libbpf: Refactor bpf_object__resolve_ksyms_btf_id

This patch refactors most of the logic from
bpf_object__resolve_ksyms_btf_id() into a new function
bpf_object__resolve_ksym_var_btf_id().
It is to get ready for a later patch adding
bpf_object__resolve_ksym_func_btf_id() which resolves
a kernel function to the running kernel btf_id.

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/20210325015207.1546749-1-kafai@fb.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index cebb0e8..e289155 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7395,75 +7395,85 @@ out:
        return err;
 }
 
-static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
+static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
+                                              struct extern_desc *ext)
 {
-       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 i, id, btf_fd, err;
        struct btf *btf;
-       int i, j, id, btf_fd, err;
 
-       for (i = 0; i < obj->nr_extern; i++) {
-               const struct btf_type *targ_var, *targ_type;
-               __u32 targ_type_id, local_type_id;
-               const char *targ_var_name;
-               int ret;
+       btf = obj->btf_vmlinux;
+       btf_fd = 0;
+       id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);
+       if (id == -ENOENT) {
+               err = load_module_btfs(obj);
+               if (err)
+                       return err;
 
-               ext = &obj->externs[i];
-               if (ext->type != EXT_KSYM || !ext->ksym.type_id)
-                       continue;
+               for (i = 0; i < obj->btf_module_cnt; i++) {
+                       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);
+                       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);
+               return -ESRCH;
+       }
 
-               btf = obj->btf_vmlinux;
-               btf_fd = 0;
-               id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);
-               if (id == -ENOENT) {
-                       err = load_module_btfs(obj);
-                       if (err)
-                               return err;
+       /* find local type_id */
+       local_type_id = ext->ksym.type_id;
 
-                       for (j = 0; j < obj->btf_module_cnt; j++) {
-                               btf = obj->btf_modules[j].btf;
-                               /* we assume module BTF FD is always >0 */
-                               btf_fd = obj->btf_modules[j].fd;
-                               id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);
-                               if (id != -ENOENT)
-                                       break;
-                       }
-               }
-               if (id <= 0) {
-                       pr_warn("extern (ksym) '%s': failed to find BTF ID in kernel BTF(s).\n",
-                               ext->name);
-                       return -ESRCH;
-               }
+       /* find target type_id */
+       targ_var = btf__type_by_id(btf, id);
+       targ_var_name = btf__name_by_offset(btf, targ_var->name_off);
+       targ_type = skip_mods_and_typedefs(btf, targ_var->type, &targ_type_id);
 
-               /* find local type_id */
-               local_type_id = ext->ksym.type_id;
+       err = bpf_core_types_are_compat(obj->btf, local_type_id,
+                                       btf, targ_type_id);
+       if (err <= 0) {
+               const struct btf_type *local_type;
+               const char *targ_name, *local_name;
 
-               /* find target type_id */
-               targ_var = btf__type_by_id(btf, id);
-               targ_var_name = btf__name_by_offset(btf, targ_var->name_off);
-               targ_type = skip_mods_and_typedefs(btf, targ_var->type, &targ_type_id);
+               local_type = btf__type_by_id(obj->btf, local_type_id);
+               local_name = btf__name_by_offset(obj->btf, local_type->name_off);
+               targ_name = btf__name_by_offset(btf, targ_type->name_off);
 
-               ret = bpf_core_types_are_compat(obj->btf, local_type_id,
-                                               btf, targ_type_id);
-               if (ret <= 0) {
-                       const struct btf_type *local_type;
-                       const char *targ_name, *local_name;
+               pr_warn("extern (var ksym) '%s': incompatible types, expected [%d] %s %s, but kernel has [%d] %s %s\n",
+                       ext->name, local_type_id,
+                       btf_kind_str(local_type), local_name, targ_type_id,
+                       btf_kind_str(targ_type), targ_name);
+               return -EINVAL;
+       }
 
-                       local_type = btf__type_by_id(obj->btf, local_type_id);
-                       local_name = btf__name_by_offset(obj->btf, local_type->name_off);
-                       targ_name = btf__name_by_offset(btf, targ_type->name_off);
+       ext->is_set = true;
+       ext->ksym.kernel_btf_obj_fd = btf_fd;
+       ext->ksym.kernel_btf_id = id;
+       pr_debug("extern (var ksym) '%s': resolved to [%d] %s %s\n",
+                ext->name, id, btf_kind_str(targ_var), targ_var_name);
 
-                       pr_warn("extern (ksym) '%s': incompatible types, expected [%d] %s %s, but kernel has [%d] %s %s\n",
-                               ext->name, local_type_id,
-                               btf_kind_str(local_type), local_name, targ_type_id,
-                               btf_kind_str(targ_type), targ_name);
-                       return -EINVAL;
-               }
+       return 0;
+}
+
+static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
+{
+       struct extern_desc *ext;
+       int i, err;
+
+       for (i = 0; i < obj->nr_extern; i++) {
+               ext = &obj->externs[i];
+               if (ext->type != EXT_KSYM || !ext->ksym.type_id)
+                       continue;
 
-               ext->is_set = true;
-               ext->ksym.kernel_btf_obj_fd = btf_fd;
-               ext->ksym.kernel_btf_id = id;
-               pr_debug("extern (ksym) '%s': resolved to [%d] %s %s\n",
-                        ext->name, id, btf_kind_str(targ_var), targ_var_name);
+               err = bpf_object__resolve_ksym_var_btf_id(obj, ext);
+               if (err)
+                       return err;
        }
        return 0;
 }