[coreboot] Questions on building a Coreboot ROM for the Dell Chromebook 11
I have a Dell Chromebook 11 (Google codename 'Wolf') which I'd like to install a custom coreboot ROM on. Although John Lewis provides ROMs here https://johnlewis.ie/custom-chromebook-firmware/rom-download/, I'd rather not use them for a few reasons: 1) It's replacing one 'closed' ROM with another, in the sense it's from a 3rd party with no public repo or build scripts. Although it's possible to extract the coreboot config used to build them, it's not possible to reproduce and modify the payloads. 2) I don't need his closed 'Jeltka' payload. 3) I'd like to experiment with other payloads, custom splash screens etc. 4) I wouldn't learn anything, and I'm interested! With that in mind, this guide here looked ideal (although there's no date on it): https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook However, that prompted some questions, which I'm hoping someone here might be able to help with. (I did ask in the #chromimum-os IRC channel, but they suggested Google coreboot developers would be more likely to help here). 1) What blobs do I use? Although the guide sensibly says to backup the existing bios with 'flashrom -r', it also says to extract a bios.bin from /usr/sbin/chromeos-firwmwareupdate (I've posted details of both at the end). From the latter, it goes on to get you to extract four blobs: - SPI Descriptor - Management Engine - MRC - VBIOS The first discrepancy is that the guide says the 'Management Engine firmware' is only in the latter, but I was able to use ifdtool on both images to extract the same set of three files. The flashregion_0_flashdescriptor.bin files were identical, though the other two were different despite being the same size. The other thing is there's no reason given as to why one would use the MRC and VBIOS blobs from the extract, rather than the backup. Curiously, they are slightly different sizes (again details below). Looking at the config it seems the extracted bios image was built with from a Google coreboot fork four months older than the one backed up from the machine. 2) Which mainboard do I use for the Dell Chromebook 11? Assuming I have the correct four proprietary blobs, the next thing is choosing the right mainboard. The guide I link to mentions suggests 'Falco', but I don't see how, without knowing the target, such a suggestion could be meaningful? Looking here https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices Falco appears to be unique to the HP Chromebook 14. The mainboard codename for my Chromebook is 'Wolf', and that's not in coreboot upstream. Comparing 'src/mainboard/google' in Google's fork, and coreboot upstream: http://review.coreboot.org/gitweb?p=coreboot.git;a=tree;f=src/mainboard/google;h=60045af24d9760f7a52555a5ef6ef3fdc77676b7;hb=HEAD https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/src/mainboard/google/ It seems there is at least some attempt to merge upstream, and yet wolf isn't there. Is there a particular reason some mainboards are missing? Did Google stop doing so for some reason? I also note the Google keep the coreboot config source controlled: https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/configs/config.wolf Thanks Marcos --- Some further ROM details --- bios extracted with 'flashrom -r' from my Dell Chromebook 11: chromebook11.rom: 8192 kB, bootblocksize 3144, romsize 8388608, offset 0x70 alignment: 64 bytes, architecture: x86 Name Offset Type Size cmos_layout.bin0x70 cmos_layout 1164 pci8086,0406.rom 0x7004c0 optionrom65536 cpu_microcode_blob.bin 0x710500 microcode41024 config 0x71a5c0 raw 5536 fallback/vboot 0x71bbc0 stage15083 (empty)0x71f700 null 2136 fallback/romstage 0x71ff80 stage42497 fallback/coreboot_ram 0x72a600 stage91450 fallback/payload 0x740b80 payload 54898 u-boot.dtb 0x74e240 mrc_cache7919 (empty)0x750180 null 327192 mrc.bin0x79ffc0 spd 190180 (empty)0x7ce700 null 120984 spd.bin0x7ebfc0 spd 1536 (empty)0x7ec600 null 77144 Extracting config shows "# This image was built using git revision 52034fc1537d4a38e792e700cbc8e9dd1fc36a9c", which is a commit hash from Google's fork: commit cef55018e4e936af9a758675353e332df4d9d1a6 Author: David Wu Date: Tue Apr 29 12:59:04 2014 -0700 bios extracted from the chromeos-firwmwareupdate utility (which on my machine is a 7.7M binary built on 27th Apr this year): bios.bin: 8192 kB, bootblocksize 3144, romsize 8388608, offset 0x700
Re: [coreboot] Questions on building a Coreboot ROM for the Dell Chromebook 11
hi Marcos, I'm not a Google dev, just a hobbyist, but I've spent a lot of time over the past year working with coreboot for the Haswell ChromeOS devices (mostly the ChromeBoxes) and can offer some answers, inline below. On 5/8/2015 2:38 PM, Marcos Scriven wrote: > I have a Dell Chromebook 11 (Google codename 'Wolf') which I'd like to > install a custom coreboot ROM on. Although John Lewis provides ROMs here > https://johnlewis.ie/custom-chromebook-firmware/rom-download/, I'd rather not > use them for a few reasons: > > 1) It's replacing one 'closed' ROM with another, in the sense it's from a 3rd > party with no public repo or build scripts. Although it's possible to extract > the coreboot config used to build them, it's not possible to reproduce and > modify the payloads. > 2) I don't need his closed 'Jeltka' payload. > 3) I'd like to experiment with other payloads, custom splash screens etc. > 4) I wouldn't learn anything, and I'm interested! > > With that in mind, this guide here looked ideal (although there's no date on > it): > https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook that's what I started with, and a good overview for what you need to build your own firmware. I'd suggest however that you first build coreboot using the same tree/branch as the shipped firmware (which you linked below) before trying to get upstream coreboot working, particularly since Wolf hasn't been upstreamed yet. Payload wise, SeaBIOS is fine to build from upstream; I build off the 1.8.1 tag currently. You're welcome to use my configs and build scripts for reference: https://github.com/MattDevo/coreboot and https://github.com/MattDevo/SeaBIOS > > However, that prompted some questions, which I'm hoping someone here might be > able to help with. (I did ask in the #chromimum-os IRC channel, but they > suggested Google coreboot developers would be more likely to help here). also try #coreboot. I loiter in there and am happy to help if I'm around (I'm MattDevo on IRC). > > 1) What blobs do I use? > > Although the guide sensibly says to backup the existing bios with 'flashrom > -r', it also says to extract a bios.bin from > /usr/sbin/chromeos-firwmwareupdate (I've posted details of both at the end). > From the latter, it goes on to get you to extract four blobs: > > - SPI Descriptor > - Management Engine > - MRC > - VBIOS that list is correct. > > The first discrepancy is that the guide says the 'Management Engine firmware' > is only in the latter, but I was able to use ifdtool on both images to > extract the same set of three files. The flashregion_0_flashdescriptor.bin > files were identical, though the other two were different despite being the > same size. The ME firmware isn't always reliably read from a running system, so using the blob extracted from the shell-ball firmware image is preferred. > > The other thing is there's no reason given as to why one would use the MRC > and VBIOS blobs from the extract, rather than the backup. Curiously, they are > slightly different sizes (again details below). Looking at the config it > seems the extracted bios image was built with from a Google coreboot fork > four months older than the one backed up from the machine. these should be identical between the backup image and shell-ball extract. > > > 2) Which mainboard do I use for the Dell Chromebook 11? Wolf > > Assuming I have the correct four proprietary blobs, the next thing is > choosing the right mainboard. The guide I link to mentions suggests 'Falco', > but I don't see how, without knowing the target, such a suggestion could be > meaningful? Falco is used as an example because it was already upstreamed. Since Wolf isn't, you would need to do so yourself, which is why I suggested starting with the stock firmware tree/branch. I upstreamed Panther, which was somewhat easier since it doesn't have a built-in display or EC to worry about, but you can use Falco as a guide, comparing the upstream Falco branch to the shipped firmware tree/branch, and make similar adjustments for Wolf. > > Looking here > https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices > Falco appears to be unique to the HP Chromebook 14. The mainboard codename > for my Chromebook is 'Wolf', and that's not in coreboot upstream. > > Comparing 'src/mainboard/google' in Google's fork, and coreboot upstream: > > http://review.coreboot.org/gitweb?p=coreboot.git;a=tree;f=src/mainboard/google;h=60045af24d9760f7a52555a5ef6ef3fdc77676b7;hb=HEAD > https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/src/mainboard/google/ > > > It seems there is at least some attempt to merge upstream, and yet wolf isn't > there. Is there a particular reason some mainboards are missing? Did Google > stop doing so for some reason? To my knowledge, upstreaming boards during the Haswell
Re: [coreboot] Questions on building a Coreboot ROM for the Dell Chromebook 11
Hi Matt Thanks for the response. After quite a bit of fiddling I successfully built and flashed my own ROM. I've put up a little repo/script that will reproduce this exactly: https://github.com/marcosscriven/chromebook-coreboot/blob/master/build.sh For posterity, some issues I faced: 1) I fiddled for some time trying to build crossgcc - however the Wolf branch has some seriously old versions (including trying to download some source code tarballs that have moved), and ultimately I gave up and used the tools in Ubuntu 14.0.4 2) I also fiddled for a while trying to get vboot compiling, before stepping back and realising that was really only for a ChromeOS rom, and just switching it off. 3) The spd.bin I built ended up looking much larger than my existing one. Looking in the file showed that instead of hex, it was full of "-e -n \xnn". Googling yielded this: http://www.coreboot.org/pipermail/coreboot/2014-March/077480.html - so I just patched the Makefile: https://github.com/marcosscriven/chromebook-coreboot/blob/master/Makefile.inc.patch 4) Flashing the ROM on the Chromebook comes up with a scary "spi_block_erase_20 failed " message. Googling told me this was a 'normal' error, in true lazy developer fashion. I couldn't find an explanation as to why this was considered normal. 5) Despite attempting to set the boot menu key to ESC rather than F12 (and verifying the boot-menu-key and boot-menu-message appeared with csfbtool), it still came up with F12 when I booted. Fortunately I have a USB keyboard handy, and was still able to boot a Lubuntu install. On the software side only things I needed to tweak from a vanilla Lubuntu install: 1) Sound didn't work straight away, I needed to install pulseaudio 2) Trackpad pressure sensitivity seemed low. Had to change the "Synaptics Finger" settings from 25,30,0 to 15,20,0 The next step is moving onto upstream coreboot, but I'll open a separate question on that. Marcos On Sat, May 9, 2015 at 5:03 AM, Matt DeVillier wrote: > hi Marcos, > > I'm not a Google dev, just a hobbyist, but I've spent a lot of time over > the past year working with coreboot for the Haswell ChromeOS devices > (mostly the ChromeBoxes) and can offer some answers, inline below. > > On 5/8/2015 2:38 PM, Marcos Scriven wrote: > > I have a Dell Chromebook 11 (Google codename 'Wolf') which I'd like to > install a custom coreboot ROM on. Although John Lewis provides ROMs here > https://johnlewis.ie/custom-chromebook-firmware/rom-download/, I'd rather > not use them for a few reasons: > > 1) It's replacing one 'closed' ROM with another, in the sense it's from > a 3rd party with no public repo or build scripts. Although it's possible to > extract the coreboot config used to build them, it's not possible to > reproduce and modify the payloads. > 2) I don't need his closed 'Jeltka' payload. > 3) I'd like to experiment with other payloads, custom splash screens etc. > 4) I wouldn't learn anything, and I'm interested! > > With that in mind, this guide here looked ideal (although there's no > date on it): > https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook > > > that's what I started with, and a good overview for what you need to build > your own firmware. I'd suggest however that you first build coreboot using > the same tree/branch as the shipped firmware (which you linked below) > before trying to get upstream coreboot working, particularly since Wolf > hasn't been upstreamed yet. > > Payload wise, SeaBIOS is fine to build from upstream; I build off the > 1.8.1 tag currently. You're welcome to use my configs and build scripts > for reference: https://github.com/MattDevo/coreboot and > https://github.com/MattDevo/SeaBIOS > > > However, that prompted some questions, which I'm hoping someone here > might be able to help with. (I did ask in the #chromimum-os IRC channel, > but they suggested Google coreboot developers would be more likely to help > here). > > > also try #coreboot. I loiter in there and am happy to help if I'm around > (I'm MattDevo on IRC). > > > 1) What blobs do I use? > > Although the guide sensibly says to backup the existing bios with > 'flashrom -r', it also says to extract a bios.bin from > /usr/sbin/chromeos-firwmwareupdate (I've posted details of both at the > end). From the latter, it goes on to get you to extract four blobs: > > - SPI Descriptor > - Management Engine > - MRC > - VBIOS > > > that list is correct. > > > The first discrepancy is that the guide says the 'Management Engine > firmware' is only in the latter, but I was able to use ifdtool on both > images to extract the same set of three files. The > flashregion_0_flashdescriptor.bin files were identical, though the other > two were different despite being the same size. > > > The ME firmware isn't always reliably read from a running system, so using > the blob extracted from the shell-ball firmware image is preferred. > > >
Re: [coreboot] Questions on building a Coreboot ROM for the Dell Chromebook 11
>> To my knowledge, upstreaming boards during the Haswell days wasn't a >> priority, and was often done by non-Google devs (like me) who happened to >> have a particular device. Within the last ~6 mos this has changed >> significantly, and there's been a large push to keep the two in sync. I don't know if we have an official policy regarding upstreaming on this, but in our own master at https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/master we often intentionally only add a few boards for every generation (keeping the others in the respective release firmware branches like https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B ). The reason for that is simply to reduce clutter, since we often have a lot of different boards using the same chipset and very similar board layouts, which essentially just gives us dozens of directories with 99% copied code (e.g. see all the veyron_* boards in https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-veyron-6588.B for some of the worst offenders, which are 100% identical except for different board ID numbers). We've been talking in the past about ways to more effectively share code between boards but didn't really have time to tackle it yet. Until then, I don't expect we'll upstream any more boards than we're keeping in our own master (which is sometimes a quite arbitrary distinction based on how early we started working on that board). The best way to build upstream firmware for one of those derivative boards (like Wolf) is probably to find the corresponding "lead" board (in this case Falco), diff the respective two boards in the Chromium firmware branch(es), and apply that (hopefully very small) diff to the current upstream version of that lead board. > 5) Despite attempting to set the boot menu key to ESC rather than F12 (and > verifying the boot-menu-key and boot menu-message appeared with csfbtool), it > still came up with F12 when I booted. Fortunately I have a USB keyboard > handy, and was still able to boot a Lubuntu install. Did you use SeaBIOS directly as a payload, or did you build an image the Chromium way (with the "depthcharge" payload that chainloads SeaBIOS when you press CTRL+L)? In the latter case SeaBIOS is wrapped into its own little CBFS in a different FMAP section, and you cannot directly access it with cbfstool without extracting it first (you would instead write your files to the main coreboot CBFS where nothing is reading them from). -- coreboot mailing list: coreboot@coreboot.org http://www.coreboot.org/mailman/listinfo/coreboot
