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CHERI-UPDATING.md

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Updating Information for CheriBSD users.

This file contains information about updating CheriBSD. It supplements the information in the UPDATING file with CheriBSD specific information. In particular it explains ABI flag days, our branching structure, and our strategy from merging from upstream FreeBSD.

Flag days and major changes

Generally speaking, flag days require a complete rebuild of CheriBSD. When building with cheribuild this is usually handled automatically, but if necessary the --clean flag can be used. When building directly, avoid the -DNO_CLEAN make option.

Flag days on master

Date Commit Description Required action
2020-06-04 cc876df74 MIPS with CHERI support now builds hybrid Clean rebuild
2020-05-11 7e76d8f71 C/C++ ABI changes Update to LLVM b7f5c847dc and a clean rebuild.
2020-03-06 6ce214d1e ELF auxargs flags altered Clean rebuild

Flag days on dev

Date Commit Description Required action
2020-06-24 e5c4980cd Enable MK_LIB64 on CHERI-RISC-V delete bin/cheritest*/*.o and usr.bin/kyua/main.o from riscv64 purecap build directores or clean rebuild
2020-05-26 cc876df74 MIPS with CHERI support now builds hybrid Clean rebuild
2020-04-21 7e76d8f71 C/C++ ABI changes Update to LLVM b7f5c847dc and a clean rebuild.
2020-03-06 6ce214d1e ELF auxargs flags altered Clean rebuild

Note: The dates listed are the date the change hit the public tree which may not correspond to the commit log.

Branches

The CheriBSD repository contains a number of branches. The two main branches are:

  • dev - The primary development branch. Pull requests should generally be targeted here. When using this branch, you should also track the LLVM dev branch.

  • master - The default branch, synced periodically with dev and kept in sync with the LLVM master branch. Outside consumers likely wish to follow this branch.

To aid comparison with upstream FreeBSD we maintain a couple of branches of stock FreeBSD:

  • freebsd-head - FreeBSD HEAD (from freebsd/freebsd) as merged to dev. We update it using fast-forward so commit hashes match upstream.

  • freebsd-crossbuild - FreeBSD HEAD with a roll up of not-yet-merged cross-building changes required to build on a macOS or Linux system. We currently merge on top of the existing changes. This branch will eventually go away.

Numerous other branches exist ranging from pull-request branches to long-term feature development and checkpoints of abandoned work. We generally delete pull-request branches after merge.

Merging strategy

Updating dev

We typically merge from upstream FreeBSD to dev in batches of one week of changes from the end of Friday UTC. These are merged one upstream commit at a time using mergify to aid bisection. Sometimes we either merge at other times because we need an upstream commit. In a steady state we merge weekly, but delay and batch updates if we need extra platform stability and the master branch isn't appropriate.

Each merge from upstream FreeBSD to dev is accompanied by a tag of the form freebsd-head-YYYYMMDD, and updates to freebsd-head and freebsd-crossbuild.

Updating master

We typically merge to master from dev at stable points at least a week apart.