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bpf: Return target info when a tracing bpf_link is queried

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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: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210413091607.58945-1-toke@redhat.com
This commit is contained in:
Toke Høiland-Jørgensen 2021-04-13 11:16:06 +02:00 committed by Alexei Starovoitov
parent db16c1fe92
commit 441e8c66b2
4 changed files with 16 additions and 0 deletions
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9
include/linux/bpf_verifier.h
View file

@ -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,

2
include/uapi/linux/bpf.h
View file

@ -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;

3
kernel/bpf/syscall.c
View file

@ -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;
}

2
tools/include/uapi/linux/bpf.h
View file

@ -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;