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: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015214.1547069-1-kafai@fb.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e289155510caac22cc191a0c4f8a913f1dbe6c8a..2f5595ae0b84dd568ebf6de5082eaaa2ef59c8ff 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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 @@ out:
        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;