arm64: efi: increase EFI PE/COFF header padding to 64 KB

Commit 76085aff ("efi/libstub/arm64: align PE/COFF sections to segment
alignment") increased the PE/COFF section alignment to match the minimum
segment alignment of the kernel image, which ensures that the kernel does
not need to be moved around in memory by the EFI stub if it was built as
relocatable.

However, the first PE/COFF section starts at _stext, which is only 4 KB
aligned, and so the section layout is inconsistent. Existing EFI loaders
seem to care little about this, but it is better to clean this up.

So let's pad the header to 64 KB to match the PE/COFF section alignment.

Fixes: 76085aff ("efi/libstub/arm64: align PE/COFF sections to segment alignment")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20201027073209.2897-2-ardb@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/efi-header.S

@@ -147,6 +147,6 @@ efi_debug_entry:
 	 * correctly at this alignment, we must ensure that .text is
 	 * placed at a 4k boundary in the Image to begin with.
 	 */
-	.align 12
+	.balign	SEGMENT_ALIGN
 efi_header_end:
 	.endm