On Fri, 23 Jan 2026 at 07:52, Anshuman Khandual
[off-list ref] wrote:

On 19/01/26 10:17 PM, Ard Biesheuvel wrote:

quoted

From: Ard Biesheuvel <ardb@kernel.org>

The linear aliases of the kernel text and rodata are mapped read-only as
well. Given that the contents of these regions are mostly identical to
the version in the loadable image, mapping them read-only 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.

Only when going into hibernation or waking up from it do these regions
need to be mapped, so take care of this using a PM notifier.

Just curious - why do we need them mapped while going into or coming back
from the hibernation ?

Because the kernel image is preserved/restored via the linear map. For
some reason, it appears to be sufficient for this mapping to be
read-only but unmapping it entirely results in failures to resume from
hibernation.