[RFC v1 00/14] Bus1 Kernel Message Bus

[David Herrmann]

Hi

This proposal introduces bus1.ko, a kernel messaging bus. This is not a request
for inclusion, yet. It is rather an initial draft and a Request For Comments.

While bus1 emerged out of the kdbus project, bus1 was started from scratch and
the concepts have little in common. In a nutshell, bus1 provides a
capability-based IPC system, similar in nature to Android Binder, Cap'n Proto,
and seL4. The module is completely generic and does neither require nor mandate
a user-space counter-part.

 o Description

    Bus1 is a local IPC system, which provides a decentralized infrastructure to
    share objects between local peers. The main building blocks are nodes and
    handles. Nodes represent objects of a local peer, while handles represent
    descriptors that point to a node. Nodes can be created and destroyed by any
    peer, and they will always remain owned by their respective creator. Handles
    on the other hand, are used to refer to nodes and can be passed around with
    messages as auxiliary data. Whenever a handle is transferred, the receiver
    will get its own handle allocated, pointing to the same node as the original
    handle.

    Any peer can send messages directed at one of their handles. This will
    transfer the message to the owner of the node the handle points to. If a
    peer does not posess a handle to a given node, it will not be able to send a
    message to that node. That is, handles provide exclusive access management.
    Anyone that somehow acquired a handle to a node is privileged to further
    send this handle to other peers. As such, access management is transitive.
    Once a peer acquired a handle, it cannot be revoked again. However, a node
    owner can, at anytime, destroy a node. This will effectively unbind all
    existing handles to that node on any peer, notifying each one of the
    destruction.

    Unlike nodes and handles, peers cannot be addressed directly. In fact, peers
    are completely disconnected entities. A peer is merely an anchor of a set of
    nodes and handles, including an incoming message queue for any of those.
    Whether multiple nodes are all part of the same peer, or part of different
    peers does not affect the remote view of those. Peers solely exist as
    management entity and command dispatcher to local processes.

    The set of actors on a system is completely decentralized. There is no
    global component involved that provides a central registry or discovery
    mechanism. Furthermore, communication between peers only involves those
    peers, and does not affect any other peer in any way. No global
    communication lock is taken. However, any communication is still globally
    ordered, including unicasts, multicasts, and notifications.

 o Prior Art

    The concepts behind bus1 are almost identical to capability systems like
    Android Binder, Google Mojo, Cap'n Proto, seL4, and more. Bus1 differs from
    them by supporting Global Ordering, Multicasts, Resource Accounting, No
    Global Locking, No Global Context.

    While the bus1 UAPI does not expose all features (like soft-references as
    supported by Binder), the in-kernel code includes support for it. Multiple
    UAPIs can be supported on top of the in-kernel bus1 code, including support
    for the Binder UAPI. Efforts on this are still on-going.

 o Documentation

    The first patch in this series provides the bus1(7) man-page. It explains
    all concepts in bus1 in more detail. Furthermore, it describes the API that
    is available on bus1 file descriptors. The pre-compiled man-page is
    available at:

        http://www.bus1.org/bus1.html

    There is also a great bunch of in-source documentation available. All
    cross-source-file APIs have KernelDoc annotations. Furthermore, we have an
    introduction for each subsystem, to be found in the header files. The total
    number in lines of code for bus1 is roughly ~4.5k. The remaining ~5k LOC
    are comments and documentation.

 o Upstream

    The upstream development repository is available on github:

        http://github.com/bus1/bus1

    It is an out-of-tree repository that allows easy and fast development of
    new bus1 features. The in-tree integration repository is available at:

        http://github.com/bus1/linux

 o Conferences

    Tom and I will be attending Linux Plumbers Conf next week. Please do not
    hesitate to contact us there in person. There will also be a presentation
    [1] of bus1 on the last day of the conference.

Thanks
Tom & David

[1] https://www.linuxplumbersconf.org/2016/ocw/proposals/3819

Tom Gundersen (14):
  bus1: add bus1(7) man-page
  bus1: provide stub cdev /dev/bus1
  bus1: util - active reference utility library
  bus1: util - fixed list utility library
  bus1: util - pool utility library
  bus1: util - queue utility library
  bus1: tracking user contexts
  bus1: implement peer management context
  bus1: provide transaction context for multicasts
  bus1: add handle management
  bus1: implement message transmission
  bus1: hook up file-operations
  bus1: limit and protect resources
  bus1: basic user-space kselftests

 Documentation/bus1/.gitignore             |    2 +
 Documentation/bus1/Makefile               |   41 +
 Documentation/bus1/bus1.xml               |  833 +++++++++++++++++++++
 Documentation/bus1/stylesheet.xsl         |   16 +
 include/uapi/linux/bus1.h                 |  138 ++++
 init/Kconfig                              |   17 +
 ipc/Makefile                              |    1 +
 ipc/bus1/Makefile                         |   16 +
 ipc/bus1/handle.c                         |  823 ++++++++++++++++++++
 ipc/bus1/handle.h                         |  312 ++++++++
 ipc/bus1/main.c                           |  146 ++++
 ipc/bus1/main.h                           |   88 +++
 ipc/bus1/message.c                        |  656 ++++++++++++++++
 ipc/bus1/message.h                        |  171 +++++
 ipc/bus1/peer.c                           | 1163 +++++++++++++++++++++++++++++
 ipc/bus1/peer.h                           |  163 ++++
 ipc/bus1/security.h                       |   45 ++
 ipc/bus1/tests.c                          |   19 +
 ipc/bus1/tests.h                          |   32 +
 ipc/bus1/tx.c                             |  360 +++++++++
 ipc/bus1/tx.h                             |  102 +++
 ipc/bus1/user.c                           |  628 ++++++++++++++++
 ipc/bus1/user.h                           |  140 ++++
 ipc/bus1/util.c                           |  214 ++++++
 ipc/bus1/util.h                           |  141 ++++
 ipc/bus1/util/active.c                    |  419 +++++++++++
 ipc/bus1/util/active.h                    |  154 ++++
 ipc/bus1/util/flist.c                     |  116 +++
 ipc/bus1/util/flist.h                     |  202 +++++
 ipc/bus1/util/pool.c                      |  572 ++++++++++++++
 ipc/bus1/util/pool.h                      |  164 ++++
 ipc/bus1/util/queue.c                     |  445 +++++++++++
 ipc/bus1/util/queue.h                     |  351 +++++++++
 tools/testing/selftests/bus1/.gitignore   |    2 +
 tools/testing/selftests/bus1/Makefile     |   19 +
 tools/testing/selftests/bus1/bus1-ioctl.h |  111 +++
 tools/testing/selftests/bus1/test-api.c   |  532 +++++++++++++
 tools/testing/selftests/bus1/test-io.c    |  198 +++++
 tools/testing/selftests/bus1/test.h       |  114 +++
 39 files changed, 9666 insertions(+)
 create mode 100644 Documentation/bus1/.gitignore
 create mode 100644 Documentation/bus1/Makefile
 create mode 100644 Documentation/bus1/bus1.xml
 create mode 100644 Documentation/bus1/stylesheet.xsl
 create mode 100644 include/uapi/linux/bus1.h
 create mode 100644 ipc/bus1/Makefile
 create mode 100644 ipc/bus1/handle.c
 create mode 100644 ipc/bus1/handle.h
 create mode 100644 ipc/bus1/main.c
 create mode 100644 ipc/bus1/main.h
 create mode 100644 ipc/bus1/message.c
 create mode 100644 ipc/bus1/message.h
 create mode 100644 ipc/bus1/peer.c
 create mode 100644 ipc/bus1/peer.h
 create mode 100644 ipc/bus1/security.h
 create mode 100644 ipc/bus1/tests.c
 create mode 100644 ipc/bus1/tests.h
 create mode 100644 ipc/bus1/tx.c
 create mode 100644 ipc/bus1/tx.h
 create mode 100644 ipc/bus1/user.c
 create mode 100644 ipc/bus1/user.h
 create mode 100644 ipc/bus1/util.c
 create mode 100644 ipc/bus1/util.h
 create mode 100644 ipc/bus1/util/active.c
 create mode 100644 ipc/bus1/util/active.h
 create mode 100644 ipc/bus1/util/flist.c
 create mode 100644 ipc/bus1/util/flist.h
 create mode 100644 ipc/bus1/util/pool.c
 create mode 100644 ipc/bus1/util/pool.h
 create mode 100644 ipc/bus1/util/queue.c
 create mode 100644 ipc/bus1/util/queue.h
 create mode 100644 tools/testing/selftests/bus1/.gitignore
 create mode 100644 tools/testing/selftests/bus1/Makefile
 create mode 100644 tools/testing/selftests/bus1/bus1-ioctl.h
 create mode 100644 tools/testing/selftests/bus1/test-api.c
 create mode 100644 tools/testing/selftests/bus1/test-io.c
 create mode 100644 tools/testing/selftests/bus1/test.h

-- 
2.10.1