From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0A2F4DD3C0; Fri, 18 Sep 2026 10:21:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.2 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789726922; cv=none; b=ZTli5gy82o+cBum/fVyxsvtFSIi6s0/eYJaNcwTWmyUU89xO2FuAt3xKULQoLCqQG6c6RVJa41JOf7wyc3P0jSwg99uqFjktwIJDysyC9/CWKi+2J7i1yu02uPcv1VjHeeQbNg2cd6eNT0dFFagaDF//w/k1oArw8juhwlnLc7U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789726922; c=relaxed/simple; bh=QFXDH9UXsakrxfEHCXhFRjO+WWgVPallibyVnpTnnkY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZHQgylybEYk5kwUDt5UYXUgldqSMEMX237Ozi1/I11tKuBj/UEXEPyKfWLKIOsZVhh2U9SX3LUZEU+NUdozd4/zFKPsfoG+KYoMECKjrI8NaR8gmo1q1iSb3mv4rF81ucXmrE8C1UaNCf49mzcJQjTF2MFx44G1AM4llYSn4png= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=Me6JNl3W; arc=none smtp.client-ip=220.197.31.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="Me6JNl3W" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=+7 teu6LWN+4dSUq6xi9dPDxZX4IejJ2vSM2DIUCr+OU=; b=Me6JNl3W5IZ1PJdOG0 rkWyNJtxSjyVGww8bboc9avoXhFJKnuPKChTQMaYtSDWUKqAniU5SJxf9kRfARri TfOXyHHhjNZcSawSHXAfBdVDtkL8hnASuqkh+UEBwUl0t1VOjzfY8zFZtKE12hI7 b8cNJOHl5DzdcfAQT5L/QTo48= Received: from localhost (unknown []) by gzsmtp2 (Coremail) with SMTP id PSgvCgB3ObOQEK1qLLNJAA--.8472S2; Fri, 18 Sep 2026 18:21:05 +0800 (CST) From: Hui Su To: qmo@kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, davem@davemloft.net, kuba@kernel.org, horms@kernel.org, Hui Su Subject: [PATCH bpf v2 1/2] bpftool: Fix CPU IDs in per-CPU map output Date: Fri, 18 Sep 2026 19:20:51 +0900 Message-ID: <20260918102052.1247819-2-sh_def@163.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260918102052.1247819-1-sh_def@163.com> References: <20260918102052.1247819-1-sh_def@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:PSgvCgB3ObOQEK1qLLNJAA--.8472S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3GryUZF4UAF4xAry8AF1fZwb_yoWDGF1Upw 45t348Kr48XrW3Ww4Ska98uF4Ygrs7Gw17JasrG3yrZFWfXrn7ZF4UKF10kr15urWFvF4j yFs0vryj9a1xCr7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0pi8pndUUUUU= X-CM-SenderInfo: xvkbvvri6rljoofrz/xtbC6hMujWqtEJP8CQAA3r bpftool uses dense per-CPU value-buffer slots when printing per-CPU map values. It also uses the slot index as the CPU ID, which produces incorrect labels when the possible CPU mask is sparse, such as 0,2-3. Parse the possible CPU mask and use the corresponding logical CPU ID in plain, JSON, and BTF-formatted output. Keep the dense slot index for accessing the per-CPU value buffer, and propagate CPU-ID lookup and map output errors through the shared output path to its callers. Tested: - Built tools/bpf/bpftool successfully on the host. - Booted an arm64 QEMU guest with a patched virt device tree reporting possible=0,2-3, present=0,2-3, and online=0,2-3. - Compared pre-fix and fixed plain and JSON map output in that guest: labels changed from CPU 0,1,2 to CPU 0,2,3. - Loaded a BTF-described per-CPU array and dumped it with the fixed bpftool in plain BTF and JSON formats; both formats reported CPU 0,2,3 while preserving the three dense per-CPU values. Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool") Link: https://lore.kernel.org/bpf/20260813155131.1022745-3-sh_def@163.com/ Signed-off-by: Hui Su --- tools/bpf/bpftool/common.c | 40 ++++++++++++++++++++ tools/bpf/bpftool/main.h | 1 + tools/bpf/bpftool/map.c | 76 ++++++++++++++++++++++++++------------ 3 files changed, 93 insertions(+), 24 deletions(-) diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index ef366ccc9650..ad10bfe8a0fc 100644 --- a/tools/bpf/bpftool/common.c +++ b/tools/bpf/bpftool/common.c @@ -31,6 +31,7 @@ #include #include #include /* libbpf_num_possible_cpus */ +#include #include #include @@ -655,6 +656,45 @@ unsigned int get_possible_cpus(void) return cpus; } +int get_possible_cpu_ids(int **cpu_ids) +{ + const char *possible_cpus_file = "/sys/devices/system/cpu/possible"; + bool *mask = NULL; + int mask_sz, nr_cpus = 0; + int *ids = NULL; + int i, res; + + *cpu_ids = NULL; + + res = parse_cpu_mask_file(possible_cpus_file, &mask, &mask_sz); + if (res) { + p_err("failed to parse possible CPU mask: %s", strerror(-res)); + return res; + } + + for (i = 0; i < mask_sz; i++) + nr_cpus += mask[i]; + + ids = calloc(nr_cpus, sizeof(*ids)); + if (!ids) { + p_err("failed to allocate possible CPU IDs: %s", strerror(ENOMEM)); + res = -ENOMEM; + goto out; + } + + for (i = 0, nr_cpus = 0; i < mask_sz; i++) { + if (mask[i]) + ids[nr_cpus++] = i; + } + *cpu_ids = ids; + ids = NULL; + res = nr_cpus; +out: + free(ids); + free(mask); + return res; +} + static char * ifindex_to_name_ns(__u32 ifindex, __u32 ns_dev, __u32 ns_ino, char *buf) { diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index 78b6e0ebb85d..6540b632a3ac 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -216,6 +216,7 @@ void print_hex_data_json(uint8_t *data, size_t len); unsigned int get_page_size(void); unsigned int get_possible_cpus(void); +int get_possible_cpu_ids(int **cpu_ids); const char * ifindex_to_arch(__u32 ifindex, __u64 ns_dev, __u64 ns_ino, const char **opt); diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c index 684a8fb72414..586c9e076a48 100644 --- a/tools/bpf/bpftool/map.c +++ b/tools/bpf/bpftool/map.c @@ -70,7 +70,7 @@ static void *alloc_value(struct bpf_map_info *info) static int do_dump_btf(const struct btf_dumper *d, struct bpf_map_info *map_info, void *key, - void *value) + void *value, const int *cpu_ids) { __u32 value_id; int ret = 0; @@ -101,7 +101,7 @@ static int do_dump_btf(const struct btf_dumper *d, step = round_up(map_info->value_size, 8); for (i = 0; i < n; i++) { jsonw_start_object(d->jw); - jsonw_int_field(d->jw, "cpu", i); + jsonw_int_field(d->jw, "cpu", cpu_ids[i]); jsonw_name(d->jw, "value"); ret = btf_dumper_type(d, value_id, value + i * step); jsonw_end_object(d->jw); @@ -130,7 +130,8 @@ static json_writer_t *get_btf_writer(void) } static void print_entry_json(struct bpf_map_info *info, unsigned char *key, - unsigned char *value, struct btf *btf) + unsigned char *value, struct btf *btf, + const int *cpu_ids) { jsonw_start_object(json_wtr); @@ -150,7 +151,7 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key, }; jsonw_name(json_wtr, "formatted"); - do_dump_btf(&d, info, key, value); + do_dump_btf(&d, info, key, value, cpu_ids); } } else { unsigned int i, n, step; @@ -166,7 +167,7 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key, for (i = 0; i < n; i++) { jsonw_start_object(json_wtr); - jsonw_int_field(json_wtr, "cpu", i); + jsonw_int_field(json_wtr, "cpu", cpu_ids[i]); jsonw_name(json_wtr, "value"); print_hex_data_json(value + i * step, @@ -183,7 +184,7 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key, }; jsonw_name(json_wtr, "formatted"); - do_dump_btf(&d, info, key, value); + do_dump_btf(&d, info, key, value, cpu_ids); } } @@ -245,7 +246,7 @@ print_entry_error(struct bpf_map_info *map_info, void *key, int lookup_errno) } static void print_entry_plain(struct bpf_map_info *info, unsigned char *key, - unsigned char *value) + unsigned char *value, const int *cpu_ids) { if (!map_is_per_cpu(info->type)) { bool single_line, break_names; @@ -285,8 +286,8 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key, } if (info->value_size) { for (i = 0; i < n; i++) { - printf("value (CPU %02u):%c", - i, info->value_size > 16 ? '\n' : ' '); + printf("value (CPU %02d):%c", + cpu_ids[i], info->value_size > 16 ? '\n' : ' '); fprint_hex(stdout, value + i * step, info->value_size, " "); printf("\n"); @@ -742,7 +743,7 @@ static int do_show(int argc, char **argv) static int dump_map_elem(int fd, void *key, void *value, struct bpf_map_info *map_info, struct btf *btf, - json_writer_t *btf_wtr) + json_writer_t *btf_wtr, const int *cpu_ids) { if (bpf_map_lookup_elem(fd, key, value)) { print_entry_error(map_info, key, errno); @@ -750,7 +751,7 @@ static int dump_map_elem(int fd, void *key, void *value, } if (json_output) { - print_entry_json(map_info, key, value, btf); + print_entry_json(map_info, key, value, btf, cpu_ids); } else if (btf) { struct btf_dumper d = { .btf = btf, @@ -758,9 +759,9 @@ static int dump_map_elem(int fd, void *key, void *value, .is_plain_text = true, }; - do_dump_btf(&d, map_info, key, value); + do_dump_btf(&d, map_info, key, value, cpu_ids); } else { - print_entry_plain(map_info, key, value); + print_entry_plain(map_info, key, value, cpu_ids); } return 0; @@ -833,6 +834,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, void *key, *value, *prev_key; unsigned int num_elems = 0; struct btf *btf = NULL; + int *cpu_ids = NULL; int err; key = malloc(info->key_size); @@ -845,6 +847,16 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, prev_key = NULL; + if (map_is_per_cpu(info->type)) { + int cpu_cnt; + + cpu_cnt = get_possible_cpu_ids(&cpu_ids); + if (cpu_cnt < 0) { + err = cpu_cnt; + goto exit_free; + } + } + if (wtr) { err = get_map_kv_btf(info, &btf); if (err) { @@ -876,7 +888,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, err = 0; break; } - if (!dump_map_elem(fd, key, value, info, btf, wtr)) + if (!dump_map_elem(fd, key, value, info, btf, wtr, cpu_ids)) num_elems++; prev_key = key; } @@ -893,6 +905,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, exit_free: free(key); free(value); + free(cpu_ids); free_map_kv_btf(btf); return err; @@ -1035,17 +1048,29 @@ static int do_update(int argc, char **argv) return err; } -static void print_key_value(struct bpf_map_info *info, void *key, - void *value) +static int print_key_value(struct bpf_map_info *info, void *key, + void *value) { json_writer_t *btf_wtr; struct btf *btf; + int *cpu_ids = NULL; + int err = 0; - if (get_map_kv_btf(info, &btf)) - return; + if (map_is_per_cpu(info->type)) { + int cpu_cnt = get_possible_cpu_ids(&cpu_ids); + + if (cpu_cnt < 0) { + err = cpu_cnt; + goto out; + } + } + + err = get_map_kv_btf(info, &btf); + if (err) + goto out; if (json_output) { - print_entry_json(info, key, value, btf); + print_entry_json(info, key, value, btf, cpu_ids); } else if (btf) { /* if here json_wtr wouldn't have been initialised, * so let's create separate writer for btf @@ -1055,7 +1080,7 @@ static void print_key_value(struct bpf_map_info *info, void *key, p_info("failed to create json writer for btf. falling back to plain output"); free_map_kv_btf(btf); btf = NULL; - print_entry_plain(info, key, value); + print_entry_plain(info, key, value, cpu_ids); } else { struct btf_dumper d = { .btf = btf, @@ -1063,13 +1088,16 @@ static void print_key_value(struct bpf_map_info *info, void *key, .is_plain_text = true, }; - do_dump_btf(&d, info, key, value); + do_dump_btf(&d, info, key, value, cpu_ids); jsonw_destroy(&btf_wtr); } } else { - print_entry_plain(info, key, value); + print_entry_plain(info, key, value, cpu_ids); } free_map_kv_btf(btf); +out: + free(cpu_ids); + return err; } static int do_lookup(int argc, char **argv) @@ -1114,7 +1142,7 @@ static int do_lookup(int argc, char **argv) } /* here means bpf_map_lookup_elem() succeeded */ - print_key_value(&info, key, value); + err = print_key_value(&info, key, value); exit_free: free(key); @@ -1404,7 +1432,7 @@ static int do_pop_dequeue(int argc, char **argv) goto exit_free; } - print_key_value(&info, key, value); + err = print_key_value(&info, key, value); exit_free: free(key); -- 2.55.0