From: Stijn Tintel stijn@linux-ipv6.be
[ Upstream commit a4fbfdd7a160eccaafc093eb5b34f838b1ca0bf0 ]
When a BPF map of type BPF_MAP_TYPE_PERF_EVENT_ARRAY doesn't have the max_entries parameter set, the map will be created with max_entries set to the number of available CPUs. When we try to reuse such a pinned map, map_is_reuse_compat will return false, as max_entries in the map definition differs from max_entries of the existing map, causing the following error:
libbpf: couldn't reuse pinned map at '/sys/fs/bpf/m_logging': parameter mismatch
Fix this by overwriting max_entries in the map definition. For this to work, we need to do this in bpf_object__create_maps, before calling bpf_object__reuse_map.
Fixes: 57a00f41644f ("libbpf: Add auto-pinning of maps when loading BPF objects") Signed-off-by: Stijn Tintel stijn@linux-ipv6.be Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Song Liu songliubraving@fb.com Link: https://lore.kernel.org/bpf/20220225152355.315204-1-stijn@linux-ipv6.be Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 44 ++++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 19 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index fdb3536afa7d..94a6a8543cbc 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -4854,7 +4854,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b LIBBPF_OPTS(bpf_map_create_opts, create_attr); struct bpf_map_def *def = &map->def; const char *map_name = NULL; - __u32 max_entries; int err = 0;
if (kernel_supports(obj, FEAT_PROG_NAME)) @@ -4864,21 +4863,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b create_attr.numa_node = map->numa_node; create_attr.map_extra = map->map_extra;
- if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !def->max_entries) { - int nr_cpus; - - nr_cpus = libbpf_num_possible_cpus(); - if (nr_cpus < 0) { - pr_warn("map '%s': failed to determine number of system CPUs: %d\n", - map->name, nr_cpus); - return nr_cpus; - } - pr_debug("map '%s': setting size to %d\n", map->name, nr_cpus); - max_entries = nr_cpus; - } else { - max_entries = def->max_entries; - } - if (bpf_map__is_struct_ops(map)) create_attr.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
@@ -4928,7 +4912,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
if (obj->gen_loader) { bpf_gen__map_create(obj->gen_loader, def->type, map_name, - def->key_size, def->value_size, max_entries, + def->key_size, def->value_size, def->max_entries, &create_attr, is_inner ? -1 : map - obj->maps); /* Pretend to have valid FD to pass various fd >= 0 checks. * This fd == 0 will not be used with any syscall and will be reset to -1 eventually. @@ -4937,7 +4921,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b } else { map->fd = bpf_map_create(def->type, map_name, def->key_size, def->value_size, - max_entries, &create_attr); + def->max_entries, &create_attr); } if (map->fd < 0 && (create_attr.btf_key_type_id || create_attr.btf_value_type_id)) { @@ -4954,7 +4938,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b map->btf_value_type_id = 0; map->fd = bpf_map_create(def->type, map_name, def->key_size, def->value_size, - max_entries, &create_attr); + def->max_entries, &create_attr); }
err = map->fd < 0 ? -errno : 0; @@ -5058,6 +5042,24 @@ static int bpf_object_init_prog_arrays(struct bpf_object *obj) return 0; }
+static int map_set_def_max_entries(struct bpf_map *map) +{ + if (map->def.type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !map->def.max_entries) { + int nr_cpus; + + nr_cpus = libbpf_num_possible_cpus(); + if (nr_cpus < 0) { + pr_warn("map '%s': failed to determine number of system CPUs: %d\n", + map->name, nr_cpus); + return nr_cpus; + } + pr_debug("map '%s': setting size to %d\n", map->name, nr_cpus); + map->def.max_entries = nr_cpus; + } + + return 0; +} + static int bpf_object__create_maps(struct bpf_object *obj) { @@ -5090,6 +5092,10 @@ bpf_object__create_maps(struct bpf_object *obj) continue; }
+ err = map_set_def_max_entries(map); + if (err) + goto err_out; + retried = false; retry: if (map->pin_path) {