Debugging

Grabbing Logs

  • If you're experiencing firmware bugs, provide output from cbmem console.
  • If you're experiencing issues with Linux, provide output from dmesg, dmidecode and journalctl or /var/log/messages, respectively
  • If you're experiencing issues with Windows, provide screenshots from Device Manager, Event Viewer, coredumps etc.
  • If you're experiencing issues with macOS, please ask for help using the Chrultrabook Forumsopen in new window.

Firmware

To debug firmware, you will need the following tools:

  1. cbmem - To view Coreboot logs
  2. ectool - To interface with ChromeOS Embedded Controller
  3. SuzyQ - If you're experiencing severe system instability (lockups, crashes), preventing you from on-device debugging.

To dump the cbmem buffer, follow these steps:

  1. Download the tar archive from MrChromebox's website:
  • wget https://mrchromebox.tech/files/util/cbmem.tar.gz
  1. Unzip the file and give the binary executable permissions:
  • tar -xf cbmem.tar.gz;rm cbmem.tar.gz;chmod +x cbmem
  1. Run cbmem and pipe its output to cbmem.log file:
  • sudo ./cbmem -1 > cbmem.log
  1. Upload cbmem.log file for further analysis.

To interface with the Embedded Controller:

  1. Download the tar archive from MrChromebox's website:
  • wget https://mrchromebox.tech/files/util/ectool.tar.gz
  1. Unzip the file and give the binary executable permissions:
  • tar -xf ectool.tar.gz;rm ectool.tar.gz;chmod +x ectool
  1. Issue commands to EC by executing commands, for example setting the fan to 100%:

SuzyQ Debug Cable

If you need to use SuzyQ, you can use minicom or picocom for example. It exposes three serial devices:

  1. AP (CR50) console under /dev/ttyUSB0:
  • minicom -D /dev/ttyUSB0 -b 115200
  1. Coreboot/platform serial under /dev/ttyUSB1:
  • minicom -D /dev/ttyUSB1 -b 115200
  1. Embedded Controller console under /dev/ttyUSB2
  • minicom -D /dev/ttyUSB2 -b 115200

  • Platform serial can be used to debug the payload or kernel, but you need to re-compile coreboot with following configuration options enabled: CONSOLE_SERIAL=yEDK2_SERIAL_SUPPORT=y

  • To use SuzyQ as platform debugger, you will also need to append the following to your kernel commandline: loglevel=15 console=ttyS4,115200n8


ACPI and Linux kernelspace

  1. Download our debugging script.
  • cd ~/Desktop;wget https://raw.githubusercontent.com/chrultrabook/linux-tools/main/debugging.sh

It will dump:

  • ACPI tables from sysfs (/sys/firmware/acpi/*)
  • DMI information (dmidecode)
  • Coreboot buffer (cbmem)
  • Linux kernel logs (dmesg)
  • List of PCI devices (lspci)
  • List of USB devices (lsusb)
  • Information about soundcards present in the system and their configuration

Into debug-logs.tar.gz archive on your desktop.

  1. Run it: chmod +x debugging.sh;./debugging.sh

  2. Upload this file if you need help with troubleshooting.

  • Remember to remove WiFi information from dmesg to protect your privacy.

flashrom

Flashrom is used to read and write from the SPI flash

Read flash:

  • sudo flashrom -p <programmer> -r <filename.rom>
  • Example:
    • sudo flashrom -p internal -r backup.rom

DANGER

If you have an Intel Chromebook, you will need to add --ifd -i bios if you want to write to the flash or else flashrom will fail.

Write flash:

  • sudo flashrom -p <programmer> -w <filename.rom>
  • Intel Example:
    • sudo flashrom -p internal --ifd -i bios -w stock.rom
  • AMD Example:
    • sudo flashrom -p internal -w stock.rom

Write protection:

View status:

  • sudo flashrom -p internal --wp-status

Enable WP:

  • sudo flashrom -p internal --wp-enable

Disable WP:

  • sudo flashrom -p internal --wp-disable

Clear WP range:

  • sudo flashrom -p internal --wp-range 0 0

Common programmers:

  • internal: Use this when you run flashrom on the chromebook you want to program.
  • ch341a_spi: Use this when you use a ch341a external programmer.
  • raiden_debug_spi:target=AP: Use then when you want to flash using a Suzy-Q cable.

gsctool

gsctool is used to communicate with the GSC (Google Security Chip) from ChromeOS and is usually used to unlock CCD without removing the back of the Chromebook.

View status:

  • sudo gsctool -a -I

Unlock CCD:

  • sudo gsctool -a -o
  • This will prompt you multiple times to press the power button, on the last time, the device will reboot back into verified mode
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