bpf: Compute map_btf_id during build time

For now, the field 'map_btf_id' in 'struct bpf_map_ops' for all map
types are computed during vmlinux-btf init:

  btf_parse_vmlinux() -> btf_vmlinux_map_ids_init()

It will lookup the btf_type according to the 'map_btf_name' field in
'struct bpf_map_ops'. This process can be done during build time,
thanks to Jiri's resolve_btfids.

selftest of map_ptr has passed:

  $96 map_ptr:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 7 insertions, 15 deletions

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 7351e61bd683..3e00e62b2218 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -10,6 +10,7 @@
 #include <linux/random.h>
 #include <uapi/linux/btf.h>
 #include <linux/rcupdate_trace.h>
+#include <linux/btf_ids.h>
 #include "percpu_freelist.h"
 #include "bpf_lru_list.h"
 #include "map_in_map.h"
@@ -2137,7 +2138,7 @@ out:
 	return num_elems;
 }
 
-static int htab_map_btf_id;
+BTF_ID_LIST_SINGLE(htab_map_btf_ids, struct, bpf_htab)
 const struct bpf_map_ops htab_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = htab_map_alloc_check,
@@ -2154,12 +2155,10 @@ const struct bpf_map_ops htab_map_ops = {
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_hash_elem,
 	BATCH_OPS(htab),
-	.map_btf_name = "bpf_htab",
-	.map_btf_id = &htab_map_btf_id,
+	.map_btf_id = &htab_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
-static int htab_lru_map_btf_id;
 const struct bpf_map_ops htab_lru_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = htab_map_alloc_check,
@@ -2177,8 +2176,7 @@ const struct bpf_map_ops htab_lru_map_ops = {
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_hash_elem,
 	BATCH_OPS(htab_lru),
-	.map_btf_name = "bpf_htab",
-	.map_btf_id = &htab_lru_map_btf_id,
+	.map_btf_id = &htab_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
@@ -2284,7 +2282,6 @@ static void htab_percpu_map_seq_show_elem(struct bpf_map *map, void *key,
 	rcu_read_unlock();
 }
 
-static int htab_percpu_map_btf_id;
 const struct bpf_map_ops htab_percpu_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = htab_map_alloc_check,
@@ -2299,12 +2296,10 @@ const struct bpf_map_ops htab_percpu_map_ops = {
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_hash_elem,
 	BATCH_OPS(htab_percpu),
-	.map_btf_name = "bpf_htab",
-	.map_btf_id = &htab_percpu_map_btf_id,
+	.map_btf_id = &htab_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
-static int htab_lru_percpu_map_btf_id;
 const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = htab_map_alloc_check,
@@ -2319,8 +2314,7 @@ const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_hash_elem,
 	BATCH_OPS(htab_lru_percpu),
-	.map_btf_name = "bpf_htab",
-	.map_btf_id = &htab_lru_percpu_map_btf_id,
+	.map_btf_id = &htab_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
@@ -2444,7 +2438,6 @@ static void htab_of_map_free(struct bpf_map *map)
 	fd_htab_map_free(map);
 }
 
-static int htab_of_maps_map_btf_id;
 const struct bpf_map_ops htab_of_maps_map_ops = {
 	.map_alloc_check = fd_htab_map_alloc_check,
 	.map_alloc = htab_of_map_alloc,
@@ -2457,6 +2450,5 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
 	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
 	.map_gen_lookup = htab_of_map_gen_lookup,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_htab",
-	.map_btf_id = &htab_of_maps_map_btf_id,
+	.map_btf_id = &htab_map_btf_ids[0],
 };