bpf: decouple btf from seq bpf fs dump and enable more maps

Commit a26ca7c982cb ("bpf: btf: Add pretty print support to
the basic arraymap") and 699c86d6ec21 ("bpf: btf: add pretty
print for hash/lru_hash maps") enabled support for BTF and
dumping via BPF fs for array and hash/lru map. However, both
can be decoupled from each other such that regular BPF maps
can be supported for attaching BTF key/value information,
while not all maps necessarily need to dump via map_seq_show_elem()
callback.

The basic sanity check which is a prerequisite for all maps
is that key/value size has to match in any case, and some maps
can have extra checks via map_check_btf() callback, e.g.
probing certain types or indicating no support in general. With
that we can also enable retrieving BTF info for per-cpu map
types and lpm.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>

1 files changed, 12 insertions, 14 deletions

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index f6ca3e712831..0c17aab3ce5f 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -358,27 +358,20 @@ static void array_map_seq_show_elem(struct bpf_map *map, void *key,
         rcu_read_unlock();
 }
 
-static int array_map_check_btf(const struct bpf_map *map, const struct btf *btf,
-                               u32 btf_key_id, u32 btf_value_id)
+static int array_map_check_btf(const struct bpf_map *map,
+                               const struct btf_type *key_type,
+                               const struct btf_type *value_type)
 {
-        const struct btf_type *key_type, *value_type;
-        u32 key_size, value_size;
         u32 int_data;
 
-        key_type = btf_type_id_size(btf, &btf_key_id, &key_size);
-        if (!key_type || BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
+        if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
                 return -EINVAL;
 
         int_data = *(u32 *)(key_type + 1);
-        /* bpf array can only take a u32 key.  This check makes
-         * sure that the btf matches the attr used during map_create.
+        /* bpf array can only take a u32 key. This check makes sure
+         * that the btf matches the attr used during map_create.
          */
-        if (BTF_INT_BITS(int_data) != 32 || key_size != 4 ||
-            BTF_INT_OFFSET(int_data))
-                return -EINVAL;
-
-        value_type = btf_type_id_size(btf, &btf_value_id, &value_size);
-        if (!value_type || value_size != map->value_size)
+        if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
                 return -EINVAL;
 
         return 0;
@@ -405,6 +398,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
         .map_lookup_elem = percpu_array_map_lookup_elem,
         .map_update_elem = array_map_update_elem,
         .map_delete_elem = array_map_delete_elem,
+        .map_check_btf = array_map_check_btf,
 };
 
 static int fd_array_map_alloc_check(union bpf_attr *attr)
@@ -546,6 +540,7 @@ const struct bpf_map_ops prog_array_map_ops = {
         .map_fd_put_ptr = prog_fd_array_put_ptr,
         .map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
         .map_release_uref = bpf_fd_array_map_clear,
+        .map_check_btf = map_check_no_btf,
 };
 
 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
@@ -634,6 +629,7 @@ const struct bpf_map_ops perf_event_array_map_ops = {
         .map_fd_get_ptr = perf_event_fd_array_get_ptr,
         .map_fd_put_ptr = perf_event_fd_array_put_ptr,
         .map_release = perf_event_fd_array_release,
+        .map_check_btf = map_check_no_btf,
 };
 
 #ifdef CONFIG_CGROUPS
@@ -665,6 +661,7 @@ const struct bpf_map_ops cgroup_array_map_ops = {
         .map_delete_elem = fd_array_map_delete_elem,
         .map_fd_get_ptr = cgroup_fd_array_get_ptr,
         .map_fd_put_ptr = cgroup_fd_array_put_ptr,
+        .map_check_btf = map_check_no_btf,
 };
 #endif
 
@@ -749,4 +746,5 @@ const struct bpf_map_ops array_of_maps_map_ops = {
         .map_fd_put_ptr = bpf_map_fd_put_ptr,
         .map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
         .map_gen_lookup = array_of_map_gen_lookup,
+        .map_check_btf = map_check_no_btf,
 };