Commit fe62de31 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: Support modules in bpf_program__set_attach_target() API 



Support finding kernel targets in kernel modules when using
bpf_program__set_attach_target() API. This brings it up to par with what
libbpf supports when doing declarative SEC()-based target determination.

Some minor internal refactoring was needed to make sure vmlinux BTF can be
loaded before bpf_object's load phase.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201211215825.3646154-2-andrii@kernel.org
parent b4fe9fec

tools/lib/bpf/libbpf.c

+40 −24
Original line number Diff line number Diff line
@@ -2518,7 +2518,7 @@ static int bpf_object__finalize_btf(struct bpf_object *obj) 
	return 0;

}



static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)

static bool prog_needs_vmlinux_btf(struct bpf_program *prog)

{

	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||

	    prog->type == BPF_PROG_TYPE_LSM)
@@ -2533,37 +2533,43 @@ static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog) 
	return false;

}



static int bpf_object__load_vmlinux_btf(struct bpf_object *obj)

static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)

{

	bool need_vmlinux_btf = false;

	struct bpf_program *prog;

	int i, err;

	int i;



	/* CO-RE relocations need kernel BTF */

	if (obj->btf_ext && obj->btf_ext->core_relo_info.len)

		need_vmlinux_btf = true;

		return true;



	/* Support for typed ksyms needs kernel BTF */

	for (i = 0; i < obj->nr_extern; i++) {

		const struct extern_desc *ext;



		ext = &obj->externs[i];

		if (ext->type == EXT_KSYM && ext->ksym.type_id) {

			need_vmlinux_btf = true;

			break;

		}

		if (ext->type == EXT_KSYM && ext->ksym.type_id)

			return true;

	}



	bpf_object__for_each_program(prog, obj) {

		if (!prog->load)

			continue;

		if (libbpf_prog_needs_vmlinux_btf(prog)) {

			need_vmlinux_btf = true;

			break;

		if (prog_needs_vmlinux_btf(prog))

			return true;

	}



	return false;

}



	if (!need_vmlinux_btf)

static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)

{

	int err;



	/* btf_vmlinux could be loaded earlier */

	if (obj->btf_vmlinux)

		return 0;



	if (!force && !obj_needs_vmlinux_btf(obj))

		return 0;



	obj->btf_vmlinux = libbpf_find_kernel_btf();
@@ -7475,7 +7481,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) 
	}



	err = bpf_object__probe_loading(obj);

	err = err ? : bpf_object__load_vmlinux_btf(obj);

	err = err ? : bpf_object__load_vmlinux_btf(obj, false);

	err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);

	err = err ? : bpf_object__sanitize_and_load_btf(obj);

	err = err ? : bpf_object__sanitize_maps(obj);
@@ -10870,23 +10876,33 @@ int bpf_program__set_attach_target(struct bpf_program *prog, 
				   int attach_prog_fd,

				   const char *attach_func_name)

{

	int btf_id;

	int btf_obj_fd = 0, btf_id = 0, err;



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

		return -EINVAL;



	if (attach_prog_fd)

	if (prog->obj->loaded)

		return -EINVAL;



	if (attach_prog_fd) {

		btf_id = libbpf_find_prog_btf_id(attach_func_name,

						 attach_prog_fd);

	else

		btf_id = libbpf_find_vmlinux_btf_id(attach_func_name,

						    prog->expected_attach_type);



		if (btf_id < 0)

			return btf_id;

	} else {

		/* load btf_vmlinux, if not yet */

		err = bpf_object__load_vmlinux_btf(prog->obj, true);

		if (err)

			return err;

		err = find_kernel_btf_id(prog->obj, attach_func_name,

					 prog->expected_attach_type,

					 &btf_obj_fd, &btf_id);

		if (err)

			return err;

	}



	prog->attach_btf_id = btf_id;

	prog->attach_btf_obj_fd = 0;

	prog->attach_btf_obj_fd = btf_obj_fd;

	prog->attach_prog_fd = attach_prog_fd;

	return 0;

}

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