(+ Mike)

On Wed, 23 Jan 2019 at 10:44, Ard Biesheuvel [off-list ref] wrote:

On Wed, 23 Jan 2019 at 06:31, Dave Young [off-list ref] wrote:

quoted

Hi,

On 01/22/19 at 04:06pm, Ard Biesheuvel wrote:

quoted

The bitmap left in the framebuffer by the firmware is described by an
ACPI table called "BGRT", which describes the size, pixel format and
the address of a BMP image in memory. While the BGRT ACPI table is
guaranteed to reside in a "ACPI reclaim" memory region, which is
never touched by Linux. The BMP image, however, typically resides
in EFI Boot Services Memory, which may have been overwritten by the
time the BGRT discovery routine runs.

I vaguely remember boot service memory is reserved on X86,  so this
is an issue of arm only?

No both ARM and x86 are affected. Harry and/or Peter should be able to
comment on the details.

OK, so ARM is definitely affected, but after having had to revert this
patch since it breaks x86, I am looking into more detail and I have
trouble figuring *why* this would fail on x86 since, as Dave points
out, the x86 Linux kernel does not release boot services data regions
for general allocation until much later.

Mike (or Peter), do you happen to have a Linux boot log of the case
where the BGRT is being corrupted?

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