libbpf: Allows disabling auto attach

Adds libbpf APIs for disabling auto-attach for individual functions.
This is motivated by the use case of cgroup iter [1]. Some iter
types require their parameters to be non-zero, therefore applying
auto-attach on them will fail. With these two new APIs, users who
want to use auto-attach and these types of iters can disable
auto-attach on the program and perform manual attach.

[1] https://lore.kernel.org/bpf/CAEf4BzZ+a2uDo_t6kGBziqdz--m2gh2_EUwkGLDtMd65uwxUjA@mail.gmail.com/

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220816234012.910255-1-haoluo@google.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index aa05a99b913db0ddeb19fbb97f37f5099f5390c3..0159a43c7efd3f41fa18909fbc5ab5e43c96f96a 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -417,6 +417,7 @@ struct bpf_program {
 
        int fd;
        bool autoload;
+       bool autoattach;
        bool mark_btf_static;
        enum bpf_prog_type type;
        enum bpf_attach_type expected_attach_type;
@@ -755,6 +756,8 @@ bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
                prog->autoload = true;
        }
 
+       prog->autoattach = true;
+
        /* inherit object's log_level */
        prog->log_level = obj->log_level;
 
@@ -8314,6 +8317,16 @@ int bpf_program__set_autoload(struct bpf_program *prog, bool autoload)
        return 0;
 }
 
+bool bpf_program__autoattach(const struct bpf_program *prog)
+{
+       return prog->autoattach;
+}
+
+void bpf_program__set_autoattach(struct bpf_program *prog, bool autoattach)
+{
+       prog->autoattach = autoattach;
+}
+
 const struct bpf_insn *bpf_program__insns(const struct bpf_program *prog)
 {
        return prog->insns;
@@ -12346,7 +12359,7 @@ int bpf_object__attach_skeleton(struct bpf_object_skeleton *s)
                struct bpf_program *prog = *s->progs[i].prog;
                struct bpf_link **link = s->progs[i].link;
 
-               if (!prog->autoload)
+               if (!prog->autoload || !prog->autoattach)
                        continue;
 
                /* auto-attaching not supported for this program */

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 61493c4cddac11c2b216b76a94414ae48c9f9c89..88a1ac34b12a9a1c2b412db6b1928ec6fa45b590 100644 (file)
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -260,6 +260,8 @@ LIBBPF_API const char *bpf_program__name(const struct bpf_program *prog);
 LIBBPF_API const char *bpf_program__section_name(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__autoload(const struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_autoload(struct bpf_program *prog, bool autoload);
+LIBBPF_API bool bpf_program__autoattach(const struct bpf_program *prog);
+LIBBPF_API void bpf_program__set_autoattach(struct bpf_program *prog, bool autoattach);
 
 struct bpf_insn;
 

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 119e6e1ea7f114d4ac2f19b068c5e94cc6046da8..2b928dc21af0ab6ab8d2ba7230fcf1a1b4736597 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -358,6 +358,8 @@ LIBBPF_1.0.0 {
                bpf_obj_get_opts;
                bpf_prog_query_opts;
                bpf_program__attach_ksyscall;
+               bpf_program__autoattach;
+               bpf_program__set_autoattach;
                btf__add_enum64;
                btf__add_enum64_value;
                libbpf_bpf_attach_type_str;