Commit ff26ce5c authored by Eelco Chaudron's avatar Eelco Chaudron Committed by Alexei Starovoitov
Browse files

libbpf: Add support for dynamic program attach target 



Currently when you want to attach a trace program to a bpf program
the section name needs to match the tracepoint/function semantics.

However the addition of the bpf_program__set_attach_target() API
allows you to specify the tracepoint/function dynamically.

The call flow would look something like this:

  xdp_fd = bpf_prog_get_fd_by_id(id);
  trace_obj = bpf_object__open_file("func.o", NULL);
  prog = bpf_object__find_program_by_title(trace_obj,
                                           "fentry/myfunc");
  bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
  bpf_program__set_attach_target(prog, xdp_fd,
                                 "xdpfilt_blk_all");
  bpf_object__load(trace_obj)

Signed-off-by: default avatarEelco Chaudron <echaudro@redhat.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/158220519486.127661.7964708960649051384.stgit@xdp-tutorial
parent dd88aed9

tools/lib/bpf/libbpf.c

+30 −4
Original line number Diff line number Diff line
@@ -4937,8 +4937,8 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver) 
{

	int err = 0, fd, i, btf_id;



	if (prog->type == BPF_PROG_TYPE_TRACING ||

	    prog->type == BPF_PROG_TYPE_EXT) {

	if ((prog->type == BPF_PROG_TYPE_TRACING ||

	     prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {

		btf_id = libbpf_find_attach_btf_id(prog);

		if (btf_id <= 0)

			return btf_id;
@@ -6581,6 +6581,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name, 
	else

		err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);



	if (err <= 0)

		pr_warn("%s is not found in vmlinux BTF\n", name);



	return err;

}
@@ -6653,8 +6656,6 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog) 
			err = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,

						    name + section_defs[i].len,

						    attach_type);

		if (err <= 0)

			pr_warn("%s is not found in vmlinux BTF\n", name);

		return err;

	}

	pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);
@@ -8130,6 +8131,31 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear) 
	}

}



int bpf_program__set_attach_target(struct bpf_program *prog,

				   int attach_prog_fd,

				   const char *attach_func_name)

{

	int btf_id;



	if (!prog || attach_prog_fd < 0 || !attach_func_name)

		return -EINVAL;



	if (attach_prog_fd)

		btf_id = libbpf_find_prog_btf_id(attach_func_name,

						 attach_prog_fd);

	else

		btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,

					       attach_func_name,

					       prog->expected_attach_type);



	if (btf_id < 0)

		return btf_id;



	prog->attach_btf_id = btf_id;

	prog->attach_prog_fd = attach_prog_fd;

	return 0;

}



int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)

{

	int err = 0, n, len, start, end = -1;

tools/lib/bpf/libbpf.h

+4 −0
Original line number Diff line number Diff line
@@ -334,6 +334,10 @@ LIBBPF_API void 
bpf_program__set_expected_attach_type(struct bpf_program *prog,

				      enum bpf_attach_type type);



LIBBPF_API int

bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,

			       const char *attach_func_name);



LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);

LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);

LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);

tools/lib/bpf/libbpf.map

+2 −0
Original line number Diff line number Diff line
@@ -237,4 +237,6 @@ LIBBPF_0.0.7 { 
} LIBBPF_0.0.6;



LIBBPF_0.0.8 {

	global:

		bpf_program__set_attach_target;

} LIBBPF_0.0.7;

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