Re: [PATCH v7 15/15] arm64: mm: Unmap kernel data/bss entirely from the linear map

[Vladimir Murzin <vladimir.murzin@arm.com>]

Hi,

On 6/9/26 07:28, Marek Szyprowski wrote:
> On 09.06.2026 08:22, Marek Szyprowski wrote:
>> On 29.05.2026 17:02, Ard Biesheuvel wrote:
>>> From: Ard Biesheuvel <ardb@kernel.org>
>>>
>>> The linear aliases of the kernel text and rodata are also mapped
>>> read-only in the linear map. Given that the contents of these regions
>>> are mostly identical to the version in the loadable image, mapping them
>>> read-only and leaving their contents visible is a reasonable hardening
>>> measure.
>>>
>>> Data and bss, however, are now also mapped read-only but the contents of
>>> these regions are more likely to contain data that we'd rather not leak.
>>> So let's unmap these entirely in the linear map when the kernel is
>>> running normally.
>>>
>>> When going into hibernation or waking up from it, these regions need to
>>> be mapped, so map the region initially, and toggle the valid bit so
>>> map/unmap the region as needed.
>>>
>>> Doing so is required because pages covering the kernel image are marked
>>> as PageReserved, and therefore disregarded for snapshotting by the
>>> hibernate logic unless they are mapped.
>>>
>>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>> This commit landed in yesterday's linux-next as commit 63e0b6a5b693
>> ("arm64: mm: Unmap kernel data/bss entirely from the linear map").
>> In my tests I found that it breaks booting of RaspberryPi3 and
>> RaspberryPi4 boards with the following kernel panic:
> One more comment - reverting 63e0b6a5b693 and 53205d56212c (dependent
> change) on top of next-20260608 fixes this issue.
> 

Thanks for report! It seems it already has been reported and discussed in
another thread [1].

[1] https://lore.kernel.org/linux-arm-kernel/aicVyebkEMs6w6UV@sirena.co.uk/

Cheers
Vladimir


> Best regards
> -- Marek Szyprowski, PhD Samsung R&D Institute Poland
>