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fs/iso9660: support building a real iso9660 filesystem

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Until now, the iso9660 filesystem handling only supported using an
initrd/initramfs to store the root filesystem, which is very different
from what we do with the other filesystems.

This commit changes the iso9660 logic to also allow using directly an
iso9660 filesystem to store the root filesystem. A new option,
BR2_TARGET_ROOTFS_ISO9660_INITRD, is created to tell the iso9660 that
we want to use an initrd and not directly the root filesystem in
iso9660 format. This option defaults to 'y' to preserve the existing
behavior.

After this commit, we therefore have three possibilities:

 * BR2_TARGET_ROOTFS_ISO9660=y, with BR2_TARGET_ROOTFS_INITRAMFS and
   BR2_TARGET_ROOTFS_ISO9660_INITRD disabled. In this case, the
   iso9660 filesystem is directly the contents of the root filesystem
   (since is possible thanks to the Rockridge extensions that were
   already enabled using the -R option of genisoimage). Obviously, it
   means that the root filesystem is read-only.

 * BR2_TARGET_ROOTFS_ISO9660=y and BR2_TARGET_ROOTFS_INITRAMFS=y (the
   value of BR2_TARGET_ROOTFS_ISO9660_INITRD doesn't matter). In this
   case, the root filesystem is already linked into the kernel image
   itself, as an initramfs. So the iso9660 filesystem doesn't contain
   the root filesystem as is, but just the bootloader and the kernel
   image.

 * BR2_TARGET_ROOTFS_ISO9660=y, BR2_TARGET_ROOTFS_ISO9660_INITRD=y and
   BR2_TARGET_ROOTFS_INITRAMFS disabled. In this case, a separate
   initrd is used. The iso9660 filesystem only contains the
   bootloader, the kernel and the initrd.

In order to support the first case out of the box, root=/dev/sr0 is
added on the kernel command line in the example Grub configuration
file, so that the kernel knows where the root filesystem is
located. This argument is ignored when initrd/initramfs are used.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
This commit is contained in:
Thomas Petazzoni 2015-06-09 00:21:41 +02:00
parent 168cce0496
commit 7080eef9b8
3 changed files with 111 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
fs/iso9660/Config.in
View File

@ -2,11 +2,23 @@ config BR2_TARGET_ROOTFS_ISO9660
bool "iso image"
depends on (BR2_i386 || BR2_x86_64)
depends on BR2_LINUX_KERNEL
select BR2_TARGET_ROOTFS_CPIO
select BR2_LINUX_KERNEL_INSTALL_TARGET \
if (!BR2_TARGET_ROOTFS_ISO9660_INITRD && !BR2_TARGET_ROOTFS_INITRAMFS)
select BR2_TARGET_GRUB
select BR2_TARGET_GRUB_FS_ISO9660
help
Build a bootable iso9660 image
Build a bootable ISO9660 image. By default, the root
filesystem is directly packed as the ISO9660 filesystem,
which means the root filesystem will be read-only. It
requires ISO9660 filesystem support and CDROM support in the
kernel.
However, if BR2_TARGET_ROOTFS_INITRAMFS or
BR2_TARGET_ROOTFS_ISO9660_INITRD have been enabled, the
ISO9660 filesystem will only contain a kernel image and
optionally an external initrd image. In this case, the
filesystem being in RAM, it will be read/write. No ISO9660
or CDROM support is needed in the kernel.
if BR2_TARGET_ROOTFS_ISO9660
@ -19,6 +31,17 @@ config BR2_TARGET_ROOTFS_ISO9660_BOOT_MENU
automatically be replaced by the path to the kernel and
initrd images respectively.
config BR2_TARGET_ROOTFS_ISO9660_INITRD
bool "Use initrd"
default y
select BR2_TARGET_ROOTFS_CPIO
help
Enable this option to have the root filesystem bundled as an
initrd/initramfs rather than directly as the ISO9660
filesystem. With this option enabled, the ISO9660 will only
contain a kernel image, an initrd image (unless an initramfs
linked into the kernel is used) and the bootloader.
endif
comment "iso image needs a Linux kernel to be built"

111
fs/iso9660/iso9660.mk
View File

@ -4,51 +4,110 @@
#
################################################################################
ROOTFS_ISO9660_TARGET_DIR = $(BUILD_DIR)/rootfs-iso9660.tmp
#
# We need to handle three cases:
#
# 1. The ISO9660 filesystem will really be the real root filesystem
# itself. This is when BR2_TARGET_ROOTFS_ISO9660_INITRD is
# disabled.
#
# 2. The ISO9660 filesystem will be a filesystem with just a kernel
# image, initrd and grub. This is when
# BR2_TARGET_ROOTFS_ISO9660_INITRD is enabled, but
# BR2_TARGET_ROOTFS_INITRAMFS is disabled.
#
# 3. The ISO9660 filesystem will be a filesystem with just a kernel
# image and grub. This is like (2), except that the initrd is
# built into the kernel image. This is when
# BR2_TARGET_ROOTFS_INITRAMFS is enabled (regardless of the value
# of BR2_TARGET_ROOTFS_ISO9660_INITRD).
ROOTFS_ISO9660_BOOT_MENU = $(call qstrip,$(BR2_TARGET_ROOTFS_ISO9660_BOOT_MENU))
ROOTFS_ISO9660_DEPENDENCIES = grub host-cdrkit host-fakeroot linux rootfs-cpio
ROOTFS_ISO9660_DEPENDENCIES = grub host-cdrkit host-fakeroot linux
ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
ROOTFS_ISO9660_USE_INITRD = YES
endif
ifeq ($(BR2_TARGET_ROOTFS_ISO9660_INITRD),y)
ROOTFS_ISO9660_USE_INITRD = YES
endif
ifeq ($(ROOTFS_ISO9660_USE_INITRD),YES)
ROOTFS_ISO9660_TARGET_DIR = $(BUILD_DIR)/rootfs-iso9660.tmp
define ROOTFS_ISO9660_CREATE_TEMPDIR
$(RM) -rf $(ROOTFS_ISO9660_TARGET_DIR)
mkdir -p $(ROOTFS_ISO9660_TARGET_DIR)
endef
else
ROOTFS_ISO9660_TARGET_DIR = $(TARGET_DIR)
endif
define ROOTFS_ISO9660_PREPARATION
$(INSTALL) -D -m 0644 $(GRUB_DIR)/stage2/stage2_eltorito \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/stage2_eltorito
$(INSTALL) -D -m 0644 $(ROOTFS_ISO9660_BOOT_MENU) \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
$(SED) "s%__KERNEL_PATH__%/boot/$(LINUX_IMAGE_NAME)%" \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
endef
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_PREPARATION
# Splash screen disabling
ifeq ($(BR2_TARGET_GRUB_SPLASH),)
define ROOTFS_ISO9660_DISABLE_SPLASHSCREEN
$(SED) '/^splashimage/d' $(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
endef
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_DISABLE_SPLASHSCREEN
endif
define ROOTFS_ISO9660_DISABLE_EXTERNAL_INITRD
$(SED) '/__INITRD_PATH__/d' $(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
endef
ifeq ($(ROOTFS_ISO9660_USE_INITRD),YES)
# Copy splashscreen to temporary filesystem
ifeq ($(BR2_TARGET_GRUB_SPLASH),y)
define ROOTFS_ISO9660_SPLASHSCREEN
define ROOTFS_ISO9660_INSTALL_SPLASHSCREEN
$(INSTALL) -D -m 0644 $(TARGET_DIR)/boot/grub/splash.xpm.gz \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/splash.xpm.gz
endef
else
define ROOTFS_ISO9660_SPLASHSCREEN
$(SED) '/^splashimage/d' $(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
endef
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_INSTALL_SPLASHSCREEN
endif
ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
define ROOTFS_ISO9660_INITRD
$(SED) '/__INITRD_PATH__/d' $(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
# Copy the kernel to temporary filesystem
define ROOTFS_ISO9660_COPY_KERNEL
$(INSTALL) -D -m 0644 $(LINUX_IMAGE_PATH) \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/$(LINUX_IMAGE_NAME)
endef
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_COPY_KERNEL
# If initramfs is used, disable loading the initrd as the rootfs is
# already inside the kernel image. Otherwise, make sure a cpio is
# generated and use it as the initrd.
ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_DISABLE_EXTERNAL_INITRD
else
define ROOTFS_ISO9660_INITRD
ROOTFS_ISO9660_DEPENDENCIES += rootfs-cpio
define ROOTFS_ISO9660_COPY_INITRD
$(INSTALL) -D -m 0644 $(BINARIES_DIR)/rootfs.cpio$(ROOTFS_CPIO_COMPRESS_EXT) \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/initrd
$(SED) "s%__INITRD_PATH__%/boot/initrd%" \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
endef
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_COPY_INITRD
endif
define ROOTFS_ISO9660_PREPARATION
$(RM) -rf $(ROOTFS_ISO9660_TARGET_DIR)
mkdir -p $(ROOTFS_ISO9660_TARGET_DIR)
$(INSTALL) -D -m 0644 $(GRUB_DIR)/stage2/stage2_eltorito \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/stage2_eltorito
$(INSTALL) -D -m 0644 $(ROOTFS_ISO9660_BOOT_MENU) \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
$(INSTALL) -D -m 0644 $(LINUX_IMAGE_PATH) \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/$(LINUX_IMAGE_NAME)
$(SED) "s%__KERNEL_PATH__%/boot/$(LINUX_IMAGE_NAME)%" \
$(ROOTFS_ISO9660_TARGET_DIR)/boot/grub/menu.lst
$(ROOTFS_ISO9660_SPLASHSCREEN)
$(ROOTFS_ISO9660_INITRD)
endef
else # ROOTFS_ISO9660_USE_INITRD
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_DISABLE_EXTERNAL_INITRD
endif # ROOTFS_ISO9660_USE_INITRD
ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_PREPARATION
define ROOTFS_ISO9660_CMD
$(HOST_DIR)/usr/bin/genisoimage -J -R -b boot/grub/stage2_eltorito \

2
fs/iso9660/menu.lst
View File

@ -12,7 +12,7 @@ foreground 000000
background cccccc
title Buildroot ISO9660 image
kernel __KERNEL_PATH__
kernel __KERNEL_PATH__ root=/dev/sr0
initrd __INITRD_PATH__
title Hard Drive (first partition)