Commit d6dd1d49 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

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: 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/20240124022127.2379740-23-andrii@kernel.org
parent ea4d5873

tools/lib/bpf/bpf.c

+3 −3
Original line number Diff line number Diff line
@@ -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);

tools/lib/bpf/libbpf.c

+15 −7
Original line number Diff line number Diff line
@@ -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;

tools/lib/bpf/libbpf_internal.h

+4 −1
Original line number Diff line number Diff line
@@ -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);