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OpenBMC cheatsheet

This document is intended to provide a set of recipes for common OpenBMC customisation tasks, without having to know the full yocto build process.

Using a local kernel build

The kernel recipe is in:

 meta-phosphor/common/recipes-kernel/linux/linux-obmc_X.Y.bb

To use a local git tree, change the SRC_URI to a git:// URL without a hostname, and remove the protocol=git parameter. For example:

SRC_URI = "git:///home/jk/devel/linux;branch=${KBRANCH}"

The SRCREV variable can be used to set an explicit git commit, or set to "${AUTOREV}" to use the latest commit in KBRANCH.

Building for Palmetto

The Palmetto target is palmetto.

$ cd openbmc
$ . setup palmetto
$ bitbake obmc-phosphor-image

Building for Zaius

The Zaius target is zaius.

$ cd openbmc
$ . setup zaius
$ bitbake obmc-phosphor-image

Building a specific machine configuration

If the system you want to build contains different machine configurations:

meta-<layer>/meta-<system>/conf/machine/machineA.conf
meta-<layer>/meta-<system>/conf/machine/machineB.conf

You can specify the machine configuration you want to build by passing the name to the setup.

$ cd openbmc
$ . setup machineB
$ bitbake obmc-phosphor-image

Building the OpenBMC SDK

Looking for a way to compile your programs for 'ARM' but you happen to be running on a 'PPC' or 'x86' system? You can build the sdk receive a fakeroot environment.

$ bitbake -c populate_sdk obmc-phosphor-image
$ ./tmp/deploy/sdk/openbmc-phosphor-glibc-x86_64-obmc-phosphor-image-armv5e-toolchain-2.1.sh

Follow the prompts. After it has been installed the default to setup your env will be similar to this command

. /opt/openbmc-phosphor/2.1/environment-setup-armv5e-openbmc-linux-gnueabi

Rebuilds & Reconfiguration

You can reconfigure your build by removing the build/conf dir:

rm -rf build/conf

and running setup again.

Useful D-Bus CLI tools

busctl

http://www.freedesktop.org/software/systemd/man/busctl.html

Great tool to issue D-Bus commands via cli. That way you don't have to wait for the code to hit the path on the system. Great for running commands with QEMU too!

Run as:

busctl call <path> <interface> <object> <method> <parameters>
  • <parameters> example : sssay "t1" "t2" "t3" 2 2 3

Using QEMU

QEMU has a palmetto-bmc machine (as of v2.6.0) which implements the core devices to boot a Linux kernel. OpenBMC also maintains a tree with patches on their way upstream or temporary work-arounds that add to QEMU's capabilities where appropriate.

qemu-system-arm -m 256 -M palmetto-bmc -nographic \
-drive file=<path>/flash-palmetto,format=raw,if=mtd \
-net nic \
-net user,hostfwd=:127.0.0.1:2222-:22,hostfwd=:127.0.0.1:2443-:443,hostname=qemu

If you get an error you likely need to build QEMU (see the section in this document). If no error and QEMU starts up just change the port when interacting with the BMC...

curl -c cjar -b cjar -k -H "Content-Type: application/json" \
-X POST https://localhost:2443/login -d "{\"data\": [ \"root\", \"0penBmc\" ] }"

or

ssh -p 2222 root@localhost

To quit, type Ctrl-a c to switch to the QEMU monitor, and then quit to exit.

Building QEMU

git clone https://github.com/openbmc/qemu.git
cd qemu
git submodule update --init dtc
mkdir build
cd build
../configure --target-list=arm-softmmu
make

Built file will be located at: arm-softmmu/qemu-system-arm

Use a bridge device

Using a bridge device requires a bit of root access to set it up. The benefit is your qemu session runs in the bridges subnet so no port forwarding is needed. There are packages needed to yourself a virbr0 such as...

apt-get install libvirt libvirt-bin bridge-utils uml-utilities qemu-system-common

qemu-system-arm -m 256 -M palmetto-bmc -nographic \
-drive file=<path>/flash-palmetto,format=raw,if=mtd \
-net nic,macaddr=C0:FF:EE:00:00:02,model=ftgmac100  \
-net bridge,id=net0,helper=/usr/lib/qemu-bridge-helper,br=virbr0

There are some other useful parms like that can redirect the console to another window. This results in having an easily accessible qemu command session. -monitor stdio -serial pty -nodefaults

Booting the host

Login:

curl -c cjar -k -X POST -H "Content-Type: application/json" -d '{"data": [ "root", "0penBmc" ] }' https://${bmc}/login

Connect to host console:

ssh -p 2200 root@bmc

Power on:

curl -c cjar -b cjar -k -H "Content-Type: application/json" -X PUT \
  -d '{"data": "xyz.openbmc_project.State.Host.Transition.On"}' \
  https://${bmc}/xyz/openbmc_project/state/host0/attr/RequestedHostTransition

GDB

SDK build provides GDB and debug symbols:

  • $GDB is available to use once SDK environment is setup
  • Debug symbols are located in .debug/ directory of each executable

To use GDB:

  1. Setup SDK environment;
  2. Run below GDB commands: 
    cd <sysroot_of_sdk_build>
$GDB <relative_path_to_exeutable> <path_to_core_file>

Coredump

By default coredump is disabled in OpenBMC. To enable coredump:

echo '/tmp/core_%e.%p' | tee /proc/sys/kernel/core_pattern
ulimit -c unlimited

Cleaning up read-write file system changes

You may want to investigate which file(s) are persisting through the overlay rwfs. To do this, you can list this path and then remove those files which you'd prefer the originals or remove the deletion overlay to restore files.

/run/initramfs/rw/cow/

Building

Share downloads directory

It takes a long time for the first build of OpenBMC. It downloads various repos from the internet.

Check build/downloads to see all the downloaded repos.

  • If a repo is a single archive, it usually looks like this:
    • zlib-1.2.11.tar.xz - The repo itself
    • zlib-1.2.11.tar.xz.done - A flag indicating the repo is downloaded
  • If a repo is managed by git, it usually looks like this:
    • git2/github.com.openbmc.linux - The git bare clone
    • git2/github.com.openbmc.linux.done - A flag indicating the repo is downloaded

Bitbake will extract the code to the working directory during build, so the downloads directory could be shared by different builds on a system:

  • Set DL_DIR Bitbake environment variable to the location of your shared downloads directory by editing the build/conf/local.conf file: 
    DL_DIR ?= "<path>/<to>/<existing>/downloads"
  • Or create a symbol link: 
    ln -sf <path>/<to>/<existing>/downloads build/downloads
    Then do the build. It will save a lot of time from downloading codes.

Using git proxy

If you experience extremely slow download speed during code fetch (e.g. if you are in China), it is possible to use a git proxy to speed up the code fetch.

Google git-proxy-wrapper will find various ways to setup the proxy for the git protocol.

Below is an example wrapper in ~/bin assuming a socks5 proxy at port 9054:

#!/bin/sh
## Use connect-proxy as git proxy wrapper which supports SOCKS5
## Install with `apt-get install connect-proxy`
## Use with `export GIT_PROXY_COMMAND=~/bin/git-proxy-wrapper`
/usr/bin/connect -S localhost:9054 "$@"

Then you can run export GIT_PROXY_COMMAND=~/bin/git-proxy-wrapper and you are now downloading git code through your proxy.

devtool

devtool is a convenient utility in Yocto to make changes in the local directory. Typical usage is:

# To create a local copy of recipe's code and build with it:
devtool modify <recipe>
cd build/workspace/sources/<recipe>  # And make changes
bitbake obmc-phosphor-image  # Build with local changes

# After you have finished, reset the recipe to ignore local changes:
devtool reset <recipe>

To use this tool, you need the build environment, e.g. . oe-init-build-env. The above script will add <WORKDIR>/scripts/ to your PATH env and devtool is in the path.

Below are real examples.

devtool on ipmi

If you want to debug or add a new function in ipmi, you probably need to change the code in phosphor-host-ipmid. Checking the recipes, you know this repo is in phosphor-ipmi-host.bb. Below are the steps to use devtool to modify the code locally, build and test it.

  1. Use devtool to create a local repo: 
    devtool modify phosphor-ipmi-host
    devtool clones the repo into build/workspace/sources/phosphor-ipmi-host, creates and checkout branch devtool.
  2. Make changes in the repo, e.g. adding code to handle new ipmi commands or simply adding trace logs.
  3. Now you can build the whole image or the ipmi recipe itself: 
    bitbake obmc-phosphor-image  # Build the whole image
bitbake phosphor-ipmi-host  # Build the recipe
  4. To test your change, either flash the whole image or replace the changed binary. Note that the changed code is built into libapphandler.so and it is used by both host and net ipmi daemon. It is recommended that you copy the changed binary to BMC because it is easier to test: 
    # Replace libapphandler.so.0.0.0
scp build/workspace/sources/phosphor-ipmi-host/oe-workdir/package/usr/lib/ipmid-providers/libapphandler.so.0.0.0 root@bmc:/usr/lib/ipmid-providers/
systemctl restart phosphor-ipmi-host.service  # Restart the inband ipmi daemon
# Or restart phosphor-ipmi-net.service if you want to test net ipmi.
  5. Now you can test your changes.

Develop linux kernel

devtool on linux kernel

If you want to work on linux kernel, you can use devtool as well, with some differences from regular repos.

Note: As of ac72846 the linux kernel recipe name is changed to linux-aspeed for Aspeed based OpenBMC builds. In the following examples, replace linux-obmc with linux-aspeed if you are on a revision later than ac72846.

  1. devtool does not create the 'devtool' branch. Instead, it checkout the branch specified in the recipe. For example, on the OpenBMC v2.2 tag, linux-obmc_4.13.bb specifies dev-4.13 branch.
  2. If there are patches, devtool applies them directly on the branch.
  3. devtool copies the defconfig and machine-specific config into oe-workdir.
  4. devtool generates the .config file based on the above configs.

You can modify the code and build the kernel as usual as follows:

bitbake linux-obmc -c build

Modify config

If you need to change the config and save it as defconfig for further use:

bitbake linux-obmc -c menuconfig
# Edit the configs and after save it generates
# .config.new as the new kernel config

bitbake linux-obmc -c savedefconfig
# It will save the new defconfig at oe-workdir/linux-obmc-<version>/defconfig

Test linux kernel

After build, you can flash the image to test the new kernel. However, it is always slow to flash an image to the chip.

There is a faster way to load the kernel via network so you can easily test kernel builds.

OpenBMC kernel build generates fit image, including kernel, dtb and initramfs. Typically we can load it via tftp, taking Romulus as an example:

  1. Put build/tmp/deploy/images/romulus/fitImage-obmc-phosphor-initramfs-romulus.bin to a tftp server, name it to fitImage
  2. Reboot BMC and press keys to enter uboot shell;
  3. In uboot: 
    setenv ethaddr <mac:addr>  # Set mac address if there it is unavailable
setenv ipaddr 192.168.0.80  # Set BMC IP
setenv serverip 192.168.0.11  # Set tftp server IP
tftp 0x83000000 fitImage  # Load fit image to ram. Use 0x43000000 on AST2400
bootm 0x83000000  # Boot from fit image
    Then you are running an OpenBMC with your updated kernel.