cbfstool/linux_trampoline: Fill the ACPI RSDP entry

With LinuxBoot Linux relied on the legacy method of fetching the RSDP
pointer to get ACPI. This uses a more modern approach available since
2018 on the Linux kernel, which involves filling in the zero page.

This method takes precedence over any other method of fetching the
RSDP in Linux (UEFI, Kexec, Legacy/BIOS). Some UEFI zealots are
threatening that legacy code will be removed from Linux so it's best
to already adapt to that possibility.

Tested on Qemu:
- With qemu the RSDP is always in the EBDA, so checking if Linux uses
  the provided pointer is better done with a forced bad entry
- With a fake bad pointer Linux correctly does not find RDSP

Change-Id: I688b94608b03b0177c42d2834c7e3beb802ae686
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62574
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

0 files changed, 0 insertions, 0 deletions