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Date:   Tue, 24 May 2022 09:11:59 +0800
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Subject: Re: [PATCH 0/2] Add support to relocate kernel image to mirrored
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From:   mawupeng <mawupeng1@huawei.com>
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在 2022/5/23 22:41, Ard Biesheuvel 写道:
> On Mon, 23 May 2022 at 03:18, mawupeng <mawupeng1@huawei.com> wrote:
>>
>>
>>
>> 在 2022/5/20 14:52, Ard Biesheuvel 写道:
>>> On Thu, 19 May 2022 at 13:09, mawupeng <mawupeng1@huawei.com> wrote:
>>>>
>>>>
>>>>
>>>> 在 2022/5/7 17:28, mawupeng 写道:
>>>>>
>>>>>
>>>>> 在 2022/5/3 17:58, Ard Biesheuvel 写道:
>>>>>> On Tue, 19 Apr 2022 at 08:43, Wupeng Ma <mawupeng1@huawei.com> wrote:
>>>>>>>
>>>>>>> From: Ma Wupeng <mawupeng1@huawei.com>
>>>>>>>
>>>>>>> Now system image will perfer to be located to mirrored regions both KASLR
>>>>>>> on and off.
>>>>>>>
>>>>>>
>>>>>> Hello Ma Wupeng,
>>>>>>
>>>>>> I wonder if we could simplify this as follows:
>>>>>> - ignore the non-KASLR case for now, and rely on the bootloader  > load the image into mirrored memory if it exists;
>>>>>
>>>>> In grub, memory for static image is allocated via the following path:
>>>>>
>>>>> grub_cmd_linux
>>>>>      kernel = grub_malloc(filelen)
>>>>>      kernel_alloc_addr = grub_efi_allocate_any_pages (kernel_alloc_pages)
>>>>>      grub_memcpy (kernel_addr, kernel, grub_min(filelen, kernel_size))
>>>>>       grub_loader_set (grub_linux_boot, grub_linux_unload, 0)
>>>>>
>>>>> Can we get memory from mirrored region by the following steps:
>>>>> 1. get memory map by calling grub_efi_get_memory_map()
>>>>> 2. iter all memory map to find a suitable mirrored memory area
>>>>> 3. locate kernel image to this area
>>>>>
>>>>> So, if kaslr is not enabled
>>>>>     - grub will load kernel into mirrored region
>>>>> else
>>>>>     - arm64-stub.c will relocate kernel image to mirrored region
>>>>>
>>>>> Is this feasible?
>>>>
>>>> Is this a feasible proposal to relocate the static kernel image itself
>>>> into more reliable memory?
>>>>
>>>
>>> I'm not sure, it all depends on the firmware.
>>>
>>> When GRUB calls LoadImage(), the firmware will reallocate the image
>>> and unpack it there. So it is really the firmware's job to ensure that
>>> the image is loaded into a suitable location.
>>>
>>> I have some code here that implements a EFI based decompressor, and
>>> which loads the kernel image into mirrored memory if it exists,
>>> without the need to move it again. It could trivially be modified to
>>> deal with non-randomized loads as well.
>>>
>>> But the bottom line is that UEFI should expose the ability to target
>>> mirrored memory, hacking around it like this is not a sustainable
>>> approach.
>>
>> Since firmware is responsible for put kernel static image into mirrored
>> region and kernel is responsible for relocate this image into mirrored
>> region if kaslr is enabled. There is no conflict between these two.
>>
>> Can we integrate the kernel part(introduce mirrored support to arm64) first?
>>
> 
> Yes. If you drop the changes related to fake memmap and rebase, please
> resend them after -rc1 is released.

Ok, I will drop the changes related to fake memmap and rebase and then
resend them after -rc1 is released.

Thanks for reviewing.

> .