libbpf: Add libbpf_kallsyms_parse function

Move the kallsyms parsing in internal libbpf_kallsyms_parse
function, so it can be used from other places.

It will be used in following changes.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-8-jolsa@kernel.org

tools/lib/bpf/libbpf.c

@@ -7171,12 +7171,10 @@ static int bpf_object__sanitize_maps(struct bpf_object *obj)
 	return 0;
 }
 
-static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
+int libbpf_kallsyms_parse(kallsyms_cb_t cb, void *ctx)
 {
 	char sym_type, sym_name[500];
 	unsigned long long sym_addr;
-	const struct btf_type *t;
-	struct extern_desc *ext;
 	int ret, err = 0;
 	FILE *f;
 
@@ -7195,33 +7193,49 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
 		if (ret != 3) {
 			pr_warn("failed to read kallsyms entry: %d\n", ret);
 			err = -EINVAL;
-			goto out;
+			break;
+		}
+
+		err = cb(sym_addr, sym_type, sym_name, ctx);
+		if (err)
+			break;
 	}
 
+	fclose(f);
+	return err;
+}
+
+static int kallsyms_cb(unsigned long long sym_addr, char sym_type,
+		       const char *sym_name, void *ctx)
+{
+	struct bpf_object *obj = ctx;
+	const struct btf_type *t;
+	struct extern_desc *ext;
+
 	ext = find_extern_by_name(obj, sym_name);
 	if (!ext || ext->type != EXT_KSYM)
-			continue;
+		return 0;
 
 	t = btf__type_by_id(obj->btf, ext->btf_id);
 	if (!btf_is_var(t))
-			continue;
+		return 0;
 
 	if (ext->is_set && ext->ksym.addr != sym_addr) {
 		pr_warn("extern (ksym) '%s' resolution is ambiguous: 0x%llx or 0x%llx\n",
 			sym_name, ext->ksym.addr, sym_addr);
-			err = -EINVAL;
-			goto out;
+		return -EINVAL;
 	}
 	if (!ext->is_set) {
 		ext->is_set = true;
 		ext->ksym.addr = sym_addr;
 		pr_debug("extern (ksym) %s=0x%llx\n", sym_name, sym_addr);
 	}
-	}
+	return 0;
+}
 
-out:
-	fclose(f);
-	return err;
+static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
+{
+	return libbpf_kallsyms_parse(kallsyms_cb, obj);
 }
 
 static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,

tools/lib/bpf/libbpf_internal.h

@@ -449,6 +449,11 @@ __s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name,
 
 extern enum libbpf_strict_mode libbpf_mode;
 
+typedef int (*kallsyms_cb_t)(unsigned long long sym_addr, char sym_type,
+			     const char *sym_name, void *ctx);
+
+int libbpf_kallsyms_parse(kallsyms_cb_t cb, void *arg);
+
 /* handle direct returned errors */
 static inline int libbpf_err(int ret)
 {