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Subject[PATCH bpf-next 2/3] bpf: add bpffs pretty print for cgroup local storage maps
Date
Implement bpffs pretty printing for cgroup local storage maps
(both shared and per-cpu).
Output example (captured for tools/testing/selftests/bpf/netcnt_prog.c):

Shared:
$ cat /sys/fs/bpf/map_2
# WARNING!! The output is for debug purpose only
# WARNING!! The output format will change
{4294968594,1}: {9999,1039896}

Per-cpu:
$ cat /sys/fs/bpf/map_1
# WARNING!! The output is for debug purpose only
# WARNING!! The output format will change
{4294968594,1}: {
cpu0: {0,0,0,0,0}
cpu1: {0,0,0,0,0}
cpu2: {1,104,0,0,0}
cpu3: {0,0,0,0,0}
}

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
---
include/linux/btf.h | 10 +++++
kernel/bpf/local_storage.c | 90 +++++++++++++++++++++++++++++++++++++-
2 files changed, 99 insertions(+), 1 deletion(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 8c2199b5d250..ac67bc4cbfd9 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -5,6 +5,7 @@
#define _LINUX_BTF_H 1

#include <linux/types.h>
+#include <uapi/linux/btf.h>

struct btf;
struct btf_type;
@@ -63,4 +64,13 @@ static inline const char *btf_name_by_offset(const struct btf *btf,
}
#endif

+static inline const struct btf_type *btf_orig_type(const struct btf *btf,
+ const struct btf_type *t)
+{
+ while (t && BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF)
+ t = btf_type_by_id(btf, t->type);
+
+ return t;
+}
+
#endif
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index b65017dead44..7b51fe1aba3c 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -1,11 +1,13 @@
//SPDX-License-Identifier: GPL-2.0
#include <linux/bpf-cgroup.h>
#include <linux/bpf.h>
+#include <linux/btf.h>
#include <linux/bug.h>
#include <linux/filter.h>
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
+#include <uapi/linux/btf.h>

DEFINE_PER_CPU(struct bpf_cgroup_storage*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);

@@ -308,6 +310,91 @@ static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
return -EINVAL;
}

+static int cgroup_storage_check_btf(const struct bpf_map *map,
+ const struct btf *btf,
+ const struct btf_type *key_type,
+ const struct btf_type *value_type)
+{
+ const struct btf_type *st, *t;
+ struct btf_member *m;
+
+ /* Key is expected to be of struct bpf_cgroup_storage_key type,
+ * which is:
+ * struct bpf_cgroup_storage_key {
+ * __u64 cgroup_inode_id;
+ * __u32 attach_type;
+ * };
+ */
+
+ /*
+ * Key_type must be a structure (or a typedef of a structure) with
+ * two members.
+ */
+ st = btf_orig_type(btf, key_type);
+ if (BTF_INFO_KIND(st->info) != BTF_KIND_STRUCT ||
+ BTF_INFO_VLEN(st->info) != 2)
+ return -EINVAL;
+
+ /*
+ * The first field must be a 64 bit integer at 0 offset.
+ */
+ m = (struct btf_member *)(st + 1);
+ t = btf_orig_type(btf, btf_type_by_id(btf, m->type));
+ if (!t || BTF_INFO_KIND(t->info) != BTF_KIND_INT || m->offset ||
+ t->size !=
+ FIELD_SIZEOF(struct bpf_cgroup_storage_key, cgroup_inode_id))
+ return -EINVAL;
+
+ /*
+ * The second field must be a 32 bit integer at 0 offset.
+ */
+ m = m + 1;
+ t = btf_orig_type(btf, btf_type_by_id(btf, m->type));
+ if (!t || BTF_INFO_KIND(t->info) != BTF_KIND_INT ||
+ m->offset != offsetof(struct bpf_cgroup_storage_key, attach_type) *
+ BITS_PER_BYTE || t->size !=
+ FIELD_SIZEOF(struct bpf_cgroup_storage_key, attach_type))
+ return -EINVAL;
+
+ return 0;
+}
+
+static void cgroup_storage_seq_show_elem(struct bpf_map *map, void *_key,
+ struct seq_file *m)
+{
+ enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
+ struct bpf_cgroup_storage_key *key = _key;
+ struct bpf_cgroup_storage *storage;
+ int cpu;
+
+ rcu_read_lock();
+ storage = cgroup_storage_lookup(map_to_storage(map), key, false);
+ if (!storage) {
+ rcu_read_unlock();
+ return;
+ }
+
+ btf_type_seq_show(map->btf, map->btf_key_type_id, key, m);
+ stype = cgroup_storage_type(map);
+ if (stype == BPF_CGROUP_STORAGE_SHARED) {
+ seq_puts(m, ": ");
+ btf_type_seq_show(map->btf, map->btf_value_type_id,
+ &READ_ONCE(storage->buf)->data[0], m);
+ seq_puts(m, "\n");
+ } else {
+ seq_puts(m, ": {\n");
+ for_each_possible_cpu(cpu) {
+ seq_printf(m, "\tcpu%d: ", cpu);
+ btf_type_seq_show(map->btf, map->btf_value_type_id,
+ per_cpu_ptr(storage->percpu_buf, cpu),
+ m);
+ seq_puts(m, "\n");
+ }
+ seq_puts(m, "}\n");
+ }
+ rcu_read_unlock();
+}
+
const struct bpf_map_ops cgroup_storage_map_ops = {
.map_alloc = cgroup_storage_map_alloc,
.map_free = cgroup_storage_map_free,
@@ -315,7 +402,8 @@ const struct bpf_map_ops cgroup_storage_map_ops = {
.map_lookup_elem = cgroup_storage_lookup_elem,
.map_update_elem = cgroup_storage_update_elem,
.map_delete_elem = cgroup_storage_delete_elem,
- .map_check_btf = map_check_no_btf,
+ .map_check_btf = cgroup_storage_check_btf,
+ .map_seq_show_elem = cgroup_storage_seq_show_elem,
};

int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *_map)
--
2.19.2
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