[PATCH v2 bpf-next 08/14] libbpf: Refactor codes for finding btf id of a kernel symbol

[Martin KaFai Lau]

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.

Acked-by: Andrii Nakryiko <and...@kernel.org>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
 tools/lib/bpf/libbpf.c | 44 +++++++++++++++++++++++++++++++-----------
 1 file changed, 33 insertions(+), 11 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 57123a2179b4..5a0cae981784 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1920,9 +1920,9 @@ 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";
@@ -1944,6 +1944,11 @@ 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
@@ -7394,18 +7399,17 @@ 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)
@@ -7415,17 +7419,35 @@ 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;
 
-- 
2.30.2