riscv: efi: enable generic EFI compressed boot

Wire up the generic EFI zboot support for RISC-V.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>

arch/riscv/Makefile

@@ -136,10 +136,14 @@ ifneq ($(CONFIG_XIP_KERNEL),y)
 ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),yy)
 KBUILD_IMAGE := $(boot)/loader.bin
 else
+ifeq ($(CONFIG_EFI_ZBOOT),)
 KBUILD_IMAGE := $(boot)/Image.gz
+else
+KBUILD_IMAGE := $(boot)/vmlinuz.efi
+endif
 endif
 endif
-BOOT_TARGETS := Image Image.gz loader loader.bin xipImage
+BOOT_TARGETS := Image Image.gz loader loader.bin xipImage vmlinuz.efi
 
 all:	$(notdir $(KBUILD_IMAGE))
 

arch/riscv/boot/.gitignore

@@ -4,4 +4,5 @@ Image.*
 loader
 loader.lds
 loader.bin
+vmlinuz*
 xipImage

arch/riscv/boot/Makefile

@@ -58,3 +58,9 @@ $(obj)/Image.lzo: $(obj)/Image FORCE
 
 $(obj)/loader.bin: $(obj)/loader FORCE
 	$(call if_changed,objcopy)
+
+EFI_ZBOOT_PAYLOAD	:= Image
+EFI_ZBOOT_BFD_TARGET	:= elf$(BITS)-littleriscv
+EFI_ZBOOT_MACH_TYPE	:= RISCV$(BITS)
+
+include $(srctree)/drivers/firmware/efi/libstub/Makefile.zboot