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2010-06-22linux: add support for initramfsThomas Petazzoni
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>
2010-06-22linux: add support for linux26-{menuconfig,xconfig,gconfig} targetsThomas Petazzoni
These targets allow the user to customize the configuration of the Linux kernel. After changing the kernel configuration, the next time the user runs "make", the kernel is rebuilt to take into account the new configuration (not rebuilt from scratch). Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2010-06-22linux: adjust kernel config according to the Buildroot configurationThomas Petazzoni
We only adjust the configuration or ARM EABI and IPv6. The (more complicated) initramfs case is handled in a separate commit. The user is expected to take care of all other configuration details (like having Netfilter enabled to make iptables work, etc.) Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2010-06-22linux: Add dependency on host-module-init-toolsThomas Petazzoni
In order to not depend on module init tools being installed on the development environment of the Buildroot user, let's build module init tools for the host. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2010-06-22New, simpler, infrastructure for building the Linux kernelThomas Petazzoni
This patch introduces a single, simple, infrastructure to build the Linux kernel. The configuration is limited to : * Kernel version: a fixed recent stable version, same as kernel headers version (for internal toolchains only), custom stable version, or custom tarball URL * Kernel patch: either a local file, directory or an URL * Kernel configuration: either the name of a defconfig or the location of a custom configuration file * Kernel image: either uImage, bzImage, zImage or vmlinux. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>