fs/iso9660: add support to Grub EFI bootloader in the image

Add support to boot the Grub bootloader from an EFI BIOS in the ISO9660
image.
For that we need to create EFI System Partition (ESP). The ESP is a vfat
partition which contain the Grub2 binary at the /EFI/BOOT/ location.
xorriso command will generate the iso image including the ESP.

We notice Grub can not read and mount the ESP, therefore we place the Grub
configuration file in the ISO9660 partition. A Grub2 builtin configuration
need to be used to tell Grub2 to search automatically its configuration
file in the ISO9660 partition. Use 'set root=(cd0)' in the configuration
file passed to BR2_TARGET_GRUB2_BUILTIN_CONFIG_EFI.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
[yann.morin.1998@free.fr: fix timestamp fixup hook]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

fs/iso9660/Config.in

@@ -2,8 +2,7 @@ config BR2_TARGET_ROOTFS_ISO9660
 	bool "iso image"
 	depends on (BR2_i386 || BR2_x86_64)
 	depends on BR2_LINUX_KERNEL
-	depends on BR2_TARGET_GRUB2_I386_PC || \
-		BR2_TARGET_SYSLINUX_ISOLINUX
+	depends on BR2_TARGET_GRUB2 || BR2_TARGET_SYSLINUX_ISOLINUX
 	select BR2_LINUX_KERNEL_INSTALL_TARGET \
 	       if (!BR2_TARGET_ROOTFS_ISO9660_INITRD && !BR2_TARGET_ROOTFS_INITRAMFS)
 	help
@@ -27,12 +26,15 @@ choice
 
 config BR2_TARGET_ROOTFS_ISO9660_GRUB2
 	bool "grub2"
-	depends on BR2_TARGET_GRUB2_I386_PC
+	depends on BR2_TARGET_GRUB2
 	help
 	  Use Grub 2 as the bootloader for the ISO9660 image. Make
 	  sure to enable the 'iso9660' module in
-	  BR2_TARGET_GRUB2_BUILTIN_MODULES and to use 'cd' as the boot
-	  partition in BR2_TARGET_GRUB2_BOOT_PARTITION=.
+	  BR2_TARGET_GRUB2_BUILTIN_MODULES_PC or
+	  BR2_TARGET_GRUB2_BUILTIN_MODULES_EFI. Use 'cd' as the boot
+	  partition in BR2_TARGET_GRUB2_BOOT_PARTITION= for GRUB on BIOS
+	  or 'set root=(cd0)' in the configuration file passed to
+	  BR2_TARGET_GRUB2_BUILTIN_CONFIG_EFI for GRUB on EFI.
 
 config BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
 	bool "isolinux"
@@ -40,6 +42,19 @@ config BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
 
 endchoice
 
+choice
+	prompt "Boot payload"
+
+config BR2_TARGET_ROOTFS_ISO9660_BIOS_BOOTLOADER
+	bool "legacy bios"
+	depends on BR2_TARGET_GRUB2_I386_PC || BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
+
+config BR2_TARGET_ROOTFS_ISO9660_EFI_BOOTLOADER
+	bool "UEFI"
+	depends on BR2_TARGET_GRUB2_I386_EFI || BR2_TARGET_GRUB2_X86_64_EFI
+
+endchoice
+
 config BR2_TARGET_ROOTFS_ISO9660_BOOT_MENU
 	string "Boot menu config file"
 	default "fs/iso9660/grub.cfg" if BR2_TARGET_ROOTFS_ISO9660_GRUB2
@@ -83,7 +98,7 @@ config BR2_TARGET_ROOTFS_ISO9660_HYBRID
 
 endif
 
-comment "iso image needs a Linux kernel and either grub2 i386-pc or isolinux to be built"
+comment "iso image needs a Linux kernel and either grub2 or isolinux to be built"
 	depends on BR2_i386 || BR2_x86_64
 	depends on !BR2_LINUX_KERNEL || \
-		!(BR2_TARGET_GRUB2_I386_PC || BR2_TARGET_SYSLINUX_ISOLINUX)
+		!(BR2_TARGET_GRUB2 || BR2_TARGET_SYSLINUX_ISOLINUX)

fs/iso9660/iso9660.mk

@@ -57,7 +57,14 @@ else
 ROOTFS_ISO9660_TMP_TARGET_DIR = $(TARGET_DIR)
 endif
 
-ifeq ($(BR2_TARGET_ROOTFS_ISO9660_GRUB2),y)
+ifeq ($(BR2_REPRODUCIBLE),y)
+ROOTFS_ISO9660_VFAT_OPTS = --invariant
+ROOTFS_ISO9660_FIX_TIME = touch -d @$(SOURCE_DATE_EPOCH)
+else
+ROOTFS_ISO9660_FIX_TIME = @:
+endif
+
+ifeq ($(BR2_TARGET_ROOTFS_ISO9660_GRUB2)$(BR2_TARGET_ROOTFS_ISO9660_BIOS_BOOTLOADER),yy)
 ROOTFS_ISO9660_DEPENDENCIES += grub2
 ROOTFS_ISO9660_BOOTLOADER_CONFIG_PATH = \
 	$(ROOTFS_ISO9660_TMP_TARGET_DIR)/boot/grub/grub.cfg
@@ -66,6 +73,23 @@ define ROOTFS_ISO9660_INSTALL_BOOTLOADER
 	$(INSTALL) -D -m 0644 $(BINARIES_DIR)/grub-eltorito.img \
 		$(ROOTFS_ISO9660_TMP_TARGET_DIR)/boot/grub/grub-eltorito.img
 endef
+else ifeq ($(BR2_TARGET_ROOTFS_ISO9660_GRUB2)$(BR2_TARGET_ROOTFS_ISO9660_EFI_BOOTLOADER),yy)
+ROOTFS_ISO9660_DEPENDENCIES += grub2 host-dosfstools host-mtools
+ROOTFS_ISO9660_EFI_PARTITION = boot/fat.efi
+ROOTFS_ISO9660_EFI_PARTITION_PATH = $(ROOTFS_ISO9660_TMP_TARGET_DIR)/$(ROOTFS_ISO9660_EFI_PARTITION)
+ROOTFS_ISO9660_EFI_PARTITION_CONTENT = $(BINARIES_DIR)/efi-part
+ROOTFS_ISO9660_BOOTLOADER_CONFIG_PATH = \
+	$(ROOTFS_ISO9660_TMP_TARGET_DIR)/boot/grub/grub.cfg
+define ROOTFS_ISO9660_INSTALL_BOOTLOADER
+	rm -rf $(ROOTFS_ISO9660_EFI_PARTITION_PATH)
+	mkdir -p $(dir $(ROOTFS_ISO9660_EFI_PARTITION_PATH))
+	dd if=/dev/zero of=$(ROOTFS_ISO9660_EFI_PARTITION_PATH) bs=1M count=1
+	$(HOST_DIR)/sbin/mkfs.vfat $(ROOTFS_ISO9660_VFAT_OPTS) $(ROOTFS_ISO9660_EFI_PARTITION_PATH)
+	$(ROOTFS_ISO9660_FIX_TIME) $(ROOTFS_ISO9660_EFI_PARTITION_CONTENT)/*
+	$(HOST_DIR)/bin/mcopy -p -m -i $(ROOTFS_ISO9660_EFI_PARTITION_PATH) -s \
+		$(ROOTFS_ISO9660_EFI_PARTITION_CONTENT)/* ::/
+	$(ROOTFS_ISO9660_FIX_TIME) $(ROOTFS_ISO9660_EFI_PARTITION_PATH)
+endef
 else ifeq ($(BR2_TARGET_ROOTFS_ISO9660_ISOLINUX),y)
 ROOTFS_ISO9660_DEPENDENCIES += syslinux
 ROOTFS_ISO9660_BOOTLOADER_CONFIG_PATH = \
@@ -128,9 +152,25 @@ ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_DISABLE_EXTERNAL_INITRD
 
 endif # ROOTFS_ISO9660_USE_INITRD
 
+ROOTFS_ISO9660_OPTS += \
+	-J \
+	-R \
+	-no-emul-boot
+
+ifeq ($(BR2_TARGET_ROOTFS_ISO9660_BIOS_BOOTLOADER),y)
+ROOTFS_ISO9660_OPTS += \
+	-boot-load-size 4 \
+	-boot-info-table \
+	-b $(ROOTFS_ISO9660_BOOT_IMAGE)
+endif
+
+ifeq ($(BR2_TARGET_ROOTFS_ISO9660_EFI_BOOTLOADER),y)
+ROOTFS_ISO9660_OPTS += \
+	--efi-boot $(ROOTFS_ISO9660_EFI_PARTITION)
+endif
+
 define ROOTFS_ISO9660_CMD
-	$(HOST_DIR)/bin/xorriso -as mkisofs -J -R -b $(ROOTFS_ISO9660_BOOT_IMAGE) \
-		-no-emul-boot -boot-load-size 4 -boot-info-table \
+	$(HOST_DIR)/bin/xorriso -as mkisofs \
 		$(ROOTFS_ISO9660_OPTS) \
 		-o $@ $(ROOTFS_ISO9660_TMP_TARGET_DIR)
 endef