Commit 441e8c66 authored by Toke Høiland-Jørgensen's avatar Toke Høiland-Jørgensen Committed by Alexei Starovoitov
Browse files

bpf: Return target info when a tracing bpf_link is queried 



There is currently no way to discover the target of a tracing program
attachment after the fact. Add this information to bpf_link_info and return
it when querying the bpf_link fd.

Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210413091607.58945-1-toke@redhat.com
parent db16c1fe

include/linux/bpf_verifier.h

+9 −0
Original line number Diff line number Diff line
@@ -487,6 +487,15 @@ static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog, 
		return ((u64)btf_obj_id(btf) << 32) | 0x80000000 | btf_id;

}



/* unpack the IDs from the key as constructed above */

static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id)

{

	if (obj_id)

		*obj_id = key >> 32;

	if (btf_id)

		*btf_id = key & 0x7FFFFFFF;

}



int bpf_check_attach_target(struct bpf_verifier_log *log,

			    const struct bpf_prog *prog,

			    const struct bpf_prog *tgt_prog,

include/uapi/linux/bpf.h

+2 −0
Original line number Diff line number Diff line
@@ -5416,6 +5416,8 @@ struct bpf_link_info { 
		} raw_tracepoint;

		struct {

			__u32 attach_type;

			__u32 target_obj_id; /* prog_id for PROG_EXT, otherwise btf object id */

			__u32 target_btf_id; /* BTF type id inside the object */

		} tracing;

		struct {

			__u64 cgroup_id;

kernel/bpf/syscall.c

+3 −0
Original line number Diff line number Diff line
@@ -2551,6 +2551,9 @@ static int bpf_tracing_link_fill_link_info(const struct bpf_link *link, 
		container_of(link, struct bpf_tracing_link, link);



	info->tracing.attach_type = tr_link->attach_type;

	bpf_trampoline_unpack_key(tr_link->trampoline->key,

				  &info->tracing.target_obj_id,

				  &info->tracing.target_btf_id);



	return 0;

}

tools/include/uapi/linux/bpf.h

+2 −0
Original line number Diff line number Diff line
@@ -5416,6 +5416,8 @@ struct bpf_link_info { 
		} raw_tracepoint;

		struct {

			__u32 attach_type;

			__u32 target_obj_id; /* prog_id for PROG_EXT, otherwise btf object id */

			__u32 target_btf_id; /* BTF type id inside the object */

		} tracing;

		struct {

			__u64 cgroup_id;