Commit 774e132e authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

libbpf: Refactor codes for finding btf id of a kernel symbol 



This patch refactors code, that finds kernel btf_id by kind
and symbol name, to a new function find_ksym_btf_id().

It also adds a new helper __btf_kind_str() to return
a string by the numeric kind value.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015214.1547069-1-kafai@fb.com
parent 933d1aa3

tools/lib/bpf/libbpf.c

+33 −11
Original line number Diff line number Diff line
@@ -1921,9 +1921,9 @@ resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id) 
	return btf_is_func_proto(t) ? t : NULL;

}



static const char *btf_kind_str(const struct btf_type *t)

static const char *__btf_kind_str(__u16 kind)

{

	switch (btf_kind(t)) {

	switch (kind) {

	case BTF_KIND_UNKN: return "void";

	case BTF_KIND_INT: return "int";

	case BTF_KIND_PTR: return "ptr";
@@ -1945,6 +1945,11 @@ static const char *btf_kind_str(const struct btf_type *t) 
	}

}



static const char *btf_kind_str(const struct btf_type *t)

{

	return __btf_kind_str(btf_kind(t));

}



/*

 * Fetch integer attribute of BTF map definition. Such attributes are

 * represented using a pointer to an array, in which dimensionality of array
@@ -7395,18 +7400,17 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj) 
	return err;

}



static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,

					       struct extern_desc *ext)

static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,

			    __u16 kind, struct btf **res_btf,

			    int *res_btf_fd)

{

	const struct btf_type *targ_var, *targ_type;

	__u32 targ_type_id, local_type_id;

	const char *targ_var_name;

	int i, id, btf_fd, err;

	struct btf *btf;



	btf = obj->btf_vmlinux;

	btf_fd = 0;

	id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);

	id = btf__find_by_name_kind(btf, ksym_name, kind);



	if (id == -ENOENT) {

		err = load_module_btfs(obj);

		if (err)
@@ -7416,17 +7420,35 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj, 
			btf = obj->btf_modules[i].btf;

			/* we assume module BTF FD is always >0 */

			btf_fd = obj->btf_modules[i].fd;

			id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);

			id = btf__find_by_name_kind(btf, ksym_name, kind);

			if (id != -ENOENT)

				break;

		}

	}

	if (id <= 0) {

		pr_warn("extern (var ksym) '%s': failed to find BTF ID in kernel BTF(s).\n",

			ext->name);

		pr_warn("extern (%s ksym) '%s': failed to find BTF ID in kernel BTF(s).\n",

			__btf_kind_str(kind), ksym_name);

		return -ESRCH;

	}



	*res_btf = btf;

	*res_btf_fd = btf_fd;

	return id;

}



static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,

					       struct extern_desc *ext)

{

	const struct btf_type *targ_var, *targ_type;

	__u32 targ_type_id, local_type_id;

	const char *targ_var_name;

	int id, btf_fd = 0, err;

	struct btf *btf = NULL;



	id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &btf_fd);

	if (id < 0)

		return id;



	/* find local type_id */

	local_type_id = ext->ksym.type_id;