libbpf: Further decouple feature checking logic from bpf_object

Add feat_supported() helper that accepts feature cache instead of
bpf_object. This allows low-level code in bpf.c to not know or care
about higher-level concept of bpf_object, yet it will be able to utilize
custom feature checking in cases where BPF token might influence the
outcome.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-23-andrii@kernel.org

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 42cde79a67c7ec1ff563b6dd67e59984eccb60d2..1ebf224b8c5664033dbc70e210ee8afe5e9f7772 100644 (file)
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -146,7 +146,7 @@ int bump_rlimit_memlock(void)
        struct rlimit rlim;
 
        /* if kernel supports memcg-based accounting, skip bumping RLIMIT_MEMLOCK */
-       if (memlock_bumped || kernel_supports(NULL, FEAT_MEMCG_ACCOUNT))
+       if (memlock_bumped || feat_supported(NULL, FEAT_MEMCG_ACCOUNT))
                return 0;
 
        memlock_bumped = true;
@@ -181,7 +181,7 @@ int bpf_map_create(enum bpf_map_type map_type,
                return libbpf_err(-EINVAL);
 
        attr.map_type = map_type;
-       if (map_name && kernel_supports(NULL, FEAT_PROG_NAME))
+       if (map_name && feat_supported(NULL, FEAT_PROG_NAME))
                libbpf_strlcpy(attr.map_name, map_name, sizeof(attr.map_name));
        attr.key_size = key_size;
        attr.value_size = value_size;
@@ -266,7 +266,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
        attr.kern_version = OPTS_GET(opts, kern_version, 0);
        attr.prog_token_fd = OPTS_GET(opts, token_fd, 0);
 
-       if (prog_name && kernel_supports(NULL, FEAT_PROG_NAME))
+       if (prog_name && feat_supported(NULL, FEAT_PROG_NAME))
                libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
        attr.license = ptr_to_u64(license);
 

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 227f9f63e2597fa7749ce2575b6364a0bbca2760..4d791660bb56c4dfdc004b64881ce814db6507eb 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5033,17 +5033,14 @@ static struct kern_feature_desc {
        },
 };
 
-bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
+bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
 {
        struct kern_feature_desc *feat = &feature_probes[feat_id];
-       struct kern_feature_cache *cache = &feature_cache;
        int ret;
 
-       if (obj && obj->gen_loader)
-               /* To generate loader program assume the latest kernel
-                * to avoid doing extra prog_load, map_create syscalls.
-                */
-               return true;
+       /* assume global feature cache, unless custom one is provided */
+       if (!cache)
+               cache = &feature_cache;
 
        if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
                ret = feat->probe();
@@ -5060,6 +5057,17 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
        return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
 }
 
+bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
+{
+       if (obj && obj->gen_loader)
+               /* To generate loader program assume the latest kernel
+                * to avoid doing extra prog_load, map_create syscalls.
+                */
+               return true;
+
+       return feat_supported(NULL, feat_id);
+}
+
 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 {
        struct bpf_map_info map_info;

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 58c547d473e007b3529f780ba657c3a609be4983..622892fc841de6a809859d5a3e07f687008a4fde 100644 (file)
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -361,8 +361,11 @@ enum kern_feature_id {
        __FEAT_CNT,
 };
 
-int probe_memcg_account(void);
+struct kern_feature_cache;
+bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id);
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id);
+
+int probe_memcg_account(void);
 int bump_rlimit_memlock(void);
 
 int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz);