: relocs: build separate 32/64-bit tools Kees Cook
2013-04-16 22:21 ` H. Peter Anvin
2013-04-16 22:38 ` Kees Cook
2013-04-16 22:39 ` H. Peter Anvin
2013-04-16 23:20 ` [tip:x86/kaslr] x86, relocs: Build " tip-bot for Kees Cook
2013-04-16 23:22 ` [tip:x86/kaslr] x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF tip-bot for H. Peter Anvin
2013-04-12 20:13 ` [PATCH 5/6] x86: kaslr: routines to choose random base offset Kees Cook
2013-04-14 0:11 ` Yinghai Lu
2013-04-12 20:13 ` [PATCH 6/6] x86: kaslr: relocate base offset at boot Kees Cook
2013-04-14 0:37 ` Yinghai Lu
2013-04-14 3:06 ` H. Peter Anvin
2013-04-15 21:06 ` Eric Northup
2013-04-15 21:25 ` H. Peter Anvin
2013-04-15 21:41 ` Kees Cook
2013-04-15 21:44 ` Eric Northup
2013-04-15 21:46 ` H. Peter Anvin [this message]
2013-04-15 21:59 ` Kees Cook
2013-04-16 2:31 ` H. Peter Anvin
2013-04-16 2:40 ` H. Peter Anvin
2013-04-16 16:08 ` Kees Cook
2013-04-15 22:00 ` Yinghai Lu
2013-04-15 22:07 ` Kees Cook
2013-04-15 22:38 ` Yinghai Lu
2013-04-15 22:42 ` Kees Cook
2013-04-15 22:57 ` Yinghai Lu
2013-04-16 2:34 ` H. Peter Anvin
2013-04-16 2:36 ` H. Peter Anvin
2013-04-16 2:56 ` Yinghai Lu
2013-04-16 3:02 ` H. Peter Anvin
2013-04-16 13:08 ` Ingo Molnar
2013-04-16 13:27 ` H. Peter Anvin
2013-04-16 18:08 ` [PATCH v2 0/6] kernel ASLR Kees Cook
2013-04-16 18:15 ` H. Peter Anvin
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