libbpf: Mark BPF subprogs with hidden visibility as static for BPF verifier

Define __hidden helper macro in bpf_helpers.h, which is a short-hand for
__attribute__((visibility("hidden"))). Add libbpf support to mark BPF
subprograms marked with __hidden as static in BTF information to enforce BPF
verifier's static function validation algorithm, which takes more information
(caller's context) into account during a subprogram validation.

Signed-off-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

1 files changed, 6 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 6017902c687e..92b7eae10c6d 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -19,6 +19,7 @@
 #pragma GCC poison reallocarray
 
 #include "libbpf.h"
+#include "btf.h"
 
 #ifndef EM_BPF
 #define EM_BPF 247
@@ -132,6 +133,11 @@ struct btf_type;
 
 struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id);
 
+static inline __u32 btf_type_info(int kind, int vlen, int kflag)
+{
+	return (kflag << 31) | (kind << 24) | vlen;
+}
+
 void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
 		     size_t cur_cnt, size_t max_cnt, size_t add_cnt);
 int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);