From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-2uec-a118.jellyfish.systems (out-2uec-a118.jellyfish.systems [63.250.43.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 650E43A963A for ; Sun, 6 Sep 2026 17:08:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=63.250.43.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788714499; cv=none; b=lbndpXJrtBTMSmLyIkaRKYzNbP0Q2r+pB9g3Hzu+e0XO8gLWSNW1HpxAoX0KtNXhbPPhLqOTb98V7pMMFxXPrARyjy1LtxYpNl9NnXFk+lGqdkMhgRS9f8LN7Rj0mU1Lvh3a5/03w6DjgdURvAzQT1aAmON+wdDeamAQThroKU0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788714499; c=relaxed/simple; bh=DS9iwohj+c+XpqsXPIoaYl5JW0FQadBGMTyGtZVVb/s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sCA5Son0HLKq/zKaws53PH3lG9Mp/Dyx55+RDjEa7AF+DnaAQCqgTNeDe4oCU9VEPBb3FLPwNabC7PCHeFglutH2M8UH5hGGHyQ67au4oqnlDFp0XGCGFdDBGh0VietEYcZtWKg26/uD0NtqsbV58QFb87XUs6AmftF7nurmT2g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tychen.cc; spf=pass smtp.mailfrom=tychen.cc; dkim=pass (2048-bit key) header.d=tychen.cc header.i=@tychen.cc header.b=NIB3l7Mi; arc=none smtp.client-ip=63.250.43.118 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tychen.cc Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tychen.cc Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=tychen.cc header.i=@tychen.cc header.b="NIB3l7Mi" Received: from fedora (unknown [69.5.53.41]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.spacemail.com (Postfix) with ESMTPSA id 4hdGqR349Yz8sWP; Sun, 06 Sep 2026 17:08:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tychen.cc; s=spacemail; t=1788714490; bh=2UZ6a0ZXQ/tONmzFl9gXaGavlzhwmEH+J/CxZ37mLwQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NIB3l7MiZmYbSE5sj0tT7dlSoMc8soZSqKvmm2iQjnd1mOEoRIa6qnWTY67n5HPRc zpsvt+O/SsjGH7/vZcn5t15bVyTW3P3yVL0pPwb9PpeQMlmZC53cXLSmM5xLxf7mj2 csbP6g2KLt+JFh7G9kMxuGVXwCFYXuASbeJpchWiFd3O8oVX1Ko+vzx2AGsCkVV4or JB5AHy0l6g9LR47uxCXTlc6j2p1YC5C37SJyyt+tuOyOX1kMlHdRJ1IcKqODyV55wF BJwn4c35jI4hdl+2YSqCcfjkIuepqqzd9m8+mIAl5G7Hz2Maou9Ipzkn9eOexWiP25 ELAlf/mq9O4Kg== From: Tianyi Chen To: bpf@vger.kernel.org Cc: Tianyi Chen , Quentin Monnet , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf-next 1/2] bpftool: Read ring buffer maps with event_pipe Date: Mon, 7 Sep 2026 01:07:46 +0800 Message-ID: <20260906170747.1212378-2-hi@tychen.cc> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260906170747.1212378-1-hi@tychen.cc> References: <20260906170747.1212378-1-hi@tychen.cc> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Envelope-From: hi@tychen.cc Allow map event_pipe to consume BPF_MAP_TYPE_RINGBUF maps using libbpf's ring buffer manager. Print each record's size and raw bytes in plain or JSON output, and flush output as records arrive. Reject CPU and index selectors for ring buffers and retain the existing perf event array path. Keep signal handlers limited to setting a stop flag, reset that flag for each command, and print the stopping message on stderr from the main path. Close the JSON array on poll errors and preserve output errors returned by the ring buffer callback. Document that consuming a ring buffer advances its shared consumer position and add ring buffer maps to event_pipe completion. Link: https://github.com/libbpf/bpftool/issues/54 Assisted-by: Codex:GPT-6 Signed-off-by: Tianyi Chen --- .../bpf/bpftool/Documentation/bpftool-map.rst | 15 +++- tools/bpf/bpftool/bash-completion/bpftool | 4 +- tools/bpf/bpftool/map_perf_ring.c | 87 ++++++++++++++----- 3 files changed, 82 insertions(+), 24 deletions(-) diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst index 5daf3de5c74..c44e6f797e5 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-map.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst @@ -120,7 +120,8 @@ bpftool map pin *MAP* *FILE* character ('.'), which is reserved for future extensions of *bpffs*. bpftool map event_pipe *MAP* [cpu *N* index *M*] - Read events from a **BPF_MAP_TYPE_PERF_EVENT_ARRAY** map. + Read events from a **BPF_MAP_TYPE_PERF_EVENT_ARRAY** or + **BPF_MAP_TYPE_RINGBUF** map. Install perf rings into a perf event array map and dump output of any **bpf_perf_event_output**\ () call in the kernel. By default read the @@ -134,6 +135,18 @@ bpftool map event_pipe *MAP* [cpu *N* index *M*] existing ring. Any other application will stop receiving events if it installed its rings earlier. + For a ring buffer map, consume records submitted by BPF programs, including + records already queued before the command starts. **cpu** and **index** + are not supported. Each record is printed as raw bytes, including embedded + zero bytes. Plain output reports the record size followed by hexadecimal + bytes; JSON output contains **size** and **data** fields, with **data** an + array of byte values. Ring buffer records have no implicit CPU or timestamp. + + Ring buffers support a single consumer. This command advances the shared + consumer position and must not run alongside another consumer of the same + map; it does not provide a passive view of events. **BPF_MAP_TYPE_USER_RINGBUF** + maps are not supported. + bpftool map peek *MAP* Peek next value in the queue or stack. diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool index 75cbcb512eb..1750b488c9e 100644 --- a/tools/bpf/bpftool/bash-completion/bpftool +++ b/tools/bpf/bpftool/bash-completion/bpftool @@ -878,11 +878,11 @@ _bpftool() return 0 ;; id) - _bpftool_get_map_ids_for_type perf_event_array + _bpftool_get_map_ids_for_type '"type": "\(perf_event_array\|ringbuf\)"' return 0 ;; name) - _bpftool_get_map_names_for_type perf_event_array + _bpftool_get_map_names_for_type '"type": "\(perf_event_array\|ringbuf\)"' return 0 ;; cpu) diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c index bcb767e2d67..7d555331f44 100644 --- a/tools/bpf/bpftool/map_perf_ring.c +++ b/tools/bpf/bpftool/map_perf_ring.c @@ -27,7 +27,7 @@ #define MMAP_PAGE_CNT 16 -static volatile bool stop; +static volatile sig_atomic_t stop; struct perf_event_sample { struct perf_event_header header; @@ -44,7 +44,6 @@ struct perf_event_lost { static void int_exit(int signo) { - fprintf(stderr, "Stopping...\n"); stop = true; } @@ -107,6 +106,27 @@ print_bpf_output(void *private_data, int cpu, struct perf_event_header *event) return LIBBPF_PERF_EVENT_CONT; } +static int print_ringbuf_output(void *ctx, void *data, size_t size) +{ + if (json_output) { + jsonw_start_object(json_wtr); + jsonw_uint_field(json_wtr, "size", size); + jsonw_name(json_wtr, "data"); + print_data_json(data, size); + jsonw_end_object(json_wtr); + } else { + printf("== size: %zu =====\n", size); + fprint_hex(stdout, data, size, " "); + printf("\n"); + } + + if (fflush(stdout)) + return errno ? -errno : -EIO; + + /* A producer can keep poll() busy even after a signal arrives. */ + return stop ? -EINTR : 0; +} + int do_event_pipe(int argc, char **argv) { struct perf_event_attr perf_attr = { @@ -123,18 +143,26 @@ int do_event_pipe(int argc, char **argv) .cpu = -1, .idx = -1, }; - struct perf_buffer *pb; + struct perf_buffer *pb = NULL; + struct ring_buffer *rb = NULL; __u32 map_info_len; int err, map_fd; + stop = false; map_info_len = sizeof(map_info); map_fd = map_parse_fd_and_info(&argc, &argv, &map_info, &map_info_len, 0); if (map_fd < 0) return -1; - if (map_info.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) { - p_err("map is not a perf event array"); + if (map_info.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY && + map_info.type != BPF_MAP_TYPE_RINGBUF) { + p_err("map is not a perf event array or ring buffer"); + goto err_close_map; + } + + if (map_info.type == BPF_MAP_TYPE_RINGBUF && argc) { + p_err("ring buffer maps do not support cpu or index arguments"); goto err_close_map; } @@ -184,15 +212,24 @@ int do_event_pipe(int argc, char **argv) ctx.idx = 0; } - opts.cpu_cnt = ctx.all_cpus ? 0 : 1; - opts.cpus = &ctx.cpu; - opts.map_keys = &ctx.idx; - pb = perf_buffer__new_raw(map_fd, MMAP_PAGE_CNT, &perf_attr, - print_bpf_output, &ctx, &opts); - if (!pb) { - p_err("failed to create perf buffer: %s (%d)", - strerror(errno), errno); - goto err_close_map; + if (map_info.type == BPF_MAP_TYPE_RINGBUF) { + rb = ring_buffer__new(map_fd, print_ringbuf_output, NULL, NULL); + if (!rb) { + p_err("failed to create ring buffer: %s (%d)", + strerror(errno), errno); + goto err_close_map; + } + } else { + opts.cpu_cnt = ctx.all_cpus ? 0 : 1; + opts.cpus = &ctx.cpu; + opts.map_keys = &ctx.idx; + pb = perf_buffer__new_raw(map_fd, MMAP_PAGE_CNT, &perf_attr, + print_bpf_output, &ctx, &opts); + if (!pb) { + p_err("failed to create perf buffer: %s (%d)", + strerror(errno), errno); + goto err_close_map; + } } signal(SIGINT, int_exit); @@ -202,25 +239,33 @@ int do_event_pipe(int argc, char **argv) if (json_output) jsonw_start_array(json_wtr); + err = 0; while (!stop) { - err = perf_buffer__poll(pb, 200); + err = rb ? ring_buffer__poll(rb, 200) : perf_buffer__poll(pb, 200); if (err < 0 && err != -EINTR) { - p_err("perf buffer polling failed: %s (%d)", - strerror(errno), errno); - goto err_close_pb; + fprintf(stderr, "Error: %s buffer polling failed: %s (%d)\n", + rb ? "ring" : "perf", strerror(-err), -err); + break; } + err = 0; } + if (stop) + fprintf(stderr, "Stopping...\n"); if (json_output) jsonw_end_array(json_wtr); + if (fflush(stdout)) { + fprintf(stderr, "Error: failed to write events: %s\n", strerror(errno)); + err = -1; + } + ring_buffer__free(rb); perf_buffer__free(pb); + /* Both buffer managers borrow map_fd. */ close(map_fd); - return 0; + return err < 0 ? -1 : 0; -err_close_pb: - perf_buffer__free(pb); err_close_map: close(map_fd); return -1; -- 2.55.0