Re: [PATCH] powerpc/32s: fix booting with CONFIG_PPC_EARLY_DEBUG_BOOTX

From: Michael Ellerman
Date: Wed Jun 12 2019 - 01:03:46 EST

On Mon, 2019-06-03 at 13:00:51 UTC, Christophe Leroy wrote:
> When booting through OF, setup_disp_bat() does nothing because
> disp_BAT are not set. By change, it used to work because BOOTX
> buffer is mapped 1:1 at address 0x81000000 by the bootloader, and
> btext_setup_display() sets virt addr same as phys addr.
> But since commit 215b823707ce ("powerpc/32s: set up an early static
> hash table for KASAN."), a temporary page table overrides the
> bootloader mapping.
> This 0x81000000 is also problematic with the newly implemented
> Kernel Userspace Access Protection (KUAP) because it is within user
> address space.
> This patch fixes those issues by properly setting disp_BAT through
> a call to btext_prepare_BAT(), allowing setup_disp_bat() to
> properly setup BAT3 for early bootx screen buffer access.
> Reported-by: Mathieu Malaterre <malat@xxxxxxxxxx>
> Fixes: 215b823707ce ("powerpc/32s: set up an early static hash table for KASAN.")
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> Tested-by: Mathieu Malaterre <malat@xxxxxxxxxx>

Applied to powerpc fixes, thanks.