Dobrica Pavlinušić's random unstructured stuff

Chromebook: Revision 34

{toc}

* https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/samsung-arm-chromebook

I have two chromebooks, one is working and one is bricked

^ Samsung ARM Chromebook (working)

.pre
localhost ~ # cat /proc/cpuinfo
processor : 0
model name : ARMv7 Processor rev 4 (v7l)
BogoMIPS : 48.00
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xc0f
CPU revision : 4

processor : 1
model name : ARMv7 Processor rev 4 (v7l)
BogoMIPS : 48.00
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xc0f
CPU revision : 4

Hardware : SAMSUNG EXYNOS5 (Flattened Device Tree)
Revision : 0000
Serial : 0000000000000000


localhost ~ # flashrom --flash-name
flashrom v0.9.4 : 244249c : Dec 09 2016 03:49:59 UTC on Linux 3.8.11 (armv7l)
flashrom v0.9.4 : 244249c : Dec 09 2016 03:49:59 UTC on Linux 3.8.11 (armv7l)
vendor="Winbond" name="W25Q32DW"
.pre

https://media.digikey.com/pdf/Data%20Sheets/Winbond%20PDFs/W25Q32DW.pdf

.pre
localhost ~ # flashrom --get-size
4194304

localhost ~ # flashrom --wp-status
WP: status: 0x00b8
WP: status.srp0: 1
WP: status.srp1: 0
WP: write protect is enabled.
WP: write protect range: start=0x00000000, len=0x00200000

localhost Downloads # flashrom -r chromebook-spi.rom
Block protection could not be disabled!
Reading flash... SUCCESS

.pre

^ bricked, recovery doesn't help

This chromebook reports that it wants to do recovery, but inserting (few different) usb sticks generated using http://www.google.com/chromeos/recovery instructions doesn't help

https://dl.google.com/dl/edgedl/chromeos/recovery/linux_recovery.sh

^ arch

https://wiki.archlinux.org/index.php/Samsung_Chromebook_(ARM)

.pre
setenv bootargs root=/dev/mmcblk1p2 rootfstype=jfs rootwait rw
mmc dev 1
ext2load mmc 1:1 42000000 vmlinux.uimg
bootm 42000000
.pre

^ custom firmware

* https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/custom-firmware
* http://selinuxproject.org/~jmorris/lss2013_slides/safford_chromebook_takeown.pdf
* https://www.chromium.org/chromium-os/firmware-porting-guide/using-nv-u-boot-on-the-samsung-arm-chromebook

.pre
dpavlin@nuc:/nuc/books/Chromebook$ wget http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/nv_uboot-snow.kpart.bz2
--2017-01-19 19:05:28-- http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/nv_uboot-snow.kpart.bz2
Resolving commondatastorage.googleapis.com (commondatastorage.googleapis.com)... 216.58.206.16, 2a00:1450:4001:820::2010
Connecting to commondatastorage.googleapis.com (commondatastorage.googleapis.com)|216.58.206.16|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 281844 (275K) [application/octet-stream]
Saving to: ‘nv_uboot-snow.kpart.bz2’

nv_uboot-snow.kpart.bz2 100%[================================================>] 275.24K 1.37MB/s in 0.2s

2017-01-19 19:05:28 (1.37 MB/s) - ‘nv_uboot-snow.kpart.bz2’ saved [281844/281844]

.pre

This might be upstream bios update, but u-boot doesn't start at beginning, so it's probably some update format and not raw image.

* https://blogs.s-osg.org/use-mainline-u-boot-non-signed-kernels-exynos-chromebooks/

^ flash using raspberry pi

unplug battery before attempting this! rpi3 can power flash memory

.pre
# backup

root@rpi3:/home/pi/flashrom-0.9.9# ./flashrom -p linux_spi:dev=/dev/spidev0.0 -r chromeboot-bricked.rom
flashrom v0.9.9-r1955 on Linux 4.4.27-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found GigaDevice flash chip "GD25LQ32" (4096 kB, SPI) on linux_spi.
Unsetting lock bit(s) failed.
Reading flash... done.

.pre

file:///nuc/books/Chromebook/GD25LQ32_Rev1.3.pdf

I repeated this twice and checked md5sum of both files to verify that I have stable connection with programmer

.pre
# flash version from another chromebook

root@rpi3:/home/pi# time ./flashrom-0.9.9/flashrom -p linux_spi:dev=/dev/spidev0.0 -w chromebook-spi.rom
flashrom v0.9.9-r1955 on Linux 4.4.27-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found GigaDevice flash chip "GD25LQ32" (4096 kB, SPI) on linux_spi.
Unsetting lock bit(s) failed.
Reading old flash chip contents... done.
Erasing and writing flash chip... FAILED at 0x00002000! Expected=0xff, Found=0x14, failed byte count from 0x00002000-0x00002fff: 0xfbb
ERASE FAILED!
Reading current flash chip contents... done. Looking for another erase function.
FAILED at 0x00000000! Expected=0xff, Found=0xa3, failed byte count from 0x00000000-0x00007fff: 0x7d35
ERASE FAILED!
Reading current flash chip contents... done. Looking for another erase function.
FAILED at 0x00000000! Expected=0xff, Found=0xa3, failed byte count from 0x00000000-0x0000ffff: 0xfac8
ERASE FAILED!
Reading current flash chip contents... done. Looking for another erase function.
FAILED at 0x00000000! Expected=0xff, Found=0xa3, failed byte count from 0x00000000-0x003fffff: 0x3dea4f
ERASE FAILED!
Reading current flash chip contents... done. Looking for another erase function.
No usable erase functions left.
FAILED!
Uh oh. Erase/write failed. Checking if anything has changed.
Reading current flash chip contents... done.
Good, writing to the flash chip apparently didn't do anything.
Please check the connections (especially those to write protection pins) between
the programmer and the flash chip. If you think the error is caused by flashrom
please report this on IRC at chat.freenode.net (channel #flashrom) or
mail flashrom@flashrom.org, thanks!

real 14m40.938s
user 0m1.600s
sys 0m9.000s


# hm?!
root@rpi3:/home/pi# time ./flashrom-0.9.9/flashrom -p linux_spi:dev=/dev/spidev0.0 -r chromebook-broken.rom.3
flashrom v0.9.9-r1955 on Linux 4.4.27-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found GigaDevice flash chip "GD25LQ32" (4096 kB, SPI) on linux_spi.
Unsetting lock bit(s) failed.
Reading flash... done.

real 1m19.653s
user 0m1.140s
sys 0m0.700s
root@rpi3:/home/pi# md5sum chromeboot-bricked.rom chromebook-broken.rom.3
1ef1d2230c27624661a86b57064057cb chromeboot-bricked.rom
1ef1d2230c27624661a86b57064057cb chromebook-broken.rom.3

# It really didn't change!

.pre

^^ ch341a attempt

.pre
root@rpi3:/home/pi# flashrom --programmer ch341a_spi -r ch341a-snow-broken-spi.rom
flashrom v0.9.9-r1955 on Linux 4.4.27-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found GigaDevice flash chip "GD25LQ32" (4096 kB, SPI) on ch341a_spi.
Reading flash... done.
root@rpi3:/home/pi# md5sum ch341a-snow-broken-spi.rom
1ef1d2230c27624661a86b57064057cb ch341a-snow-broken-spi.rom

root@rpi3:/home/pi# md5sum *.rom
1ef1d2230c27624661a86b57064057cb ch341a-snow-broken-spi.rom
11e616f5dcf18d775f6484b78953ada0 chromebook-spi.rom
1ef1d2230c27624661a86b57064057cb chromeboot-bricked.rom

root@rpi3:/home/pi# time flashrom --programmer ch341a_spi -w chromebook-spi.rom
flashrom v0.9.9-r1955 on Linux 4.4.27-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found GigaDevice flash chip "GD25LQ32" (4096 kB, SPI) on ch341a_spi.
Reading old flash chip contents... done.
Erasing and writing flash chip... Erase/write done.
Verifying flash... VERIFIED.

real 5m21.170s
user 0m48.300s
sys 0m18.330s

.pre

https://dl.google.com/dl/edgedl/chromeos/recovery/linux_recovery.sh

https://dl.google.com/dl/edgedl/chromeos/recovery/chromeos_8743.85.0_daisy_recovery_stable-channel_snow-mp-v4.bin.zip


^ u-boot

.pre
dpavlin@klin:/klin$ git clone git://git.denx.de/u-boot.git
Cloning into 'u-boot'...
remote: Counting objects: 442911, done.
remote: Compressing objects: 100% (77033/77033), done.
remote: Total 442911 (delta 360952), reused 440666 (delta 358805)
Receiving objects: 100% (442911/442911), 93.64 MiB | 11.14 MiB/s, done.
Resolving deltas: 100% (360952/360952), done.

git remote add u-boot-samsung git://git.denx.de/u-boot-samsung.git
git checkout u-boot-samsung/master -b u-boot-samsung/master

dpavlin@klin:/klin/u-boot$ find . -name 'snow*'
./include/configs/snow.h
./configs/snow_defconfig

export CROSS_COMPILE="arm-none-eabi-" ARCH=arm

dpavlin@klin:/klin/u-boot$ make snow_defconfig
HOSTCC scripts/basic/fixdep
HOSTCC scripts/kconfig/conf.o
SHIPPED scripts/kconfig/zconf.tab.c
SHIPPED scripts/kconfig/zconf.lex.c
SHIPPED scripts/kconfig/zconf.hash.c
HOSTCC scripts/kconfig/zconf.tab.o
HOSTLD scripts/kconfig/conf
#
# configuration written to .config
#

make



.pre


^^ chromiumos

.pre
dpavlin@klin:/klin/chromebook/u-boot$ git remote -v
origin https://chromium.googlesource.com/chromiumos/third_party/u-boot/ (fetch)
origin https://chromium.googlesource.com/chromiumos/third_party/u-boot/ (push)

dpavlin@klin:/klin/chromebook/u-boot$ git checkout -b firmware-snow-2695.B remotes/origin/firmware-snow-2695.B
Branch firmware-snow-2695.B set up to track remote branch firmware-snow-2695.B from origin.




.pre


^ servo debug header

{image: servo-v1-debug-40pin.png}

^ spi flash layout

.pre
dpavlin@nuc:/nuc/flashmap$ git remote -v
origin https://github.com/dhendrix/flashmap (fetch)
origin https://github.com/dhendrix/flashmap (push)

dpavlin@nuc:/nuc/chromebook/flashmap$ ./fmap_decode /nuc/books/Chromebook/spi/snow-spi.rom | sort | grep -v R[OW]_ | grep -v WP_
area_offset="0x00000000" area_size="0x00002000" area_name="BL1 PRE_BOOT" area_flags_raw="0x01" area_flags="static"
area_offset="0x00002000" area_size="0x00004000" area_name="BL2 SPL" area_flags_raw="0x01" area_flags="static"
area_offset="0x00006000" area_size="0x0009a000" area_name="U_BOOT" area_flags_raw="0x01" area_flags="static"
area_offset="0x000a0000" area_size="0x00001000" area_name="FMAP" area_flags_raw="0x01" area_flags="static"
area_offset="0x000b0000" area_size="0x000ef000" area_name="GBB" area_flags_raw="0x01" area_flags="static"
area_offset="0x00200000" area_size="0x00002000" area_name="VBLOCK_A" area_flags_raw="0x01" area_flags="static"
area_offset="0x00202000" area_size="0x000edf00" area_name="FW_MAIN_A" area_flags_raw="0x01" area_flags="static"
area_offset="0x00300000" area_size="0x00002000" area_name="VBLOCK_B" area_flags_raw="0x01" area_flags="static"
area_offset="0x00302000" area_size="0x000edf00" area_name="FW_MAIN_B" area_flags_raw="0x01" area_flags="static"
area_offset="0x003f8000" area_size="0x00004000" area_name="SHARED_DATA" area_flags_raw="0x01" area_flags="static"
fmap_signature="0x5f5f464d41505f5f" fmap_ver_major="1" fmap_ver_minor="0" fmap_base="0x0000000000000000" fmap_size="0x400000" fmap_name="FMAP" fmap_nareas="23"

.pre

^ enable development mode from recovery

https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/workaround-for-battery-discharge-in-dev-mode

.pre
(parted) unit b
(parted) print
Model: MEM Drive Mini Metal (scsi)
Disk /dev/sdc: 2021654528B
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
11 32768B 8421375B 8388608B RWFW
6 8421376B 8421887B 512B KERN-C
7 8421888B 8422399B 512B ROOT-C
9 8422400B 8422911B 512B reserved
10 8422912B 8423423B 512B reserved
2 10485760B 27262975B 16777216B KERN-A
4 27262976B 44040191B 16777216B KERN-B
8 44040192B 60817407B 16777216B ext4 OEM msftdata
12 127926272B 144703487B 16777216B fat16 EFI-SYSTEM boot, esp
5 144703488B 146800639B 2097152B ROOT-B
3 146800640B 1499463679B 1352663040B ext2 ROOT-A
1 1499463680B 1518338047B 18874368B ext2 STATE msftdata

(parted) quit
dpavlin@nuc:/nuc/flashmap$ ./enable_rw_mount.sh /dev/sdc 146800640B
./enable_rw_mount.sh: line 9: 146800640B: value too great for base (error token is "146800640B")
enable_rw_mount called on non-ext2 filesystem: /dev/sdc 146800640B
dpavlin@nuc:/nuc/flashmap$ ./enable_rw_mount.sh /dev/sdc 146800640
dpavlin@nuc:/nuc/flashmap$ sudo mount /dev/sdc3 /tmp/sdc3/
.pre

^ coreboot

* https://www.coreboot.org/Exynos5