From dbf8cef936c7783ca909c38097a69f73173a19a7 Mon Sep 17 00:00:00 2001 From: Hui Su Date: Wed, 23 Sep 2026 09:42:42 +0900 Subject: [PATCH] bpftool: Fix CPU IDs in per-CPU map output 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. Pass the parsed CPU count together with the CPU ID array so that the printed CPU IDs and loop bounds come from the same possible-CPU mask. Propagate CPU-ID lookup and map output errors through the shared output path to its callers. Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool") Signed-off-by: Hui Su Link: https://lore.kernel.org/bpf/20260813155131.1022745-3-sh_def@163.com/ Link: https://lore.kernel.org/bpf/20260923004243.969919-2-sh_def@163.com Signed-off-by: Kumar Kartikeya Dwivedi --- tools/bpf/bpftool/common.c | 40 ++++++++++++++++ tools/bpf/bpftool/main.h | 1 + tools/bpf/bpftool/map.c | 95 +++++++++++++++++++++++++------------- 3 files changed, 103 insertions(+), 33 deletions(-) diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index ef366ccc9650..f9b87efa7c9a 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("mem alloc failed"); + 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 9315a1db1f7c..48eedcb9f6c0 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..20d59eab09a1 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, int cpu_cnt) { __u32 value_id; int ret = 0; @@ -93,15 +93,15 @@ static int do_dump_btf(const struct btf_dumper *d, jsonw_name(d->jw, "value"); ret = btf_dumper_type(d, value_id, value); } else { - unsigned int i, n, step; + unsigned int step; + int i; jsonw_name(d->jw, "values"); jsonw_start_array(d->jw); - n = get_possible_cpus(); step = round_up(map_info->value_size, 8); - for (i = 0; i < n; i++) { + for (i = 0; i < cpu_cnt; 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, int cpu_cnt) { jsonw_start_object(json_wtr); @@ -150,12 +151,12 @@ 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, cpu_cnt); } } else { - unsigned int i, n, step; + unsigned int step; + int i; - n = get_possible_cpus(); step = round_up(info->value_size, 8); jsonw_name(json_wtr, "key"); @@ -163,10 +164,10 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key, jsonw_name(json_wtr, "values"); jsonw_start_array(json_wtr); - for (i = 0; i < n; i++) { + for (i = 0; i < cpu_cnt; 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, cpu_cnt); } } @@ -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, int cpu_cnt) { if (!map_is_per_cpu(info->type)) { bool single_line, break_names; @@ -273,9 +274,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key, printf("\n"); } else { - unsigned int i, n, step; + unsigned int step; + int i; - n = get_possible_cpus(); step = round_up(info->value_size, 8); if (info->key_size) { @@ -284,9 +285,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key, printf("\n"); } if (info->value_size) { - for (i = 0; i < n; i++) { - printf("value (CPU %02u):%c", - i, info->value_size > 16 ? '\n' : ' '); + for (i = 0; i < cpu_cnt; i++) { + 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, int cpu_cnt) { 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, cpu_cnt); } 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, cpu_cnt); } else { - print_entry_plain(map_info, key, value); + print_entry_plain(map_info, key, value, cpu_ids, cpu_cnt); } return 0; @@ -833,6 +834,8 @@ 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 cpu_cnt = 0; int err; key = malloc(info->key_size); @@ -845,6 +848,14 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, prev_key = NULL; + if (map_is_per_cpu(info->type)) { + 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 +887,8 @@ 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, cpu_cnt)) 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 +1048,30 @@ 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 cpu_cnt = 0; + int err = 0; - if (get_map_kv_btf(info, &btf)) - return; + if (map_is_per_cpu(info->type)) { + 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, cpu_cnt); } else if (btf) { /* if here json_wtr wouldn't have been initialised, * so let's create separate writer for btf @@ -1055,7 +1081,7 @@ 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, cpu_cnt); } else { struct btf_dumper d = { .btf = btf, @@ -1063,13 +1089,16 @@ 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, cpu_cnt); jsonw_destroy(&btf_wtr); } } else { - print_entry_plain(info, key, value); + print_entry_plain(info, key, value, cpu_ids, cpu_cnt); } free_map_kv_btf(btf); +out: + free(cpu_ids); + return err; } static int do_lookup(int argc, char **argv) @@ -1114,7 +1143,7 @@ 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 +1433,7 @@ 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);