From nobody Sun Dec 17 00:27:58 2023 X-Original-To: freebsd-arm@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4St3hX1kWrz53jWT for ; Sun, 17 Dec 2023 00:28:12 +0000 (UTC) (envelope-from stanislav.silnicki@mailgate.us) Received: from mailgate.us (mailgate.us [185.72.246.236]) by mx1.freebsd.org (Postfix) with ESMTP id 4St3hV6885z3Llw for ; Sun, 17 Dec 2023 00:28:10 +0000 (UTC) (envelope-from stanislav.silnicki@mailgate.us) Authentication-Results: mx1.freebsd.org; dkim=pass header.d=mailgate.us header.s=mail header.b=MbstH7b9; spf=pass (mx1.freebsd.org: domain of stanislav.silnicki@mailgate.us designates 185.72.246.236 as permitted sender) smtp.mailfrom=stanislav.silnicki@mailgate.us; dmarc=none Received: from localhost (api.telegram.org [192.168.2.1]) by mailgate.us (Postfix) with ESMTPSA id 1EC4B7A625 for ; Sun, 17 Dec 2023 03:28:08 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailgate.us; s=mail; t=1702772889; bh=bQS3ESzuyZoq+UsCBlVi/pzKMEMduCSj5N9LSKYvtg8=; h=From:Subject:To:References:Date; b=MbstH7b94MOT9V7Ew9PrH6ca8BKbfwxCkXW45jm/qTOhB+mr2T5zoH7bsgniUxhkn XIemq05uady02Ejm4cchWPW+IQ3/BwujIIzAn+G4zqWgRFbbmlMZnMdXyHRilGYR5B w872uJVBcvxRkWW03emi582nltvKX1k8I3H3vcQY= Content-Type: multipart/alternative; boundary="----sinikael-?=_1-17027728790910.910944075536489" From: Stanislav Silnicki Subject: Re: How to boot FreeBSD for arm 32 bit as DomU with u-boot on my ARM Chromebook X-Type: replyAll To: freebsd-arm@freebsd.org User-Agent: Desktop Message-Id: References: <97aa980b9b44.6eb7f9d5c54e7@mailgate.us> Content-Transfer-Encoding: quoted-printable Date: Sun, 17 Dec 2023 00:27:58 +0000 List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@freebsd.org MIME-Version: 1.0 X-Spamd-Result: default: False [-3.39 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[mailgate.us:s=mail]; R_SPF_ALLOW(-0.20)[+ip4:185.72.246.236/32:c]; MIME_GOOD(-0.10)[multipart/alternative,text/plain]; RCVD_NO_TLS_LAST(0.10)[]; XM_UA_NO_VERSION(0.01)[]; MIME_TRACE(0.00)[0:+,1:+,2:~]; FROM_EQ_ENVFROM(0.00)[]; MLMMJ_DEST(0.00)[freebsd-arm@freebsd.org]; RCVD_COUNT_ONE(0.00)[1]; DKIM_TRACE(0.00)[mailgate.us:+]; ARC_NA(0.00)[]; ASN(0.00)[asn:47447, ipnet:185.72.246.0/24, country:DE]; FROM_HAS_DN(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DMARC_NA(0.00)[mailgate.us]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-arm@freebsd.org]; RCPT_COUNT_ONE(0.00)[1]; MID_RHS_MATCH_FROM(0.00)[] X-Rspamd-Queue-Id: 4St3hV6885z3Llw X-Spamd-Bar: --- ------sinikael-?=_1-17027728790910.910944075536489 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable I'm not an expert in the topic, I only know, that ARM has divided hardware = into two worlds - Secure and Not-So, strictly limiting any software, = running in non-secure world with access to functions and resources. = https://developer.arm.com/documentation/den0013/d/Security/TrustZone-hardwa= re-architecture=3Flang=3Den I'm not sure, that I'm getting you right, as I don't understand what you = mean under =22the first u-boot=22. As I understand, virtualization (HYP) is running in non-secure world = (https://developer.arm.com/documentation/ddi0406/c/System-Level-Architectur= e/The-System-Level-Programmers--Model/The-Virtualization-Extensions), so my= guess (only guess!!!), virtualization software has to prepare (configure) = HW platform in the way, that FreeBSD kernel will not lack any resources, = required to configure MPU, VA, etc. So, if you lucky to boot virtualizer, which is aware of target OS, that = maybe you can boot the kernel. Although, I doubt, that you need to boot = 'second' u-boot to boot the kernel - there is simply ubldr, which you can = hook somehow from virtualizer.... Stan Mario Marietto wrote: ---> As I understand, it makes sure that u-boot keeps in secure mode during= boot and passes control to ubldr, which boots FreeBSD kernel, in that mode= . Can you elaborate your sentence more =3F I know that the bootloader secure = mode is bypassed by the virtual open systems u-boot. Are you saying that = when the control passes to the second u-boot,it will happen in secure mode,= so that the bypass that happened loading the first u-boot,is annulled =3F = If this is true,maybe can I boot FreeBSD using the virtual-open-system = custom u-boot =3F Is this compatible with FreeBSD =3F Where can I find the = u-boot.bin that the xen developer talked about =3F thanks bro'.=20 On Sun, Dec 17, 2023 at 12:35=E2=80=AFAM Stanislav Silnicki > wrote: Hi Mario, U-Boot beast is hiding in this den: https://source.denx.de/u-boot/u-boot.= git =20 I took a brief look at your post and it seems to me, that option = CONFIG=5FCMO=5FBY=5FVA=5FONLY is irrelevant to your target armv7 32 bit = platform: https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/cpu/a= rmv8/Kconfig=3Fref=5Ftype=3Dheads#L3 =20 As for compiling the u-boot, it is a doable task, given that you understand= what you are doing. There are no specific options in u-boot devoted to = FreeBSD. It is a boot loader, whose mission to make basic hardware = initialization, read you kernel file from some media into RAM and then pass= it control.=20 Basically, you can grab some defconfig, prepared for any other Exynos5250 = based board (say, this one: https://source.denx.de/u-boot/u-boot/-/blob/mas= ter/configs/arndale=5Fdefconfig=3Fref=5Ftype=3Dheads) and adopt it somehow. As per my experience, you have to respect these two options, compiling = u-boot for FreeBSD: https://github.com/freebsd/freebsd-ports/blob/main/sysu= tils/u-boot-master/files/FreeBSD=5FFragment =20 As I understand, it makes sure, that u-boot keeps in secure mode during = boot and passes control to ubldr, which boots FreBSD kernel, in that mode. = Otherwise, there a lot of surprises you may realize. Hope, this will help to progress you tasks Stan Mario Marietto wrote: Hello. I'm trying to boot FreeBSD for arm32 bit as DomU on my ARM Chromebook. = Basically there are two ways to accomplish this task : 1) to write a patch that allows the FreeBSD kernel to boot as a zImage file= . This could be accomplished applying this patch to a specific file that's = on the source code of FreeBSD : https://xenbits.xen.org/gitweb/=3Fp=3Dp...8;hb=3D0782e25d98cc1391472717035f= 986c979edef0c9 =20 This patch was written by Julien Grall a lot of time ago and now it does = not work anymore. This is the reason : It appears FreeBSD-CURRENT removed the last step converting the kernel file= to kernel.bin. The patch can be readily rebased, but without kernel.bin = that doesn't do too much.=20 So,without a rebase of that patch the first option is not applicable. And = I'm not able to fix it. 2) booting FreeBSD using U-Boot,as explained to me by a xen developer : I was trying to explain why and how Julien's patch works so that you could = be the one to re-do something similar or fix the patch on the FreeBSD = kernel that you are working with. I am happy to help review and write = patches but I don't work with the FreeBSD kernel so I wouldn't be able to = help you quickly. However, I might have a suggestion. Do you know if = FreeBSD can be booted by U-Boot =3F Because U-Boot definitely boots as Xen = on ARM guest firmware/bootloader. You should be able to build U-Boot and = use the U-Boot binary as Xen guest kernel, then U-Boot could load FreeBSD = from disk or network and start it. For instance as domU config file: kernel=3D=22/home/petalinux/u-boot.bin=22 disk =3D [ '/home/petalinux/test.img,raw,xvda' ] I know it is important to build u-boot with the following config to make it= work on Xen. CONFIG=5FCMO=5FBY=5FVA=5FONLY=3Dy=20 This option seems more doable to me according to my knowledge. But I need = to understand how to do it. Well,let's say that on the ARM Chromebook I'm forced to use and install a = customized version of u-boot,created by virtual open systems,because it is = the only one that allows bypassing its bootloader protection. You can find = more information here : http://www.virtualopensystems.com/en/solutions/guides/kvm-on-chromebook/=3F= vos=3Dtech =20 This is the relevant section to read : Bootloader : If you wish to skip this chapter you can download a pre-compiled binary of = the bootloader: $ wget http://www.virtualopensystems.com/downloads/guides/kvm=5Fon=5Fchrome= book/nv=5Fu-boot-snow.kpart =20 To be able to run KVM on ARM platforms, the kernel has to be booted in = hypervisor mode. Because of this relatively recent requirement (due to the = introduction of the virtualization extensions), up until now all booting = methods would boot the kernel in the standard Supervisor mode. For the ARM = Chromebook the default boot procedure doesn't allow us to boot in = hypervisor mode. Although the laptop's boot mechanism is based on the = frequently used u-boot, the binary is located in RO memory. Fortunately, a = chained u-boot mechanism can be used (i.e. starting another u-boot after = the original). We can then enter hypervisor mode from our custom iteration = of u-boot and subsequently load our kernel and userspace. Checkout the needed u-boot code : $ git clone git://github.com/virtualopensystems/u-boot.git$ cd u-boot$ ./scripts/build.sh If successful, a message about how to copy the bootloader on the USB flash = disk or SD card will appear. We will use it later when preparing the boot = medium to start our system. If you have followed the Setting up the boot = medium chapter and you have a prepared boot device, then you can update = u-boot by running : $ sudo dd if=3Dnv=5Fuboot-snow.kpart of=3D/dev/sdX1=20 so,the needed u-boot that we must use should be installed on the first = partition of the sd card. There is another relevant section to read : Setting up the boot medium Now it is time to copy all the relevant files that we created in the = previous chapters,and use them to boot Chromebook with a different kernel = and OS. In all these examples the device /dev/sdX is used. Take extra care = to change the examples to the device that you have attached. Insert the = boot medium on your workstation and carefully execute the following step. = First we need to properly format the boot medium. In the uboot source directory : $ sudo ./scripts/sdcard.sh /dev/sdX This will erase all data and create 4 partitions in the medium, along with = copying the u-boot binary to the first partition: Partition 1 =3D ChromeOS signed binary (V.O.S chained u-boot) Partition 2 =3D not used Partition 3 =3D EXT2 partition for u-boot files (uImage and exynos5250-snow= .dtb) Partition 4 =3D EXT4 partition for userspace files With u-boot being copied, next is the kernel image and DTB file. From the = kernel source execute : $ mkdir ../mnt/ $ sudo mount /dev/sdX3 ../mnt/ $ sudo cp arch/arm/boot/uImage ../mnt/ $ sudo cp arch/arm/boot/dts/exynos5250-snow.dtb ../mnt/ $ sudo umount /dev/sdX3 Finally, we have to copy the Ubuntu userspace filesystem that we created = earlier: $ sudo mount /dev/sdX4 mnt/$ sudo cp -a ./precise/* mnt/$ sudo umount = /dev/sdX4=20 Now,my idea is to chainload the already chain loaded u-boot created by V.O.= S to the new u-boot that we need for booting FreeBSD and that can be = installed in the partition n.2,as shown in this scheme,because it is not = used : Partition 1 =3D ChromeOS signed binary (V.O.S chained u-boot) Partition 2 =3D not used (maybe we can install the u-boot for arm 32 bit,= compatible with FreeBSD on this partition) Partition 3 =3D EXT2 partition for u-boot files (uImage and exynos5250-snow= .dtb) Partition 4 =3D EXT4 partition for userspace files Take in consideration that default boot string is hardcoded here,in the = snow.h file of the custom u-boot created by VOS : https://github.com/virtualopensyste...18a39b6c177dff58a/include/configs/sno= w.h#L101 =20 and it needs to be recompiled because it should point to the partition n.2,= where I will install the u-boot files as explained here : https://wiki.freebsd.org/arm/Chromebook =20 I have some questions to ask before I start working on this. 1) The xen developer said : You should be able to build U-Boot and use the U-Boot binary as Xen guest = kernel...=20 where is the u-boot binary,according to this document =3F https://wiki.freebsd.org/arm/Chromebook =20 I don't see it. 2) where is the source code of the file that I can get here : http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/nv= =5Fuboot-snow-simplefb.kpart.bz2 I need the source code if I want to recompile u-boot so that it can point = to the partition 4. Maybe it can be found on this link : http://linux-exynos.org/dist/chromebook/nv=5Fuboot/ =20 but it can't be opened.... 3) in this specific scenario the source code of u-boot should run on arm 32= bit,not on arm 64,because I have the Samsung Chromebook =22SNOW=22 model = XE303C12,that's powered by a Samsung Exynos 5250 (ARMv7 32 bit Cortex A15) = Soc. 4) I'm not sure if I can chainload the customized u-boot created by V.O.S = that should be installed on the first partition with the u-boot tailored = for booting FreeBSD that should be installed on the partition 2.... 5) the xen developer said that u-boot should be compiled enabling this = option : Code:=20 CONFIG=5FCMO=5FBY=5FVA=5FONLY=3Dy=20 Well,can you provide some good source that can help me to understand how I = can recompile u-boot for FreeBSD =3F thanks. --=20 Mario. --=20 Mario. ------sinikael-?=_1-17027728790910.910944075536489 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
=20 =20 =20 =20 =20 =20
I'm not an expert in the topic, I only know, that ARM has = divided hardware into two worlds - Secure and Not-So, strictly limiting any= software, running in non-secure world with access to functions and = resources. https://developer.arm.com/documentation/den0013/d/Security/= TrustZone-hardware-architecture=3Flang=3Den

I'm not sure, that I'm getting you right, as I = don't understand what you mean under =22the first u-boot=22.

As I understand, = virtualization (HYP) is running in non-secure world (https://developer.arm.= com/documentation/ddi0406/c/System-Level-Architecture/The-System-Level-Prog= rammers--Model/The-Virtualization-Extensions), so my guess (only guess!!!),= virtualization software has to prepare (configure) HW platform in the way,= that FreeBSD kernel will not lack any resources, required to configure MPU= , VA, etc.
So, if = you lucky to boot virtualizer, which is aware of target OS, that maybe you = can boot the kernel. Although, I doubt, that you need to boot 'second' = u-boot to boot the kernel - there is simply ubldr, which you can hook = somehow from virtualizer....

Stan



Mario Marietto = wrote:


---> As=20 I understand, it makes sure that u-boot keeps in secure mode during = boot=20 and passes control to ubldr, which boots FreeBSD kernel, in that mode.=

Can you elaborate your sentence more =3F I know = that the bootloader secure mode is bypassed by the virtual open systems = u-boot. Are you saying that when the control passes to the second u-boot,it= will happen in secure mode,so that the bypass that happened loading the = first u-boot,is annulled =3F If this is true,maybe can I boot FreeBSD using= the virtual-open-system custom u-boot =3F Is this compatible with FreeBSD = =3F Where can I find the u-boot.bin that the xen developer talked about =3F= thanks bro'.



On Sun, Dec 17, 2023 at 12:35=E2=80=AFAM Stanislav Silnicki <stanislav.= silnicki@mailgate.us> wrote:
= =20 =20 =20 =20 =20 =20 =20
=20 =20 =20 =20 =20 =20 =20
Hi=20 Mario,

U-Boot&nb= sp; beast is=20 hiding in this den: https://source.denx.de/u-boot/u-boot.= git
I took a brief look at your post and it = seems to me, that=20 option CONFIG=5FCMO=5FBY=5FVA=5FONLY is= irrelevant to=20 your target armv7 32 bit=20 platform: https://source.denx.de/u-boot/u-boot/-/blob/master/= arch/arm/cpu/armv8/Kconfig=3Fref=5Ftype=3Dheads#L3

As=20 for compiling the u-boot, it is a doable task, given that you = understand=20 what you are doing. There are no specific options in u-boot devoted to=20 FreeBSD. It is a boot loader, whose mission to make basic hardware=20 initialization, read you kernel file from some media into RAM and then = pass=20 it control.

Basically, you can grab some defconfig,=20 prepared for any other Exynos5250 based board  (say, this one: https://sour= ce.denx.de/u-boot/u-boot/-/blob/master/configs/arndale=5Fdefconfig=3Fref=5F= type=3Dheads)=20 and adopt it somehow.

As per my experience, = you have to respect=20 these two options, compiling u-boot for FreeBSD: https://github= .com/freebsd/freebsd-ports/blob/main/sysutils/u-boot-master/files/FreeBSD= =5FFragment

As=20 I understand, it makes sure, that u-boot keeps in secure mode during = boot=20 and passes control to ubldr, which boots FreBSD kernel, in that mode.=20 Otherwise, there a lot of surprises you may realize.

Hope, this=20 will help to progress you tasks
Stan

Mario=20 Marietto wrote:


Hello.

I'm trying to boot FreeBSD for arm32 bit as DomU on my ARM Chromebook.=20 Basically there are two ways to accomplish this task :

1) to write a patch that allows the FreeBSD kernel to boot as a zImage=20 file. This could be accomplished applying this patch to a specific file=20 that's on the source code of FreeBSD :


https://xenbits.= xen.org/gitweb/=3Fp=3Dp...8;hb=3D0782e25d98cc1391472717035f986c979edef0c9


This patch was written by Julien Grall a lot of time ago and now it = does=20 not work anymore. This is the reason :


=09
=09
It appears FreeBSD-CURRENT removed the last step converting the=20 kernel file to kernel.bin. The patch can be readily rebased, but without kernel.bin that doesn't do too much.
=09


So,without a rebase of that patch the first option is not applicable. = And=20 I'm not able to fix it.

2) booting FreeBSD using U-Boot,as explained to me by a xen developer = :


=09
=09
I was trying to explain why and how Julien's patch works so that you=20 could be the one to re-do something similar or fix the patch on the=20 FreeBSD kernel that you are working with. I am happy to help review and=20 write patches but I don't work with the FreeBSD kernel so I wouldn't be=20 able to help you quickly. However, I might have a suggestion. Do you=20 know if FreeBSD can be booted by U-Boot =3F Because U-Boot definitely=20 boots as Xen on ARM guest firmware/bootloader. You should be able to=20 build U-Boot and use the U-Boot binary as Xen guest kernel, then U-Boot=20 could load FreeBSD from disk or network and start it. For instance as=20 domU config file:

kernel=3D=22/home/petalinux/u-boot.bin=22
disk =3D [ '/home/petalinux/test.img,raw,xvda' ]

I know it is important to build u-boot with the following config to make = it=20 work on Xen.

CONFIG=5FCMO=5FBY=5FVA=5FONLY=3Dy
=09


This option seems more doable to me according to my knowledge. But I = need=20 to understand how to do it.

Well,let's say that on the ARM Chromebook I'm forced to use and install a customized version of u-boot,created by virtual open systems,because it is the only one that allows bypassing its bootloader protection. You=20 can find more information here :

http://www.virtualopensystems.= com/en/solutions/guides/kvm-on-chromebook/=3Fvos=3Dtech

This is the relevant section to read :


=09
=09
Bootloader :

If you wish to skip this chapter you can download a pre-compiled binary = of=20 the bootloader:


$ wget http://www.virtualopensystems.= com/downloads/guides/kvm=5Fon=5Fchromebook/nv=5Fu-boot-snow.kpart


To be able to run KVM on ARM platforms, the kernel has to be booted in=20 hypervisor mode. Because of this relatively recent requirement (due to=20 the introduction of the virtualization extensions), up until now all=20 booting methods would boot the kernel in the standard Supervisor mode.=20 For the ARM Chromebook the default boot procedure doesn't allow us to=20 boot in hypervisor mode. Although the laptop's boot mechanism is based=20 on the frequently used u-boot, the binary is located in RO memory.=20 Fortunately, a chained u-boot mechanism can be used (i.e. starting=20 another u-boot after the original). We can then enter hypervisor mode=20 from our custom iteration of u-boot and subsequently load our kernel and userspace.

Checkout the needed u-boot code :


$ git clone git://github.com/virtualopensystems/u-boot.= git$ cd=20 u-boot$ ./scripts/build.sh


If successful, a message about how to copy the bootloader on the USB=20 flash disk or SD card will appear. We will use it later when preparing=20 the boot medium to start our system. If you have followed the Setting up the boot medium chapter and you have a prepared boot device, then you=20 can update u-boot by running :


$ sudo dd if=3Dnv=5Fuboot-snow.kpart of=3D/dev/sdX1
=09


so,the needed u-boot that we must use should be installed on the first=20 partition of the sd card.

There is another relevant section to read :


=09
=09
Setting up the boot medium

Now it is time to copy all the relevant files that we created in the=20 previous chapters,and use them to boot Chromebook with a different=20 kernel and OS. In all these examples the device /dev/sdX is used. Take=20 extra care to change the examples to the device that you have attached.=20 Insert the boot medium on your workstation and carefully execute the=20 following step. First we need to properly format the boot medium.

In the uboot source directory :


$ sudo ./scripts/sdcard.sh /dev/sdX


This will erase all data and create 4 partitions in the medium, along = with=20 copying the u-boot binary to the first partition:


Partition 1 =3D ChromeOS signed binary (V.O.S chained u-boot)
Partition 2 =3D not used
Partition 3 =3D EXT2 partition for u-boot files (uImage and=20 exynos5250-snow.dtb)
Partition 4 =3D EXT4 partition for userspace files


With u-boot being copied, next is the kernel image and DTB file. From = the=20 kernel source execute :


$ mkdir ../mnt/
$ sudo mount /dev/sdX3 ../mnt/
$ sudo cp arch/arm/boot/uImage ../mnt/
$ sudo cp arch/arm/boot/dts/exynos5250-snow.dtb ../mnt/
$ sudo umount /dev/sdX3


Finally, we have to copy the Ubuntu userspace filesystem that we = created=20 earlier:


$ sudo mount /dev/sdX4 mnt/$ sudo cp -a ./precise/* mnt/$ sudo umount=20 /dev/sdX4
=09


Now,my idea is to chainload the already chain loaded u-boot created by=20 V.O.S to the new u-boot that we need for booting FreeBSD and that can be installed in the partition n.2,as shown in this scheme,because it is=20 not used :


Partition 1 =3D ChromeOS signed binary (V.O.S chained u-boot)
Partition 2 =3D not used (maybe we can install the u-boot for arm 32=20 bit,compatible with FreeBSD on this partition)
Partition 3 =3D EXT2 partition for u-boot files (uImage and=20 exynos5250-snow.dtb)
Partition 4 =3D EXT4 partition for userspace files


Take in consideration that default boot string is hardcoded here,in the=20 snow.h file of the custom u-boot created by VOS :


https://github.= com/virtualopensyste...18a39b6c177dff58a/include/configs/snow.= h#L101


and it needs to be recompiled because it should point to the partition=20 n.2,where I will install the u-boot files as explained here :


https://wiki.freebsd.= org/arm/Chromebook


I have some questions to ask before I start working on this.

1) The xen developer said :


=09
=09
You should be able to build U-Boot and use the U-Boot binary as Xen=20 guest kernel...
=09


where is the u-boot binary,according to this document =3F

https://wiki.freebsd.= org/arm/Chromebook

I don't see it.


2) where is the source code of the file that I can get here :

http://commondatastorage.googleapis.com/chromeos-localmirror/di= stfiles/nv=5Fuboot-snow-simplefb.kpart.bz2

I need the source code if I want to recompile u-boot so that it can = point=20 to the partition 4.

Maybe it can be found on this link :

http://linux-exynos.= org/dist/chromebook/nv=5Fuboot/

but it can't be opened....


3) in this specific scenario the source code of u-boot should run on arm 32 bit,not on arm 64,because I have the Samsung Chromebook =22SNOW=22 = model XE303C12,that's powered by a Samsung Exynos 5250 (ARMv7 32 bit Cortex=20 A15) Soc.


4) I'm not sure if I can chainload the customized u-boot created by=20 V.O.S that should be installed on the first partition with the u-boot=20 tailored for booting FreeBSD that should be installed on the partition=20 2....


5) the xen developer said that u-boot should be compiled enabling this=20 option :


=09 =09
Code: 

CONFIG=5FCMO=5FBY=5FVA=5FONLY=3Dy
=


Well,can you provide some good source that can help me to understand how = I=20 can recompile u-boot for FreeBSD =3F=20 thanks.
--
Mario.=
=20 =20 =20 =20 =20

--
Mario.
=20 =20 =20 ------sinikael-?=_1-17027728790910.910944075536489--