2007-07-08 21:22:18 +02:00
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#############################################################
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#
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# Make a initramfs_list file to be used by gen_init_cpio
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2007-08-22 14:35:41 +02:00
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# gen_init_cpio is part of the 2.6 linux kernels to build an
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2007-07-08 21:22:18 +02:00
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# initial ramdisk filesystem based on cpio
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#
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#############################################################
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2010-03-10 00:23:58 +01:00
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define ROOTFS_INITRAMFS_INIT_SYMLINK
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2010-08-29 23:32:33 +02:00
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if [ ! -e $(TARGET_DIR)/init ]; then \
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ln -s sbin/init $(TARGET_DIR)/init; \
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fi
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2010-03-10 00:23:58 +01:00
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endef
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2007-07-08 21:22:18 +02:00
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2010-04-20 16:31:01 +02:00
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ROOTFS_INITRAMFS_PRE_GEN_HOOKS += ROOTFS_INITRAMFS_INIT_SYMLINK
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2010-03-10 00:23:58 +01:00
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define ROOTFS_INITRAMFS_CMD
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2010-04-14 23:41:56 +02:00
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$(SHELL) fs/initramfs/gen_initramfs_list.sh -u 0 -g 0 $(TARGET_DIR) > $$@
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2010-03-10 00:23:58 +01:00
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endef
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2007-07-08 21:22:18 +02:00
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linux: add support for initramfs
In Buildroot, the kernel is built and installed *before* the root
filesystems are built. This allows the root filesystem to correctly
contain the kernel modules that have been installed.
However, in the initramfs case, the root filesystem is part of the
kernel. Therefore, the kernel should be built *after* the root
filesystem (which, in the initramfs case simply builds a text file
listing all files/directories/devices/symlinks that should be part of
the initramfs). However, this isn't possible as the initramfs text
file would lack all kernel modules.
So, the solution choosen here is to keep the normal order: kernel is
built before the root filesystem is generated, and to add a little
quirk to retrigger a kernel compilation after the root filesystem
generation.
To do so, we add a ROOTFS_$(FSTYPE)_POST_TARGETS variable to the
fs/common.mk infrastructure. This allows individual filesystems to set
a target name that we should depend on *after* generating the root
filesystem itself (contrary to normal ROOTFS_$(FSTYPE)_DEPENDENCIES,
on which we depend *before* generating the root filesystem).
The initramfs code in fs/initramfs/initramfs.mk uses this to add a
dependency on 'linux26-rebuild-with-initramfs'.
In linux/linux.mk, we do various things :
* If BR2_TARGET_ROOTFS_INITRAMFS is enabled (i.e if initramfs is
enabled as a root filesystem type), then we create an empty
rootfs.initramfs file (remember that at this point, the root
filesystem hasn't been generated) and we adjust the kernel
configuration to include an initramfs. Of course, in the initial
kernel build, this initramfs will be empty.
* In the linux26-rebuild-with-initramfs target, we retrigger a
compilation of the kernel image, after removing the initramfs in
the kernel sources to make sure it gets properly rebuilt (we've
experienced cases were modifying the rootfs.initramfs file wouldn't
retrigger the generation of the initramfs at the kernel level).
This is fairly quirky, but initramfs really is a special case, so in
one way or another, we need a little quirk to solve its specialness.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2010-06-13 19:19:38 +02:00
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ROOTFS_INITRAMFS_POST_TARGETS += linux26-rebuild-with-initramfs
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2010-03-10 00:23:58 +01:00
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$(eval $(call ROOTFS_TARGET,initramfs))
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