[PATCH] efi/libstub/arm64: handle randomized TEXT_OFFSET

[Kim Phillips]

On Tue, 24 Apr 2018 12:00:58 +0100
Mark Rutland <mark.rutland at arm.com> wrote:

> When CONFIG_RANDOMIZE_TEXT_OFFSET is selected, TEXT_OFFSET is an
> arbitrary multiple of PAGE_SIZE in the interval [0, 2MB).
> 
> The EFI stub doesn't accuont for this, and only handles the case where
> TEXT_OFFSET is multiple of EFI_KIMG_ALIGN. This can result in the kernel
> being loaded to an erroneous physical alignment. This has been observed
> to result in spurious stack overflow reports and failure to make use of
> the IRQ stacks, and theoretically could result in a number of other
> issues.
> 
> We can OR in the low bits of TEXT_OFFSET to ensure that we have the
> necessary offset (and hence have the necessary alignment), so let's do
> that.
> 
> Fixes: 6f26b3671184c36d ("arm64: kaslr: increase randomization granularity")
> Reported-by: Kim Phillips <kim.phillips at arm.com>
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: linux-efi at vger.kernel.org
> ---

Tested-by: Kim Phillips <kim.phillips at arm.com>

Thanks,

Kim