diff options
Diffstat (limited to 'docs/HACKING.md')
| -rw-r--r-- | docs/HACKING.md | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/docs/HACKING.md b/docs/HACKING.md new file mode 100644 index 0000000000..17136060ce --- /dev/null +++ b/docs/HACKING.md @@ -0,0 +1,123 @@ +# Hacking on systemd + +We welcome all contributions to systemd. If you notice a bug or a missing +feature, please feel invited to fix it, and submit your work as a GitHub Pull +Request (PR) at https://github.com/systemd/systemd/pull/new. + +Please make sure to follow our [Coding Style](CODING_STYLE.md) when submitting patches. +Also have a look at our [Contribution Guidelines](CONTRIBUTING.md). + +When adding new functionality, tests should be added. For shared functionality +(in `src/basic/` and `src/shared/`) unit tests should be sufficient. The general +policy is to keep tests in matching files underneath `src/test/`, +e.g. `src/test/test-path-util.c` contains tests for any functions in +`src/basic/path-util.c`. If adding a new source file, consider adding a matching +test executable. For features at a higher level, tests in `src/test/` are very +strongly recommended. If that is not possible, integration tests in `test/` are +encouraged. + +Please also have a look at our list of [code quality tools](CODE_QUALITY.md) we have setup for systemd, +to ensure our codebase stays in good shape. + +Please always test your work before submitting a PR. For many of the components +of systemd testing is straight-forward as you can simply compile systemd and +run the relevant tool from the build directory. + +For some components (most importantly, systemd/PID1 itself) this is not +possible, however. In order to simplify testing for cases like this we provide +a set of `mkosi` build files directly in the source tree. `mkosi` is a tool for +building clean OS images from an upstream distribution in combination with a +fresh build of the project in the local working directory. To make use of this, +please acquire `mkosi` from https://github.com/systemd/mkosi first, unless your +distribution has packaged it already and you can get it from there. After the +tool is installed it is sufficient to type `mkosi` in the systemd project +directory to generate a disk image `image.raw` you can boot either in +`systemd-nspawn` or in an UEFI-capable VM: + +``` +# systemd-nspawn -bi image.raw +``` + +or: + +``` +# qemu-system-x86_64 -enable-kvm -m 512 -smp 2 -bios /usr/share/edk2/ovmf/OVMF_CODE.fd -hda image.raw +``` + +Every time you rerun the `mkosi` command a fresh image is built, incorporating +all current changes you made to the project tree. + +Alternatively, you may install the systemd version from your git check-out +directly on top of your host system's directory tree. This mostly works fine, +but of course you should know what you are doing as you might make your system +unbootable in case of a bug in your changes. Also, you might step into your +package manager's territory with this. Be careful! + +And never forget: most distributions provide very simple and convenient ways to +install all development packages necessary to build systemd. For example, on +Fedora the following command line should be sufficient to install all of +systemd's build dependencies: + +``` +# dnf builddep systemd +``` + +Putting this all together, here's a series of commands for preparing a patch +for systemd (this example is for Fedora): + +```sh +$ sudo dnf builddep systemd # install build dependencies +$ sudo dnf install mkosi # install tool to quickly build images +$ git clone https://github.com/systemd/systemd.git +$ cd systemd +$ vim src/core/main.c # or wherever you'd like to make your changes +$ meson build # configure the build +$ ninja -C build # build it locally, see if everything compiles fine +$ ninja -C build test # run some simple regression tests +$ (umask 077; echo 123 > mkosi.rootpw) # set root password used by mkosi +$ sudo mkosi # build a test image +$ sudo systemd-nspawn -bi image.raw # boot up the test image +$ git add -p # interactively put together your patch +$ git commit # commit it +$ git push REMOTE HEAD:refs/heads/BRANCH + # where REMOTE is your "fork" on GitHub + # and BRANCH is a branch name. +``` + +And after that, head over to your repo on GitHub and click "Compare & pull request" + +Happy hacking! + + +## Fuzzers + +systemd includes fuzzers in `src/fuzz/` that use libFuzzer and are automatically +run by [OSS-Fuzz](https://github.com/google/oss-fuzz) with sanitizers. To add a +fuzz target, create a new `src/fuzz/fuzz-foo.c` file with a `LLVMFuzzerTestOneInput` +function and add it to the list in `src/fuzz/meson.build`. + +Whenever possible, a seed corpus and a dictionary should also be added with new +fuzz targets. The dictionary should be named `src/fuzz/fuzz-foo.dict` and the seed +corpus should be built and exported as `$OUT/fuzz-foo_seed_corpus.zip` in +`tools/oss-fuzz.sh`. + +The fuzzers can be built locally if you have libFuzzer installed by running +`tools/oss-fuzz.sh`. You should also confirm that the fuzzer runs in the +OSS-Fuzz environment by checking out the OSS-Fuzz repo, and then running +commands like this: + +``` +python infra/helper.py build_image systemd +python infra/helper.py build_fuzzers --sanitizer memory systemd ../systemd +python infra/helper.py run_fuzzer systemd fuzz-foo +``` + +If you find a bug that impacts the security of systemd, please follow the +guidance in [CONTRIBUTING.md](CONTRIBUTING.md) on how to report a security vulnerability. + +For more details on building fuzzers and integrating with OSS-Fuzz, visit: + +- https://github.com/google/oss-fuzz/blob/master/docs/new_project_guide.md +- https://llvm.org/docs/LibFuzzer.html +- https://github.com/google/fuzzer-test-suite/blob/master/tutorial/libFuzzerTutorial.md +- https://chromium.googlesource.com/chromium/src/testing/libfuzzer/+/HEAD/efficient_fuzzer.md |