[PATCH v3 4/4] ARM: Implement PAN for LPAE by TTBR0 page table walks disablement

[Linus Walleij]

On Tue, May 14, 2024 at 8:41 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:

> I sent you a small initramfs by PM.

Booted this just fine on Vexpress QEMU:

Run /init as init process
sysctl: error: 'kernel.hotplug' is an unknown key


boot (Linux 6.9.0-rc1+, BusyBox v1.16.0.git, kexec-tools 2.0.1-git)
/ # mount -t debugfs none /sys/kernel/debug
/ # echo "ACCESS_USERSPACE" | cat >/sys/kernel/debug/provoke-crash/DIRECT
lkdtm: Performing direct entry ACCESS_USERSPACE
lkdtm: attempting bad read at 76fea000
8<--- cut here ---
Unable to handle kernel paging request at virtual address 76fea000 when read
[76fea000] *pgd=82c93003, *pmd=82c94003, *pte=a00000811e2f5f
Internal error: Oops: 206 [#1] SMP ARM
CPU: 1 PID: 86 Comm: cat Not tainted 6.9.0-rc1+ #46
Hardware name: ARM-Versatile Express
PC is at lkdtm_ACCESS_USERSPACE+0xc0/0x138
LR is at lkdtm_ACCESS_USERSPACE+0xc0/0x138

I'm starting to think it is something about different LPAE implementations here.

Yours,
Linus Walleij