From: Jean-Paul Saman The file init/initramfs.c is always compiled and linked in the kernel vmlinux even when BLK_DEV_RAM and BLK_DEV_INITRD are disabled and the system isn't using any form of an initramfs or initrd. In this situation the code is only used to unpack a (static) default initial rootfilesystem. The current init/initramfs.c code. usr/initramfs_data.o compiles to a size of ~15 kbytes. Disabling BLK_DEV_RAM and BLK_DEV_INTRD shrinks the kernel code size with ~60 Kbytes. This patch avoids compiling in the code and data for initramfs support if CONFIG_BLK_DEV_INITRD is not defined. Instead of the initramfs code and data it uses a small routine in init/noinitramfs.c to setup an initial static default environment for mounting a rootfilesystem later on in the kernel initialisation process. The new code is: 164 bytes of size. The patch is separated in two parts: 1) doesn't compile initramfs code when CONFIG_BLK_DEV_INITRD is not set 2) changing all plaforms vmlinux.lds.S files to not reserve an area of PAGE_SIZE when CONFIG_BLK_DEV_INITRD is not set. Signed-off-by: Jean-Paul Saman Cc: Al Viro Cc: Signed-off-by: Andrew Morton --- drivers/block/Kconfig | 4 ++- init/Kconfig | 4 +++ init/Makefile | 7 +++++- init/noinitramfs.c | 42 ++++++++++++++++++++++++++++++++++++++++ usr/Makefile | 2 - 5 files changed, 56 insertions(+), 3 deletions(-) diff -puN drivers/block/Kconfig~disable-init-initramfsc-updated drivers/block/Kconfig --- a/drivers/block/Kconfig~disable-init-initramfsc-updated +++ a/drivers/block/Kconfig @@ -417,8 +417,10 @@ config BLK_DEV_INITRD etc. See for details. If RAM disk support (BLK_DEV_RAM) is also included, this - also enables initial RAM disk (initrd) support. + also enables initial RAM disk (initrd) support and adds + 15 Kbytes (more on some other architectures) to the kernel size. + If unsure say Y. config CDROM_PKTCDVD tristate "Packet writing on CD/DVD media" diff -puN init/Kconfig~disable-init-initramfsc-updated init/Kconfig --- a/init/Kconfig~disable-init-initramfsc-updated +++ a/init/Kconfig @@ -280,8 +280,12 @@ config RELAY If unsure, say N. +if BLK_DEV_INITRD + source "usr/Kconfig" +endif + config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size (Look out for broken compilers!)" default y diff -puN init/Makefile~disable-init-initramfsc-updated init/Makefile --- a/init/Makefile~disable-init-initramfsc-updated +++ a/init/Makefile @@ -2,7 +2,12 @@ # Makefile for the linux kernel. # -obj-y := main.o version.o mounts.o initramfs.o +obj-y := main.o version.o mounts.o +ifneq ($(CONFIG_BLK_DEV_INITRD),y) +obj-y += noinitramfs.o +else +obj-$(CONFIG_BLK_DEV_INITRD) += initramfs.o +endif obj-$(CONFIG_GENERIC_CALIBRATE_DELAY) += calibrate.o mounts-y := do_mounts.o diff -puN /dev/null init/noinitramfs.c --- /dev/null +++ a/init/noinitramfs.c @@ -0,0 +1,42 @@ +/* + * init/noinitramfs.c + * + * Copyright (C) 2006, NXP Semiconductors, All Rights Reserved + * Author: Jean-Paul Saman + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * Create a simple rootfs that is similar to the default initramfs + */ +static void __init default_rootfs(void) +{ + int mkdir_err = sys_mkdir("/dev", 0755); + int err = sys_mknod((const char __user *) "/dev/console", + S_IFCHR | S_IRUSR | S_IWUSR, + new_encode_dev(MKDEV(5, 1))); + if (err == -EROFS) + printk("Warning: Failed to create a rootfs\n"); + mkdir_err = sys_mkdir("/root", 0700); +} +rootfs_initcall(default_rootfs); diff -puN usr/Makefile~disable-init-initramfsc-updated usr/Makefile --- a/usr/Makefile~disable-init-initramfsc-updated +++ a/usr/Makefile @@ -7,7 +7,7 @@ PHONY += klibcdirs # Generate builtin.o based on initramfs_data.o -obj-y := initramfs_data.o +obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data.o # initramfs_data.o contains the initramfs_data.cpio.gz image. # The image is included using .incbin, a dependency which is not _