efi: disentangle the generic EFI stub from FDT

EFI architectures other than x86 rely on FDT to pass information between the stub and the core kernel. In hindsight, this is probably a mistake, given the issues around abuse of the internal ABI, and potential inconsistencies between two sources of information that both originate in the firmware (memory map, command line, etc)

Another reason for avoiding updates to the DT is the fact that it interferes with secure boot and measured boot. Even if we measure the original firmware provided DT into the TPM, the DT that the kernel receives is a completely different blob, and verifying it against the TPM event log is currently impossible.

So let's start hacking away at this, and refactor the generic stub so that all the FDT pieces are isolated in a singe source file, and rely on generic EFI config tables for passing the initrd base and size. Ultimately, this should permit all EFI architectures doing DT boot to perform the handover to the core kernel in a different way, and pass on the firmware provided DT unmodified, but this requires some future work for ARM/arm64 and RISC-V.

However, we can easily convert the newly added LoongArch code to adopt this approach, and to consume the DT strictly for hardware descriptions (if not doing ACPI boot), and pass the initrd, memory map and everything else via EFI config tables. Generating empty DTBs on ACPI platforms will no longer be needed.

The first six patches as well as patch #10 are general cleanup, and can be merged separately. The remaining patches refactor the FDT code in the EFI stub so that we can avoid it on platforms that don't need it for other reasons. Finally, LoongArch is updated to use DT only for hardware descriptions when doing EFI boot.

Changes since v1:
- to ease merging this with the loongarch tree, drop unrelated cleanup changes, which will be merged separately;
- drop the patch to enable DT for hw descriptions - it will be picked up again later
- avoid creating the INITRD table if no initrd was actually loaded;
- incorporate feedback from Huacai on the arch/loongarch changes;
- other minor tweaks.

Ard Biesheuvel (8):
efi: libstub: drop pointless get_memory_map() call
efi: libstub: avoid efi_get_memory_map() for allocating the virt map
efi: libstub: simplify efi_get_memory_map() and struct efi_boot_memmap
efi: libstub: remove pointless goto kludge
efi: libstub: unify initrd loading between architectures
efi: libstub: remove DT dependency from generic stub
efi: libstub: install boot-time memory map as config table efi/loongarch: libstub: remove dependency on flattened DT

 Documentation/arm/uefi.rst                     |   4 -
 arch/loongarch/Kconfig                         |   3 -
 arch/loongarch/include/asm/bootinfo.h          |   2 +-
 arch/loongarch/kernel/efi.c                    |  30 +++-
 arch/loongarch/kernel/env.c                    |  13 +-
 arch/loongarch/kernel/head.S                   |   2 +
 arch/loongarch/kernel/setup.c                  |   4 +-
 drivers/firmware/efi/efi.c                     |  15 ++
 drivers/firmware/efi/libstub/Makefile          |  13 +-
 drivers/firmware/efi/libstub/arm64-stub.c      |  19 +--
 drivers/firmware/efi/libstub/efi-stub-helper.c | 139 ++++++++--------
 drivers/firmware/efi/libstub/efi-stub.c        |  90 ++++------
 drivers/firmware/efi/libstub/efistub.h         |  28 +---
 drivers/firmware/efi/libstub/fdt.c             | 176 +++++++++++---------
 drivers/firmware/efi/libstub/loongarch-stub.c  |  56 ++++++-
 drivers/firmware/efi/libstub/mem.c             |  93 +++++------
 drivers/firmware/efi/libstub/randomalloc.c     |  25 +--
 drivers/firmware/efi/libstub/relocate.c        |  21 +--
 drivers/firmware/efi/libstub/x86-stub.c        |  30 +---
 include/linux/efi.h                            |  15 ++
 20 files changed, 395 insertions(+), 383 deletions(-)

2.35.1