From: Hui Su <sh_def@163.com>
To: bpf@vger.kernel.org
Cc: qmo@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,
linux-kernel@vger.kernel.org, Hui Su <sh_def@163.com>
Subject: [PATCH bpf-next v3 1/2] bpftool: Fix CPU IDs in per-CPU map output
Date: Wed, 23 Sep 2026 09:42:42 +0900 [thread overview]
Message-ID: <20260923004243.969919-2-sh_def@163.com> (raw)
In-Reply-To: <20260923004243.969919-1-sh_def@163.com>
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")
Link: https://lore.kernel.org/bpf/20260813155131.1022745-3-sh_def@163.com/
Signed-off-by: Hui Su <sh_def@163.com>
---
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 <bpf/bpf.h>
#include <bpf/hashmap.h>
#include <bpf/libbpf.h> /* libbpf_num_possible_cpus */
+#include <bpf/libbpf_internal.h>
#include <bpf/btf.h>
#include <zlib.h>
@@ -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);
--
2.55.0
next prev parent reply other threads:[~2026-09-23 0:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-23 0:42 [PATCH bpf-next v3 0/2] bpftool: Fix sparse CPU IDs Hui Su
2026-09-23 0:42 ` Hui Su [this message]
2026-09-23 0:42 ` [PATCH bpf-next v3 2/2] bpftool: Fix sparse CPU IDs in prog profile Hui Su
2026-09-23 1:27 ` bot+bpf-ci
2026-09-24 10:20 ` [PATCH bpf-next v3 0/2] bpftool: Fix sparse CPU IDs patchwork-bot+netdevbpf
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