Commit ea4d5873 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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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.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-22-andrii@kernel.org
parent 0350f9d9

tools/lib/bpf/libbpf.c

+12 −6
Original line number Diff line number Diff line
@@ -4958,12 +4958,17 @@ 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,
@@ -5031,6 +5036,7 @@ 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)
@@ -5039,19 +5045,19 @@ 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)