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libbpf: Introduce libbpf_attach_type_by_name
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There is a common use-case when ELF object contains multiple BPF
programs and every program has its own section name. If it's cgroup-bpf
then programs have to be 1) loaded and 2) attached to a cgroup.

It's convenient to have information necessary to load BPF program
together with program itself. This is where section name works fine in
conjunction with libbpf_prog_type_by_name that identifies prog_type and
expected_attach_type and these can be used with BPF_PROG_LOAD.

But there is currently no way to identify attach_type by section name
and it leads to messy code in user space that reinvents guessing logic
every time it has to identify attach type to use with BPF_PROG_ATTACH.

The patch introduces libbpf_attach_type_by_name that guesses attach type
by section name if a program can be attached.

The difference between expected_attach_type provided by
libbpf_prog_type_by_name and attach_type provided by
libbpf_attach_type_by_name is the former is used at BPF_PROG_LOAD time
and can be zero if a program of prog_type X has only one corresponding
attach type Y whether the latter provides specific attach type to use
with BPF_PROG_ATTACH.

No new section names were added to section_names array. Only existing
ones were reorganized and attach_type was added where appropriate.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Andrey Ignatov authored and Daniel Borkmann committed Sep 27, 2018
1 parent 1008119 commit 956b620
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Showing 2 changed files with 84 additions and 39 deletions.
121 changes: 82 additions & 39 deletions tools/lib/bpf/libbpf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2085,58 +2085,82 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
prog->expected_attach_type = type;
}

#define BPF_PROG_SEC_FULL(string, ptype, atype) \
{ string, sizeof(string) - 1, ptype, atype }
#define BPF_PROG_SEC_IMPL(string, ptype, eatype, atype) \
{ string, sizeof(string) - 1, ptype, eatype, atype }

#define BPF_PROG_SEC(string, ptype) BPF_PROG_SEC_FULL(string, ptype, 0)
/* Programs that can NOT be attached. */
#define BPF_PROG_SEC(string, ptype) BPF_PROG_SEC_IMPL(string, ptype, 0, -EINVAL)

#define BPF_S_PROG_SEC(string, ptype) \
BPF_PROG_SEC_FULL(string, BPF_PROG_TYPE_CGROUP_SOCK, ptype)
/* Programs that can be attached. */
#define BPF_APROG_SEC(string, ptype, atype) \
BPF_PROG_SEC_IMPL(string, ptype, 0, atype)

#define BPF_SA_PROG_SEC(string, ptype) \
BPF_PROG_SEC_FULL(string, BPF_PROG_TYPE_CGROUP_SOCK_ADDR, ptype)
/* Programs that must specify expected attach type at load time. */
#define BPF_EAPROG_SEC(string, ptype, eatype) \
BPF_PROG_SEC_IMPL(string, ptype, eatype, eatype)

/* Programs that can be attached but attach type can't be identified by section
* name. Kept for backward compatibility.
*/
#define BPF_APROG_COMPAT(string, ptype) BPF_PROG_SEC(string, ptype)

static const struct {
const char *sec;
size_t len;
enum bpf_prog_type prog_type;
enum bpf_attach_type expected_attach_type;
enum bpf_attach_type attach_type;
} section_names[] = {
BPF_PROG_SEC("socket", BPF_PROG_TYPE_SOCKET_FILTER),
BPF_PROG_SEC("kprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("kretprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("classifier", BPF_PROG_TYPE_SCHED_CLS),
BPF_PROG_SEC("action", BPF_PROG_TYPE_SCHED_ACT),
BPF_PROG_SEC("tracepoint/", BPF_PROG_TYPE_TRACEPOINT),
BPF_PROG_SEC("raw_tracepoint/", BPF_PROG_TYPE_RAW_TRACEPOINT),
BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
BPF_PROG_SEC("cgroup/skb", BPF_PROG_TYPE_CGROUP_SKB),
BPF_PROG_SEC("cgroup/sock", BPF_PROG_TYPE_CGROUP_SOCK),
BPF_PROG_SEC("cgroup/dev", BPF_PROG_TYPE_CGROUP_DEVICE),
BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
BPF_PROG_SEC("lwt_out", BPF_PROG_TYPE_LWT_OUT),
BPF_PROG_SEC("lwt_xmit", BPF_PROG_TYPE_LWT_XMIT),
BPF_PROG_SEC("lwt_seg6local", BPF_PROG_TYPE_LWT_SEG6LOCAL),
BPF_PROG_SEC("sockops", BPF_PROG_TYPE_SOCK_OPS),
BPF_PROG_SEC("sk_skb", BPF_PROG_TYPE_SK_SKB),
BPF_PROG_SEC("sk_msg", BPF_PROG_TYPE_SK_MSG),
BPF_PROG_SEC("lirc_mode2", BPF_PROG_TYPE_LIRC_MODE2),
BPF_PROG_SEC("flow_dissector", BPF_PROG_TYPE_FLOW_DISSECTOR),
BPF_SA_PROG_SEC("cgroup/bind4", BPF_CGROUP_INET4_BIND),
BPF_SA_PROG_SEC("cgroup/bind6", BPF_CGROUP_INET6_BIND),
BPF_SA_PROG_SEC("cgroup/connect4", BPF_CGROUP_INET4_CONNECT),
BPF_SA_PROG_SEC("cgroup/connect6", BPF_CGROUP_INET6_CONNECT),
BPF_SA_PROG_SEC("cgroup/sendmsg4", BPF_CGROUP_UDP4_SENDMSG),
BPF_SA_PROG_SEC("cgroup/sendmsg6", BPF_CGROUP_UDP6_SENDMSG),
BPF_S_PROG_SEC("cgroup/post_bind4", BPF_CGROUP_INET4_POST_BIND),
BPF_S_PROG_SEC("cgroup/post_bind6", BPF_CGROUP_INET6_POST_BIND),
BPF_PROG_SEC("socket", BPF_PROG_TYPE_SOCKET_FILTER),
BPF_PROG_SEC("kprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("kretprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("classifier", BPF_PROG_TYPE_SCHED_CLS),
BPF_PROG_SEC("action", BPF_PROG_TYPE_SCHED_ACT),
BPF_PROG_SEC("tracepoint/", BPF_PROG_TYPE_TRACEPOINT),
BPF_PROG_SEC("raw_tracepoint/", BPF_PROG_TYPE_RAW_TRACEPOINT),
BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
BPF_PROG_SEC("lwt_out", BPF_PROG_TYPE_LWT_OUT),
BPF_PROG_SEC("lwt_xmit", BPF_PROG_TYPE_LWT_XMIT),
BPF_PROG_SEC("lwt_seg6local", BPF_PROG_TYPE_LWT_SEG6LOCAL),
BPF_APROG_COMPAT("cgroup/skb", BPF_PROG_TYPE_CGROUP_SKB),
BPF_APROG_SEC("cgroup/sock", BPF_PROG_TYPE_CGROUP_SOCK,
BPF_CGROUP_INET_SOCK_CREATE),
BPF_EAPROG_SEC("cgroup/post_bind4", BPF_PROG_TYPE_CGROUP_SOCK,
BPF_CGROUP_INET4_POST_BIND),
BPF_EAPROG_SEC("cgroup/post_bind6", BPF_PROG_TYPE_CGROUP_SOCK,
BPF_CGROUP_INET6_POST_BIND),
BPF_APROG_SEC("cgroup/dev", BPF_PROG_TYPE_CGROUP_DEVICE,
BPF_CGROUP_DEVICE),
BPF_APROG_SEC("sockops", BPF_PROG_TYPE_SOCK_OPS,
BPF_CGROUP_SOCK_OPS),
BPF_APROG_COMPAT("sk_skb", BPF_PROG_TYPE_SK_SKB),
BPF_APROG_SEC("sk_msg", BPF_PROG_TYPE_SK_MSG,
BPF_SK_MSG_VERDICT),
BPF_APROG_SEC("lirc_mode2", BPF_PROG_TYPE_LIRC_MODE2,
BPF_LIRC_MODE2),
BPF_APROG_SEC("flow_dissector", BPF_PROG_TYPE_FLOW_DISSECTOR,
BPF_FLOW_DISSECTOR),
BPF_EAPROG_SEC("cgroup/bind4", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_INET4_BIND),
BPF_EAPROG_SEC("cgroup/bind6", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_INET6_BIND),
BPF_EAPROG_SEC("cgroup/connect4", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_INET4_CONNECT),
BPF_EAPROG_SEC("cgroup/connect6", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_INET6_CONNECT),
BPF_EAPROG_SEC("cgroup/sendmsg4", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_UDP4_SENDMSG),
BPF_EAPROG_SEC("cgroup/sendmsg6", BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_CGROUP_UDP6_SENDMSG),
};

#undef BPF_PROG_SEC_IMPL
#undef BPF_PROG_SEC
#undef BPF_PROG_SEC_FULL
#undef BPF_S_PROG_SEC
#undef BPF_SA_PROG_SEC
#undef BPF_APROG_SEC
#undef BPF_EAPROG_SEC
#undef BPF_APROG_COMPAT

int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
enum bpf_attach_type *expected_attach_type)
Expand All @@ -2156,6 +2180,25 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
return -EINVAL;
}

int libbpf_attach_type_by_name(const char *name,
enum bpf_attach_type *attach_type)
{
int i;

if (!name)
return -EINVAL;

for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (strncmp(name, section_names[i].sec, section_names[i].len))
continue;
if (section_names[i].attach_type == -EINVAL)
return -EINVAL;
*attach_type = section_names[i].attach_type;
return 0;
}
return -EINVAL;
}

static int
bpf_program__identify_section(struct bpf_program *prog,
enum bpf_prog_type *prog_type,
Expand Down
2 changes: 2 additions & 0 deletions tools/lib/bpf/libbpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,8 @@ void *bpf_object__priv(struct bpf_object *prog);

int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
enum bpf_attach_type *expected_attach_type);
int libbpf_attach_type_by_name(const char *name,
enum bpf_attach_type *attach_type);

/* Accessors of bpf_program */
struct bpf_program;
Expand Down

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