On Tue, 9 Jun 2026 at 08:28, Marek Szyprowski [off-list ref] wrote:

On 09.06.2026 08:22, Marek Szyprowski wrote:

quoted

On 29.05.2026 17:02, Ard Biesheuvel wrote:

quoted

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:

Seeing the same panic on R-Car H3 ES2.0 (Cortex A57/A53), but not
on R-Car V4M (Cortex A76).

One more comment - reverting 63e0b6a5b693 and 53205d56212c (dependent
change) on top of next-20260608 fixes this issue.

Confirmed, too.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds