[Buildroot] [PATCH 2/2] fs/initramfs: refactor with fs/cpio

Arnout Vandecappelle (Essensium/Mind) arnout at mind.be
Tue Sep 6 21:16:09 UTC 2011


From: "Arnout Vandecappelle (Essensium/Mind)" <arnout at mind.be>

An initramfs is in fact the same as a cpio archive, but embedded in
the kernel.  So instead of duplicating the cpio infrastructure,
we can simply build images/rootfs.cpio and link that into the
kernel.
---
 fs/initramfs/Config.in             |   13 ++-
 fs/initramfs/gen_initramfs_list.sh |  203 ------------------------------------
 fs/initramfs/init                  |    7 --
 fs/initramfs/initramfs.mk          |   35 ++----
 linux/linux.mk                     |   17 ++--
 5 files changed, 25 insertions(+), 250 deletions(-)
 delete mode 100644 fs/initramfs/gen_initramfs_list.sh
 delete mode 100755 fs/initramfs/init

diff --git a/fs/initramfs/Config.in b/fs/initramfs/Config.in
index abb3c0c..bbc2ab0 100644
--- a/fs/initramfs/Config.in
+++ b/fs/initramfs/Config.in
@@ -1,20 +1,21 @@
 config BR2_TARGET_ROOTFS_INITRAMFS
 	bool "initramfs for initial ramdisk of linux kernel"
 	depends on BR2_LINUX_KERNEL
+	select BR2_TARGET_ROOTFS_CPIO
 	help
 	  Integrate the root filesystem generated by Buildroot as an
 	  initramfs inside the kernel image. This integration will
 	  take place automatically.
 
-	  The rootfs.initramfs file generated in the images/ directory
-	  is only a text file describing the contents of the initramfs
-	  in a format understood by the CONFIG_INITRAMFS_SOURCE kernel
-	  configuration option.
+	  A rootfs.cpio file will be generated in the images/ directory.
+	  This is the archive that will be included in the kernel image.
+	  The rootfs in the kernel will always be gzip'ed, regardless
+	  of how buildroot's cpio archive is configured.
 
-	  Note that enabling initramfs together with other filesystem
+	  Note that enabling initramfs together with another filesystem
 	  formats doesn't make sense: you would end up having two
 	  identical root filesystems, one embedded inside the kernel
-	  image, and one separatly.
+	  image, and one separately.
 
 comment "initramfs requires a Linux kernel to be built"
 	depends on !BR2_LINUX_KERNEL
diff --git a/fs/initramfs/gen_initramfs_list.sh b/fs/initramfs/gen_initramfs_list.sh
deleted file mode 100644
index 26252b6..0000000
--- a/fs/initramfs/gen_initramfs_list.sh
+++ /dev/null
@@ -1,203 +0,0 @@
-#!/bin/sh
-# Copyright (C) Martin Schlemmer <azarah at nosferatu.za.org>
-# Released under the terms of the GNU GPL
-#
-# Generate a newline separated list of entries from the file/directory
-# supplied as an argument.
-#
-# If a file/directory is not supplied then generate a small dummy file.
-#
-# The output is suitable for gen_init_cpio built from usr/gen_init_cpio.c.
-#
-
-default_initramfs() {
-	cat <<-EOF
-		# This is a very simple, default initramfs
-
-		dir /dev 0755 0 0
-		nod /dev/console 0600 0 0 c 5 1
-		dir /root 0700 0 0
-	EOF
-}
-
-filetype() {
-	local argv1="$1"
-
-	# symlink test must come before file test
-	if [ -L "$argv1" ]; then
-		echo "slink"
-	elif [ -f "$argv1" ]; then
-		echo "file"
-	elif [ -d "$argv1" ]; then
-		echo "dir"
-	elif [ -b "$argv1" -o -c "$argv1" ]; then
-		echo "nod"
-	elif [ -p "$argv1" ]; then
-		echo "pipe"
-	elif [ -S "$argv1" ]; then
-		echo "sock"
-	else
-		echo "invalid"
-	fi
-	return 0
-}
-
-print_mtime() {
-	local argv1="$1"
-	local mymtime="0"
-
-	if [ -e "$argv1" ]; then
-		mymtime=$(find "$argv1" -printf "%T@\n" | sort -r | head -n 1)
-	fi
-	
-	echo "# Last modified: $mymtime"
-	echo
-}
-
-parse() {
-	local location="$1"
-	local name=$(echo "$location" | sed -e "s,$srcdir,,")
-	# change '//' into '/'
-	name=$(echo $name | sed -e 's,/[/]*,/,g')
-	local mode="$2"
-	local uid="$3"
-	local gid="$4"
-	local ftype=$(filetype "$location")
-	# remap uid/gid to 0 if necessary
-	[ "x$uid" != "x" ] && [ $uid -eq $root_uid ] && uid=0
-	[ "x$gid" != "x" ] && [ $gid -eq $root_gid ] && gid=0
-	local str="$mode $uid $gid"
-
-	[ "$ftype" = "invalid" ] && return 0
-	[ "$location" = "$srcdir" ] && return 0
-
-	case "$ftype" in
-		"file")
-			str="$ftype $name $location $str"
-			;;
-		"nod")
-			local devtype=
-			local maj=$(LC_ALL=C ls -l "$location" | \
-					awk '{sub(/,/, "", $5); print $5}')
-			local min=$(LC_ALL=C ls -l "$location" | \
-					awk '{print $6}')
-
-			if [ -b "$location" ]; then
-				devtype="b"
-			else
-				devtype="c"
-			fi
-			str="$ftype $name $str $devtype $maj $min"
-			;;
-		"slink")
-			local target=$(LC_ALL=C ls -l "$location" | \
-					awk '{print $11}')
-			str="$ftype $name $target $str"
-			;;
-		*)
-			str="$ftype $name $str"
-			;;
-	esac
-
-	echo "$str"
-
-	return 0
-}
-
-usage() {
-	printf    "Usage:\n"
-	printf    "$0 [ [-u <root_uid>] [-g <root_gid>] [-d | <cpio_source>] ] . . .\n"
-	printf    "\n"
-	printf -- "-u <root_uid>  User ID to map to user ID 0 (root).\n"
-	printf    "               <root_uid> is only meaningful if <cpio_source>\n"
-	printf    "               is a directory.\n"
-	printf -- "-g <root_gid>  Group ID to map to group ID 0 (root).\n"
-	printf    "               <root_gid> is only meaningful if <cpio_source>\n"
-	printf    "               is a directory.\n"
-	printf    "<cpio_source>  File list or directory for cpio archive.\n"
-	printf    "               If <cpio_source> is not provided then a\n"
-	printf    "               a default list will be output.\n"
-	printf -- "-d             Output the default cpio list.  If no <cpio_source>\n"
-	printf    "               is given then the default cpio list will be output.\n"
-	printf    "\n"
-	printf    "All options may be repeated and are interpreted sequentially\n"
-	printf    "and immediately.  -u and -g states are preserved across\n"
-	printf    "<cpio_source> options so an explicit \"-u 0 -g 0\" is required\n"
-	printf    "to reset the root/group mapping.\n"
-}
-
-build_list() {
-	printf "\n#####################\n# $cpio_source\n"
-
-	if [ -f "$cpio_source" ]; then
-		print_mtime "$cpio_source"
-		cat "$cpio_source"
-	elif [ -d "$cpio_source" ]; then
-		srcdir=$(echo "$cpio_source" | sed -e 's://*:/:g;s:/$::')
-		dirlist=$(find "$srcdir" -printf "%p %m %U %G\n" 2>/dev/null)
-
-		# If $dirlist is only one line, then the directory is empty
-		if [  "$(echo "$dirlist" | wc -l)" -gt 1 ]; then
-			print_mtime "$cpio_source"
-		
-			echo "$dirlist" | \
-			while read x; do
-				parse $x
-			done
-		else
-			# Failsafe in case directory is empty
-			default_initramfs
-		fi
-	else
-		echo "  $0: Cannot open '$cpio_source'" >&2
-		exit 1
-	fi
-}
-
-
-root_uid=0
-root_gid=0
-
-while [ $# -gt 0 ]; do
-	arg="$1"
-	shift
-	case "$arg" in
-		"-u")
-			root_uid="$1"
-			shift
-			;;
-		"-g")
-			root_gid="$1"
-			shift
-			;;
-		"-d")
-			default_list="$arg"
-			default_initramfs
-			;;
-		"-h")
-			usage
-			exit 0
-			;;
-		*)
-			case "$arg" in
-				"-"*)
-					printf "ERROR: unknown option \"$arg\"\n" >&2
-					printf "If the filename validly begins with '-', then it must be prefixed\n" >&2
-					printf "by './' so that it won't be interpreted as an option." >&2
-					printf "\n" >&2
-					usage >&2
-					exit 1
-					;;
-				*)
-					cpio_source="$arg"
-					build_list
-					;;
-			esac
-			;;
-	esac
-done
-
-# spit out the default cpio list if a source hasn't been specified
-[ -z "$cpio_source" -a -z "$default_list" ] && default_initramfs
-
-exit 0
diff --git a/fs/initramfs/init b/fs/initramfs/init
deleted file mode 100755
index a275482..0000000
--- a/fs/initramfs/init
+++ /dev/null
@@ -1,7 +0,0 @@
-#!/bin/sh
-# devtmpfs does not get automounted for initramfs
-/bin/mount -t devtmpfs devtmpfs /dev
-exec 0</dev/console
-exec 1>/dev/console
-exec 2>/dev/console
-exec /sbin/init $*
diff --git a/fs/initramfs/initramfs.mk b/fs/initramfs/initramfs.mk
index 1cd48b6..f1eb8b6 100644
--- a/fs/initramfs/initramfs.mk
+++ b/fs/initramfs/initramfs.mk
@@ -1,36 +1,23 @@
 #############################################################
 #
-# Make a initramfs_list file to be used by gen_init_cpio
-# gen_init_cpio is part of the 2.6 linux kernels to build an
-# initial ramdisk filesystem based on cpio
+# Build a kernel with an integrated initial ramdisk
+# filesystem based on cpio.
 #
 #############################################################
 
-ifeq ($(BR2_ROOTFS_DEVICE_CREATION_STATIC),y)
+ROOTFS_INITRAMFS_DEPENDENCIES += rootfs-cpio
 
-define ROOTFS_INITRAMFS_ADD_INIT
-	if [ ! -e $(TARGET_DIR)/init ]; then \
-		ln -sf sbin/init $(TARGET_DIR)/init; \
-	fi
-endef
+ROOTFS_INITRAMFS_POST_TARGETS += linux26-rebuild-with-initramfs
 
-else
-# devtmpfs does not get automounted when initramfs is used.
-# Add a pre-init script to mount it before running init
-define ROOTFS_INITRAMFS_ADD_INIT
-	if [ ! -e $(TARGET_DIR)/init ]; then \
-		$(INSTALL) -m 0755 fs/initramfs/init $(TARGET_DIR)/init; \
-	fi
-endef
 
-endif # BR2_ROOTFS_DEVICE_CREATION_STATIC
+# The generic fs infrastructure isn't very useful here.
 
-ROOTFS_INITRAMFS_PRE_GEN_HOOKS += ROOTFS_INITRAMFS_ADD_INIT
+rootfs-initramfs: $(ROOTFS_INITRAMFS_DEPENDENCIES) $(ROOTFS_INITRAMFS_POST_TARGETS)
 
-define ROOTFS_INITRAMFS_CMD
-	$(SHELL) fs/initramfs/gen_initramfs_list.sh -u 0 -g 0 $(TARGET_DIR) > $$@
-endef
+rootfs-initramfs-show-depends:
+	@echo $(ROOTFS_INITRAMFS_DEPENDENCIES)
 
-ROOTFS_INITRAMFS_POST_TARGETS += linux26-rebuild-with-initramfs
+ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
+TARGETS += rootfs-initramfs
+endif
 
-$(eval $(call ROOTFS_TARGET,initramfs))
diff --git a/linux/linux.mk b/linux/linux.mk
index e6cf01a..52cc460 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -126,13 +126,13 @@ define LINUX_CONFIGURE_CMDS
 		$(call KCONFIG_ENABLE_OPT,CONFIG_AEABI,$(@D)/.config),
 		$(call KCONFIG_DISABLE_OPT,CONFIG_AEABI,$(@D)/.config))
 	# As the kernel gets compiled before root filesystems are
-	# built, we create a fake initramfs file list. It'll be
-	# replaced later by the real list, and the kernel will be
+	# built, we create a fake cpio file. It'll be
+	# replaced later by the real cpio archive, and the kernel will be
 	# rebuilt using the linux26-rebuild-with-initramfs target.
 	$(if $(BR2_TARGET_ROOTFS_INITRAMFS),
-		touch $(BINARIES_DIR)/rootfs.initramfs
+		touch $(BINARIES_DIR)/rootfs.cpio
 		$(call KCONFIG_ENABLE_OPT,CONFIG_BLK_DEV_INITRD,$(@D)/.config)
-		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,\"$(BINARIES_DIR)/rootfs.initramfs\",$(@D)/.config)
+		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,\"$(BINARIES_DIR)/rootfs.cpio\",$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_UID,0,$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config)
 		$(call KCONFIG_DISABLE_OPT,CONFIG_INITRAMFS_COMPRESSION_NONE,$(@D)/.config)
@@ -184,13 +184,10 @@ linux-menuconfig linux-xconfig linux-gconfig linux-nconfig linux26-menuconfig li
 		$(subst linux-,,$(subst linux26-,,$@))
 	rm -f $(LINUX_DIR)/.stamp_{built,target_installed,images_installed}
 
-# Support for rebuilding the kernel after the initramfs file list has
-# been generated in $(BINARIES_DIR)/rootfs.initramfs.
-$(LINUX_DIR)/.stamp_initramfs_rebuilt: $(LINUX_DIR)/.stamp_target_installed $(LINUX_DIR)/.stamp_images_installed $(BINARIES_DIR)/rootfs.initramfs
+# Support for rebuilding the kernel after the cpio archive has
+# been generated in $(BINARIES_DIR)/rootfs.cpio.
+$(LINUX_DIR)/.stamp_initramfs_rebuilt: $(LINUX_DIR)/.stamp_target_installed $(LINUX_DIR)/.stamp_images_installed $(BINARIES_DIR)/rootfs.cpio
 	@$(call MESSAGE,"Rebuilding kernel with initramfs")
-	# Remove the previously generated initramfs which was empty,
-	# to make sure the kernel will actually regenerate it.
-	$(RM) -f $(@D)/usr/initramfs_data.cpio*
 	# Build the kernel.
 	$(TARGET_MAKE_ENV) $(MAKE) $(LINUX_MAKE_FLAGS) -C $(@D) $(LINUX_IMAGE_NAME)
 	# Copy the kernel image to its final destination
-- 
1.7.5.4



More information about the buildroot mailing list