efi: libstub: Add image code and data size to the zimage metadata

In order to be able to switch from LoadImage() [which treats the
supplied PE/COFF image as file input only, and reconstructs the memory
image based on the section descriptors] to a mode where we allocate the
memory directly, and invoke the image in place, we need to now how much
memory to allocate beyond the end of the image. So copy this information
from the payload's PE/COFF header to the end of the compressed version
of the payload, so that the decompressor app can access it before
performing the decompression itself.

We'll also need to size of the code region once we switch arm64 to
jumping to the kernel proper with MMU and caches enabled, so let's
capture that information as well. Note that SizeOfCode does not account
for the header, so we need SizeOfHeaders as well.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/Makefile.zboot

@@ -10,18 +10,17 @@ comp-type-$(CONFIG_KERNEL_LZO)		:= lzo
 comp-type-$(CONFIG_KERNEL_XZ)		:= xzkern
 comp-type-$(CONFIG_KERNEL_ZSTD)		:= zstd22
 
-# in GZIP, the appended le32 carrying the uncompressed size is part of the
-# format, but in other cases, we just append it at the end for convenience,
-# causing the original tools to complain when checking image integrity.
-# So disregard it when calculating the payload size in the zimage header.
-zboot-method-y				:= $(comp-type-y)_with_size
-zboot-size-len-y			:= 4
-
-zboot-method-$(CONFIG_KERNEL_GZIP)	:= gzip
-zboot-size-len-$(CONFIG_KERNEL_GZIP)	:= 0
+# Copy the SizeOfHeaders, SizeOfCode and SizeOfImage fields from the payload to
+# the end of the compressed image. Note that this presupposes a PE header
+# offset of 64 bytes, which is what arm64, RISC-V and LoongArch use.
+quiet_cmd_compwithsize = $(quiet_cmd_$(comp-type-y))
+      cmd_compwithsize = $(cmd_$(comp-type-y)) && ( \
+			   dd status=none if=$< bs=4 count=1 skip=37 ; \
+			   dd status=none if=$< bs=4 count=1 skip=23 ; \
+			   dd status=none if=$< bs=4 count=1 skip=36 ) >> $@
 
 $(obj)/vmlinuz: $(obj)/$(EFI_ZBOOT_PAYLOAD) FORCE
-	$(call if_changed,$(zboot-method-y))
+	$(call if_changed,compwithsize)
 
 OBJCOPYFLAGS_vmlinuz.o := -I binary -O $(EFI_ZBOOT_BFD_TARGET) \
 			  --rename-section .data=.gzdata,load,alloc,readonly,contents
@@ -30,7 +29,6 @@ $(obj)/vmlinuz.o: $(obj)/vmlinuz FORCE
 
 AFLAGS_zboot-header.o += -DMACHINE_TYPE=IMAGE_FILE_MACHINE_$(EFI_ZBOOT_MACH_TYPE) \
 			 -DZBOOT_EFI_PATH="\"$(realpath $(obj)/vmlinuz.efi.elf)\"" \
-			 -DZBOOT_SIZE_LEN=$(zboot-size-len-y) \
 			 -DCOMP_TYPE="\"$(comp-type-y)\""
 
 $(obj)/zboot-header.o: $(srctree)/drivers/firmware/efi/libstub/zboot-header.S FORCE
@@ -46,4 +44,4 @@ OBJCOPYFLAGS_vmlinuz.efi := -O binary
 $(obj)/vmlinuz.efi: $(obj)/vmlinuz.efi.elf FORCE
 	$(call if_changed,objcopy)
 
-targets += zboot-header.o vmlinuz vmlinuz.o vmlinuz.efi.elf vmlinuz.efi
+targets += zboot-header.o vmlinuz.o vmlinuz.efi.elf vmlinuz.efi

drivers/firmware/efi/libstub/zboot-header.S

@@ -17,7 +17,7 @@ __efistub_efi_zboot_header:
 	.long		MZ_MAGIC
 	.ascii		"zimg"					// image type
 	.long		__efistub__gzdata_start - .Ldoshdr	// payload offset
-	.long		__efistub__gzdata_size - ZBOOT_SIZE_LEN	// payload size
+	.long		__efistub__gzdata_size - 12		// payload size
 	.long		0, 0					// reserved
 	.asciz		COMP_TYPE				// compression type
 	.org		.Ldoshdr + 0x3c