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Date: Mon, 15 Apr 2013 15:57:09 -0700
Message-ID: <CAE9FiQXZcXpyEqHvON0D3u2ivcWQo1=rC1kkt5GLU4rEYaVoQw@mail.gmail.com>
Subject: Re: [PATCH 6/6] x86: kaslr: relocate base offset at boot
From: Yinghai Lu <yinghai@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Eric Northup <digitaleric@google.com>,
        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>
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On Mon, Apr 15, 2013 at 3:42 PM, Kees Cook <keescook@chromium.org> wrote:
> On Mon, Apr 15, 2013 at 3:38 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>
>> so the decompressed image is not moved high?
>
> No, I mean the size of the relocated image is using z_extract_offset
> as the end size of the relocated memory. See select_aslr_address. It
> takes the chosen aslr offset plus the location of z_extract_offset and
> keeps reducing the offset until it's inside the physical end of
> memory.

My point is:
If you move the decompressed high, for example, before aslr uncompressed
vmlinx is on [1024g+16M, 1024g+256M).
after aslr, it is on [1024g+16M + 32M, 1024g+256M + 32M).

You will need to make sure that 32M is still RAM in e820 memmap.
also those range should not be with boot_param, command line, and initrd.
as bootloader could put boot_param, commandline and initrd in that 32M range.

Yinghai
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