image: allow building FIT and uImage with ramdisk

Instead of embedding the initrd cpio archive into the kernel, allow
for having an external ramdisk added to the FIT or uImage.
This is useful to overcome kernel size limitations present in many
stock bootloaders, as the ramdisk is then loaded seperately and doesn't
add to the kernel size. Hence we can have larger ramdisks to host ie.
installers with all binaries to flash included (or a web-based
firmware selector).
In terms of performance and total size the differences are neglectible.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

include/image-commands.mk

@@ -196,11 +196,22 @@ define Build/eva-image
 	mv $@.new $@
 endef
 
+define Build/initrd_compression
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),.bzip2) \
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),.gzip) \
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA),.lzma) \
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ),.xz) \
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD),.zstd)
+endef
+
 define Build/fit
 	$(TOPDIR)/scripts/mkits.sh \
 		-D $(DEVICE_NAME) -o $@.its -k $@ \
 		$(if $(word 2,$(1)),-d $(word 2,$(1))) -C $(word 1,$(1)) \
 		$(if $(findstring with-rootfs,$(word 3,$(1))),-r $(IMAGE_ROOTFS)) \
+		$(if $(findstring with-initrd,$(word 3,$(1))), \
+			$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPERATE), \
+				-i $(KERNEL_BUILD_DIR)/initrd.cpio$(strip $(call Build/initrd_compression)))) \
 		-a $(KERNEL_LOADADDR) -e $(if $(KERNEL_ENTRY),$(KERNEL_ENTRY),$(KERNEL_LOADADDR)) \
 		$(if $(DEVICE_FDT_NUM),-n $(DEVICE_FDT_NUM)) \
 		-c $(if $(DEVICE_DTS_CONFIG),$(DEVICE_DTS_CONFIG),"config@1") \
@@ -450,6 +461,22 @@ define Build/uImage
 	mv $@.new $@
 endef
 
+define Build/uImage-with-ramdisk
+	mkimage \
+		-A $(LINUX_KARCH) \
+		-O linux \
+		-T kernel \
+		-C $(word 1,$(1)) \
+		-a $(KERNEL_LOADADDR) \
+		-e $(if $(KERNEL_ENTRY),$(KERNEL_ENTRY),$(KERNEL_LOADADDR)) \
+		-i $(KERNEL_BUILD_DIR)/initrd.cpio.$(strip $(call Build/initrd_compression)) \
+		-n '$(if $(UIMAGE_NAME),$(UIMAGE_NAME),$(call toupper,$(LINUX_KARCH)) $(VERSION_DIST) Linux-$(LINUX_VERSION))' \
+		$(if $(UIMAGE_MAGIC),-M $(UIMAGE_MAGIC)) \
+		$(wordlist 2,$(words $(1)),$(1)) \
+		-d $@ $@.new
+	mv $@.new $@
+endef
+
 define Build/xor-image
 	$(STAGING_DIR_HOST)/bin/xorimage -i $@ -o $@.xor $(1)
 	mv $@.xor $@

include/kernel-defaults.mk

@@ -48,6 +48,13 @@ else
 endif
 
 ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
+  ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPERATE),y)
+    define Kernel/SetInitramfs/PreConfigure
+	grep -v -e CONFIG_BLK_DEV_INITRD $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config
+	echo 'CONFIG_BLK_DEV_INITRD=y' >> $(LINUX_DIR)/.config
+	echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(LINUX_DIR)/.config
+    endef
+  else
   ifeq ($(strip $(CONFIG_EXTERNAL_CPIO)),"")
     define Kernel/SetInitramfs/PreConfigure
 	grep -v -e INITRAMFS -e CONFIG_RD_ -e CONFIG_BLK_DEV_INITRD $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config
@@ -60,14 +67,19 @@ ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
 	echo 'CONFIG_INITRAMFS_SOURCE="$(call qstrip,$(CONFIG_EXTERNAL_CPIO))"' >> $(LINUX_DIR)/.config
     endef
   endif
+endif
 
   define Kernel/SetInitramfs
 	rm -f $(LINUX_DIR)/.config.prev
 	mv $(LINUX_DIR)/.config $(LINUX_DIR)/.config.old
 	$(call Kernel/SetInitramfs/PreConfigure)
+  ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPERATE),y)
 	echo 'CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)' >> $(LINUX_DIR)/.config
 	echo 'CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)' >> $(LINUX_DIR)/.config
 	echo "$(if $(CONFIG_TARGET_INITRAMFS_FORCE),CONFIG_INITRAMFS_FORCE=y,# CONFIG_INITRAMFS_FORCE is not set)" >> $(LINUX_DIR)/.config
+  else
+	echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(LINUX_DIR)/.config
+  endif
 	echo "$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_NONE),CONFIG_INITRAMFS_COMPRESSION_NONE=y,# CONFIG_INITRAMFS_COMPRESSION_NONE is not set)" >> $(LINUX_DIR)/.config
 	echo -e "$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),CONFIG_INITRAMFS_COMPRESSION_GZIP=y\nCONFIG_RD_GZIP=y,# CONFIG_INITRAMFS_COMPRESSION_GZIP is not set\n# CONFIG_RD_GZIP is not set)" >> $(LINUX_DIR)/.config
 	echo -e "$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),CONFIG_INITRAMFS_COMPRESSION_BZIP2=y\nCONFIG_RD_BZIP2=y,# CONFIG_INITRAMFS_COMPRESSION_BZIP2 is not set\n# CONFIG_RD_BZIP2 is not set)" >> $(LINUX_DIR)/.config
@@ -147,6 +159,20 @@ define Kernel/CompileImage/Initramfs
 	$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(TARGET_DIR)/init
 	$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(TARGET_DIR)/init)
 	rm -rf $(KERNEL_BUILD_DIR)/linux-$(LINUX_VERSION)/usr/initramfs_data.cpio*
+ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPERATE),y)
+ifeq ($(CONFIG_EXTERNAL_CPIO),y)
+	$(CP) $(CONFIG_EXTERNAL_CPIO) $(KERNEL_BUILD_DIR)/initrd.cpio
+else
+	( cd $(TARGET_DIR); find . | cpio -o -H newc -R root:root > $(KERNEL_BUILD_DIR)/initrd.cpio )
+endif
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),bzip2 -9 -c < $(KERNEL_BUILD_DIR)/initrd.cpio > $(KERNEL_BUILD_DIR)/initrd.cpio.bzip2)
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),gzip -f -S .gzip -9n $(KERNEL_BUILD_DIR)/initrd.cpio)
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA),$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(KERNEL_BUILD_DIR)/initrd.cpio $(KERNEL_BUILD_DIR)/initrd.cpio.lzma)
+# ?	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZO),)
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_XZ),$(STAGING_DIR_HOST)/bin/xz -9 -fz --check=crc32 $(KERNEL_BUILD_DIR)/initrd.cpio)
+# ?	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4),)
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD),$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(KERNEL_BUILD_DIR)/initrd.cpio.zstd $(KERNEL_BUILD_DIR)/initrd.cpio)
+endif
 	+$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all)
 	$(call Kernel/CopyImage,-initramfs)
 endef