linux/io_uring/Makefile

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io_uring: introduce callback driven main loop The io_uring_enter() has a fixed order of execution: it submits requests, waits for completions, and returns to the user. Allow to optionally replace it with a custom loop driven by a callback called loop_step. The basic requirements to the callback is that it should be able to submit requests, wait for completions, parse them and repeat. Most of the communication including parameter passing can be implemented via shared memory. The callback should return IOU_LOOP_CONTINUE to continue execution or IOU_LOOP_STOP to return to the user space. Note that the kernel may decide to prematurely terminate it as well, e.g. in case the process was signalled or killed. The hook takes a structure with parameters. It can be used to ask the kernel to wait for CQEs by setting cq_wait_idx to the CQE index it wants to wait for. Spurious wake ups are possible and even likely, the callback is expected to handle it. There will be more parameters in the future like timeout. It can be used with kernel callbacks, for example, as a slow path deprecation mechanism overwiting SQEs and emulating the wanted behaviour, however it's more useful together with BPF programs implemented in following patches. Note that keeping it separately from the normal io_uring wait loop makes things much simpler and cleaner. It keeps it in one place instead of spreading a bunch of checks in different places including disabling the submission path. It holds the lock by default, which is a better fit for BPF synchronisation and the loop execution model. It nicely avoids existing quirks like forced wake ups on timeout request completion. And it should be easier to implement new features. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://patch.msgid.link/a2d369aa1c9dd23ad7edac9220cffc563abcaed6.1772109579.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2026-02-26 12:48:38 +00:00
io_uring: add support for futex wake and wait Add support for FUTEX_WAKE/WAIT primitives. IORING_OP_FUTEX_WAKE is mix of FUTEX_WAKE and FUTEX_WAKE_BITSET, as it does support passing in a bitset. Similary, IORING_OP_FUTEX_WAIT is a mix of FUTEX_WAIT and FUTEX_WAIT_BITSET. For both of them, they are using the futex2 interface. FUTEX_WAKE is straight forward, as those can always be done directly from the io_uring submission without needing async handling. For FUTEX_WAIT, things are a bit more complicated. If the futex isn't ready, then we rely on a callback via futex_queue->wake() when someone wakes up the futex. From that calback, we queue up task_work with the original task, which will post a CQE and wake it, if necessary. Cancelations are supported, both from the application point-of-view, but also to be able to cancel pending waits if the ring exits before all events have occurred. The return value of futex_unqueue() is used to gate who wins the potential race between cancelation and futex wakeups. Whomever gets a 'ret == 1' return from that claims ownership of the io_uring futex request. This is just the barebones wait/wake support. PI or REQUEUE support is not added at this point, unclear if we might look into that later. Likewise, explicit timeouts are not supported either. It is expected that users that need timeouts would do so via the usual io_uring mechanism to do that using linked timeouts. The SQE format is as follows: `addr` Address of futex `fd` futex2(2) FUTEX2_* flags `futex_flags` io_uring specific command flags. None valid now. `addr2` Value of futex `addr3` Mask to wake/wait Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-08 11:57:40 -06:00
io_uring: add support for BPF filtering for opcode restrictions Add support for loading classic BPF programs with io_uring to provide fine-grained filtering of SQE operations. Unlike IORING_REGISTER_RESTRICTIONS which only allows bitmap-based allow/deny of opcodes, BPF filters can inspect request attributes and make dynamic decisions. The filter is registered via IORING_REGISTER_BPF_FILTER with a struct io_uring_bpf: struct io_uring_bpf_filter { __u32 opcode; /* io_uring opcode to filter */ __u32 flags; __u32 filter_len; /* number of BPF instructions */ __u32 resv; __u64 filter_ptr; /* pointer to BPF filter */ __u64 resv2[5]; }; enum { IO_URING_BPF_CMD_FILTER = 1, }; struct io_uring_bpf { __u16 cmd_type; /* IO_URING_BPF_* values */ __u16 cmd_flags; /* none so far */ __u32 resv; union { struct io_uring_bpf_filter filter; }; }; and the filters get supplied a struct io_uring_bpf_ctx: struct io_uring_bpf_ctx { __u64 user_data; __u8 opcode; __u8 sqe_flags; __u8 pdu_size; __u8 pad[5]; }; where it's possible to filter on opcode and sqe_flags, with pdu_size indicating how much extra data is being passed in beyond the pad field. This will used for specific finer grained filtering inside an opcode. An example of that for sockets is in one of the following patches. Anything the opcode supports can end up in this struct, populated by the opcode itself, and hence can be filtered for. Filters have the following semantics: - Return 1 to allow the request - Return 0 to deny the request with -EACCES - Multiple filters can be stacked per opcode. All filters must return 1 for the opcode to be allowed. - Filters are evaluated in registration order (most recent first) The implementation uses classic BPF (cBPF) rather than eBPF for as that's required for containers, and since they can be used by any user in the system. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2026-01-15 08:24:02 -07:00