From patchwork Fri Sep 2 23:43:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 12964823 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9897ECAAA1 for ; Fri, 2 Sep 2022 23:43:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230435AbiIBXnd (ORCPT ); Fri, 2 Sep 2022 19:43:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230251AbiIBXn3 (ORCPT ); Fri, 2 Sep 2022 19:43:29 -0400 Received: from mail-qk1-f174.google.com (mail-qk1-f174.google.com [209.85.222.174]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79D04E396A; Fri, 2 Sep 2022 16:43:28 -0700 (PDT) Received: by mail-qk1-f174.google.com with SMTP id f4so2911240qkl.7; Fri, 02 Sep 2022 16:43:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date; bh=vtjt2UcQpSWZBV7PlLy46qmppUUbKwNCV8fSMMcdAbg=; b=7gPZdoPqDyKCazNVxyhIqiCfTa5cM7ocqymeni4pNH//5HePfFl61AmUo/DRU9TGGH ANWwjhoHGIu0qr6j0rmn7fDDcakhFRXbMUBWiqWraOfuMOP1tj46Gd5n1A8nX5vq/5SW 9Z+Cn9shhrWGV375cMkD5EPjYd4EOZPrz9GFMdxIIavcDc124HY8shmjKG9jbPjoPLMZ bw3Rl/rs7ygJlskGaOR33BOubq7shZFdSXO1Qk/fTqgTNepY0/357Dtxp+C2MO4LGNAB DsNn9QTmRWWg5QOPw3BLOADFvRWCFnh39svv8q8A4HvKIczkrt+RlQ3XvjAegNYofAV4 awOA== X-Gm-Message-State: ACgBeo0GtxQhjfc17+28FAZGzwn1yBxZ30GMeRfpUuTyY3mI2QBKsaX5 V4FbXuLo1owbo/GIPev/a+ETDcOD+m2S/3FR0fg= X-Google-Smtp-Source: AA6agR4U5eLMfKKIXFqxvPgXipnvHwbHtIW1wrVDAeRkkCdWhFKX83YS6gtMfoQQWIeTJqmsUWwjxA== X-Received: by 2002:a05:620a:6012:b0:6bc:2de8:ae4d with SMTP id dw18-20020a05620a601200b006bc2de8ae4dmr23635210qkb.363.1662162207261; Fri, 02 Sep 2022 16:43:27 -0700 (PDT) Received: from localhost (c-24-15-214-156.hsd1.il.comcast.net. [24.15.214.156]) by smtp.gmail.com with ESMTPSA id h5-20020a05620a284500b006bc192d277csm2395137qkp.10.2022.09.02.16.43.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Sep 2022 16:43:26 -0700 (PDT) From: David Vernet To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev Cc: bpf@vger.kernel.org, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, tj@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v5 0/4] bpf: Add user-space-publisher ring buffer map type Date: Fri, 2 Sep 2022 18:43:13 -0500 Message-Id: <20220902234317.2518808-1-void@manifault.com> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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 ring buffer. 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 --- v4 -> v5: - DENYLISTed the user-ringbuf test suite on s390x. We have a number of functions in the progs/user_ringbuf_success.c prog that user-space fires by invoking a syscall. Not all of these syscalls are available on s390x. If and when we add the ability to kick the kernel from user-space, or if we end up using iterators for that per Hao's suggestion, we could re-enable this test suite on s390x. - Fixed a few more places that needed ringbuffer -> ring buffer. v3 -> v4: - Update BPF_MAX_USER_RINGBUF_SAMPLES to not specify a bit, and instead just specify a number of samples. (Andrii) - Update "ringbuffer" in comments and commit summaries to say "ring buffer". (Andrii) - Return -E2BIG from bpf_user_ringbuf_drain() both when a sample can't fit into the ring buffer, and when it can't fit into a dynptr. (Andrii) - Don't loop over samples in __bpf_user_ringbuf_peek() if a sample was discarded. Instead, return -EAGAIN so the caller can deal with it. Also updated the caller to detect -EAGAIN and skip over it when iterating. (Andrii) - Removed the heuristic for notifying user-space when a sample is drained, causing the ring buffer to no longer be full. This may be useful in the future, but is being removed now because it's strictly a heuristic. - Re-add BPF_RB_FORCE_WAKEUP flag to bpf_user_ringbuf_drain(). (Andrii) - Remove helper_allocated_dynptr tracker from verifier. (Andrii) - Add libbpf function header comments to tools/lib/bpf/libbpf.h, so that they will be included in rendered libbpf docs. (Andrii) - Add symbols to a new LIBBPF_1.1.0 section in linker version script, rather than including them in LIBBPF_1.0.0. (Andrii) - Remove libbpf_err() calls from static libbpf functions. (Andrii) - Check user_ring_buffer_opts instead of ring_buffer_opts in user_ring_buffer__new(). (Andrii) - Avoid an extra if in the hot path in user_ringbuf__commit(). (Andrii) - Use ENOSPC rather than ENODATA if no space is available in the ring buffer. (Andrii) - Don't round sample size in header to 8, but still round size that is reserved and written to 8, and validate positions are multiples of 8 (Andrii). - Use nanoseconds for most calculations in user_ring_buffer__reserve_blocking(). (Andrii) - Don't use CHECK() in testcases, instead use ASSERT_*. (Andrii) - Use SEC("?raw_tp") instead of SEC("?raw_tp/sys_nanosleep") in negative test. (Andrii) - Move test_user_ringbuf.h header to live next to BPF program instead of a directory up from both it and the user-space test program. (Andrii) - Update bpftool help message / docs to also include user_ringbuf. 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