diff options
Diffstat (limited to 'doc/README.chromium')
| -rw-r--r-- | doc/README.chromium | 296 |
1 files changed, 117 insertions, 179 deletions
diff --git a/doc/README.chromium b/doc/README.chromium index 45eaeced2d..096bc4f1f7 100644 --- a/doc/README.chromium +++ b/doc/README.chromium @@ -1,239 +1,177 @@ -Running U-Boot from coreboot on Chromebooks -=========================================== +Chromium OS Support in U-Boot +============================= -U-Boot can be used as a secondary boot loader in a few situations such as from -UEFI and coreboot (see README.x86). Recent Chromebooks use coreboot even on -ARM platforms to start up the machine. +Introduction +------------ -This document aims to provide a guide to booting U-Boot on a Chromebook. It -is only a starting point, and there are many guides on the interwebs. But -placing this information in the U-Boot tree should make it easier to find for -those who use U-Boot habitually. +This describes how to use U-Boot with Chromium OS. Several options are +available: -Most of these platforms are supported by U-Boot natively, but it is risky to -replace the ROM unless you have a servo board and cable to restore it with. + - Running U-Boot from the 'altfw' feature, which is available on selected + Chromebooks from 2019 onwards (initially Grunt). Press '1' from the + developer-mode screen to get into U-Boot. See here for details: + https://sites.google.com/a/chromium.org/dev/chromium-os/poking-around-your-chrome-os-device?pli=1 + - Running U-Boot from the disk partition. This involves signing U-Boot and + placing it on the disk, for booting as a 'kernel'. See + README.chromium-chainload for information on this. This is the only + option on non-U-Boot Chromebooks from 2013 to 2018 and is somewhat + more involved. -For all of these the standard U-Boot build instructions apply. For example on -ARM: + - Running U-Boot with Chromium OS verified boot. This allows U-Boot to be + used instead of either or both of depthcharge (a bootloader which forked + from U-Boot in 2013) and coreboot. See below for more information on + this. - sudo apt install gcc-arm-linux-gnueabi - mkdir b - make O=b/nyan_big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all -You can obtain the vbutil_kernel utility here: +U-Boot with Chromium OS verified boot +------------------------------------- - https://drive.google.com/open?id=0B7WYZbZ9zd-3dHlVVXo4VXE2T0U +To obtain: + git clone https://github.com/sglass68/u-boot.git + cd u-boot + git checkout cros-master -Snow (Samsung ARM Chromebook) ------------------------------ +To build for sandbox: -See here: + UB=/tmp/b/chromeos_sandbox # U-Boot build directory + CROS=/home/sglass/cosarm # Chromium OS directory + make O=$UB/chromeos_sandbox_defconfig + make O=$UB -j20 -s VBOOT_SOURCE=$CROS/src/platform/vboot_reference \ + MAKEFLAGS_VBOOT=DEBUG=1 QUIET=1 -https://www.chromium.org/chromium-os/firmware-porting-guide/using-nv-u-boot-on-the-samsung-arm-chromebook +Replace sandbox with another supported target. +This produces $UB/image.bin which contains the firmware binaries in a SPI +flash image. -Nyan-big --------- - -Compiled based on information here: -https://lists.denx.de/pipermail/u-boot/2015-March/209530.html -https://git.collabora.com/cgit/user/tomeu/u-boot.git/commit/?h=nyan-big -https://lists.denx.de/pipermail/u-boot/2017-May/289491.html -https://github.com/chromeos-nvidia-androidtv/gnu-linux-on-acer-chromebook-13#copy-data-to-the-sd-card - -1. Build U-Boot - - mkdir b - make -j8 O=b/nyan-big CROSS_COMPILE=arm-linux-gnueabi- nyan-big_defconfig all - - -2. Select a .its file - -Select something from doc/chromium which matches your board, or create your -own. - -Note that the device tree node is required, even though it is not actually -used by U-Boot. This is because the Chromebook expects to pass it to the -kernel, and crashes if it is not present. - - -3. Build and sign an image - - ./b/nyan-big/tools/mkimage -f doc/chromium/nyan-big.its u-boot-chromium.fit - echo test >dummy.txt - vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \ - --signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \ - --version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \ - --bootloader dummy.txt --pack u-boot.kpart - - -4. Prepare an SD card - - DISK=/dev/sdc # Replace with your actual SD card device - sudo cgpt create $DISK - sudo cgpt add -b 34 -s 32768 -P 1 -S 1 -t kernel $DISK - sudo cgpt add -b 32802 -s 2000000 -t rootfs $DISK - sudo gdisk $DISK # Enter command 'w' to write a protective MBR to the disk - - -5. Write U-Boot to the SD card +To run on sandbox: - sudo dd if=u-boot.kpart of=/dev/sdc1; sync + $UB/tpl/u-boot-tpl -d $UB/u-boot.dtb.out \ + -L6 -c "host bind 0 $CROS/src/build/images/cheza/latest/chromiumos_image.bin; vboot go auto" \ + -l -w -s state.dtb -r +To run on other boards: + Install image.bin in the SPI flash of your device + Boot your system -6. Start it up -Reboot the device in dev mode. Make sure that you have USB booting enabled. To -do this, login as root (via Ctrl-Alt-forward_arrow) and type -'enable_dev_usb_boot'. You only need to do this once. +Sandbox +------- -Reboot the device with the SD card inserted. Press Clrl-U at the developer -mode screen. It should show something like the following on the display: +Most Chromium OS development with U-Boot is undertaken using sandbox. There is +a sandbox target available (chromeos_sandbox) which allows running U-Boot on +a Linux machine completion with emulations of the display, TPM, disk, etc. - U-Boot 2017.07-00637-g242eb42-dirty (May 22 2017 - 06:14:21 -0600) +Running sandbox starts TPL, which contains the first phase of vboot, providing +a device tree and binding a Chromium OS disk image for use to find kernels +(any Chromium OS image will do). It also saves driver state between U-Boot +phases into state.dtb and will automatically ensure that memory is shared +between all phases. TPL will jump to SPL and then on to U-Boot proper. - Model: Acer Chromebook 13 CB5-311 - Board: Google/NVIDIA Nyan-big, ID: 1 +It is possible to run with debugging on, e.g. - Net: No ethernet found. - Hit any key to stop autoboot: 0 - Tegra124 (Nyan-big) # + gdb --args $UB/tpl/u-boot-tpl -d .... +Breakpoints can be set in any U-Boot phase. Overall this is a good debugging +environment for new verified-boot features. -7. Known problems -On the serial console the word MMC is chopped at the start of the line: +Samus +----- -C: sdhci@700b0000: 2, sdhci@700b0400: 1, sdhci@700b0600: 0 +Basic support is available for samus, using the chromeos_samus target. If you +have an em100, use: -This is likely due to some problem with change-over of the serial driver -during relocation (or perhaps updating the clock setup in board_init()). + sudo em100 -s -c W25Q128FW -d $UB/image.bin -t -r +to write the image and then boot samus (Power-Refresh). -9. Notes -To check that you copied the u-boot.its file correctly, use these commands. -You should see that the data at 0x100 in u-boot-chromium.fit is the first few -bytes of U-Boot: +Boot flow +--------- - hd u-boot-chromium.fit |head -20 - ... - 00000100 b8 00 00 ea 14 f0 9f e5 14 f0 9f e5 14 f0 9f e5 |................| +Verified boot starts in TPL, which selects the A or B SPL, which in turn selects +the A or B U-Boot. Then this jumps to the selected kernel. If anything goes +wrong, the device reboots and the recovery SPL and U-Boot are used instead. - hd b/nyan-big/u-boot.bin |head - 00000000 b8 00 00 ea 14 f0 9f e5 14 f0 9f e5 14 f0 9f e5 |................| +More details are available here: + https://www.chromium.org/chromium-os/chromiumos-design-docs/firmware-boot-and-recovery -The 'data' property of the FIT is set up to start at offset 0x100 bytes into -the file. The change to CONFIG_SYS_TEXT_BASE is also an offset of 0x100 bytes -from the load address. If this changes, you either need to modify U-Boot to be -fully relocatable, or expect it to hang. +New uclasses +------------ -chromebook_jerry ----------------- +Several uclasses are provided in cros/: -The instruction are similar to those for Nyan with changes as noted below: + UCLASS_CROS_AUX_FW Chrome OS auxiliary firmware + UCLASS_CROS_FWSTORE Chrome OS firmware storage + UCLASS_CROS_NVDATA Chrome OS non-volatile data device + UCLASS_CROS_VBOOT_EC Chrome OS vboot EC operations + UCLASS_CROS_VBOOT_FLAG Chrome OS verified boot flag -1. Patch U-Boot +The existing UCLASS_CROS_EC is also used. -Open include/configs/rk3288_common.h -Change: - -#define CONFIG_SYS_TEXT_BASE 0x00100000 - -to: - -#define CONFIG_SYS_TEXT_BASE 0x02000100 - - - -2. Build U-Boot - - mkdir b - make -j8 O=b/chromebook_jerry CROSS_COMPILE=arm-linux-gnueabi- \ - chromebook_jerry_defconfig all - - -3. See above - -4. Build and sign an image - - ./b/chromebook_jerry/tools/mkimage -f doc/chromium/chromebook_jerry.its \ - u-boot-chromium.fit - echo test >dummy.txt - vbutil_kernel --arch arm --keyblock doc/chromium/devkeys/kernel.keyblock \ - --signprivate doc/chromium/devkeys/kernel_data_key.vbprivk \ - --version 1 --config dummy.txt --vmlinuz u-boot-chromium.fit \ - --bootloader dummy.txt --pack u-boot.kpart - - -5. See above +Commands +-------- -6. See above +A new 'vboot' command is provided to run particular vboot stages. The most +useful command is 'vboot go auto', which continues where the last stage left +off. -7. Start it up +Note that TPL and SPL do not supports commands as yet, so the vboot code is +called directly from the SPL boot devices (BOOT_DEVICE_CROS_VBOOT). See +cros_load_image_tpl() and cros_load_image_spl() which both call +vboot_run_auto(). -Reboot the device in dev mode. Make sure that you have USB booting enabled. To -do this, login as root (via Ctrl-Alt-forward_arrow) and type -'enable_dev_usb_boot'. You only need to do this once. -Reboot the device with the SD card inserted. Press Clrl-U at the developer -mode screen. It should show something like the following on the display: +Config options +-------------- - U-Boot 2017.05-00649-g72acdbf-dirty (May 29 2017 - 14:57:05 -0600) +The main option is CONFIG_CHROMEOS, which enables a wide array of other options +so that the required features are present. - Model: Google Jerry - Net: Net Initialization Skipped - No ethernet found. - Hit any key to stop autoboot: 0 +Device-tree config +------------------ -8. Known problems +Various options are available which control the operation of verified boot. +See cros/dts/bindings/config.txt for details. Most config is handled at run- +time, although build-time config (with Kconfig) could also be added fairly +easily. -None as yet. +Porting to other hardware +------------------------- -9. Notes +A basic port to samus (Chromebook Pixel 2015) is in a basic working state, +using the chromeos_samus target. Patches will likely be forthcoming in early +2019. Ports to an ARM board and coreboot (for x86 Chromebooks) are in the +dreaming state. -None as yet. +Tests +----- -Other notes -=========== +Chromium OS firmware has a very limited set of tests. The tests that originally +existed in U-Boot were not brought over to coreboot or depthcharge. -flashrom --------- +The U-Boot tests ('make check') do operate, but at present there are no +Chromium OS tests available. These will hopefully come together over time. Of +course the above sandbox feature provides a sort of functional test and can +detecte problems that affect the flow or particular vboot features. - Used to make a backup of your firmware, or to replace it. - See: https://www.chromium.org/chromium-os/packages/cros-flashrom +TO DO +----- +- Support for booting from coreboot (patches expected March 2019) +- Support for booting from an ARM board, e.g. bob -coreboot --------- -Coreboot itself is not designed to actually boot an OS. Instead, a program -called Depthcharge is used. This originally came out of U-Boot and was then -heavily hacked and modified such that is is almost unrecognisable. It does -include a very small part of the U-Boot command-line interface but is not -usable as a general-purpose boot loader. - -In addition, it has a very unusual design in that it does not do device init -itself, but instead relies on coreboot. This is similar to (in U-Boot) having -a SPI driver with an empty probe() method, relying on whatever was set up -beforehand. It can be quite hard to figure out between these two code bases -what settings are actually used. When chain-loading into U-Boot we must be -careful to reinit anything that U-Boot expects. If not, some peripherals (or -the whole machine) may not work. This makes the process of chainloading more -complicated than it could be on some platforms. - -Finally, it supports only a subset of the U-Boot's FIT format. In particular -it uses a fixed address to load the FIT and does not support load/exec -addresses. This means that U-Boot must be able to boot from whatever -address Depthcharge happens to use (it is the CONFIG_KERNEL_START setting -in Depthcharge). In practice this means that the data in the kernel@1 FIT node -(see above) must start at the same address as U-Boot's CONFIG_SYS_TEXT_BASE. +Simon Glass +sjg@chromium.org +7 October 2018 |