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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
This commit is contained in:
Andrii Nakryiko 2024-01-23 18:21:19 -08:00 committed by Alexei Starovoitov
parent ea4d587354
commit d6dd1d4936
3 changed files with 22 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
tools/lib/bpf/bpf.c
View File

@ -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);

22
tools/lib/bpf/libbpf.c
View File

@ -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;

5
tools/lib/bpf/libbpf_internal.h
View File

@ -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);