From: Andy Lutomirski <luto@amacapital.net>
To: Baoquan He <bhe@redhat.com>, linux-kernel@vger.kernel.org
Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
x86@kernel.org, keescook@chromium.org, vgoyal@redhat.com,
whissi@whissi.de
Subject: Re: [PATCH 0/6] randomize kernel physical address and virtual address separately
Date: Tue, 20 Jan 2015 20:19:36 -0800 [thread overview]
Message-ID: <54BF28D8.70107@amacapital.net> (raw)
In-Reply-To: <1421811437-2787-1-git-send-email-bhe@redhat.com>
On 01/20/2015 07:37 PM, Baoquan He wrote:
> Currently kaslr only randomize physical address of kernel loading, then add the delta
> to virtual address of kernel text mapping. Because kernel virtual address can only be
> from __START_KERNEL_map to LOAD_PHYSICAL_ADDR+CONFIG_RANDOMIZE_BASE_MAX_OFFSET, namely
> [0xffffffff80000000, 0xffffffffc0000000], so physical address can only be randomized
> in region [LOAD_PHYSICAL_ADDR, CONFIG_RANDOMIZE_BASE_MAX_OFFSET], namely [16M, 1G].
>
> So hpa and Vivek suggested the randomization should be done separately for both physical
> and virtual address. In this patchset I tried it. And after randomization, relocation
> handling only depends on virtual address changing, means I only check whether virtual
> address is randomized to other position, if yes relocation need be handled, if no just
> skip the relocation handling though physical address is randomized to different place.
> Now physical address can be randomized from 16M to 4G, virtual address offset can be
> from 16M to 1G.
>
> Leftover problem:
> hpa want to see the physical randomization can cover the whole physical memory. I
> checked code and found it's hard to do. Because in arch/x86/boot/compressed/head_64.S
> an identity mapping of 4G is built and then kaslr and decompressing are done. The #PF
> handler solution which he suggested is only available after jump into decompressed
> kernel, namely in arch/x86/kernel/head_64.S. I didn't think of a way to do the whole
> memory covering for physical address randomization, any suggestion or idea?
>
I have no idea what the #PF thing you're referring to is, but I have
code to implement a #PF handler in boot/compressed if it would be
helpful. It's two patches:
https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=89476ea6a2becbaee4f45c3b6689ff31b6aa959a
https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=142d86921e6f271261584016fc8cfa5cdbf455ba
You can't recover from a page fault in my version of this code, but that
would be straightforward to add.
--Andy
next prev parent reply other threads:[~2015-01-21 4:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-21 3:37 [PATCH 0/6] randomize kernel physical address and virtual address separately Baoquan He
2015-01-21 3:37 ` [PATCH 1/6] remove a unused function parameter Baoquan He
2015-01-21 3:37 ` [PATCH 2/6] a bug that relocation can not be handled when kernel is loaded above 2G Baoquan He
2015-01-21 3:37 ` [PATCH 3/6] Introduce a function to randomize the kernel text mapping address Baoquan He
2015-01-21 3:37 ` [PATCH 4/6] adapt choose_kernel_location to add the kernel virtual address randomzation Baoquan He
2015-01-21 3:37 ` [PATCH 5/6] change the relocations behavior for kaslr on x86_64 Baoquan He
2015-01-21 3:37 ` [PATCH 6/6] extend the upper limit of kernel physical address randomization to 4G Baoquan He
2015-01-21 4:19 ` Andy Lutomirski [this message]
2015-01-21 4:46 ` [PATCH 0/6] randomize kernel physical address and virtual address separately Baoquan He
2015-02-01 8:10 ` Baoquan He
2015-02-01 13:13 ` Andy Lutomirski
2015-02-02 9:34 ` Baoquan He
2015-02-02 12:10 ` Baoquan He
2015-01-21 6:18 ` Kees Cook
2015-02-02 16:42 ` H. Peter Anvin
2015-02-03 15:30 ` Baoquan He
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