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

On 09.06.2026 08:22, Marek Szyprowski wrote:
> On 29.05.2026 17:02, Ard Biesheuvel wrote:
>> From: Ard Biesheuvel <[email protected]>
>>
>> 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 <[email protected]>
> 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.

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