1 files changed, 42 insertions, 54 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8c3f236c86e4..8802e06c5569 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1461,15 +1461,12 @@ static int find_elf_sec_sz(const struct bpf_object *obj, const char *name, __u32
 	return -ENOENT;
 }
 
-static int find_elf_var_offset(const struct bpf_object *obj, const char *name, __u32 *off)
+static Elf64_Sym *find_elf_var_sym(const struct bpf_object *obj, const char *name)
 {
 	Elf_Data *symbols = obj->efile.symbols;
 	const char *sname;
 	size_t si;
 
-	if (!name || !off)
-		return -EINVAL;
-
 	for (si = 0; si < symbols->d_size / sizeof(Elf64_Sym); si++) {
 		Elf64_Sym *sym = elf_sym_by_idx(obj, si);
 
@@ -1483,15 +1480,13 @@ static int find_elf_var_offset(const struct bpf_object *obj, const char *name, _
 		sname = elf_sym_str(obj, sym->st_name);
 		if (!sname) {
 			pr_warn("failed to get sym name string for var %s\n", name);
-			return -EIO;
-		}
-		if (strcmp(name, sname) == 0) {
-			*off = sym->st_value;
-			return 0;
+			return ERR_PTR(-EIO);
 		}
+		if (strcmp(name, sname) == 0)
+			return sym;
 	}
 
-	return -ENOENT;
+	return ERR_PTR(-ENOENT);
 }
 
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
@@ -2850,57 +2845,63 @@ static int compare_vsi_off(const void *_a, const void *_b)
 static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
 			     struct btf_type *t)
 {
-	__u32 size = 0, off = 0, i, vars = btf_vlen(t);
-	const char *name = btf__name_by_offset(btf, t->name_off);
-	const struct btf_type *t_var;
+	__u32 size = 0, i, vars = btf_vlen(t);
+	const char *sec_name = btf__name_by_offset(btf, t->name_off);
 	struct btf_var_secinfo *vsi;
-	const struct btf_var *var;
-	int ret;
+	int err;
 
-	if (!name) {
+	if (!sec_name) {
 		pr_debug("No name found in string section for DATASEC kind.\n");
 		return -ENOENT;
 	}
 
-	/* .extern datasec size and var offsets were set correctly during
-	 * extern collection step, so just skip straight to sorting variables
+	/* extern-backing datasecs (.ksyms, .kconfig) have their size and
+	 * variable offsets set at the previous step, so we skip any fixups
+	 * for such sections
 	 */
 	if (t->size)
 		goto sort_vars;
 
-	ret = find_elf_sec_sz(obj, name, &size);
-	if (ret || !size) {
-		pr_debug("Invalid size for section %s: %u bytes\n", name, size);
+	err = find_elf_sec_sz(obj, sec_name, &size);
+	if (err || !size) {
+		pr_debug("sec '%s': failed to determine size from ELF: size %u, err %d\n",
+			 sec_name, size, err);
 		return -ENOENT;
 	}
 
 	t->size = size;
 
 	for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
+		const struct btf_type *t_var;
+		struct btf_var *var;
+		const char *var_name;
+		Elf64_Sym *sym;
+
 		t_var = btf__type_by_id(btf, vsi->type);
 		if (!t_var || !btf_is_var(t_var)) {
-			pr_debug("Non-VAR type seen in section %s\n", name);
+			pr_debug("sec '%s': unexpected non-VAR type found\n", sec_name);
 			return -EINVAL;
 		}
 
 		var = btf_var(t_var);
-		if (var->linkage == BTF_VAR_STATIC)
+		if (var->linkage == BTF_VAR_STATIC || var->linkage == BTF_VAR_GLOBAL_EXTERN)
 			continue;
 
-		name = btf__name_by_offset(btf, t_var->name_off);
-		if (!name) {
-			pr_debug("No name found in string section for VAR kind\n");
+		var_name = btf__name_by_offset(btf, t_var->name_off);
+		if (!var_name) {
+			pr_debug("sec '%s': failed to find name of DATASEC's member #%d\n",
+				 sec_name, i);
 			return -ENOENT;
 		}
 
-		ret = find_elf_var_offset(obj, name, &off);
-		if (ret) {
-			pr_debug("No offset found in symbol table for VAR %s\n",
-				 name);
+		sym = find_elf_var_sym(obj, var_name);
+		if (IS_ERR(sym)) {
+			pr_debug("sec '%s': failed to find ELF symbol for VAR '%s'\n",
+				 sec_name, var_name);
 			return -ENOENT;
 		}
 
-		vsi->offset = off;
+		vsi->offset = sym->st_value;
 	}
 
 sort_vars:
@@ -2908,13 +2909,16 @@ sort_vars:
 	return 0;
 }
 
-static int btf_finalize_data(struct bpf_object *obj, struct btf *btf)
+static int bpf_object_fixup_btf(struct bpf_object *obj)
 {
-	int err = 0;
-	__u32 i, n = btf__type_cnt(btf);
+	int i, n, err = 0;
 
+	if (!obj->btf)
+		return 0;
+
+	n = btf__type_cnt(obj->btf);
 	for (i = 1; i < n; i++) {
-		struct btf_type *t = btf_type_by_id(btf, i);
+		struct btf_type *t = btf_type_by_id(obj->btf, i);
 
 		/* Loader needs to fix up some of the things compiler
 		 * couldn't get its hands on while emitting BTF. This
@@ -2922,28 +2926,12 @@ static int btf_finalize_data(struct bpf_object *obj, struct btf *btf)
 		 * the info from the ELF itself for this purpose.
 		 */
 		if (btf_is_datasec(t)) {
-			err = btf_fixup_datasec(obj, btf, t);
+			err = btf_fixup_datasec(obj, obj->btf, t);
 			if (err)
-				break;
+				return err;
 		}
 	}
 
-	return libbpf_err(err);
-}
-
-static int bpf_object__finalize_btf(struct bpf_object *obj)
-{
-	int err;
-
-	if (!obj->btf)
-		return 0;
-
-	err = btf_finalize_data(obj, obj->btf);
-	if (err) {
-		pr_warn("Error finalizing %s: %d.\n", BTF_ELF_SEC, err);
-		return err;
-	}
-
 	return 0;
 }
 
@@ -7233,7 +7221,7 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
 	err = err ? : bpf_object__check_endianness(obj);
 	err = err ? : bpf_object__elf_collect(obj);
 	err = err ? : bpf_object__collect_externs(obj);
-	err = err ? : bpf_object__finalize_btf(obj);
+	err = err ? : bpf_object_fixup_btf(obj);
 	err = err ? : bpf_object__init_maps(obj, opts);
 	err = err ? : bpf_object_init_progs(obj, opts);
 	err = err ? : bpf_object__collect_relos(obj);