[PATCH bpf-next 1/2] libbpf: Support uniform BTF-defined key/value specification across all BPF maps

From: Hengqi Chen <hengqi.chen@gmail.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	yhs@fb.com, john.fastabend@gmail.com, hengqi.chen@gmail.com
Subject: [PATCH bpf-next 1/2] libbpf: Support uniform BTF-defined key/value specification across all BPF maps
Date: Sun,  5 Sep 2021 18:09:13 +0800	[thread overview]
Message-ID: <20210905100914.33007-1-hengqi.chen@gmail.com> (raw)

A bunch of BPF maps do not support specifying types for key and value.
This is non-uniform and inconvenient[0]. Currently, libbpf uses a retry
logic which removes BTF type IDs when BPF map creation failed. Instead
of retrying, this commit recognizes those specialized map and removes
BTF type IDs when creating BPF map.

  [0] Closes: https://github.com/libbpf/libbpf/issues/355

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 tools/lib/bpf/libbpf.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 88d8825fc6f6..7068c4d07337 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4613,6 +4613,26 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 			create_attr.inner_map_fd = map->inner_map_fd;
 	}
 
+	if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY ||
+	    def->type == BPF_MAP_TYPE_STACK_TRACE ||
+	    def->type == BPF_MAP_TYPE_CGROUP_ARRAY ||
+	    def->type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
+	    def->type == BPF_MAP_TYPE_HASH_OF_MAPS ||
+	    def->type == BPF_MAP_TYPE_DEVMAP ||
+	    def->type == BPF_MAP_TYPE_SOCKMAP ||
+	    def->type == BPF_MAP_TYPE_CPUMAP ||
+	    def->type == BPF_MAP_TYPE_XSKMAP ||
+	    def->type == BPF_MAP_TYPE_SOCKHASH ||
+	    def->type == BPF_MAP_TYPE_QUEUE ||
+	    def->type == BPF_MAP_TYPE_STACK ||
+	    def->type == BPF_MAP_TYPE_DEVMAP_HASH) {
+		create_attr.btf_fd = 0;
+		create_attr.btf_key_type_id = 0;
+		create_attr.btf_value_type_id = 0;
+		map->btf_key_type_id = 0;
+		map->btf_value_type_id = 0;
+	}
+
 	if (obj->gen_loader) {
 		bpf_gen__map_create(obj->gen_loader, &create_attr, is_inner ? -1 : map - obj->maps);
 		/* Pretend to have valid FD to pass various fd >= 0 checks.
@@ -4622,21 +4642,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 	} else {
 		map->fd = bpf_create_map_xattr(&create_attr);
 	}
-	if (map->fd < 0 && (create_attr.btf_key_type_id ||
-			    create_attr.btf_value_type_id)) {
-		char *cp, errmsg[STRERR_BUFSIZE];
-
-		err = -errno;
-		cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
-		pr_warn("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
-			map->name, cp, err);
-		create_attr.btf_fd = 0;
-		create_attr.btf_key_type_id = 0;
-		create_attr.btf_value_type_id = 0;
-		map->btf_key_type_id = 0;
-		map->btf_value_type_id = 0;
-		map->fd = bpf_create_map_xattr(&create_attr);
-	}
 
 	err = map->fd < 0 ? -errno : 0;
 
-- 
2.25.1

