Commit c33df4ea authored by Jean-Paul Saman's avatar Jean-Paul Saman Committed by Linus Torvalds
Browse files

[PATCH] disable init/initramfs.c 



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.

[deweerdt@free.fr: warning fix]
Signed-off-by: default avatarJean-Paul Saman <jean-paul.saman@nxp.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: default avatarFrederik Deweerdt <frederik.deweerdt@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dd65aa66

drivers/block/Kconfig

+3 −1
Original line number Diff line number Diff line
@@ -417,8 +417,10 @@ config BLK_DEV_INITRD 
	  etc. See <file:Documentation/initrd.txt> 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"

init/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -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

init/Makefile

+6 −1
Original line number Diff line number Diff line
@@ -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

init/noinitramfs.c

0 → 100644
+52 −0
Original line number Diff line number Diff line 
/*

 * init/noinitramfs.c

 *

 * Copyright (C) 2006, NXP Semiconductors, All Rights Reserved

 * Author: Jean-Paul Saman <jean-paul.saman@nxp.com>

 *

 * 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 <linux/init.h>

#include <linux/stat.h>

#include <linux/kdev_t.h>

#include <linux/syscalls.h>



/*

 * Create a simple rootfs that is similar to the default initramfs

 */

static int __init default_rootfs(void)

{

	int err;



	err = sys_mkdir("/dev", 0755);

	if (err < 0)

		goto out;



	err = sys_mknod((const char __user *) "/dev/console",

			S_IFCHR | S_IRUSR | S_IWUSR,

			new_encode_dev(MKDEV(5, 1)));

	if (err < 0)

		goto out;



	err = sys_mkdir("/root", 0700);

	if (err < 0)

		goto out;



	return 0;



out:

	printk(KERN_WARNING "Failed to create a rootfs\n");

	return err;

}

rootfs_initcall(default_rootfs);

usr/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

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