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  of bus1 on the last day of the conference. Thanks Tom & David  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