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

On Tue, 9 Jun 2026 at 08:28, Marek Szyprowski <[email protected]> wrote:
> 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:

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 -- [email protected]

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