arm64: efi: Move dcache cleaning of loaded image out of efi_enter_kernel()

The efi_enter_kernel() routine will be shared between the existing EFI
stub and the zboot decompressor, and the version of
dcache_clean_to_poc() that the core kernel exports to the stub will not
be available in the latter case.

So move the handling into the .c file which will remain part of the stub
build that integrates directly with the kernel proper.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/efi-entry.S

@@ -23,15 +23,6 @@ SYM_CODE_START(efi_enter_kernel)
 	add	x19, x0, x2		// relocated Image entrypoint
 	mov	x20, x1			// DTB address
 
-	/*
-	 * Clean the copied Image to the PoC, and ensure it is not shadowed by
-	 * stale icache entries from before relocation.
-	 */
-	ldr	w1, =kernel_size
-	add	x1, x0, x1
-	bl	dcache_clean_poc
-	ic	ialluis
-
 	/*
 	 * Clean the remainder of this routine to the PoC
 	 * so that we can safely disable the MMU and caches.

arch/arm64/kernel/image-vars.h

@@ -10,7 +10,6 @@
 #error This file should only be included in vmlinux.lds.S
 #endif
 
-PROVIDE(__efistub_kernel_size		= _edata - _text);
 PROVIDE(__efistub_primary_entry_offset	= primary_entry - _text);
 
 /*

drivers/firmware/efi/libstub/arm64-stub.c

@@ -156,7 +156,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 			 */
 			*image_addr = (u64)_text;
 			*reserve_size = 0;
-			return EFI_SUCCESS;
+			goto clean_image_to_poc;
 		}
 
 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
@@ -172,5 +172,13 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 	*image_addr = *reserve_addr;
 	memcpy((void *)*image_addr, _text, kernel_size);
 
+clean_image_to_poc:
+	/*
+	 * Clean the copied Image to the PoC, and ensure it is not shadowed by
+	 * stale icache entries from before relocation.
+	 */
+	dcache_clean_poc(*image_addr, *image_addr + kernel_size);
+	asm("ic ialluis");
+
 	return EFI_SUCCESS;
 }