[Buildroot] [PATCH] grub: add host support

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello Arnout,

Since you had a look some time ago at Grub (and the problem of building
it on x86-64), could you have a look at the below proposal from Richard?

Richard proposes to add a host variant of Grub. At some point, I think
we discussed changing the target variant so that it gets built with the
host compiler (since Grub is always built for x86/x86-64 systems).

With Richard's proposal below, I'm a bit worried about the fact that
the user needs to do "make host-grub" manually. Of course, we can add
the host-grub package for the "Host utilities" menu. But anyway, I want
your opinion on this.

Thanks!

Thomas

Le Wed, 15 Aug 2012 16:57:54 +0200,
Richard Braun <rbraun@sceen.net> a ?crit :

> This change makes it possible to use a grub executable built for the
> host to install the boot loader inside an image. It's also a hack to
> make it possible to work around x86_64 issues, as long as the user has
> 32-bits libraries available to his native toolchain.
> 
> -- Informative part --
> 
> This change alone doesn't mean you'll have grub magically installed in
> your rootfs. First, legacy grub apparently requires a partition table to
> mount file systems. You must work around this limitation yourself. Then,
> it requires crafting the file system so that grub stuff is provided at
> the proper location (e.g. in boot/grub inside your rootfs). On x86_64
> systems, the target grub simply doesn't build, so you'll need to build
> host-grub manually and, for example, make your post-build script do
> anything necessary so that the host grub is able to setup the boot
> loader on your disk image.
> 
> This part is intended as a hint to people trying to use buildroot for
> embedded x86 targets in the hope it helps. Included here is a reference
> shell script that doesn't require root privileges, which you can use as
> a template for your own projects :
> 
> set -e
> 
> CF_SIZE=1024966656       # 1024 MB
> CF_BOOT_SIZE=8388608     # 8 MiB
> CF_HPC=16   # Heads per cylinder
> CF_SPT=63   # Sectors per track
> 
> IMAGES_DIR="output/images"
> KERNEL_IMG="$IMAGES_DIR/bzImage"
> CF_IMG="$IMAGES_DIR/cf.img"
> BOOT_DIR="output/target_boot"
> BOOT_IMG="$IMAGES_DIR/bootfs.ext2"
> ROOTFS_IMG="$IMAGES_DIR/rootfs.squashfs"
> 
> HOST_DIR="output/host"
> SFDISK="$HOST_DIR/usr/sbin/sfdisk"
> GENEXT2FS="$HOST_DIR/usr/bin/genext2fs"
> E2FSCK="$HOST_DIR/usr/sbin/e2fsck"
> GRUB="$HOST_DIR/usr/sbin/grub"
> 
> rm -f $CF_IMG $BOOT_IMG
> 
> make host-util-linux host-genext2fs host-e2fsprogs host-grub
> 
> echo
> 
> cf_boot_start=64
> cf_boot_size=$(($CF_BOOT_SIZE / 512))
> cf_rootfs_start=$(($cf_boot_start + $cf_boot_size))
> cf_sectors=$(($CF_SIZE / 512))
> cf_rootfs_size=$(($cf_sectors - $cf_rootfs_start))
> 
> cat << EOF
> CF layout :
>   boot: $cf_boot_start ($cf_boot_size)
> rootfs: $cf_rootfs_start ($cf_rootfs_size)
> 
> EOF
> 
> cf_cylinders=$(($cf_sectors / ($CF_SPT * $CF_HPC)))
> cf_heads=$((($cf_sectors / $CF_SPT) % $CF_HPC))
> cf_sectors=$((($cf_sectors % $CF_SPT) + 1))
> 
> cat << EOF
> CHS emulation:
> cylinders: $cf_cylinders
>     heads: $cf_heads
>   sectors: $cf_sectors
> 
> EOF
> 
> dd if=/dev/zero of=$CF_IMG bs=1 count=0 seek=$CF_SIZE
> $SFDISK -q -L -uS -C $cf_cylinders -H $cf_heads -S $cf_sectors --no-reread $CF_IMG << EOF
> $cf_boot_start $cf_boot_size L *
> $cf_rootfs_start $cf_rootfs_size
> EOF
> 
> $GENEXT2FS -m 0 -b $(($cf_boot_size / 2)) -d $BOOT_DIR -N 64 -U $BOOT_IMG
> $E2FSCK -fyDC0 $BOOT_IMG || true
> dd if=$BOOT_IMG of=$CF_IMG conv=notrunc seek=$cf_boot_start bs=512
> 
> dd if=$ROOTFS_IMG of=$CF_IMG conv=notrunc seek=$cf_rootfs_start bs=512
> 
> $GRUB --device-map=/dev/null --batch << EOF
> device (hd0) $CF_IMG
> root (hd0,0)
> setup (hd0)
> EOF
> 
> echo
> 
> Signed-off-by: Richard Braun <rbraun@sceen.net>
> ---
>  boot/grub/grub.mk |   19 +++++++++++++++++++
>  1 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/boot/grub/grub.mk b/boot/grub/grub.mk
> index e8d66f1..c4f52cc 100644
> --- a/boot/grub/grub.mk
> +++ b/boot/grub/grub.mk
> @@ -82,4 +82,23 @@ define GRUB_UNINSTALL_TARGET_CMDS
>  	rm -rf $(TARGET_DIR)/boot/grub
>  endef
>  
> +HOST_GRUB_POST_PATCH_HOOKS += GRUB_DEBIAN_PATCHES
> +
> +HOST_GRUB_CONF_ENV = \
> +	CFLAGS="$(GRUB_CFLAGS) -fno-stack-protector" \
> +	grub_cv_prog_objcopy_absolute=yes
> +
> +HOST_GRUB_CONF_OPT = \
> +	--disable-auto-linux-mem-opt \
> +	--disable-graphics
> +
> +define HOST_GRUB_INSTALL_CMDS
> +	install -m 0755 -D $(@D)/grub/grub $(HOST_DIR)/usr/sbin/grub
> +	mkdir -p $(HOST_DIR)/boot/grub
> +	cp $(@D)/stage1/stage1 $(HOST_DIR)/boot/grub
> +	cp $(@D)/stage2/*1_5   $(HOST_DIR)/boot/grub
> +	cp $(@D)/stage2/stage2 $(HOST_DIR)/boot/grub
> +endef
> +
>  $(eval $(autotools-package))
> +$(eval $(host-autotools-package))



-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com