* [PATCH bpf-next v5 1/2] bpftool: Add recursive map dumping
2026-09-11 3:47 [PATCH bpf-next v5 0/2] bpftool: Add recursive map dumping Tianyi Chen
@ 2026-09-11 3:47 ` Tianyi Chen
2026-09-11 4:28 ` bot+bpf-ci
2026-09-11 3:47 ` [PATCH bpf-next v5 2/2] selftests/bpf: Cover recursive bpftool map dumps Tianyi Chen
1 sibling, 1 reply; 5+ messages in thread
From: Tianyi Chen @ 2026-09-11 3:47 UTC (permalink / raw)
To: qmo, bpf; +Cc: andrii, eddyz87, ihor.solodrai, linux-kselftest
From: Tianyi Chen <hi@tychen.cc>
Dumping a map-of-maps currently shows inner map IDs without their
contents. Add -r/--recursive to dump referenced inner maps as well,
leaving the default output unchanged. Show the selected maps followed
by distinct discovered inner maps, preserving plain and BTF formatting
and using an array of map objects for JSON output.
Holding every discovered inner-map FD open would make descriptor use
grow with the number of maps and could exhaust RLIMIT_NOFILE. Keep the
selected map FDs open, queue distinct inner map IDs, and open, dump and
close each queued map in turn. This needs only one additional map FD.
The tradeoff is deferred ID resolution: concurrently removed inner
maps can disappear before they are opened, so the dump is not atomic.
Report failure when an inner map cannot be opened, retain per-entry
lookup errors, and close JSON containers before returning.
Link: https://github.com/libbpf/bpftool/issues/58
Assisted-by: LLM
Signed-off-by: Tianyi Chen <hi@tychen.cc>
---
.../bpf/bpftool/Documentation/bpftool-map.rst | 22 ++-
tools/bpf/bpftool/bash-completion/bpftool | 2 +-
tools/bpf/bpftool/main.c | 7 +-
tools/bpf/bpftool/main.h | 1 +
tools/bpf/bpftool/map.c | 131 ++++++++++++++++--
5 files changed, 152 insertions(+), 11 deletions(-)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 5daf3de5c74..23faa672685 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -16,7 +16,8 @@ SYNOPSIS
**bpftool** [*OPTIONS*] **map** *COMMAND*
-*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }
+*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } |
+{ **-n** | **--nomount** } | { **-r** | **--recursive** } }
*COMMANDS* :=
{ **show** | **list** | **create** | **dump** | **update** | **lookup** | **getnext** |
@@ -170,6 +171,25 @@ OPTIONS
Do not automatically attempt to mount any virtual file system (such as
tracefs or BPF virtual file system) when necessary.
+-r, --recursive
+ Also dump the inner maps referenced by **array_of_maps** and **hash_of_maps**
+ entries when running **map dump**. Each map ID is visited once, even if
+ several entries refer to it. Selected maps are followed by their inner maps.
+
+ Plain output includes a header identifying each map. On success, JSON output
+ is always an array of map objects, each containing an **id** and an
+ **elements** array, including when only one map is dumped. Outer map entries
+ retain their **inner_map_id** field, which identifies the corresponding inner
+ map object.
+
+ Inner map IDs are resolved when the maps are visited. The dump is not an
+ atomic snapshot: concurrent updates can change map contents or remove a
+ referenced inner map before it is visited. Failure to open a referenced
+ inner map stops the dump and returns a nonzero exit status. Output may
+ contain maps or entries printed before the error.
+
+ In JSON mode, the enclosing arrays and objects are closed before returning.
+
EXAMPLES
========
**# bpftool map show**
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 75cbcb512eb..45c336d63be 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -261,7 +261,7 @@ _bpftool()
# Deal with options
if [[ ${words[cword]} == -* ]]; then
- local c='--version --json --pretty --bpffs --mapcompat --debug \
+ local c='--version --json --pretty --recursive --bpffs --mapcompat --debug \
--use-loader --base-btf --sign -i -k'
COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
return 0
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 5ababd8f7d0..c0f4df10102 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -26,6 +26,7 @@ static int (*last_do_help)(int argc, char **argv);
json_writer_t *json_wtr;
bool pretty_output;
bool json_output;
+bool recursive_dump;
bool show_pinned;
bool block_mount;
bool verifier_logs;
@@ -456,6 +457,7 @@ int main(int argc, char **argv)
{ "json", no_argument, NULL, 'j' },
{ "help", no_argument, NULL, 'h' },
{ "pretty", no_argument, NULL, 'p' },
+ { "recursive", no_argument, NULL, 'r' },
{ "version", no_argument, NULL, 'V' },
{ "bpffs", no_argument, NULL, 'f' },
{ "mapcompat", no_argument, NULL, 'm' },
@@ -479,7 +481,7 @@ int main(int argc, char **argv)
bin_name = "bpftool";
opterr = 0;
- while ((opt = getopt_long(argc, argv, "VhpjfLmndSi:k:B:l",
+ while ((opt = getopt_long(argc, argv, "VhpjrfLmndSi:k:B:l",
options, NULL)) >= 0) {
switch (opt) {
case 'V':
@@ -501,6 +503,9 @@ int main(int argc, char **argv)
}
jsonw_pretty(json_wtr, pretty_output);
break;
+ case 'r':
+ recursive_dump = true;
+ break;
case 'f':
show_pinned = true;
break;
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 9315a1db1f7..43ef0aa592d 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -83,6 +83,7 @@ extern const char *bin_name;
extern json_writer_t *json_wtr;
extern bool json_output;
+extern bool recursive_dump;
extern bool show_pinned;
extern bool show_pids;
extern bool block_mount;
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 684a8fb7241..c0505f50496 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -17,6 +17,7 @@
#include <bpf/bpf.h>
#include <bpf/btf.h>
#include <bpf/hashmap.h>
+#include <bpf/libbpf_internal.h>
#include "json_writer.h"
#include "main.h"
@@ -826,12 +827,44 @@ static void free_map_kv_btf(struct btf *btf)
btf__free(btf);
}
+struct map_dump_ctx {
+ struct hashmap *seen;
+ __u32 *pending_ids;
+ size_t pending_cnt;
+};
+
+static int collect_inner_map(struct map_dump_ctx *ctx, __u32 id)
+{
+ __u32 *ids;
+ int err;
+
+ if (hashmap__find(ctx->seen, id, NULL))
+ return 0;
+
+ ids = libbpf_reallocarray(ctx->pending_ids, ctx->pending_cnt + 1,
+ sizeof(*ids));
+ if (!ids) {
+ p_err("mem alloc failed");
+ return -1;
+ }
+ ctx->pending_ids = ids;
+
+ err = hashmap__add(ctx->seen, id, 0);
+ if (err) {
+ p_err("failed to record inner map id %u: %s", id, strerror(-err));
+ return -1;
+ }
+ ids[ctx->pending_cnt++] = id;
+ return 0;
+}
+
static int
map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
- bool show_header)
+ bool show_header, struct map_dump_ctx *ctx)
{
void *key, *value, *prev_key;
unsigned int num_elems = 0;
+ json_writer_t *plain_btf_wtr = NULL;
struct btf *btf = NULL;
int err;
@@ -845,6 +878,17 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
prev_key = NULL;
+ if (ctx && !wtr && (info->btf_value_type_id ||
+ info->btf_vmlinux_value_type_id)) {
+ plain_btf_wtr = get_btf_writer();
+ if (plain_btf_wtr) {
+ if (show_header)
+ show_map_header_plain(info);
+ show_header = false;
+ wtr = plain_btf_wtr;
+ }
+ }
+
if (wtr) {
err = get_map_kv_btf(info, &btf);
if (err) {
@@ -874,10 +918,20 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
if (err) {
if (errno == ENOENT)
err = 0;
+ else if (ctx)
+ p_err("can't get next key for map id %u: %s",
+ info->id, strerror(errno));
break;
}
- if (!dump_map_elem(fd, key, value, info, btf, wtr))
+ err = dump_map_elem(fd, key, value, info, btf, wtr);
+ if (!err) {
num_elems++;
+ if (ctx && map_is_map_of_maps(info->type)) {
+ err = collect_inner_map(ctx, *(__u32 *)value);
+ if (err)
+ break;
+ }
+ }
prev_key = key;
}
@@ -894,18 +948,25 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
free(key);
free(value);
free_map_kv_btf(btf);
+ if (plain_btf_wtr)
+ jsonw_destroy(&plain_btf_wtr);
return err;
}
static int do_dump(int argc, char **argv)
{
+ LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts,
+ .open_flags = BPF_F_RDONLY,
+ );
json_writer_t *wtr = NULL, *btf_wtr = NULL;
struct bpf_map_info info = {};
+ struct map_dump_ctx ctx = {};
int nb_fds, i = 0;
__u32 len = sizeof(info);
int *fds = NULL;
int err = -1;
+ size_t j;
if (argc != 2)
usage();
@@ -919,9 +980,35 @@ static int do_dump(int argc, char **argv)
if (nb_fds < 1)
goto exit_free;
+ if (recursive_dump) {
+ ctx.seen = hashmap__new(hash_fn_for_key_as_id,
+ equal_fn_for_key_as_id, NULL);
+ if (IS_ERR(ctx.seen)) {
+ ctx.seen = NULL;
+ p_err("failed to create hashmap for recursive dump");
+ goto exit_close;
+ }
+ /* Record the selected maps before discovering any inner maps. */
+ for (i = 0; i < nb_fds; i++) {
+ len = sizeof(info);
+ if (bpf_map_get_info_by_fd(fds[i], &info, &len)) {
+ p_err("can't get map info: %s", strerror(errno));
+ err = -1;
+ goto exit_close;
+ }
+ err = hashmap__add(ctx.seen, info.id, 0);
+ if (err) {
+ p_err("failed to record map id %u: %s", info.id,
+ strerror(-err));
+ err = -1;
+ goto exit_close;
+ }
+ }
+ }
+
if (json_output) {
wtr = json_wtr;
- } else {
+ } else if (!recursive_dump) {
int do_plain_btf;
do_plain_btf = maps_have_btf(fds, nb_fds);
@@ -936,7 +1023,7 @@ static int do_dump(int argc, char **argv)
}
}
- if (wtr && nb_fds > 1)
+ if (wtr && (nb_fds > 1 || recursive_dump))
jsonw_start_array(wtr); /* root array */
for (i = 0; i < nb_fds; i++) {
if (bpf_map_get_info_by_fd(fds[i], &info, &len)) {
@@ -944,22 +1031,50 @@ static int do_dump(int argc, char **argv)
err = -1;
break;
}
- err = map_dump(fds[i], &info, wtr, nb_fds > 1);
+ err = map_dump(fds[i], &info, wtr, nb_fds > 1 || recursive_dump,
+ recursive_dump ? &ctx : NULL);
if (!wtr && i != nb_fds - 1)
printf("\n");
if (err)
break;
- close(fds[i]);
+ /* Keep selected maps alive while visiting their inner maps. */
+ if (!recursive_dump)
+ close(fds[i]);
+ }
+ for (j = 0; !err && j < ctx.pending_cnt; j++) {
+ int fd;
+
+ fd = bpf_map_get_fd_by_id_opts(ctx.pending_ids[j], &opts);
+ if (fd < 0) {
+ p_err("can't open inner map id %u: %s",
+ ctx.pending_ids[j], strerror(errno));
+ err = -1;
+ break;
+ }
+ len = sizeof(info);
+ if (bpf_map_get_info_by_fd(fd, &info, &len)) {
+ p_err("can't get map info: %s", strerror(errno));
+ err = -1;
+ } else {
+ if (!wtr)
+ printf("\n");
+ err = map_dump(fd, &info, wtr, true, &ctx);
+ }
+ close(fd);
}
- if (wtr && nb_fds > 1)
+ if (wtr && (nb_fds > 1 || recursive_dump))
jsonw_end_array(wtr); /* root array */
if (btf_wtr)
jsonw_destroy(&btf_wtr);
exit_close:
+ if (recursive_dump)
+ i = 0;
for (; i < nb_fds; i++)
close(fds[i]);
+ hashmap__free(ctx.seen);
+ free(ctx.pending_ids);
exit_free:
free(fds);
free_btf_vmlinux();
@@ -1484,7 +1599,7 @@ static int do_help(int argc, char **argv)
" task_storage | bloom_filter | user_ringbuf | cgrp_storage | arena |\n"
" insn_array | rhash }\n"
" " HELP_SPEC_OPTIONS " |\n"
- " {-f|--bpffs} | {-n|--nomount} }\n"
+ " {-f|--bpffs} | {-n|--nomount} | {-r|--recursive} }\n"
"",
bin_name, argv[-2]);
--
2.55.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH bpf-next v5 2/2] selftests/bpf: Cover recursive bpftool map dumps
2026-09-11 3:47 [PATCH bpf-next v5 0/2] bpftool: Add recursive map dumping Tianyi Chen
2026-09-11 3:47 ` [PATCH bpf-next v5 1/2] " Tianyi Chen
@ 2026-09-11 3:47 ` Tianyi Chen
2026-09-11 4:28 ` bot+bpf-ci
1 sibling, 1 reply; 5+ messages in thread
From: Tianyi Chen @ 2026-09-11 3:47 UTC (permalink / raw)
To: qmo, bpf; +Cc: andrii, eddyz87, ihor.solodrai, linux-kselftest
From: Tianyi Chen <hi@tychen.cc>
Exercise recursive map dumping for array-of-maps and hash-of-maps,
including shared inner maps, empty outer and inner maps, BTF-formatted
values and multiple selected roots.
Check complete JSON documents against the existing nonrecursive entry
representations, and check plain headers and typed values. Verify both
short and long options, root ordering, deduplication and unchanged
default output.
Cover ordinary and nested perf event arrays to ensure unsupported
element lookups retain their error markers without failing the dump.
Dump 64 distinct inner maps under RLIMIT_NOFILE=32 in both JSON and
plain modes to catch holding every discovered inner-map FD open.
Open 32 extra descriptors before forking, close inherited descriptors
in the child before imposing the limit, and verify the parent's file
descriptors and outer map remain usable.
Assisted-by: LLM
Signed-off-by: Tianyi Chen <hi@tychen.cc>
---
.../bpf/prog_tests/bpftool_map_dump.c | 474 ++++++++++++++++++
1 file changed, 474 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/bpftool_map_dump.c
diff --git a/tools/testing/selftests/bpf/prog_tests/bpftool_map_dump.c b/tools/testing/selftests/bpf/prog_tests/bpftool_map_dump.c
new file mode 100644
index 00000000000..1fb877fc68c
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bpftool_map_dump.c
@@ -0,0 +1,474 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <test_progs.h>
+#include <bpftool_helpers.h>
+#include <bpf/btf.h>
+#include <sys/resource.h>
+#include <dirent.h>
+
+#define OUTPUT_SIZE 8192
+
+static bool dump_map(__u32 id, const char *options, char *output)
+{
+ char command[MAX_BPFTOOL_CMD_LEN];
+
+ snprintf(command, sizeof(command), "%s map dump id %u", options, id);
+ memset(output, 0, OUTPUT_SIZE);
+ if (!ASSERT_OK(get_bpftool_command_output(command, output, OUTPUT_SIZE - 1),
+ "dump_map"))
+ return false;
+ /* The helper leaves the trailing newline in place. */
+ output[strcspn(output, "\n")] = '\0';
+ return true;
+}
+
+static __u32 map_id(int fd)
+{
+ struct bpf_map_info info = {};
+ __u32 len = sizeof(info);
+
+ if (!ASSERT_OK(bpf_map_get_info_by_fd(fd, &info, &len), "map_info"))
+ return 0;
+ return info.id;
+}
+
+static int count_token(const char *output, const char *token)
+{
+ int count = 0;
+
+ while ((output = strstr(output, token))) {
+ count++;
+ output += strlen(token);
+ }
+ return count;
+}
+
+static void check_plain(__u32 root_id, __u32 inner_id, const char *type,
+ int entries, bool typed)
+{
+ char command[MAX_BPFTOOL_CMD_LEN], header[128];
+ char output[OUTPUT_SIZE] = {};
+ const char *root, *inner;
+
+ snprintf(command, sizeof(command), "--recursive map dump id %u", root_id);
+ if (!ASSERT_OK(get_bpftool_command_output(command, output, sizeof(output) - 1),
+ "plain_dump"))
+ return;
+ snprintf(header, sizeof(header), "%u: %s name dump_outer ", root_id, type);
+ root = strstr(output, header);
+ if (!ASSERT_OK_PTR(root, "plain_root_header"))
+ return;
+ ASSERT_EQ(root - output, 0, "plain_root_first");
+ ASSERT_EQ(count_token(output, "inner_map_id:"), entries, "plain_references");
+ if (entries) {
+ snprintf(header, sizeof(header), "%u: hash name dump_inner ", inner_id);
+ inner = strstr(output, header);
+ if (ASSERT_OK_PTR(inner, "plain_inner_header"))
+ ASSERT_GT(inner - root, 0, "plain_inner_after_root");
+ ASSERT_EQ(count_token(output, header), 1, "plain_inner_once");
+ }
+ ASSERT_EQ(count_token(output, "Found "), entries && !typed ? 2 : 1,
+ "plain_map_count");
+ if (typed) {
+ ASSERT_HAS_SUBSTR(output, "\"key\": 0", "plain_btf_key");
+ ASSERT_HAS_SUBSTR(output, "\"value\": 16843009", "plain_btf_value");
+ }
+}
+
+static void test_outer(enum bpf_map_type type, int entries, bool empty_inner,
+ bool typed)
+{
+ LIBBPF_OPTS(bpf_map_create_opts, opts);
+ LIBBPF_OPTS(bpf_map_create_opts, inner_opts);
+ struct btf *btf = NULL;
+ char outer[OUTPUT_SIZE], inner[OUTPUT_SIZE], output[OUTPUT_SIZE];
+ char expected[OUTPUT_SIZE * 3], reference[64];
+ const char *type_name = libbpf_bpf_map_type_str(type);
+ int inner_fd = -1, outer_fd = -1;
+ __u32 root_id, inner_id, key, value = 0x01010101;
+
+ if (typed) {
+ btf = btf__new_empty();
+ if (!ASSERT_OK_PTR(btf, "create_btf") ||
+ !ASSERT_EQ(btf__add_int(btf, "unsigned int", 4, 0), 1, "btf_int") ||
+ !ASSERT_OK(btf__load_into_kernel(btf), "load_btf"))
+ goto out;
+ inner_opts.btf_fd = btf__fd(btf);
+ inner_opts.btf_key_type_id = 1;
+ inner_opts.btf_value_type_id = 1;
+ }
+ inner_fd = bpf_map_create(BPF_MAP_TYPE_HASH, "dump_inner", sizeof(key),
+ sizeof(value), 2, &inner_opts);
+ if (!ASSERT_OK_FD(inner_fd, "create_inner"))
+ goto out;
+ key = 0;
+ if (!empty_inner &&
+ !ASSERT_OK(bpf_map_update_elem(inner_fd, &key, &value, BPF_ANY),
+ "populate_inner"))
+ goto out;
+ opts.inner_map_fd = inner_fd;
+ outer_fd = bpf_map_create(type, "dump_outer", sizeof(key), sizeof(__u32),
+ 3, &opts);
+ if (!ASSERT_OK_FD(outer_fd, "create_outer"))
+ goto out;
+ /* The unused third array slot also exercises failed lookups. */
+ for (key = 0; key < entries; key++)
+ if (!ASSERT_OK(bpf_map_update_elem(outer_fd, &key, &inner_fd, BPF_ANY),
+ "populate_outer"))
+ goto out;
+ root_id = map_id(outer_fd);
+ inner_id = map_id(inner_fd);
+ if (!root_id || !inner_id || !dump_map(root_id, "-j", outer) ||
+ !dump_map(inner_id, "-j", inner))
+ goto out;
+
+ ASSERT_EQ(outer[0], '[', "default_array");
+ ASSERT_EQ(count_token(outer, "\"elements\":"), 0, "default_no_wrapper");
+ ASSERT_EQ(count_token(outer, "\"id\":"), 0, "default_no_header");
+ snprintf(reference, sizeof(reference), "\"inner_map_id\":%u", inner_id);
+ ASSERT_EQ(count_token(outer, reference), entries, "default_references");
+ if (!entries)
+ ASSERT_STREQ(outer, "[]", "empty_outer_default");
+ if (empty_inner)
+ ASSERT_STREQ(inner, "[]", "empty_inner_default");
+ else if (typed)
+ ASSERT_HAS_SUBSTR(inner, "\"formatted\":{\"key\":0,\"value\":16843009}",
+ "typed_inner");
+ else
+ ASSERT_STREQ(inner,
+ "[{\"key\":[\"0x00\",\"0x00\",\"0x00\",\"0x00\"],"
+ "\"value\":[\"0x01\",\"0x01\",\"0x01\",\"0x01\"]}]",
+ "ordinary_default");
+
+ /*
+ * Compare the complete JSON document: a flat array with the root first,
+ * one copy of the shared inner map, and unchanged entry representations.
+ */
+ if (entries)
+ snprintf(expected, sizeof(expected),
+ "[{\"id\":%u,\"type\":\"%s\",\"name\":\"dump_outer\","
+ "\"flags\":0,\"elements\":%s},{\"id\":%u,\"type\":\"hash\","
+ "\"name\":\"dump_inner\",\"flags\":0,\"elements\":%s}]",
+ root_id, type_name, outer, inner_id, inner);
+ else
+ snprintf(expected, sizeof(expected),
+ "[{\"id\":%u,\"type\":\"%s\",\"name\":\"dump_outer\","
+ "\"flags\":0,\"elements\":[]}]", root_id, type_name);
+ if (dump_map(root_id, "-j -r", output))
+ ASSERT_STREQ(output, expected, "recursive_json");
+ if (dump_map(root_id, "--json --recursive", output))
+ ASSERT_STREQ(output, expected, "recursive_long_options");
+ check_plain(root_id, inner_id, type_name, entries, typed);
+
+ /* Recursion on an ordinary map still emits a single map object. */
+ snprintf(expected, sizeof(expected),
+ "[{\"id\":%u,\"type\":\"hash\",\"name\":\"dump_inner\","
+ "\"flags\":0,\"elements\":%s}]", inner_id, inner);
+ if (dump_map(inner_id, "-j -r", output))
+ ASSERT_STREQ(output, expected, "ordinary_recursive");
+out:
+ if (outer_fd >= 0)
+ close(outer_fd);
+ if (inner_fd >= 0)
+ close(inner_fd);
+ btf__free(btf);
+}
+
+static void test_multiple_roots(void)
+{
+ LIBBPF_OPTS(bpf_map_create_opts, opts);
+ char command[MAX_BPFTOOL_CMD_LEN], name[BPF_OBJ_NAME_LEN];
+ char output[OUTPUT_SIZE] = {}, expected[OUTPUT_SIZE * 4], elements[OUTPUT_SIZE];
+ static const char * const types[] = { "hash", "array_of_maps", "hash_of_maps", "hash" };
+ int fds[] = { -1, -1, -1, -1 };
+ __u32 ids[4], key;
+ int i, len = 0;
+
+ /*
+ * Select the first inner map and both outers as roots. The other inner
+ * map must be appended after all three roots, even though it is found
+ * while dumping the first outer. A process-specific name avoids other
+ * tests' maps joining the selection.
+ */
+ snprintf(name, sizeof(name), "dump_%u", getpid());
+ fds[0] = bpf_map_create(BPF_MAP_TYPE_HASH, name, 4, 4, 1, NULL);
+ if (!ASSERT_OK_FD(fds[0], "create_selected_inner"))
+ goto out;
+ fds[3] = bpf_map_create(BPF_MAP_TYPE_HASH, "dump_discovered", 4, 4, 1, NULL);
+ if (!ASSERT_OK_FD(fds[3], "create_discovered_inner"))
+ goto out;
+ opts.inner_map_fd = fds[0];
+ fds[1] = bpf_map_create(BPF_MAP_TYPE_ARRAY_OF_MAPS, name, 4, 4, 2, &opts);
+ if (!ASSERT_OK_FD(fds[1], "create_array_root"))
+ goto out;
+ fds[2] = bpf_map_create(BPF_MAP_TYPE_HASH_OF_MAPS, name, 4, 4, 2, &opts);
+ if (!ASSERT_OK_FD(fds[2], "create_hash_root"))
+ goto out;
+ for (i = 1; i <= 2; i++) {
+ key = 0;
+ if (!ASSERT_OK(bpf_map_update_elem(fds[i], &key, &fds[0], BPF_ANY),
+ "reference_selected_inner"))
+ goto out;
+ key = 1;
+ if (!ASSERT_OK(bpf_map_update_elem(fds[i], &key, &fds[3], BPF_ANY),
+ "reference_discovered_inner"))
+ goto out;
+ }
+ for (i = 0; i < ARRAY_SIZE(fds); i++) {
+ ids[i] = map_id(fds[i]);
+ if (!ids[i] || !dump_map(ids[i], "-j", elements))
+ goto out;
+ len += snprintf(expected + len, sizeof(expected) - len,
+ "%s{\"id\":%u,\"type\":\"%s\",\"name\":\"%s\","
+ "\"flags\":0,\"elements\":%s}%s",
+ i ? "," : "[", ids[i], types[i],
+ i == 3 ? "dump_discovered" : name, elements, i == 3 ? "]" : "");
+ }
+ snprintf(command, sizeof(command), "-j -r map dump name %s", name);
+ if (ASSERT_OK(get_bpftool_command_output(command, output, sizeof(output) - 1),
+ "dump_multiple_roots")) {
+ output[strcspn(output, "\n")] = '\0';
+ ASSERT_STREQ(output, expected, "roots_first_and_seed_dedup");
+ }
+out:
+ for (i = 0; i < ARRAY_SIZE(fds); i++)
+ if (fds[i] >= 0)
+ close(fds[i]);
+}
+
+static void test_unreadable(bool outer)
+{
+ LIBBPF_OPTS(bpf_map_create_opts, opts);
+ char elements[OUTPUT_SIZE], output[OUTPUT_SIZE], root[OUTPUT_SIZE];
+ char expected[OUTPUT_SIZE * 3], plain[OUTPUT_SIZE] = {};
+ char command[MAX_BPFTOOL_CMD_LEN];
+ int inner_fd = -1, outer_fd = -1, lookup_errno;
+ __u32 inner_id, root_id, key = 0, value;
+
+ /*
+ * Every key is enumerable, but PERF_EVENT_ARRAY lookup returns
+ * ENOTSUPP (the kernel-internal errno). Check both entries so an
+ * early exit on the first lookup failure cannot pass.
+ */
+ inner_fd = bpf_map_create(BPF_MAP_TYPE_PERF_EVENT_ARRAY, "dump_unreadable",
+ sizeof(key), sizeof(value), 2, NULL);
+ if (!ASSERT_OK_FD(inner_fd, "create_unreadable"))
+ goto out;
+ if (!ASSERT_LT(bpf_map_lookup_elem(inner_fd, &key, &value), 0,
+ "unreadable_lookup"))
+ goto out;
+ lookup_errno = errno;
+ if (!ASSERT_NEQ(lookup_errno, ENOENT, "unreadable_not_missing"))
+ goto out;
+ inner_id = map_id(inner_fd);
+ if (!inner_id || !dump_map(inner_id, "-j", elements))
+ goto out;
+ ASSERT_EQ(count_token(elements, "\"error\":"), 2, "default_json_errors");
+ snprintf(command, sizeof(command), "map dump id %u", inner_id);
+ if (!ASSERT_OK(get_bpftool_command_output(command, plain, sizeof(plain) - 1),
+ "default_plain_unreadable"))
+ goto out;
+ ASSERT_EQ(count_token(plain, strerror(lookup_errno)), 2, "default_plain_errors");
+ ASSERT_HAS_SUBSTR(plain, "Found 0 elements", "default_plain_count");
+
+ root_id = inner_id;
+ if (outer) {
+ opts.inner_map_fd = inner_fd;
+ outer_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY_OF_MAPS, "dump_outer",
+ sizeof(key), sizeof(value), 1, &opts);
+ if (!ASSERT_OK_FD(outer_fd, "create_outer") ||
+ !ASSERT_OK(bpf_map_update_elem(outer_fd, &key, &inner_fd, BPF_ANY),
+ "populate_outer"))
+ goto out;
+ root_id = map_id(outer_fd);
+ if (!root_id || !dump_map(root_id, "-j", root))
+ goto out;
+ snprintf(expected, sizeof(expected),
+ "[{\"id\":%u,\"type\":\"array_of_maps\",\"name\":\"dump_outer\","
+ "\"flags\":0,\"elements\":%s},{\"id\":%u,"
+ "\"type\":\"perf_event_array\",\"name\":\"dump_unreadable\","
+ "\"flags\":0,\"elements\":%s}]", root_id, root, inner_id, elements);
+ } else {
+ snprintf(expected, sizeof(expected),
+ "[{\"id\":%u,\"type\":\"perf_event_array\","
+ "\"name\":\"dump_unreadable\",\"flags\":0,\"elements\":%s}]",
+ inner_id, elements);
+ }
+ if (dump_map(root_id, "-j -r", output))
+ ASSERT_STREQ(output, expected, "recursive_unreadable_json");
+ memset(output, 0, sizeof(output));
+ snprintf(command, sizeof(command), "-r map dump id %u", root_id);
+ if (ASSERT_OK(get_bpftool_command_output(command, output, sizeof(output) - 1),
+ "recursive_unreadable_plain")) {
+ ASSERT_HAS_SUBSTR(output, plain, "recursive_plain_preserves_errors");
+ ASSERT_EQ(count_token(output, strerror(lookup_errno)), 2,
+ "recursive_plain_errors");
+ ASSERT_EQ(count_token(output, "Found "), outer ? 2 : 1,
+ "recursive_plain_maps");
+ }
+out:
+ if (outer_fd >= 0)
+ close(outer_fd);
+ if (inner_fd >= 0)
+ close(inner_fd);
+}
+
+static void test_many_inner_maps(bool json)
+{
+ enum {
+ DUMP_OK,
+ DUMP_ERR_RLIMIT,
+ DUMP_ERR_COMMAND,
+ DUMP_ERR_COUNTS,
+ DUMP_ERR_IDS,
+ DUMP_ERR_JSON,
+ DUMP_ERR_FDS,
+ };
+ LIBBPF_OPTS(bpf_map_create_opts, opts);
+ const struct rlimit limit = { .rlim_cur = 32, .rlim_max = 32 };
+ char command[MAX_BPFTOOL_CMD_LEN], token[64];
+ __u32 ids[64], root_id, key;
+ int inner_fd = -1, outer_fd = -1, status;
+ int inherited_fds[32], nr_inherited = 0, i;
+ char *output = NULL;
+ pid_t pid;
+
+ inner_fd = bpf_map_create(BPF_MAP_TYPE_HASH, "dump_inner", 4, 4, 1, NULL);
+ if (!ASSERT_OK_FD(inner_fd, "create_template"))
+ goto out;
+ opts.inner_map_fd = inner_fd;
+ outer_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY_OF_MAPS, "dump_outer", 4, 4,
+ ARRAY_SIZE(ids), &opts);
+ close(inner_fd);
+ inner_fd = -1;
+ if (!ASSERT_OK_FD(outer_fd, "create_outer"))
+ goto out;
+ for (key = 0; key < ARRAY_SIZE(ids); key++) {
+ inner_fd = bpf_map_create(BPF_MAP_TYPE_HASH, "dump_inner", 4, 4, 1, NULL);
+ if (!ASSERT_OK_FD(inner_fd, "create_inner") ||
+ !ASSERT_OK(bpf_map_update_elem(outer_fd, &key, &inner_fd, BPF_ANY),
+ "populate_outer"))
+ goto out;
+ ids[key] = map_id(inner_fd);
+ if (!ids[key])
+ goto out;
+ /* The outer map keeps each distinct inner map alive. */
+ close(inner_fd);
+ inner_fd = -1;
+ }
+ root_id = map_id(outer_fd);
+ output = calloc(1, 65536);
+ if (!root_id || !ASSERT_OK_PTR(output, "allocate_output"))
+ goto out;
+
+ /* Fill the low FD slots to exercise inherited descriptor cleanup. */
+ for (i = 0; i < ARRAY_SIZE(inherited_fds); i++) {
+ int fd = open("/dev/null", O_RDONLY);
+
+ if (!ASSERT_OK_FD(fd, "open_inherited_fd"))
+ goto out;
+ inherited_fds[nr_inherited++] = fd;
+ }
+
+ /*
+ * Create all fixtures before lowering the limit, and keep the test
+ * runner's limit unchanged. Retaining every discovered FD would exceed
+ * this limit before the recursive dump could visit all inner maps.
+ */
+ pid = fork();
+ if (!ASSERT_GE(pid, 0, "fork"))
+ goto out;
+ if (!pid) {
+ struct dirent *entry;
+ DIR *dir;
+
+ /* Reserve a slot for the directory even if the parent is full. */
+ close(inherited_fds[nr_inherited - 1]);
+ dir = opendir("/proc/self/fd");
+ if (!dir)
+ _exit(DUMP_ERR_FDS);
+ /* The parent keeps the outer map and its inner maps alive. */
+ for (;;) {
+ char *end;
+ long fd;
+
+ errno = 0;
+ entry = readdir(dir);
+ if (!entry) {
+ if (errno)
+ _exit(DUMP_ERR_FDS);
+ break;
+ }
+ fd = strtol(entry->d_name, &end, 10);
+ if (*end || fd < 3 || fd == dirfd(dir))
+ continue;
+ close(fd);
+ }
+ if (closedir(dir))
+ _exit(DUMP_ERR_FDS);
+ if (setrlimit(RLIMIT_NOFILE, &limit))
+ _exit(DUMP_ERR_RLIMIT);
+ snprintf(command, sizeof(command), "%s -r map dump id %u",
+ json ? "-j" : "", root_id);
+ if (get_bpftool_command_output(command, output, 65535))
+ _exit(DUMP_ERR_COMMAND);
+ if (count_token(output, json ? "\"id\":" : "Found ") != ARRAY_SIZE(ids) + 1 ||
+ count_token(output, json ? "\"inner_map_id\":" : "inner_map_id:") !=
+ ARRAY_SIZE(ids))
+ _exit(DUMP_ERR_COUNTS);
+ for (key = 0; key < ARRAY_SIZE(ids); key++) {
+ if (json)
+ snprintf(token, sizeof(token), "\"id\":%u,", ids[key]);
+ else
+ snprintf(token, sizeof(token), "\n%u: hash name dump_inner ",
+ ids[key]);
+ if (count_token(output, token) != 1)
+ _exit(DUMP_ERR_IDS);
+ }
+ if (json && (output[0] != '[' ||
+ strcmp(output + strlen(output) - 2, "]\n")))
+ _exit(DUMP_ERR_JSON);
+ _exit(DUMP_OK);
+ }
+ if (ASSERT_EQ(waitpid(pid, &status, 0), pid, "waitpid") &&
+ ASSERT_TRUE(WIFEXITED(status), "child_exited"))
+ ASSERT_EQ(WEXITSTATUS(status), DUMP_OK, "dump_with_low_fd_limit");
+ for (i = 0; i < nr_inherited; i++)
+ ASSERT_GE(fcntl(inherited_fds[i], F_GETFD), 0, "parent_fd_preserved");
+ ASSERT_EQ(map_id(outer_fd), root_id, "parent_outer_preserved");
+out:
+ while (nr_inherited)
+ close(inherited_fds[--nr_inherited]);
+ free(output);
+ if (outer_fd >= 0)
+ close(outer_fd);
+ if (inner_fd >= 0)
+ close(inner_fd);
+}
+
+void test_bpftool_map_dump(void)
+{
+ if (test__start_subtest("unreadable_ordinary"))
+ test_unreadable(false);
+ if (test__start_subtest("unreadable_inner"))
+ test_unreadable(true);
+ if (test__start_subtest("many_inner_maps_json"))
+ test_many_inner_maps(true);
+ if (test__start_subtest("many_inner_maps_plain"))
+ test_many_inner_maps(false);
+ if (test__start_subtest("multiple_roots"))
+ test_multiple_roots();
+ if (test__start_subtest("array_of_maps"))
+ test_outer(BPF_MAP_TYPE_ARRAY_OF_MAPS, 1, false, false);
+ if (test__start_subtest("hash_of_maps"))
+ test_outer(BPF_MAP_TYPE_HASH_OF_MAPS, 1, false, false);
+ if (test__start_subtest("shared_inner"))
+ test_outer(BPF_MAP_TYPE_ARRAY_OF_MAPS, 2, false, false);
+ if (test__start_subtest("empty_array_of_maps"))
+ test_outer(BPF_MAP_TYPE_ARRAY_OF_MAPS, 0, false, false);
+ if (test__start_subtest("empty_hash_of_maps"))
+ test_outer(BPF_MAP_TYPE_HASH_OF_MAPS, 0, false, false);
+ if (test__start_subtest("btf_inner"))
+ test_outer(BPF_MAP_TYPE_HASH_OF_MAPS, 1, false, true);
+ if (test__start_subtest("empty_inner"))
+ test_outer(BPF_MAP_TYPE_HASH_OF_MAPS, 1, true, false);
+}
--
2.55.0
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