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https://github.com/torvalds/linux.git
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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: 71bb428fe2 ("tools: bpf: add bpftool")
Signed-off-by: Hui Su <sh_def@163.com>
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 <memxor@gmail.com>
This commit is contained in:
Hui Su
Kumar Kartikeya Dwivedi
parent
35a0673aee
commit
dbf8cef936
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@ -31,6 +31,7 @@
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#include <bpf/bpf.h>
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#include <bpf/hashmap.h>
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#include <bpf/libbpf.h> /* libbpf_num_possible_cpus */
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#include <bpf/libbpf_internal.h>
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#include <bpf/btf.h>
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#include <zlib.h>
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@ -655,6 +656,45 @@ unsigned int get_possible_cpus(void)
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return cpus;
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}
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int get_possible_cpu_ids(int **cpu_ids)
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{
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const char *possible_cpus_file = "/sys/devices/system/cpu/possible";
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bool *mask = NULL;
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int mask_sz, nr_cpus = 0;
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int *ids = NULL;
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int i, res;
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*cpu_ids = NULL;
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res = parse_cpu_mask_file(possible_cpus_file, &mask, &mask_sz);
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if (res) {
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p_err("failed to parse possible CPU mask: %s", strerror(-res));
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return res;
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}
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for (i = 0; i < mask_sz; i++)
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nr_cpus += mask[i];
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ids = calloc(nr_cpus, sizeof(*ids));
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if (!ids) {
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p_err("mem alloc failed");
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res = -ENOMEM;
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goto out;
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}
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for (i = 0, nr_cpus = 0; i < mask_sz; i++) {
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if (mask[i])
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ids[nr_cpus++] = i;
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}
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*cpu_ids = ids;
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ids = NULL;
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res = nr_cpus;
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out:
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free(ids);
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free(mask);
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return res;
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}
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static char *
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ifindex_to_name_ns(__u32 ifindex, __u32 ns_dev, __u32 ns_ino, char *buf)
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{
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@ -216,6 +216,7 @@ void print_hex_data_json(uint8_t *data, size_t len);
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unsigned int get_page_size(void);
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unsigned int get_possible_cpus(void);
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int get_possible_cpu_ids(int **cpu_ids);
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const char *
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ifindex_to_arch(__u32 ifindex, __u64 ns_dev, __u64 ns_ino, const char **opt);
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@ -70,7 +70,7 @@ static void *alloc_value(struct bpf_map_info *info)
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static int do_dump_btf(const struct btf_dumper *d,
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struct bpf_map_info *map_info, void *key,
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void *value)
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void *value, const int *cpu_ids, int cpu_cnt)
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{
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__u32 value_id;
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int ret = 0;
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@ -93,15 +93,15 @@ static int do_dump_btf(const struct btf_dumper *d,
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jsonw_name(d->jw, "value");
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ret = btf_dumper_type(d, value_id, value);
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} else {
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unsigned int i, n, step;
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unsigned int step;
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int i;
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jsonw_name(d->jw, "values");
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jsonw_start_array(d->jw);
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n = get_possible_cpus();
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step = round_up(map_info->value_size, 8);
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for (i = 0; i < n; i++) {
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for (i = 0; i < cpu_cnt; i++) {
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jsonw_start_object(d->jw);
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jsonw_int_field(d->jw, "cpu", i);
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jsonw_int_field(d->jw, "cpu", cpu_ids[i]);
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jsonw_name(d->jw, "value");
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ret = btf_dumper_type(d, value_id, value + i * step);
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jsonw_end_object(d->jw);
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@ -130,7 +130,8 @@ static json_writer_t *get_btf_writer(void)
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}
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static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
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unsigned char *value, struct btf *btf)
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unsigned char *value, struct btf *btf,
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const int *cpu_ids, int cpu_cnt)
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{
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jsonw_start_object(json_wtr);
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@ -150,12 +151,12 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
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};
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jsonw_name(json_wtr, "formatted");
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do_dump_btf(&d, info, key, value);
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do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
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}
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} else {
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unsigned int i, n, step;
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unsigned int step;
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int i;
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n = get_possible_cpus();
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step = round_up(info->value_size, 8);
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jsonw_name(json_wtr, "key");
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@ -163,10 +164,10 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
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jsonw_name(json_wtr, "values");
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jsonw_start_array(json_wtr);
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for (i = 0; i < n; i++) {
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for (i = 0; i < cpu_cnt; i++) {
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jsonw_start_object(json_wtr);
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jsonw_int_field(json_wtr, "cpu", i);
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jsonw_int_field(json_wtr, "cpu", cpu_ids[i]);
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jsonw_name(json_wtr, "value");
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print_hex_data_json(value + i * step,
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@ -183,7 +184,7 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
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};
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jsonw_name(json_wtr, "formatted");
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do_dump_btf(&d, info, key, value);
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do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
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}
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}
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@ -245,7 +246,7 @@ print_entry_error(struct bpf_map_info *map_info, void *key, int lookup_errno)
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}
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static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
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unsigned char *value)
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unsigned char *value, const int *cpu_ids, int cpu_cnt)
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{
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if (!map_is_per_cpu(info->type)) {
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bool single_line, break_names;
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@ -273,9 +274,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
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printf("\n");
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} else {
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unsigned int i, n, step;
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unsigned int step;
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int i;
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n = get_possible_cpus();
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step = round_up(info->value_size, 8);
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if (info->key_size) {
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@ -284,9 +285,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
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printf("\n");
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}
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if (info->value_size) {
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for (i = 0; i < n; i++) {
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printf("value (CPU %02u):%c",
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i, info->value_size > 16 ? '\n' : ' ');
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for (i = 0; i < cpu_cnt; i++) {
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printf("value (CPU %02d):%c",
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cpu_ids[i], info->value_size > 16 ? '\n' : ' ');
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fprint_hex(stdout, value + i * step,
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info->value_size, " ");
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printf("\n");
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@ -742,7 +743,7 @@ static int do_show(int argc, char **argv)
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static int dump_map_elem(int fd, void *key, void *value,
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struct bpf_map_info *map_info, struct btf *btf,
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json_writer_t *btf_wtr)
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json_writer_t *btf_wtr, const int *cpu_ids, int cpu_cnt)
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{
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if (bpf_map_lookup_elem(fd, key, value)) {
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print_entry_error(map_info, key, errno);
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@ -750,7 +751,7 @@ static int dump_map_elem(int fd, void *key, void *value,
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}
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if (json_output) {
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print_entry_json(map_info, key, value, btf);
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print_entry_json(map_info, key, value, btf, cpu_ids, cpu_cnt);
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} else if (btf) {
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struct btf_dumper d = {
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.btf = btf,
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@ -758,9 +759,9 @@ static int dump_map_elem(int fd, void *key, void *value,
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.is_plain_text = true,
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};
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do_dump_btf(&d, map_info, key, value);
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do_dump_btf(&d, map_info, key, value, cpu_ids, cpu_cnt);
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} else {
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print_entry_plain(map_info, key, value);
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print_entry_plain(map_info, key, value, cpu_ids, cpu_cnt);
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}
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return 0;
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@ -833,6 +834,8 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
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void *key, *value, *prev_key;
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unsigned int num_elems = 0;
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struct btf *btf = NULL;
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int *cpu_ids = NULL;
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int cpu_cnt = 0;
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int err;
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key = malloc(info->key_size);
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@ -845,6 +848,14 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
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prev_key = NULL;
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if (map_is_per_cpu(info->type)) {
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cpu_cnt = get_possible_cpu_ids(&cpu_ids);
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if (cpu_cnt < 0) {
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err = cpu_cnt;
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goto exit_free;
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}
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}
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if (wtr) {
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err = get_map_kv_btf(info, &btf);
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if (err) {
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@ -876,7 +887,8 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
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err = 0;
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break;
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}
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if (!dump_map_elem(fd, key, value, info, btf, wtr))
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if (!dump_map_elem(fd, key, value, info, btf, wtr,
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cpu_ids, cpu_cnt))
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num_elems++;
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prev_key = key;
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}
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@ -893,6 +905,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
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exit_free:
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free(key);
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free(value);
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free(cpu_ids);
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free_map_kv_btf(btf);
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return err;
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@ -1035,17 +1048,30 @@ static int do_update(int argc, char **argv)
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return err;
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}
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static void print_key_value(struct bpf_map_info *info, void *key,
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void *value)
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static int print_key_value(struct bpf_map_info *info, void *key,
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void *value)
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{
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json_writer_t *btf_wtr;
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struct btf *btf;
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int *cpu_ids = NULL;
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int cpu_cnt = 0;
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int err = 0;
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if (get_map_kv_btf(info, &btf))
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return;
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if (map_is_per_cpu(info->type)) {
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cpu_cnt = get_possible_cpu_ids(&cpu_ids);
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if (cpu_cnt < 0) {
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err = cpu_cnt;
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goto out;
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}
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}
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err = get_map_kv_btf(info, &btf);
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if (err)
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goto out;
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if (json_output) {
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print_entry_json(info, key, value, btf);
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print_entry_json(info, key, value, btf, cpu_ids, cpu_cnt);
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} else if (btf) {
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/* if here json_wtr wouldn't have been initialised,
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* so let's create separate writer for btf
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@ -1055,7 +1081,7 @@ static void print_key_value(struct bpf_map_info *info, void *key,
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p_info("failed to create json writer for btf. falling back to plain output");
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free_map_kv_btf(btf);
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btf = NULL;
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print_entry_plain(info, key, value);
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print_entry_plain(info, key, value, cpu_ids, cpu_cnt);
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} else {
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struct btf_dumper d = {
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.btf = btf,
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@ -1063,13 +1089,16 @@ static void print_key_value(struct bpf_map_info *info, void *key,
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.is_plain_text = true,
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};
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do_dump_btf(&d, info, key, value);
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do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
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jsonw_destroy(&btf_wtr);
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}
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} else {
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print_entry_plain(info, key, value);
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print_entry_plain(info, key, value, cpu_ids, cpu_cnt);
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}
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free_map_kv_btf(btf);
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out:
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free(cpu_ids);
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return err;
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}
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static int do_lookup(int argc, char **argv)
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@ -1114,7 +1143,7 @@ static int do_lookup(int argc, char **argv)
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}
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/* here means bpf_map_lookup_elem() succeeded */
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print_key_value(&info, key, value);
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err = print_key_value(&info, key, value);
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exit_free:
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free(key);
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@ -1404,7 +1433,7 @@ static int do_pop_dequeue(int argc, char **argv)
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goto exit_free;
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}
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print_key_value(&info, key, value);
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err = print_key_value(&info, key, value);
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exit_free:
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free(key);
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