From: Stijn Tintel <stijn@linux-ipv6.be>
Date: Fri, 25 Feb 2022 17:23:55 +0200
Subject: libbpf: Fix BPF_MAP_TYPE_PERF_EVENT_ARRAY auto-pinning
Patch-mainline: v5.18-rc1
Git-commit: a4fbfdd7a160eccaafc093eb5b34f838b1ca0bf0
References: jsc#PED-1377
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
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/libbpf.c | 44 +++++++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 19 deletions(-)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4859,7 +4859,6 @@ static int bpf_object__create_map(struct
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))
@@ -4869,21 +4868,6 @@ static int bpf_object__create_map(struct
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;
@@ -4933,7 +4917,7 @@ static int bpf_object__create_map(struct
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.
@@ -4942,7 +4926,7 @@ static int bpf_object__create_map(struct
} 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)) {
@@ -4959,7 +4943,7 @@ static int bpf_object__create_map(struct
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;
@@ -5063,6 +5047,24 @@ static int bpf_object_init_prog_arrays(s
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)
{
@@ -5095,6 +5097,10 @@ bpf_object__create_maps(struct bpf_objec
continue;
}
+ err = map_set_def_max_entries(map);
+ if (err)
+ goto err_out;
+
retried = false;
retry:
if (map->pin_path) {