aarch64: add ability to generate image header

Image header is compatible with Linux aarch64 boot protocol,
so zephyr can be booted with U-boot or Xen loader.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>

arch/arm/core/aarch64/CMakeLists.txt

@@ -31,5 +31,6 @@ zephyr_library_sources_ifdef(CONFIG_GEN_SW_ISR_TABLE isr_wrapper.S)
 zephyr_library_sources_ifdef(CONFIG_IRQ_OFFLOAD irq_offload.c)
 zephyr_library_sources_ifdef(CONFIG_THREAD_LOCAL_STORAGE ../common/tls.c)
 zephyr_library_sources_ifdef(CONFIG_ARM_PSCI smccc-call.S)
+zephyr_library_sources_ifdef(CONFIG_AARCH64_IMAGE_HEADER header.S)
 
 add_subdirectory_ifdef(CONFIG_ARM_MMU mmu)

arch/arm/core/aarch64/Kconfig

@@ -56,6 +56,12 @@ config CMSIS_V2_THREAD_DYNAMIC_STACK_SIZE
 config IPM_CONSOLE_STACK_SIZE
 	default 2048
 
+config AARCH64_IMAGE_HEADER
+	bool "Add image header"
+	help
+	  This option enables standard ARM64 boot image header used by Linux
+	  and understood by loaders such as u-boot on Xen xl tool.
+
 if CPU_CORTEX_A
 
 config ARMV8_A_NS

arch/arm/core/aarch64/header.S

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020 EPAM Systems
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <linker/sections.h>
+#include <arch/cpu.h>
+#include "mmu/arm_mmu.h"
+
+#if CONFIG_MMU_PAGE_SIZE == 4096
+#define HEADER_PGSIZE	1
+#elif CONFIG_MMU_PAGE_SIZE == 16384
+#define HEADER_PGSIZE	2
+#elif CONFIG_MMU_PAGE_SIZE == 65536
+#define HEADER_PGSIZE	3
+#else
+#define HEADER_PGSIZE 0
+#warning "Can't determine page size for header flags"
+#endif
+
+#define HEADER_FLAGS	(HEADER_PGSIZE << 1)
+
+_ASM_FILE_PROLOGUE
+
+SECTION_SUBSEC_FUNC(image_header,_image_header_section,_image_header)
+	b	__start				// branch to kernel start
+	.long	0				// reserved
+	.quad	0				// Image load offset from start
+						// of RAM, little-endian
+
+	.quad	_flash_used			// Effective size of kernel
+						// image, little-endian
+
+	.quad	HEADER_FLAGS			// Informative flags,
+						// little-endian
+
+	.quad	0				// reserved
+	.quad	0				// reserved
+	.quad	0				// reserved
+	.ascii	"ARM\x64"			// Magic number
+	.long	0				// reserved

include/arch/arm/aarch64/scripts/linker.ld

@@ -107,6 +107,12 @@ SECTIONS
 #ifndef CONFIG_XIP
         z_mapped_start = .;
 #endif
+
+#ifdef CONFIG_AARCH64_IMAGE_HEADER
+        KEEP(*(.image_header))
+        KEEP(*(".image_header.*"))
+#endif
+
         _vector_start = .;
         KEEP(*(.exc_vector_table))
         KEEP(*(".exc_vector_table.*"))