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Message-ID: <20170615080329.GB16181@x1>
Date: Thu, 15 Jun 2017 16:03:29 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-kernel@...r.kernel.org, izumi.taku@...fujitsu.com
Cc: keescook@...omium.org, x86@...nel.org, fanc.fnst@...fujitsu.com,
caoj.fnst@...fujitsu.com, douly.fnst@...fujitsu.com
Subject: Re: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be
randomized in mirror regions if existed
Sorry, forget adding Taku to the list.
Hi Taku,
On 06/15/17 at 03:52pm, Baoquan He wrote:
> Our customer reported that Kernel text may be located on non-mirror
> region (movable zone) when both address range mirroring feature and
> KASLR are enabled.
>
> The functions of address range mirroring feature are as follows.
> - The physical memory region whose descriptors in EFI memory map have
> EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored
> - The function arranges such mirror region into normal zone and other region
> into movable zone in order to locate kernel code and data on mirror region
>
> So we need restrict kernel to be located inside mirror region if it
> is existed.
>
> The method is very simple. If efi is enabled, just iterate all efi
> memory map and pick up mirror region to process for adding candidate
> of slot. If efi disabled or no mirror region existed, still process
> e820 memory map. This won't bring much efficiency loss, at worst we
> just go through all efi memory maps and found no mirror.
>
> One question:
> From code, though mirror regions are existed, they are meaningful only
> if kernelcore=mirror kernel option is specified. Not sure if my understanding
> is correct.
Since you are the author of kernelcore=mirror related code and expert on
mirror feature, could you help answer above question?
Thanks
Baoquan
>
> NOTE:
> I haven't got a machine with efi mirror region enabled, so only test the
> e820 map processing case and the case of no mirror region on efi machine.
> So set this as a RFC patchset, will post formal one after above question
> is made clear and mirror issue test passed.
>
> Baoquan He (2):
> x86/boot/KASLR: Adapt process_e820_entry for all kinds of memory map
> x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if
> existed
>
> arch/x86/boot/compressed/kaslr.c | 129 +++++++++++++++++++++++++++++++--------
> 1 file changed, 104 insertions(+), 25 deletions(-)
>
> --
> 2.5.5
>
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