libbpf: split feature detectors definitions from cached results

Split a list of supported feature detectors with their corresponding
callbacks from actual cached supported/missing values. This will allow
to have more flexible per-token or per-object feature detectors in
subsequent refactorings.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231213190842.3844987-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ac54ebc0629f185f581f884e9675ba90e879f79a..d2828a26b011c6443b753b84c08bc6e4425174b2 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4999,12 +4999,17 @@ enum kern_feature_result {
        FEAT_MISSING = 2,
 };
 
+struct kern_feature_cache {
+       enum kern_feature_result res[__FEAT_CNT];
+};
+
 typedef int (*feature_probe_fn)(void);
 
+static struct kern_feature_cache feature_cache;
+
 static struct kern_feature_desc {
        const char *desc;
        feature_probe_fn probe;
-       enum kern_feature_result res;
 } feature_probes[__FEAT_CNT] = {
        [FEAT_PROG_NAME] = {
                "BPF program name", probe_kern_prog_name,
@@ -5072,6 +5077,7 @@ static struct kern_feature_desc {
 bool kernel_supports(const struct bpf_object *obj, 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)
@@ -5080,19 +5086,19 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
                 */
                return true;
 
-       if (READ_ONCE(feat->res) == FEAT_UNKNOWN) {
+       if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
                ret = feat->probe();
                if (ret > 0) {
-                       WRITE_ONCE(feat->res, FEAT_SUPPORTED);
+                       WRITE_ONCE(cache->res[feat_id], FEAT_SUPPORTED);
                } else if (ret == 0) {
-                       WRITE_ONCE(feat->res, FEAT_MISSING);
+                       WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
                } else {
                        pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
-                       WRITE_ONCE(feat->res, FEAT_MISSING);
+                       WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
                }
        }
 
-       return READ_ONCE(feat->res) == FEAT_SUPPORTED;
+       return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
 }
 
 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)