| Message ID | 20220818221212.464487-1-void@manifault.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | bpf: Add user-space-publisher ringbuffer map type | expand |
Hey David, On 8/19/22 12:12 AM, David Vernet wrote: > This patch set defines a new map type, BPF_MAP_TYPE_USER_RINGBUF, which > provides single-user-space-producer / single-kernel-consumer semantics over > a ringbuffer. Along with the new map type, a helper function called > bpf_user_ringbuf_drain() is added which allows a BPF program to specify a > callback with the following signature, to which samples are posted by the > helper: Looks like this series fail BPF CI, ptal: https://github.com/kernel-patches/bpf/runs/7996821883?check_suite_focus=true [...] bpftool_checks - Running bpftool checks... Comparing /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h (bpf_map_type) and /tmp/work/bpf/bpf/tools/bpf/bpftool/map.c (do_help() TYPE): {'user_ringbuf'} Comparing /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h (bpf_map_type) and /tmp/work/bpf/bpf/tools/bpf/bpftool/Documentation/bpftool-map.rst (TYPE): {'user_ringbuf'} bpftool checks returned 1. [...]
On Wed, Aug 24, 2022 at 07:38:34PM +0200, Daniel Borkmann wrote: Hey Daniel, > On 8/19/22 12:12 AM, David Vernet wrote: > > This patch set defines a new map type, BPF_MAP_TYPE_USER_RINGBUF, which > > provides single-user-space-producer / single-kernel-consumer semantics over > > a ringbuffer. Along with the new map type, a helper function called > > bpf_user_ringbuf_drain() is added which allows a BPF program to specify a > > callback with the following signature, to which samples are posted by the > > helper: > > Looks like this series fail BPF CI, ptal: > > https://github.com/kernel-patches/bpf/runs/7996821883?check_suite_focus=true Thanks for the heads up. I'll make sure these are fixed these before submitting v4 by following the instructions in [0]. [0]: https://github.com/qmonnet/whirl-offload/blob/wip/bpf-ci-check/_posts/2022-08-05-bpf-ci-check.md#running-the-bpf-ci-on-your-own-github-linux-fork. Thanks, David
This patch set defines a new map type, BPF_MAP_TYPE_USER_RINGBUF, which provides single-user-space-producer / single-kernel-consumer semantics over a ringbuffer. Along with the new map type, a helper function called bpf_user_ringbuf_drain() is added which allows a BPF program to specify a callback with the following signature, to which samples are posted by the helper: void (struct bpf_dynptr *dynptr, void *context); The program can then use the bpf_dynptr_read() or bpf_dynptr_data() helper functions to safely read the sample from the dynptr. There are currently no helpers available to determine the size of the sample, but one could easily be added if required. On the user-space side, libbpf has been updated to export a new 'struct ring_buffer_user' type, along with the following symbols: struct ring_buffer_user * ring_buffer_user__new(int map_fd, const struct ring_buffer_user_opts *opts); void ring_buffer_user__free(struct ring_buffer_user *rb); void *ring_buffer_user__reserve(struct ring_buffer_user *rb, uint32_t size); void *ring_buffer_user__poll(struct ring_buffer_user *rb, uint32_t size, int timeout_ms); void ring_buffer_user__discard(struct ring_buffer_user *rb, void *sample); void ring_buffer_user__submit(struct ring_buffer_user *rb, void *sample); These symbols are exported for inclusion in libbpf version 1.0.0. Signed-off-by: David Vernet <void@manifault.com> -- v2 -> v3: - Lots of formatting fixes, such as keeping things on one line if they fit within 100 characters, and removing some extraneous newlines. Applies to all diffs in the patch-set. (Andrii) - Renamed ring_buffer_user__* symbols to user_ring_buffer__*. (Andrii) - Added a missing smb_mb__before_atomic() in __bpf_user_ringbuf_sample_release(). (Hao) - Restructure how and when notification events are sent from the kernel to the user-space producers via the .map_poll() callback for the BPF_MAP_TYPE_USER_RINGBUF map. Before, we only sent a notification when the ringbuffer was fully drained. Now, we guarantee user-space that we'll send an event at least once per bpf_user_ringbuf_drain(), as long as at least one sample was drained, and BPF_RB_NO_WAKEUP was not passed. As a heuristic, we also send a notification event any time a sample being drained causes the ringbuffer to no longer be full. (Andrii) - Continuing on the above point, updated user_ring_buffer__reserve_blocking() to loop around epoll_wait() until a sufficiently large sample is found. (Andrii) - Communicate BPF_RINGBUF_BUSY_BIT and BPF_RINGBUF_DISCARD_BIT in sample headers. The ringbuffer implementation still only supports single-producer semantics, but we can now add synchronization support in user_ring_buffer__reserve(), and will automatically get multi-producer semantics. (Andrii) - Updated some commit summaries, specifically adding more details where warranted. (Andrii) - Improved function documentation for bpf_user_ringbuf_drain(), more clearly explaining all function arguments and return types, as well as the semantics for waking up user-space producers. - Add function header comments for user_ring_buffer__reserve{_blocking}(). (Andrii) - Rounding-up all samples to 8-bytes in the user-space producer, and enforcing that all samples are properly aligned in the kernel. (Andrii) - Added testcases that verify that bpf_user_ringbuf_drain() properly validates samples, and returns error conditions if any invalid samples are encountered. (Andrii) - Move atomic_t busy field out of the consumer page, and into the struct bpf_ringbuf. (Andrii) - Split ringbuf_map_{mmap, poll}_{kern, user}() into separate implementations. (Andrii) - Don't silently consume errors in bpf_user_ringbuf_drain(). (Andrii) - Remove magic number of samples (4096) from bpf_user_ringbuf_drain(), and instead use BPF_MAX_USER_RINGBUF_SAMPLES macro, which allows 128k samples. (Andrii) - Remove MEM_ALLOC modifier from PTR_TO_DYNPTR register in verifier, and instead rely solely on the register being PTR_TO_DYNPTR. (Andrii) - Move freeing of atomic_t busy bit to before we invoke irq_work_queue() in __bpf_user_ringbuf_sample_release(). (Andrii) - Only check for BPF_RB_NO_WAKEUP flag in bpf_ringbuf_drain(). - Remove libbpf function names from kernel smp_{load, store}* comments in the kernel. (Andrii) - Don't use double-underscore naming convention in libbpf functions. (Andrii) - Use proper __u32 and __u64 for types where we need to guarantee their size. (Andrii) v1 -> v2: - Following Joanne landing 883743422ced ("bpf: Fix ref_obj_id for dynptr data slices in verifier") [0], removed [PATCH 1/5] bpf: Clear callee saved regs after updating REG0 [1]. (Joanne) - Following the above adjustment, updated check_helper_call() to not store a reference for bpf_dynptr_data() if the register containing the dynptr is of type MEM_ALLOC. (Joanne) - Fixed casting issue pointed out by kernel test robot by adding a missing (uintptr_t) cast. (lkp) [0] https://lore.kernel.org/all/20220809214055.4050604-1-joannelkoong@gmail.com/ [1] https://lore.kernel.org/all/20220808155341.2479054-1-void@manifault.com/ David Vernet (4): bpf: Define new BPF_MAP_TYPE_USER_RINGBUF map type bpf: Add bpf_user_ringbuf_drain() helper bpf: Add libbpf logic for user-space ring buffer selftests/bpf: Add selftests validating the user ringbuf include/linux/bpf.h | 11 +- include/linux/bpf_types.h | 1 + include/uapi/linux/bpf.h | 37 + kernel/bpf/helpers.c | 2 + kernel/bpf/ringbuf.c | 272 ++++++- kernel/bpf/verifier.c | 73 +- tools/include/uapi/linux/bpf.h | 37 + tools/lib/bpf/libbpf.c | 11 +- tools/lib/bpf/libbpf.h | 21 + tools/lib/bpf/libbpf.map | 6 + tools/lib/bpf/libbpf_probes.c | 1 + tools/lib/bpf/ringbuf.c | 327 ++++++++ .../selftests/bpf/prog_tests/user_ringbuf.c | 715 ++++++++++++++++++ .../selftests/bpf/progs/user_ringbuf_fail.c | 177 +++++ .../bpf/progs/user_ringbuf_success.c | 220 ++++++ .../testing/selftests/bpf/test_user_ringbuf.h | 35 + 16 files changed, 1924 insertions(+), 22 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/user_ringbuf.c create mode 100644 tools/testing/selftests/bpf/progs/user_ringbuf_fail.c create mode 100644 tools/testing/selftests/bpf/progs/user_ringbuf_success.c create mode 100644 tools/testing/selftests/bpf/test_user_ringbuf.h