diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 62953bbf68b4..385d5c955cf3 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -71,7 +71,9 @@ static const char *btf_var_linkage_str(__u32 linkage)
 	case BTF_VAR_STATIC:
 		return "static";
 	case BTF_VAR_GLOBAL_ALLOCATED:
-		return "global-alloc";
+		return "global";
+	case BTF_VAR_GLOBAL_EXTERN:
+		return "extern";
 	default:
 		return "(unknown)";
 	}
@@ -98,26 +100,28 @@ static const char *btf_str(const struct btf *btf, __u32 off)
 	return btf__name_by_offset(btf, off) ? : "(invalid)";
 }
 
+static int btf_kind_safe(int kind)
+{
+	return kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
+}
+
 static int dump_btf_type(const struct btf *btf, __u32 id,
 			 const struct btf_type *t)
 {
 	json_writer_t *w = json_wtr;
-	int kind, safe_kind;
-
-	kind = BTF_INFO_KIND(t->info);
-	safe_kind = kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
+	int kind = btf_kind(t);
 
 	if (json_output) {
 		jsonw_start_object(w);
 		jsonw_uint_field(w, "id", id);
-		jsonw_string_field(w, "kind", btf_kind_str[safe_kind]);
+		jsonw_string_field(w, "kind", btf_kind_str[btf_kind_safe(kind)]);
 		jsonw_string_field(w, "name", btf_str(btf, t->name_off));
 	} else {
-		printf("[%u] %s '%s'", id, btf_kind_str[safe_kind],
+		printf("[%u] %s '%s'", id, btf_kind_str[btf_kind_safe(kind)],
 		       btf_str(btf, t->name_off));
 	}
 
-	switch (BTF_INFO_KIND(t->info)) {
+	switch (kind) {
 	case BTF_KIND_INT: {
 		__u32 v = *(__u32 *)(t + 1);
 		const char *enc;
@@ -300,7 +304,8 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
 		break;
 	}
 	case BTF_KIND_DATASEC: {
-		const struct btf_var_secinfo *v = (const void *)(t+1);
+		const struct btf_var_secinfo *v = (const void *)(t + 1);
+		const struct btf_type *vt;
 		__u16 vlen = BTF_INFO_VLEN(t->info);
 		int i;
 
@@ -322,6 +327,13 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
 			} else {
 				printf("\n\ttype_id=%u offset=%u size=%u",
 				       v->type, v->offset, v->size);
+
+				if (v->type <= btf__get_nr_types(btf)) {
+					vt = btf__type_by_id(btf, v->type);
+					printf(" (%s '%s')",
+					       btf_kind_str[btf_kind_safe(btf_kind(vt))],
+					       btf_str(btf, vt->name_off));
+				}
 			}
 		}
 		if (json_output)
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index b904128626c2..9720dc0b4605 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -25,9 +25,16 @@
 /*
  * Helper macro to place programs, maps, license in
  * different sections in elf_bpf file. Section names
- * are interpreted by elf_bpf loader
+ * are interpreted by libbpf depending on the context (BPF programs, BPF maps,
+ * extern variables, etc).
+ * To allow use of SEC() with externs (e.g., for extern .maps declarations),
+ * make sure __attribute__((unused)) doesn't trigger compilation warning.
  */
-#define SEC(NAME) __attribute__((section(NAME), used))
+#define SEC(name) \
+	_Pragma("GCC diagnostic push")					    \
+	_Pragma("GCC diagnostic ignored \"-Wignored-attributes\"")	    \
+	__attribute__((section(name), used))				    \
+	_Pragma("GCC diagnostic pop")					    \
 
 /* Avoid 'linux/stddef.h' definition of '__always_inline'. */
 #undef __always_inline
@@ -40,6 +47,14 @@
 #define __weak __attribute__((weak))
 #endif
 
+/*
+ * Use __hidden attribute to mark a non-static BPF subprogram effectively
+ * static for BPF verifier's verification algorithm purposes, allowing more
+ * extensive and permissive BPF verification process, taking into account
+ * subprogram's caller context.
+ */
+#define __hidden __attribute__((visibility("hidden")))
+
 /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include
  * any system-level headers (such as stddef.h, linux/version.h, etc), and
  * commonly-used macros like NULL and KERNEL_VERSION aren't available through
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d30e67e7e1e5..d57e13a13798 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1605,11 +1605,6 @@ static void *btf_add_type_mem(struct btf *btf, size_t add_sz)
 			      btf->hdr->type_len, UINT_MAX, add_sz);
 }
 
-static __u32 btf_type_info(int kind, int vlen, int kflag)
-{
-	return (kflag << 31) | (kind << 24) | vlen;
-}
-
 static void btf_type_inc_vlen(struct btf_type *t)
 {
 	t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t));
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9cc2d45b0080..a1cddd17af7d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -69,8 +69,7 @@
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
-static const struct btf_type *
-skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);
+static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);
 
 static int __base_pr(enum libbpf_print_level level, const char *format,
 		     va_list args)
@@ -274,6 +273,7 @@ struct bpf_program {
 	bpf_program_clear_priv_t clear_priv;
 
 	bool load;
+	bool mark_btf_static;
 	enum bpf_prog_type type;
 	enum bpf_attach_type expected_attach_type;
 	int prog_ifindex;
@@ -500,8 +500,6 @@ static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name);
 static int elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn, GElf_Shdr *hdr);
 static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn);
 static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn);
-static int elf_sym_by_sec_off(const struct bpf_object *obj, size_t sec_idx,
-			      size_t off, __u32 sym_type, GElf_Sym *sym);
 
 void bpf_program__unload(struct bpf_program *prog)
 {
@@ -642,25 +640,29 @@ static int
 bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
 			 const char *sec_name, int sec_idx)
 {
+	Elf_Data *symbols = obj->efile.symbols;
 	struct bpf_program *prog, *progs;
 	void *data = sec_data->d_buf;
-	size_t sec_sz = sec_data->d_size, sec_off, prog_sz;
-	int nr_progs, err;
+	size_t sec_sz = sec_data->d_size, sec_off, prog_sz, nr_syms;
+	int nr_progs, err, i;
 	const char *name;
 	GElf_Sym sym;
 
 	progs = obj->programs;
 	nr_progs = obj->nr_programs;
+	nr_syms = symbols->d_size / sizeof(GElf_Sym);
 	sec_off = 0;
 
-	while (sec_off < sec_sz) {
-		if (elf_sym_by_sec_off(obj, sec_idx, sec_off, STT_FUNC, &sym)) {
-			pr_warn("sec '%s': failed to find program symbol at offset %zu\n",
-				sec_name, sec_off);
-			return -LIBBPF_ERRNO__FORMAT;
-		}
+	for (i = 0; i < nr_syms; i++) {
+		if (!gelf_getsym(symbols, i, &sym))
+			continue;
+		if (sym.st_shndx != sec_idx)
+			continue;
+		if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
+			continue;
 
 		prog_sz = sym.st_size;
+		sec_off = sym.st_value;
 
 		name = elf_sym_str(obj, sym.st_name);
 		if (!name) {
@@ -698,10 +700,17 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
 		if (err)
 			return err;
 
+		/* if function is a global/weak symbol, but has hidden
+		 * visibility (STV_HIDDEN), mark its BTF FUNC as static to
+		 * enable more permissive BPF verification mode with more
+		 * outside context available to BPF verifier
+		 */
+		if (GELF_ST_BIND(sym.st_info) != STB_LOCAL
+		    && GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN)
+			prog->mark_btf_static = true;
+
 		nr_progs++;
 		obj->nr_programs = nr_progs;
-
-		sec_off += prog_sz;
 	}
 
 	return 0;
@@ -1895,7 +1904,7 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict)
 	return 0;
 }
 
-static const struct btf_type *
+const struct btf_type *
 skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
 {
 	const struct btf_type *t = btf__type_by_id(btf, id);
@@ -1950,16 +1959,11 @@ static const char *__btf_kind_str(__u16 kind)
 	}
 }
 
-static const char *btf_kind_str(const struct btf_type *t)
+const char *btf_kind_str(const struct btf_type *t)
 {
 	return __btf_kind_str(btf_kind(t));
 }
 
-static enum btf_func_linkage btf_func_linkage(const struct btf_type *t)
-{
-	return (enum btf_func_linkage)BTF_INFO_VLEN(t->info);
-}
-
 /*
  * Fetch integer attribute of BTF map definition. Such attributes are
  * represented using a pointer to an array, in which dimensionality of array
@@ -2014,255 +2018,262 @@ static int build_map_pin_path(struct bpf_map *map, const char *path)
 	return bpf_map__set_pin_path(map, buf);
 }
 
-
-static int parse_btf_map_def(struct bpf_object *obj,
-			     struct bpf_map *map,
-			     const struct btf_type *def,
-			     bool strict, bool is_inner,
-			     const char *pin_root_path)
+int parse_btf_map_def(const char *map_name, struct btf *btf,
+		      const struct btf_type *def_t, bool strict,
+		      struct btf_map_def *map_def, struct btf_map_def *inner_def)
 {
 	const struct btf_type *t;
 	const struct btf_member *m;
+	bool is_inner = inner_def == NULL;
 	int vlen, i;
 
-	vlen = btf_vlen(def);
-	m = btf_members(def);
+	vlen = btf_vlen(def_t);
+	m = btf_members(def_t);
 	for (i = 0; i < vlen; i++, m++) {
-		const char *name = btf__name_by_offset(obj->btf, m->name_off);
+		const char *name = btf__name_by_offset(btf, m->name_off);
 
 		if (!name) {
-			pr_warn("map '%s': invalid field #%d.\n", map->name, i);
+			pr_warn("map '%s': invalid field #%d.\n", map_name, i);
 			return -EINVAL;
 		}
 		if (strcmp(name, "type") == 0) {
-			if (!get_map_field_int(map->name, obj->btf, m,
-					       &map->def.type))
+			if (!get_map_field_int(map_name, btf, m, &map_def->map_type))
 				return -EINVAL;
-			pr_debug("map '%s': found type = %u.\n",
-				 map->name, map->def.type);
+			map_def->parts |= MAP_DEF_MAP_TYPE;
 		} else if (strcmp(name, "max_entries") == 0) {
-			if (!get_map_field_int(map->name, obj->btf, m,
-					       &map->def.max_entries))
+			if (!get_map_field_int(map_name, btf, m, &map_def->max_entries))
 				return -EINVAL;
-			pr_debug("map '%s': found max_entries = %u.\n",
-				 map->name, map->def.max_entries);
+			map_def->parts |= MAP_DEF_MAX_ENTRIES;
 		} else if (strcmp(name, "map_flags") == 0) {
-			if (!get_map_field_int(map->name, obj->btf, m,
-					       &map->def.map_flags))
+			if (!get_map_field_int(map_name, btf, m, &map_def->map_flags))
 				return -EINVAL;
-			pr_debug("map '%s': found map_flags = %u.\n",
-				 map->name, map->def.map_flags);
+			map_def->parts |= MAP_DEF_MAP_FLAGS;
 		} else if (strcmp(name, "numa_node") == 0) {
-			if (!get_map_field_int(map->name, obj->btf, m, &map->numa_node))
+			if (!get_map_field_int(map_name, btf, m, &map_def->numa_node))
 				return -EINVAL;
-			pr_debug("map '%s': found numa_node = %u.\n", map->name, map->numa_node);
+			map_def->parts |= MAP_DEF_NUMA_NODE;
 		} else if (strcmp(name, "key_size") == 0) {
 			__u32 sz;
 
-			if (!get_map_field_int(map->name, obj->btf, m, &sz))
+			if (!get_map_field_int(map_name, btf, m, &sz))
 				return -EINVAL;
-			pr_debug("map '%s': found key_size = %u.\n",
-				 map->name, sz);
-			if (map->def.key_size && map->def.key_size != sz) {
+			if (map_def->key_size && map_def->key_size != sz) {
 				pr_warn("map '%s': conflicting key size %u != %u.\n",
-					map->name, map->def.key_size, sz);
+					map_name, map_def->key_size, sz);
 				return -EINVAL;
 			}
-			map->def.key_size = sz;
+			map_def->key_size = sz;
+			map_def->parts |= MAP_DEF_KEY_SIZE;
 		} else if (strcmp(name, "key") == 0) {
 			__s64 sz;
 
-			t = btf__type_by_id(obj->btf, m->type);
+			t = btf__type_by_id(btf, m->type);
 			if (!t) {
 				pr_warn("map '%s': key type [%d] not found.\n",
-					map->name, m->type);
+					map_name, m->type);
 				return -EINVAL;
 			}
 			if (!btf_is_ptr(t)) {
 				pr_warn("map '%s': key spec is not PTR: %s.\n",
-					map->name, btf_kind_str(t));
+					map_name, btf_kind_str(t));
 				return -EINVAL;
 			}
-			sz = btf__resolve_size(obj->btf, t->type);
+			sz = btf__resolve_size(btf, t->type);
 			if (sz < 0) {
 				pr_warn("map '%s': can't determine key size for type [%u]: %zd.\n",
-					map->name, t->type, (ssize_t)sz);
+					map_name, t->type, (ssize_t)sz);
 				return sz;
 			}
-			pr_debug("map '%s': found key [%u], sz = %zd.\n",
-				 map->name, t->type, (ssize_t)sz);
-			if (map->def.key_size && map->def.key_size != sz) {
+			if (map_def->key_size && map_def->key_size != sz) {
 				pr_warn("map '%s': conflicting key size %u != %zd.\n",
-					map->name, map->def.key_size, (ssize_t)sz);
+					map_name, map_def->key_size, (ssize_t)sz);
 				return -EINVAL;
 			}
-			map->def.key_size = sz;
-			map->btf_key_type_id = t->type;
+			map_def->key_size = sz;
+			map_def->key_type_id = t->type;
+			map_def->parts |= MAP_DEF_KEY_SIZE | MAP_DEF_KEY_TYPE;
 		} else if (strcmp(name, "value_size") == 0) {
 			__u32 sz;
 
-			if (!get_map_field_int(map->name, obj->btf, m, &sz))
+			if (!get_map_field_int(map_name, btf, m, &sz))
 				return -EINVAL;
-			pr_debug("map '%s': found value_size = %u.\n",
-				 map->name, sz);
-			if (map->def.value_size && map->def.value_size != sz) {
+			if (map_def->value_size && map_def->value_size != sz) {
 				pr_warn("map '%s': conflicting value size %u != %u.\n",
-					map->name, map->def.value_size, sz);
+					map_name, map_def->value_size, sz);
 				return -EINVAL;
 			}
-			map->def.value_size = sz;
+			map_def->value_size = sz;
+			map_def->parts |= MAP_DEF_VALUE_SIZE;
 		} else if (strcmp(name, "value") == 0) {
 			__s64 sz;
 
-			t = btf__type_by_id(obj->btf, m->type);
+			t = btf__type_by_id(btf, m->type);
 			if (!t) {
 				pr_warn("map '%s': value type [%d] not found.\n",
-					map->name, m->type);
+					map_name, m->type);
 				return -EINVAL;
 			}
 			if (!btf_is_ptr(t)) {
 				pr_warn("map '%s': value spec is not PTR: %s.\n",
-					map->name, btf_kind_str(t));
+					map_name, btf_kind_str(t));
 				return -EINVAL;
 			}
-			sz = btf__resolve_size(obj->btf, t->type);
+			sz = btf__resolve_size(btf, t->type);
 			if (sz < 0) {
 				pr_warn("map '%s': can't determine value size for type [%u]: %zd.\n",
-					map->name, t->type, (ssize_t)sz);
+					map_name, t->type, (ssize_t)sz);
 				return sz;
 			}
-			pr_debug("map '%s': found value [%u], sz = %zd.\n",
-				 map->name, t->type, (ssize_t)sz);
-			if (map->def.value_size && map->def.value_size != sz) {
+			if (map_def->value_size && map_def->value_size != sz) {
 				pr_warn("map '%s': conflicting value size %u != %zd.\n",
-					map->name, map->def.value_size, (ssize_t)sz);
+					map_name, map_def->value_size, (ssize_t)sz);
 				return -EINVAL;
 			}
-			map->def.value_size = sz;
-			map->btf_value_type_id = t->type;
+			map_def->value_size = sz;
+			map_def->value_type_id = t->type;
+			map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;
 		}
 		else if (strcmp(name, "values") == 0) {
+			char inner_map_name[128];
 			int err;
 
 			if (is_inner) {
 				pr_warn("map '%s': multi-level inner maps not supported.\n",
-					map->name);
+					map_name);
 				return -ENOTSUP;
 			}
 			if (i != vlen - 1) {
 				pr_warn("map '%s': '%s' member should be last.\n",
-					map->name, name);
+					map_name, name);
 				return -EINVAL;
 			}
-			if (!bpf_map_type__is_map_in_map(map->def.type)) {
+			if (!bpf_map_type__is_map_in_map(map_def->map_type)) {
 				pr_warn("map '%s': should be map-in-map.\n",
-					map->name);
+					map_name);
 				return -ENOTSUP;
 			}
-			if (map->def.value_size && map->def.value_size != 4) {
+			if (map_def->value_size && map_def->value_size != 4) {
 				pr_warn("map '%s': conflicting value size %u != 4.\n",
-					map->name, map->def.value_size);
+					map_name, map_def->value_size);
 				return -EINVAL;
 			}
-			map->def.value_size = 4;
-			t = btf__type_by_id(obj->btf, m->type);
+			map_def->value_size = 4;
+			t = btf__type_by_id(btf, m->type);
 			if (!t) {
 				pr_warn("map '%s': map-in-map inner type [%d] not found.\n",
-					map->name, m->type);
+					map_name, m->type);
 				return -EINVAL;
 			}
 			if (!btf_is_array(t) || btf_array(t)->nelems) {
 				pr_warn("map '%s': map-in-map inner spec is not a zero-sized array.\n",
-					map->name);
+					map_name);
 				return -EINVAL;
 			}
-			t = skip_mods_and_typedefs(obj->btf, btf_array(t)->type,
-						   NULL);
+			t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);
 			if (!btf_is_ptr(t)) {
 				pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
-					map->name, btf_kind_str(t));
+					map_name, btf_kind_str(t));
 				return -EINVAL;
 			}
-			t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
+			t = skip_mods_and_typedefs(btf, t->type, NULL);
 			if (!btf_is_struct(t)) {
 				pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
-					map->name, btf_kind_str(t));
+					map_name, btf_kind_str(t));
 				return -EINVAL;
 			}
 
-			map->inner_map = calloc(1, sizeof(*map->inner_map));
-			if (!map->inner_map)
-				return -ENOMEM;
-			map->inner_map->fd = -1;
-			map->inner_map->sec_idx = obj->efile.btf_maps_shndx;
-			map->inner_map->name = malloc(strlen(map->name) +
-						      sizeof(".inner") + 1);
-			if (!map->inner_map->name)
-				return -ENOMEM;
-			sprintf(map->inner_map->name, "%s.inner", map->name);
-
-			err = parse_btf_map_def(obj, map->inner_map, t, strict,
-						true /* is_inner */, NULL);
+			snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", map_name);
+			err = parse_btf_map_def(inner_map_name, btf, t, strict, inner_def, NULL);
 			if (err)
 				return err;
+
+			map_def->parts |= MAP_DEF_INNER_MAP;
 		} else if (strcmp(name, "pinning") == 0) {
 			__u32 val;
-			int err;
 
 			if (is_inner) {
-				pr_debug("map '%s': inner def can't be pinned.\n",
-					 map->name);
+				pr_warn("map '%s': inner def can't be pinned.\n", map_name);
 				return -EINVAL;
 			}
-			if (!get_map_field_int(map->name, obj->btf, m, &val))
+			if (!get_map_field_int(map_name, btf, m, &val))
 				return -EINVAL;
-			pr_debug("map '%s': found pinning = %u.\n",
-				 map->name, val);
-
-			if (val != LIBBPF_PIN_NONE &&
-			    val != LIBBPF_PIN_BY_NAME) {
+			if (val != LIBBPF_PIN_NONE && val != LIBBPF_PIN_BY_NAME) {
 				pr_warn("map '%s': invalid pinning value %u.\n",
-					map->name, val);
+					map_name, val);
 				return -EINVAL;
 			}
-			if (val == LIBBPF_PIN_BY_NAME) {
-				err = build_map_pin_path(map, pin_root_path);
-				if (err) {
-					pr_warn("map '%s': couldn't build pin path.\n",
-						map->name);
-					return err;
-				}
-			}
+			map_def->pinning = val;
+			map_def->parts |= MAP_DEF_PINNING;
 		} else {
 			if (strict) {
-				pr_warn("map '%s': unknown field '%s'.\n",
-					map->name, name);
+				pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
 				return -ENOTSUP;
 			}
-			pr_debug("map '%s': ignoring unknown field '%s'.\n",
-				 map->name, name);
+			pr_debug("map '%s': ignoring unknown field '%s'.\n", map_name, name);
 		}
 	}
 
-	if (map->def.type == BPF_MAP_TYPE_UNSPEC) {
-		pr_warn("map '%s': map type isn't specified.\n", map->name);
+	if (map_def->map_type == BPF_MAP_TYPE_UNSPEC) {
+		pr_warn("map '%s': map type isn't specified.\n", map_name);
 		return -EINVAL;
 	}
 
 	return 0;
 }
 
+static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
+{
+	map->def.type = def->map_type;
+	map->def.key_size = def->key_size;
+	map->def.value_size = def->value_size;
+	map->def.max_entries = def->max_entries;
+	map->def.map_flags = def->map_flags;
+
+	map->numa_node = def->numa_node;
+	map->btf_key_type_id = def->key_type_id;
+	map->btf_value_type_id = def->value_type_id;
+
+	if (def->parts & MAP_DEF_MAP_TYPE)
+		pr_debug("map '%s': found type = %u.\n", map->name, def->map_type);
+
+	if (def->parts & MAP_DEF_KEY_TYPE)
+		pr_debug("map '%s': found key [%u], sz = %u.\n",
+			 map->name, def->key_type_id, def->key_size);
+	else if (def->parts & MAP_DEF_KEY_SIZE)
+		pr_debug("map '%s': found key_size = %u.\n", map->name, def->key_size);
+
+	if (def->parts & MAP_DEF_VALUE_TYPE)
+		pr_debug("map '%s': found value [%u], sz = %u.\n",
+			 map->name, def->value_type_id, def->value_size);
+	else if (def->parts & MAP_DEF_VALUE_SIZE)
+		pr_debug("map '%s': found value_size = %u.\n", map->name, def->value_size);
+
+	if (def->parts & MAP_DEF_MAX_ENTRIES)
+		pr_debug("map '%s': found max_entries = %u.\n", map->name, def->max_entries);
+	if (def->parts & MAP_DEF_MAP_FLAGS)
+		pr_debug("map '%s': found map_flags = %u.\n", map->name, def->map_flags);
+	if (def->parts & MAP_DEF_PINNING)
+		pr_debug("map '%s': found pinning = %u.\n", map->name, def->pinning);
+	if (def->parts & MAP_DEF_NUMA_NODE)
+		pr_debug("map '%s': found numa_node = %u.\n", map->name, def->numa_node);
+
+	if (def->parts & MAP_DEF_INNER_MAP)
+		pr_debug("map '%s': found inner map definition.\n", map->name);
+}
+
 static int bpf_object__init_user_btf_map(struct bpf_object *obj,
 					 const struct btf_type *sec,
 					 int var_idx, int sec_idx,
 					 const Elf_Data *data, bool strict,
 					 const char *pin_root_path)
 {
+	struct btf_map_def map_def = {}, inner_def = {};
 	const struct btf_type *var, *def;
 	const struct btf_var_secinfo *vi;
 	const struct btf_var *var_extra;
 	const char *map_name;
 	struct bpf_map *map;
+	int err;
 
 	vi = btf_var_secinfos(sec) + var_idx;
 	var = btf__type_by_id(obj->btf, vi->type);
@@ -2316,7 +2327,35 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
 	pr_debug("map '%s': at sec_idx %d, offset %zu.\n",
 		 map_name, map->sec_idx, map->sec_offset);
 
-	return parse_btf_map_def(obj, map, def, strict, false, pin_root_path);
+	err = parse_btf_map_def(map->name, obj->btf, def, strict, &map_def, &inner_def);
+	if (err)
+		return err;
+
+	fill_map_from_def(map, &map_def);
+
+	if (map_def.pinning == LIBBPF_PIN_BY_NAME) {
+		err = build_map_pin_path(map, pin_root_path);
+		if (err) {
+			pr_warn("map '%s': couldn't build pin path.\n", map->name);
+			return err;
+		}
+	}
+
+	if (map_def.parts & MAP_DEF_INNER_MAP) {
+		map->inner_map = calloc(1, sizeof(*map->inner_map));
+		if (!map->inner_map)
+			return -ENOMEM;
+		map->inner_map->fd = -1;
+		map->inner_map->sec_idx = sec_idx;
+		map->inner_map->name = malloc(strlen(map_name) + sizeof(".inner") + 1);
+		if (!map->inner_map->name)
+			return -ENOMEM;
+		sprintf(map->inner_map->name, "%s.inner", map_name);
+
+		fill_map_from_def(map->inner_map, &inner_def);
+	}
+
+	return 0;
 }
 
 static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
@@ -2618,7 +2657,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 {
 	struct btf *kern_btf = obj->btf;
 	bool btf_mandatory, sanitize;
-	int err = 0;
+	int i, err = 0;
 
 	if (!obj->btf)
 		return 0;
@@ -2632,6 +2671,38 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 		return 0;
 	}
 
+	/* Even though some subprogs are global/weak, user might prefer more
+	 * permissive BPF verification process that BPF verifier performs for
+	 * static functions, taking into account more context from the caller
+	 * functions. In such case, they need to mark such subprogs with
+	 * __attribute__((visibility("hidden"))) and libbpf will adjust
+	 * corresponding FUNC BTF type to be marked as static and trigger more
+	 * involved BPF verification process.
+	 */
+	for (i = 0; i < obj->nr_programs; i++) {
+		struct bpf_program *prog = &obj->programs[i];
+		struct btf_type *t;
+		const char *name;
+		int j, n;
+
+		if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))
+			continue;
+
+		n = btf__get_nr_types(obj->btf);
+		for (j = 1; j <= n; j++) {
+			t = btf_type_by_id(obj->btf, j);
+			if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)
+				continue;
+
+			name = btf__str_by_offset(obj->btf, t->name_off);
+			if (strcmp(name, prog->name) != 0)
+				continue;
+
+			t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);
+			break;
+		}
+	}
+
 	sanitize = btf_needs_sanitization(obj);
 	if (sanitize) {
 		const void *raw_data;
@@ -2782,26 +2853,6 @@ static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn)
 	return data;
 }
 
-static int elf_sym_by_sec_off(const struct bpf_object *obj, size_t sec_idx,
-			      size_t off, __u32 sym_type, GElf_Sym *sym)
-{
-	Elf_Data *symbols = obj->efile.symbols;
-	size_t n = symbols->d_size / sizeof(GElf_Sym);
-	int i;
-
-	for (i = 0; i < n; i++) {
-		if (!gelf_getsym(symbols, i, sym))
-			continue;
-		if (sym->st_shndx != sec_idx || sym->st_value != off)
-			continue;
-		if (GELF_ST_TYPE(sym->st_info) != sym_type)
-			continue;
-		return 0;
-	}
-
-	return -ENOENT;
-}
-
 static bool is_sec_name_dwarf(const char *name)
 {
 	/* approximation, but the actual list is too long */
@@ -3680,11 +3731,16 @@ bpf_object__collect_prog_relos(struct bpf_object *obj, GElf_Shdr *shdr, Elf_Data
 	int err, i, nrels;
 	const char *sym_name;
 	__u32 insn_idx;
+	Elf_Scn *scn;
+	Elf_Data *scn_data;
 	GElf_Sym sym;
 	GElf_Rel rel;
 
+	scn = elf_sec_by_idx(obj, sec_idx);
+	scn_data = elf_sec_data(obj, scn);
+
 	relo_sec_name = elf_sec_str(obj, shdr->sh_name);
-	sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
+	sec_name = elf_sec_name(obj, scn);
 	if (!relo_sec_name || !sec_name)
 		return -EINVAL;
 
@@ -3702,7 +3758,8 @@ bpf_object__collect_prog_relos(struct bpf_object *obj, GElf_Shdr *shdr, Elf_Data
 				relo_sec_name, (size_t)GELF_R_SYM(rel.r_info), i);
 			return -LIBBPF_ERRNO__FORMAT;
 		}
-		if (rel.r_offset % BPF_INSN_SZ) {
+
+		if (rel.r_offset % BPF_INSN_SZ || rel.r_offset >= scn_data->d_size) {
 			pr_warn("sec '%s': invalid offset 0x%zx for relo #%d\n",
 				relo_sec_name, (size_t)GELF_R_SYM(rel.r_info), i);
 			return -LIBBPF_ERRNO__FORMAT;
@@ -3726,9 +3783,9 @@ bpf_object__collect_prog_relos(struct bpf_object *obj, GElf_Shdr *shdr, Elf_Data
 
 		prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
 		if (!prog) {
-			pr_warn("sec '%s': relo #%d: program not found in section '%s' for insn #%u\n",
+			pr_debug("sec '%s': relo #%d: couldn't find program in section '%s' for insn #%u, probably overridden weak function, skipping...\n",
 				relo_sec_name, i, sec_name, insn_idx);
-			return -LIBBPF_ERRNO__RELOC;
+			continue;
 		}
 
 		relos = libbpf_reallocarray(prog->reloc_desc,
@@ -6972,7 +7029,7 @@ static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id
 	return false;
 }
 
-static int bpf_object__sanitize_prog(struct bpf_object* obj, struct bpf_program *prog)
+static int bpf_object__sanitize_prog(struct bpf_object *obj, struct bpf_program *prog)
 {
 	struct bpf_insn *insn = prog->insns;
 	enum bpf_func_id func_id;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 6017902c687e..ee426226928f 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -19,6 +19,7 @@
 #pragma GCC poison reallocarray
 
 #include "libbpf.h"
+#include "btf.h"
 
 #ifndef EM_BPF
 #define EM_BPF 247
@@ -131,6 +132,50 @@ struct btf;
 struct btf_type;
 
 struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id);
+const char *btf_kind_str(const struct btf_type *t);
+const struct btf_type *skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);
+
+static inline enum btf_func_linkage btf_func_linkage(const struct btf_type *t)
+{
+	return (enum btf_func_linkage)(int)btf_vlen(t);
+}
+
+static inline __u32 btf_type_info(int kind, int vlen, int kflag)
+{
+	return (kflag << 31) | (kind << 24) | vlen;
+}
+
+enum map_def_parts {
+	MAP_DEF_MAP_TYPE	= 0x001,
+	MAP_DEF_KEY_TYPE	= 0x002,
+	MAP_DEF_KEY_SIZE	= 0x004,
+	MAP_DEF_VALUE_TYPE	= 0x008,
+	MAP_DEF_VALUE_SIZE	= 0x010,
+	MAP_DEF_MAX_ENTRIES	= 0x020,
+	MAP_DEF_MAP_FLAGS	= 0x040,
+	MAP_DEF_NUMA_NODE	= 0x080,
+	MAP_DEF_PINNING		= 0x100,
+	MAP_DEF_INNER_MAP	= 0x200,
+
+	MAP_DEF_ALL		= 0x3ff, /* combination of all above */
+};
+
+struct btf_map_def {
+	enum map_def_parts parts;
+	__u32 map_type;
+	__u32 key_type_id;
+	__u32 key_size;
+	__u32 value_type_id;
+	__u32 value_size;
+	__u32 max_entries;
+	__u32 map_flags;
+	__u32 numa_node;
+	__u32 pinning;
+};
+
+int parse_btf_map_def(const char *map_name, struct btf *btf,
+		      const struct btf_type *def_t, bool strict,
+		      struct btf_map_def *map_def, struct btf_map_def *inner_def);
 
 void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
 		     size_t cur_cnt, size_t max_cnt, size_t add_cnt);
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 4e08bc07e635..9de084b1c699 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -22,6 +22,8 @@
 #include "libbpf_internal.h"
 #include "strset.h"
 
+#define BTF_EXTERN_SEC ".extern"
+
 struct src_sec {
 	const char *sec_name;
 	/* positional (not necessarily ELF) index in an array of sections */
@@ -74,11 +76,36 @@ struct btf_ext_sec_data {
 	void *recs;
 };
 
+struct glob_sym {
+	/* ELF symbol index */
+	int sym_idx;
+	/* associated section id for .ksyms, .kconfig, etc, but not .extern */
+	int sec_id;
+	/* extern name offset in STRTAB */
+	int name_off;
+	/* optional associated BTF type ID */
+	int btf_id;
+	/* BTF type ID to which VAR/FUNC type is pointing to; used for
+	 * rewriting types when extern VAR/FUNC is resolved to a concrete
+	 * definition
+	 */
+	int underlying_btf_id;
+	/* sec_var index in the corresponding dst_sec, if exists */
+	int var_idx;
+
+	/* extern or resolved/global symbol */
+	bool is_extern;
+	/* weak or strong symbol, never goes back from strong to weak */
+	bool is_weak;
+};
+
 struct dst_sec {
 	char *sec_name;
 	/* positional (not necessarily ELF) index in an array of sections */
 	int id;
 
+	bool ephemeral;
+
 	/* ELF info */
 	size_t sec_idx;
 	Elf_Scn *scn;
@@ -120,22 +147,28 @@ struct bpf_linker {
 
 	struct btf *btf;
 	struct btf_ext *btf_ext;
+
+	/* global (including extern) ELF symbols */
+	int glob_sym_cnt;
+	struct glob_sym *glob_syms;
 };
 
 #define pr_warn_elf(fmt, ...)									\
-do {												\
-	libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1));	\
-} while (0)
+	libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
 
 static int init_output_elf(struct bpf_linker *linker, const char *file);
 
 static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj);
 static int linker_sanity_check_elf(struct src_obj *obj);
+static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec);
+static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec);
 static int linker_sanity_check_btf(struct src_obj *obj);
 static int linker_sanity_check_btf_ext(struct src_obj *obj);
 static int linker_fixup_btf(struct src_obj *obj);
 static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj);
 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj);
+static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
+				 Elf64_Sym *sym, const char *sym_name, int src_sym_idx);
 static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj);
 static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj);
 static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj);
@@ -282,7 +315,7 @@ static int init_output_elf(struct bpf_linker *linker, const char *file)
 
 	/* ELF header */
 	linker->elf_hdr = elf64_newehdr(linker->elf);
-	if (!linker->elf_hdr){
+	if (!linker->elf_hdr) {
 		pr_warn_elf("failed to create ELF header");
 		return -EINVAL;
 	}
@@ -663,8 +696,8 @@ static bool is_pow_of_2(size_t x)
 
 static int linker_sanity_check_elf(struct src_obj *obj)
 {
-	struct src_sec *sec, *link_sec;
-	int i, j, n;
+	struct src_sec *sec;
+	int i, err;
 
 	if (!obj->symtab_sec_idx) {
 		pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
@@ -692,43 +725,11 @@ static int linker_sanity_check_elf(struct src_obj *obj)
 			return -EINVAL;
 
 		switch (sec->shdr->sh_type) {
-		case SHT_SYMTAB: {
-			Elf64_Sym *sym;
-
-			if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
-				return -EINVAL;
-			if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
-				return -EINVAL;
-
-			if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
-				pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
-				return -EINVAL;
-			}
-			link_sec = &obj->secs[sec->shdr->sh_link];
-			if (link_sec->shdr->sh_type != SHT_STRTAB) {
-				pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
-				return -EINVAL;
-			}
-
-			n = sec->shdr->sh_size / sec->shdr->sh_entsize;
-			sym = sec->data->d_buf;
-			for (j = 0; j < n; j++, sym++) {
-				if (sym->st_shndx
-				    && sym->st_shndx < SHN_LORESERVE
-				    && sym->st_shndx >= obj->sec_cnt) {
-					pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
-						j, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
-					return -EINVAL;
-				}
-				if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION) {
-					if (sym->st_value != 0)
-						return -EINVAL;
-				}
-			}
+		case SHT_SYMTAB:
+			err = linker_sanity_check_elf_symtab(obj, sec);
+			if (err)
+				return err;
 			break;
-		}
 		case SHT_STRTAB:
 			break;
 		case SHT_PROGBITS:
@@ -739,80 +740,11 @@ static int linker_sanity_check_elf(struct src_obj *obj)
 			break;
 		case SHT_NOBITS:
 			break;
-		case SHT_REL: {
-			Elf64_Rel *relo;
-			struct src_sec *sym_sec;
-
-			if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
-				return -EINVAL;
-			if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
-				return -EINVAL;
-
-			/* SHT_REL's sh_link should point to SYMTAB */
-			if (sec->shdr->sh_link != obj->symtab_sec_idx) {
-				pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
-				return -EINVAL;
-			}
-
-			/* SHT_REL's sh_info points to relocated section */
-			if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
-				pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
-				return -EINVAL;
-			}
-			link_sec = &obj->secs[sec->shdr->sh_info];
-
-			/* .rel<secname> -> <secname> pattern is followed */
-			if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
-			    || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
-				pr_warn("ELF relo section #%zu name has invalid name in %s\n",
-					sec->sec_idx, obj->filename);
-				return -EINVAL;
-			}
-
-			/* don't further validate relocations for ignored sections */
-			if (link_sec->skipped)
-				break;
-
-			/* relocatable section is data or instructions */
-			if (link_sec->shdr->sh_type != SHT_PROGBITS
-			    && link_sec->shdr->sh_type != SHT_NOBITS) {
-				pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
-				return -EINVAL;
-			}
-
-			/* check sanity of each relocation */
-			n = sec->shdr->sh_size / sec->shdr->sh_entsize;
-			relo = sec->data->d_buf;
-			sym_sec = &obj->secs[obj->symtab_sec_idx];
-			for (j = 0; j < n; j++, relo++) {
-				size_t sym_idx = ELF64_R_SYM(relo->r_info);
-				size_t sym_type = ELF64_R_TYPE(relo->r_info);
-
-				if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) {
-					pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
-						j, sec->sec_idx, sym_type, obj->filename);
-					return -EINVAL;
-				}
-
-				if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
-					pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
-						j, sec->sec_idx, sym_idx, obj->filename);
-					return -EINVAL;
-				}
-
-				if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
-					if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
-						pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
-							j, sec->sec_idx, sym_idx, obj->filename);
-						return -EINVAL;
-					}
-				}
-			}
+		case SHT_REL:
+			err = linker_sanity_check_elf_relos(obj, sec);
+			if (err)
+				return err;
 			break;
-		}
 		case SHT_LLVM_ADDRSIG:
 			break;
 		default:
@@ -825,6 +757,157 @@ static int linker_sanity_check_elf(struct src_obj *obj)
 	return 0;
 }
 
+static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
+{
+	struct src_sec *link_sec;
+	Elf64_Sym *sym;
+	int i, n;
+
+	if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
+		return -EINVAL;
+	if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
+		return -EINVAL;
+
+	if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
+		pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+		return -EINVAL;
+	}
+	link_sec = &obj->secs[sec->shdr->sh_link];
+	if (link_sec->shdr->sh_type != SHT_STRTAB) {
+		pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+		return -EINVAL;
+	}
+
+	n = sec->shdr->sh_size / sec->shdr->sh_entsize;
+	sym = sec->data->d_buf;
+	for (i = 0; i < n; i++, sym++) {
+		int sym_type = ELF64_ST_TYPE(sym->st_info);
+		int sym_bind = ELF64_ST_BIND(sym->st_info);
+		int sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
+
+		if (i == 0) {
+			if (sym->st_name != 0 || sym->st_info != 0
+			    || sym->st_other != 0 || sym->st_shndx != 0
+			    || sym->st_value != 0 || sym->st_size != 0) {
+				pr_warn("ELF sym #0 is invalid in %s\n", obj->filename);
+				return -EINVAL;
+			}
+			continue;
+		}
+		if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) {
+			pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n",
+				i, sec->sec_idx, sym_bind);
+			return -EINVAL;
+		}
+		if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) {
+			pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n",
+				i, sec->sec_idx, sym_vis);
+			return -EINVAL;
+		}
+		if (sym->st_shndx == 0) {
+			if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL
+			    || sym->st_value != 0 || sym->st_size != 0) {
+				pr_warn("ELF sym #%d is invalid extern symbol in %s\n",
+					i, obj->filename);
+
+				return -EINVAL;
+			}
+			continue;
+		}
+		if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) {
+			pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
+				i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
+			return -EINVAL;
+		}
+		if (sym_type == STT_SECTION) {
+			if (sym->st_value != 0)
+				return -EINVAL;
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
+{
+	struct src_sec *link_sec, *sym_sec;
+	Elf64_Rel *relo;
+	int i, n;
+
+	if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
+		return -EINVAL;
+	if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
+		return -EINVAL;
+
+	/* SHT_REL's sh_link should point to SYMTAB */
+	if (sec->shdr->sh_link != obj->symtab_sec_idx) {
+		pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+		return -EINVAL;
+	}
+
+	/* SHT_REL's sh_info points to relocated section */
+	if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
+		pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
+		return -EINVAL;
+	}
+	link_sec = &obj->secs[sec->shdr->sh_info];
+
+	/* .rel<secname> -> <secname> pattern is followed */
+	if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
+	    || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
+		pr_warn("ELF relo section #%zu name has invalid name in %s\n",
+			sec->sec_idx, obj->filename);
+		return -EINVAL;
+	}
+
+	/* don't further validate relocations for ignored sections */
+	if (link_sec->skipped)
+		return 0;
+
+	/* relocatable section is data or instructions */
+	if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
+		pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
+		return -EINVAL;
+	}
+
+	/* check sanity of each relocation */
+	n = sec->shdr->sh_size / sec->shdr->sh_entsize;
+	relo = sec->data->d_buf;
+	sym_sec = &obj->secs[obj->symtab_sec_idx];
+	for (i = 0; i < n; i++, relo++) {
+		size_t sym_idx = ELF64_R_SYM(relo->r_info);
+		size_t sym_type = ELF64_R_TYPE(relo->r_info);
+
+		if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) {
+			pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
+				i, sec->sec_idx, sym_type, obj->filename);
+			return -EINVAL;
+		}
+
+		if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
+			pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
+				i, sec->sec_idx, sym_idx, obj->filename);
+			return -EINVAL;
+		}
+
+		if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
+			if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
+				pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
+					i, sec->sec_idx, sym_idx, obj->filename);
+				return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+}
+
 static int check_btf_type_id(__u32 *type_id, void *ctx)
 {
 	struct btf *btf = ctx;
@@ -897,6 +980,7 @@ static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct s
 
 	dst_sec->sec_sz = 0;
 	dst_sec->sec_idx = 0;
+	dst_sec->ephemeral = src_sec->ephemeral;
 
 	/* ephemeral sections are just thin section shells lacking most parts */
 	if (src_sec->ephemeral)
@@ -904,13 +988,13 @@ static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct s
 
 	scn = elf_newscn(linker->elf);
 	if (!scn)
-		return -1;
+		return -ENOMEM;
 	data = elf_newdata(scn);
 	if (!data)
-		return -1;
+		return -ENOMEM;
 	shdr = elf64_getshdr(scn);
 	if (!shdr)
-		return -1;
+		return -ENOMEM;
 
 	dst_sec->scn = scn;
 	dst_sec->shdr = shdr;
@@ -960,6 +1044,9 @@ static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const cha
 
 static bool secs_match(struct dst_sec *dst, struct src_sec *src)
 {
+	if (dst->ephemeral || src->ephemeral)
+		return true;
+
 	if (dst->shdr->sh_type != src->shdr->sh_type) {
 		pr_warn("sec %s types mismatch\n", dst->sec_name);
 		return false;
@@ -985,13 +1072,33 @@ static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec
 	return true;
 }
 
-static int extend_sec(struct dst_sec *dst, struct src_sec *src)
+static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src)
 {
 	void *tmp;
-	size_t dst_align = dst->shdr->sh_addralign;
-	size_t src_align = src->shdr->sh_addralign;
+	size_t dst_align, src_align;
 	size_t dst_align_sz, dst_final_sz;
+	int err;
 
+	/* Ephemeral source section doesn't contribute anything to ELF
+	 * section data.
+	 */
+	if (src->ephemeral)
+		return 0;
+
+	/* Some sections (like .maps) can contain both externs (and thus be
+	 * ephemeral) and non-externs (map definitions). So it's possible that
+	 * it has to be "upgraded" from ephemeral to non-ephemeral when the
+	 * first non-ephemeral entity appears. In such case, we add ELF
+	 * section, data, etc.
+	 */
+	if (dst->ephemeral) {
+		err = init_sec(linker, dst, src);
+		if (err)
+			return err;
+	}
+
+	dst_align = dst->shdr->sh_addralign;
+	src_align = src->shdr->sh_addralign;
 	if (dst_align == 0)
 		dst_align = 1;
 	if (dst_align < src_align)
@@ -1087,10 +1194,7 @@ static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj
 		/* record mapped section index */
 		src_sec->dst_id = dst_sec->id;
 
-		if (src_sec->ephemeral)
-			continue;
-
-		err = extend_sec(dst_sec, src_sec);
+		err = extend_sec(linker, dst_sec, src_sec);
 		if (err)
 			return err;
 	}
@@ -1101,68 +1205,778 @@ static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj
 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj)
 {
 	struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
-	Elf64_Sym *sym = symtab->data->d_buf, *dst_sym;
-	int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
+	Elf64_Sym *sym = symtab->data->d_buf;
+	int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize, err;
 	int str_sec_idx = symtab->shdr->sh_link;
+	const char *sym_name;
 
 	obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map));
 	if (!obj->sym_map)
 		return -ENOMEM;
 
 	for (i = 0; i < n; i++, sym++) {
-		struct src_sec *src_sec = NULL;
-		struct dst_sec *dst_sec = NULL;
-		const char *sym_name;
-		size_t dst_sym_idx;
-		int name_off;
-
-		/* we already have all-zero initial symbol */
-		if (sym->st_name == 0 && sym->st_info == 0 &&
-		    sym->st_other == 0 && sym->st_shndx == SHN_UNDEF &&
-		    sym->st_value == 0 && sym->st_size ==0)
+		/* We already validated all-zero symbol #0 and we already
+		 * appended it preventively to the final SYMTAB, so skip it.
+		 */
+		if (i == 0)
 			continue;
 
 		sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
 		if (!sym_name) {
 			pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename);
-			return -1;
+			return -EINVAL;
 		}
 
-		if (sym->st_shndx && sym->st_shndx < SHN_LORESERVE) {
-			src_sec = &obj->secs[sym->st_shndx];
-			if (src_sec->skipped)
-				continue;
-			dst_sec = &linker->secs[src_sec->dst_id];
+		err = linker_append_elf_sym(linker, obj, sym, sym_name, i);
+		if (err)
+			return err;
+	}
 
-			/* allow only one STT_SECTION symbol per section */
-			if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sec->sec_sym_idx) {
-				obj->sym_map[i] = dst_sec->sec_sym_idx;
-				continue;
+	return 0;
+}
+
+static Elf64_Sym *get_sym_by_idx(struct bpf_linker *linker, size_t sym_idx)
+{
+	struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
+	Elf64_Sym *syms = symtab->raw_data;
+
+	return &syms[sym_idx];
+}
+
+static struct glob_sym *find_glob_sym(struct bpf_linker *linker, const char *sym_name)
+{
+	struct glob_sym *glob_sym;
+	const char *name;
+	int i;
+
+	for (i = 0; i < linker->glob_sym_cnt; i++) {
+		glob_sym = &linker->glob_syms[i];
+		name = strset__data(linker->strtab_strs) + glob_sym->name_off;
+
+		if (strcmp(name, sym_name) == 0)
+			return glob_sym;
+	}
+
+	return NULL;
+}
+
+static struct glob_sym *add_glob_sym(struct bpf_linker *linker)
+{
+	struct glob_sym *syms, *sym;
+
+	syms = libbpf_reallocarray(linker->glob_syms, linker->glob_sym_cnt + 1,
+				   sizeof(*linker->glob_syms));
+	if (!syms)
+		return NULL;
+
+	sym = &syms[linker->glob_sym_cnt];
+	memset(sym, 0, sizeof(*sym));
+	sym->var_idx = -1;
+
+	linker->glob_syms = syms;
+	linker->glob_sym_cnt++;
+
+	return sym;
+}
+
+static bool glob_sym_btf_matches(const char *sym_name, bool exact,
+				 const struct btf *btf1, __u32 id1,
+				 const struct btf *btf2, __u32 id2)
+{
+	const struct btf_type *t1, *t2;
+	bool is_static1, is_static2;
+	const char *n1, *n2;
+	int i, n;
+
+recur:
+	n1 = n2 = NULL;
+	t1 = skip_mods_and_typedefs(btf1, id1, &id1);
+	t2 = skip_mods_and_typedefs(btf2, id2, &id2);
+
+	/* check if only one side is FWD, otherwise handle with common logic */
+	if (!exact && btf_is_fwd(t1) != btf_is_fwd(t2)) {
+		n1 = btf__str_by_offset(btf1, t1->name_off);
+		n2 = btf__str_by_offset(btf2, t2->name_off);
+		if (strcmp(n1, n2) != 0) {
+			pr_warn("global '%s': incompatible forward declaration names '%s' and '%s'\n",
+				sym_name, n1, n2);
+			return false;
+		}
+		/* validate if FWD kind matches concrete kind */
+		if (btf_is_fwd(t1)) {
+			if (btf_kflag(t1) && btf_is_union(t2))
+				return true;
+			if (!btf_kflag(t1) && btf_is_struct(t2))
+				return true;
+			pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
+				sym_name, btf_kflag(t1) ? "union" : "struct", btf_kind_str(t2));
+		} else {
+			if (btf_kflag(t2) && btf_is_union(t1))
+				return true;
+			if (!btf_kflag(t2) && btf_is_struct(t1))
+				return true;
+			pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
+				sym_name, btf_kflag(t2) ? "union" : "struct", btf_kind_str(t1));
+		}
+		return false;
+	}
+
+	if (btf_kind(t1) != btf_kind(t2)) {
+		pr_warn("global '%s': incompatible BTF kinds %s and %s\n",
+			sym_name, btf_kind_str(t1), btf_kind_str(t2));
+		return false;
+	}
+
+	switch (btf_kind(t1)) {
+	case BTF_KIND_STRUCT:
+	case BTF_KIND_UNION:
+	case BTF_KIND_ENUM:
+	case BTF_KIND_FWD:
+	case BTF_KIND_FUNC:
+	case BTF_KIND_VAR:
+		n1 = btf__str_by_offset(btf1, t1->name_off);
+		n2 = btf__str_by_offset(btf2, t2->name_off);
+		if (strcmp(n1, n2) != 0) {
+			pr_warn("global '%s': incompatible %s names '%s' and '%s'\n",
+				sym_name, btf_kind_str(t1), n1, n2);
+			return false;
+		}
+		break;
+	default:
+		break;
+	}
+
+	switch (btf_kind(t1)) {
+	case BTF_KIND_UNKN: /* void */
+	case BTF_KIND_FWD:
+		return true;
+	case BTF_KIND_INT:
+	case BTF_KIND_FLOAT:
+	case BTF_KIND_ENUM:
+		/* ignore encoding for int and enum values for enum */
+		if (t1->size != t2->size) {
+			pr_warn("global '%s': incompatible %s '%s' size %u and %u\n",
+				sym_name, btf_kind_str(t1), n1, t1->size, t2->size);
+			return false;
+		}
+		return true;
+	case BTF_KIND_PTR:
+		/* just validate overall shape of the referenced type, so no
+		 * contents comparison for struct/union, and allowd fwd vs
+		 * struct/union
+		 */
+		exact = false;
+		id1 = t1->type;
+		id2 = t2->type;
+		goto recur;
+	case BTF_KIND_ARRAY:
+		/* ignore index type and array size */
+		id1 = btf_array(t1)->type;
+		id2 = btf_array(t2)->type;
+		goto recur;
+	case BTF_KIND_FUNC:
+		/* extern and global linkages are compatible */
+		is_static1 = btf_func_linkage(t1) == BTF_FUNC_STATIC;
+		is_static2 = btf_func_linkage(t2) == BTF_FUNC_STATIC;
+		if (is_static1 != is_static2) {
+			pr_warn("global '%s': incompatible func '%s' linkage\n", sym_name, n1);
+			return false;
+		}
+
+		id1 = t1->type;
+		id2 = t2->type;
+		goto recur;
+	case BTF_KIND_VAR:
+		/* extern and global linkages are compatible */
+		is_static1 = btf_var(t1)->linkage == BTF_VAR_STATIC;
+		is_static2 = btf_var(t2)->linkage == BTF_VAR_STATIC;
+		if (is_static1 != is_static2) {
+			pr_warn("global '%s': incompatible var '%s' linkage\n", sym_name, n1);
+			return false;
+		}
+
+		id1 = t1->type;
+		id2 = t2->type;
+		goto recur;
+	case BTF_KIND_STRUCT:
+	case BTF_KIND_UNION: {
+		const struct btf_member *m1, *m2;
+
+		if (!exact)
+			return true;
+
+		if (btf_vlen(t1) != btf_vlen(t2)) {
+			pr_warn("global '%s': incompatible number of %s fields %u and %u\n",
+				sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
+			return false;
+		}
+
+		n = btf_vlen(t1);
+		m1 = btf_members(t1);
+		m2 = btf_members(t2);
+		for (i = 0; i < n; i++, m1++, m2++) {
+			n1 = btf__str_by_offset(btf1, m1->name_off);
+			n2 = btf__str_by_offset(btf2, m2->name_off);
+			if (strcmp(n1, n2) != 0) {
+				pr_warn("global '%s': incompatible field #%d names '%s' and '%s'\n",
+					sym_name, i, n1, n2);
+				return false;
 			}
+			if (m1->offset != m2->offset) {
+				pr_warn("global '%s': incompatible field #%d ('%s') offsets\n",
+					sym_name, i, n1);
+				return false;
+			}
+			if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
+				return false;
 		}
 
-		name_off = strset__add_str(linker->strtab_strs, sym_name);
-		if (name_off < 0)
-			return name_off;
+		return true;
+	}
+	case BTF_KIND_FUNC_PROTO: {
+		const struct btf_param *m1, *m2;
 
-		dst_sym = add_new_sym(linker, &dst_sym_idx);
-		if (!dst_sym)
-			return -ENOMEM;
+		if (btf_vlen(t1) != btf_vlen(t2)) {
+			pr_warn("global '%s': incompatible number of %s params %u and %u\n",
+				sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
+			return false;
+		}
 
-		dst_sym->st_name = name_off;
-		dst_sym->st_info = sym->st_info;
-		dst_sym->st_other = sym->st_other;
-		dst_sym->st_shndx = src_sec ? dst_sec->sec_idx : sym->st_shndx;
-		dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
+		n = btf_vlen(t1);
+		m1 = btf_params(t1);
+		m2 = btf_params(t2);
+		for (i = 0; i < n; i++, m1++, m2++) {
+			/* ignore func arg names */
+			if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
+				return false;
+		}
+
+		/* now check return type as well */
+		id1 = t1->type;
+		id2 = t2->type;
+		goto recur;
+	}
+
+	/* skip_mods_and_typedefs() make this impossible */
+	case BTF_KIND_TYPEDEF:
+	case BTF_KIND_VOLATILE:
+	case BTF_KIND_CONST:
+	case BTF_KIND_RESTRICT:
+	/* DATASECs are never compared with each other */
+	case BTF_KIND_DATASEC:
+	default:
+		pr_warn("global '%s': unsupported BTF kind %s\n",
+			sym_name, btf_kind_str(t1));
+		return false;
+	}
+}
+
+static bool map_defs_match(const char *sym_name,
+			   const struct btf *main_btf,
+			   const struct btf_map_def *main_def,
+			   const struct btf_map_def *main_inner_def,
+			   const struct btf *extra_btf,
+			   const struct btf_map_def *extra_def,
+			   const struct btf_map_def *extra_inner_def)
+{
+	const char *reason;
+
+	if (main_def->map_type != extra_def->map_type) {
+		reason = "type";
+		goto mismatch;
+	}
+
+	/* check key type/size match */
+	if (main_def->key_size != extra_def->key_size) {
+		reason = "key_size";
+		goto mismatch;
+	}
+	if (!!main_def->key_type_id != !!extra_def->key_type_id) {
+		reason = "key type";
+		goto mismatch;
+	}
+	if ((main_def->parts & MAP_DEF_KEY_TYPE)
+	     && !glob_sym_btf_matches(sym_name, true /*exact*/,
+				      main_btf, main_def->key_type_id,
+				      extra_btf, extra_def->key_type_id)) {
+		reason = "key type";
+		goto mismatch;
+	}
+
+	/* validate value type/size match */
+	if (main_def->value_size != extra_def->value_size) {
+		reason = "value_size";
+		goto mismatch;
+	}
+	if (!!main_def->value_type_id != !!extra_def->value_type_id) {
+		reason = "value type";
+		goto mismatch;
+	}
+	if ((main_def->parts & MAP_DEF_VALUE_TYPE)
+	     && !glob_sym_btf_matches(sym_name, true /*exact*/,
+				      main_btf, main_def->value_type_id,
+				      extra_btf, extra_def->value_type_id)) {
+		reason = "key type";
+		goto mismatch;
+	}
+
+	if (main_def->max_entries != extra_def->max_entries) {
+		reason = "max_entries";
+		goto mismatch;
+	}
+	if (main_def->map_flags != extra_def->map_flags) {
+		reason = "map_flags";
+		goto mismatch;
+	}
+	if (main_def->numa_node != extra_def->numa_node) {
+		reason = "numa_node";
+		goto mismatch;
+	}
+	if (main_def->pinning != extra_def->pinning) {
+		reason = "pinning";
+		goto mismatch;
+	}
+
+	if ((main_def->parts & MAP_DEF_INNER_MAP) != (extra_def->parts & MAP_DEF_INNER_MAP)) {
+		reason = "inner map";
+		goto mismatch;
+	}
+
+	if (main_def->parts & MAP_DEF_INNER_MAP) {
+		char inner_map_name[128];
+
+		snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", sym_name);
+
+		return map_defs_match(inner_map_name,
+				      main_btf, main_inner_def, NULL,
+				      extra_btf, extra_inner_def, NULL);
+	}
+
+	return true;
+
+mismatch:
+	pr_warn("global '%s': map %s mismatch\n", sym_name, reason);
+	return false;
+}
+
+static bool glob_map_defs_match(const char *sym_name,
+				struct bpf_linker *linker, struct glob_sym *glob_sym,
+				struct src_obj *obj, Elf64_Sym *sym, int btf_id)
+{
+	struct btf_map_def dst_def = {}, dst_inner_def = {};
+	struct btf_map_def src_def = {}, src_inner_def = {};
+	const struct btf_type *t;
+	int err;
+
+	t = btf__type_by_id(obj->btf, btf_id);
+	if (!btf_is_var(t)) {
+		pr_warn("global '%s': invalid map definition type [%d]\n", sym_name, btf_id);
+		return false;
+	}
+	t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
+
+	err = parse_btf_map_def(sym_name, obj->btf, t, true /*strict*/, &src_def, &src_inner_def);
+	if (err) {
+		pr_warn("global '%s': invalid map definition\n", sym_name);
+		return false;
+	}
+
+	/* re-parse existing map definition */
+	t = btf__type_by_id(linker->btf, glob_sym->btf_id);
+	t = skip_mods_and_typedefs(linker->btf, t->type, NULL);
+	err = parse_btf_map_def(sym_name, linker->btf, t, true /*strict*/, &dst_def, &dst_inner_def);
+	if (err) {
+		/* this should not happen, because we already validated it */
+		pr_warn("global '%s': invalid dst map definition\n", sym_name);
+		return false;
+	}
+
+	/* Currently extern map definition has to be complete and match
+	 * concrete map definition exactly. This restriction might be lifted
+	 * in the future.
+	 */
+	return map_defs_match(sym_name, linker->btf, &dst_def, &dst_inner_def,
+			      obj->btf, &src_def, &src_inner_def);
+}
+
+static bool glob_syms_match(const char *sym_name,
+			    struct bpf_linker *linker, struct glob_sym *glob_sym,
+			    struct src_obj *obj, Elf64_Sym *sym, size_t sym_idx, int btf_id)
+{
+	const struct btf_type *src_t;
+
+	/* if we are dealing with externs, BTF types describing both global
+	 * and extern VARs/FUNCs should be completely present in all files
+	 */
+	if (!glob_sym->btf_id || !btf_id) {
+		pr_warn("BTF info is missing for global symbol '%s'\n", sym_name);
+		return false;
+	}
+
+	src_t = btf__type_by_id(obj->btf, btf_id);
+	if (!btf_is_var(src_t) && !btf_is_func(src_t)) {
+		pr_warn("only extern variables and functions are supported, but got '%s' for '%s'\n",
+			btf_kind_str(src_t), sym_name);
+		return false;
+	}
+
+	/* deal with .maps definitions specially */
+	if (glob_sym->sec_id && strcmp(linker->secs[glob_sym->sec_id].sec_name, MAPS_ELF_SEC) == 0)
+		return glob_map_defs_match(sym_name, linker, glob_sym, obj, sym, btf_id);
+
+	if (!glob_sym_btf_matches(sym_name, true /*exact*/,
+				  linker->btf, glob_sym->btf_id, obj->btf, btf_id))
+		return false;
+
+	return true;
+}
+
+static bool btf_is_non_static(const struct btf_type *t)
+{
+	return (btf_is_var(t) && btf_var(t)->linkage != BTF_VAR_STATIC)
+	       || (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_STATIC);
+}
+
+static int find_glob_sym_btf(struct src_obj *obj, Elf64_Sym *sym, const char *sym_name,
+			     int *out_btf_sec_id, int *out_btf_id)
+{
+	int i, j, n = btf__get_nr_types(obj->btf), m, btf_id = 0;
+	const struct btf_type *t;
+	const struct btf_var_secinfo *vi;
+	const char *name;
+
+	for (i = 1; i <= n; i++) {
+		t = btf__type_by_id(obj->btf, i);
+
+		/* some global and extern FUNCs and VARs might not be associated with any
+		 * DATASEC, so try to detect them in the same pass
+		 */
+		if (btf_is_non_static(t)) {
+			name = btf__str_by_offset(obj->btf, t->name_off);
+			if (strcmp(name, sym_name) != 0)
+				continue;
+
+			/* remember and still try to find DATASEC */
+			btf_id = i;
+			continue;
+		}
+
+		if (!btf_is_datasec(t))
+			continue;
+
+		vi = btf_var_secinfos(t);
+		for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
+			t = btf__type_by_id(obj->btf, vi->type);
+			name = btf__str_by_offset(obj->btf, t->name_off);
+
+			if (strcmp(name, sym_name) != 0)
+				continue;
+			if (btf_is_var(t) && btf_var(t)->linkage == BTF_VAR_STATIC)
+				continue;
+			if (btf_is_func(t) && btf_func_linkage(t) == BTF_FUNC_STATIC)
+				continue;
+
+			if (btf_id && btf_id != vi->type) {
+				pr_warn("global/extern '%s' BTF is ambiguous: both types #%d and #%u match\n",
+					sym_name, btf_id, vi->type);
+				return -EINVAL;
+			}
+
+			*out_btf_sec_id = i;
+			*out_btf_id = vi->type;
+
+			return 0;
+		}
+	}
+
+	/* free-floating extern or global FUNC */
+	if (btf_id) {
+		*out_btf_sec_id = 0;
+		*out_btf_id = btf_id;
+		return 0;
+	}
+
+	pr_warn("failed to find BTF info for global/extern symbol '%s'\n", sym_name);
+	return -ENOENT;
+}
+
+static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name)
+{
+	struct src_sec *sec;
+	int i;
+
+	for (i = 1; i < obj->sec_cnt; i++) {
+		sec = &obj->secs[i];
+
+		if (strcmp(sec->sec_name, sec_name) == 0)
+			return sec;
+	}
+
+	return NULL;
+}
+
+static int complete_extern_btf_info(struct btf *dst_btf, int dst_id,
+				    struct btf *src_btf, int src_id)
+{
+	struct btf_type *dst_t = btf_type_by_id(dst_btf, dst_id);
+	struct btf_type *src_t = btf_type_by_id(src_btf, src_id);
+	struct btf_param *src_p, *dst_p;
+	const char *s;
+	int i, n, off;
+
+	/* We already made sure that source and destination types (FUNC or
+	 * VAR) match in terms of types and argument names.
+	 */
+	if (btf_is_var(dst_t)) {
+		btf_var(dst_t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
+		return 0;
+	}
+
+	dst_t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_GLOBAL, 0);
+
+	/* now onto FUNC_PROTO types */
+	src_t = btf_type_by_id(src_btf, src_t->type);
+	dst_t = btf_type_by_id(dst_btf, dst_t->type);
+
+	/* Fill in all the argument names, which for extern FUNCs are missing.
+	 * We'll end up with two copies of FUNCs/VARs for externs, but that
+	 * will be taken care of by BTF dedup at the very end.
+	 * It might be that BTF types for extern in one file has less/more BTF
+	 * information (e.g., FWD instead of full STRUCT/UNION information),
+	 * but that should be (in most cases, subject to BTF dedup rules)
+	 * handled and resolved by BTF dedup algorithm as well, so we won't
+	 * worry about it. Our only job is to make sure that argument names
+	 * are populated on both sides, otherwise BTF dedup will pedantically
+	 * consider them different.
+	 */
+	src_p = btf_params(src_t);
+	dst_p = btf_params(dst_t);
+	for (i = 0, n = btf_vlen(dst_t); i < n; i++, src_p++, dst_p++) {
+		if (!src_p->name_off)
+			continue;
+
+		/* src_btf has more complete info, so add name to dst_btf */
+		s = btf__str_by_offset(src_btf, src_p->name_off);
+		off = btf__add_str(dst_btf, s);
+		if (off < 0)
+			return off;
+		dst_p->name_off = off;
+	}
+	return 0;
+}
+
+static void sym_update_bind(Elf64_Sym *sym, int sym_bind)
+{
+	sym->st_info = ELF64_ST_INFO(sym_bind, ELF64_ST_TYPE(sym->st_info));
+}
+
+static void sym_update_type(Elf64_Sym *sym, int sym_type)
+{
+	sym->st_info = ELF64_ST_INFO(ELF64_ST_BIND(sym->st_info), sym_type);
+}
+
+static void sym_update_visibility(Elf64_Sym *sym, int sym_vis)
+{
+	/* libelf doesn't provide setters for ST_VISIBILITY,
+	 * but it is stored in the lower 2 bits of st_other
+	 */
+	sym->st_other &= 0x03;
+	sym->st_other |= sym_vis;
+}
+
+static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
+				 Elf64_Sym *sym, const char *sym_name, int src_sym_idx)
+{
+	struct src_sec *src_sec = NULL;
+	struct dst_sec *dst_sec = NULL;
+	struct glob_sym *glob_sym = NULL;
+	int name_off, sym_type, sym_bind, sym_vis, err;
+	int btf_sec_id = 0, btf_id = 0;
+	size_t dst_sym_idx;
+	Elf64_Sym *dst_sym;
+	bool sym_is_extern;
+
+	sym_type = ELF64_ST_TYPE(sym->st_info);
+	sym_bind = ELF64_ST_BIND(sym->st_info);
+	sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
+	sym_is_extern = sym->st_shndx == SHN_UNDEF;
+
+	if (sym_is_extern) {
+		if (!obj->btf) {
+			pr_warn("externs without BTF info are not supported\n");
+			return -ENOTSUP;
+		}
+	} else if (sym->st_shndx < SHN_LORESERVE) {
+		src_sec = &obj->secs[sym->st_shndx];
+		if (src_sec->skipped)
+			return 0;
+		dst_sec = &linker->secs[src_sec->dst_id];
+
+		/* allow only one STT_SECTION symbol per section */
+		if (sym_type == STT_SECTION && dst_sec->sec_sym_idx) {
+			obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx;
+			return 0;
+		}
+	}
+
+	if (sym_bind == STB_LOCAL)
+		goto add_sym;
+
+	/* find matching BTF info */
+	err = find_glob_sym_btf(obj, sym, sym_name, &btf_sec_id, &btf_id);
+	if (err)
+		return err;
+
+	if (sym_is_extern && btf_sec_id) {
+		const char *sec_name = NULL;
+		const struct btf_type *t;
+
+		t = btf__type_by_id(obj->btf, btf_sec_id);
+		sec_name = btf__str_by_offset(obj->btf, t->name_off);
+
+		/* Clang puts unannotated extern vars into
+		 * '.extern' BTF DATASEC. Treat them the same
+		 * as unannotated extern funcs (which are
+		 * currently not put into any DATASECs).
+		 * Those don't have associated src_sec/dst_sec.
+		 */
+		if (strcmp(sec_name, BTF_EXTERN_SEC) != 0) {
+			src_sec = find_src_sec_by_name(obj, sec_name);
+			if (!src_sec) {
+				pr_warn("failed to find matching ELF sec '%s'\n", sec_name);
+				return -ENOENT;
+			}
+			dst_sec = &linker->secs[src_sec->dst_id];
+		}
+	}
+
+	glob_sym = find_glob_sym(linker, sym_name);
+	if (glob_sym) {
+		/* Preventively resolve to existing symbol. This is
+		 * needed for further relocation symbol remapping in
+		 * the next step of linking.
+		 */
+		obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
+
+		/* If both symbols are non-externs, at least one of
+		 * them has to be STB_WEAK, otherwise they are in
+		 * a conflict with each other.
+		 */
+		if (!sym_is_extern && !glob_sym->is_extern
+		    && !glob_sym->is_weak && sym_bind != STB_WEAK) {
+			pr_warn("conflicting non-weak symbol #%d (%s) definition in '%s'\n",
+				src_sym_idx, sym_name, obj->filename);
+			return -EINVAL;
+		}
+
+		if (!glob_syms_match(sym_name, linker, glob_sym, obj, sym, src_sym_idx, btf_id))
+			return -EINVAL;
+
+		dst_sym = get_sym_by_idx(linker, glob_sym->sym_idx);
+
+		/* If new symbol is strong, then force dst_sym to be strong as
+		 * well; this way a mix of weak and non-weak extern
+		 * definitions will end up being strong.
+		 */
+		if (sym_bind == STB_GLOBAL) {
+			/* We still need to preserve type (NOTYPE or
+			 * OBJECT/FUNC, depending on whether the symbol is
+			 * extern or not)
+			 */
+			sym_update_bind(dst_sym, STB_GLOBAL);
+			glob_sym->is_weak = false;
+		}
+
+		/* Non-default visibility is "contaminating", with stricter
+		 * visibility overwriting more permissive ones, even if more
+		 * permissive visibility comes from just an extern definition.
+		 * Currently only STV_DEFAULT and STV_HIDDEN are allowed and
+		 * ensured by ELF symbol sanity checks above.
+		 */
+		if (sym_vis > ELF64_ST_VISIBILITY(dst_sym->st_other))
+			sym_update_visibility(dst_sym, sym_vis);
+
+		/* If the new symbol is extern, then regardless if
+		 * existing symbol is extern or resolved global, just
+		 * keep the existing one untouched.
+		 */
+		if (sym_is_extern)
+			return 0;
+
+		/* If existing symbol is a strong resolved symbol, bail out,
+		 * because we lost resolution battle have nothing to
+		 * contribute. We already checked abover that there is no
+		 * strong-strong conflict. We also already tightened binding
+		 * and visibility, so nothing else to contribute at that point.
+		 */
+		if (!glob_sym->is_extern && sym_bind == STB_WEAK)
+			return 0;
+
+		/* At this point, new symbol is strong non-extern,
+		 * so overwrite glob_sym with new symbol information.
+		 * Preserve binding and visibility.
+		 */
+		sym_update_type(dst_sym, sym_type);
+		dst_sym->st_shndx = dst_sec->sec_idx;
+		dst_sym->st_value = src_sec->dst_off + sym->st_value;
 		dst_sym->st_size = sym->st_size;
 
-		obj->sym_map[i] = dst_sym_idx;
+		/* see comment below about dst_sec->id vs dst_sec->sec_idx */
+		glob_sym->sec_id = dst_sec->id;
+		glob_sym->is_extern = false;
 
-		if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sym) {
-			dst_sec->sec_sym_idx = dst_sym_idx;
-			dst_sym->st_value = 0;
-		}
+		if (complete_extern_btf_info(linker->btf, glob_sym->btf_id,
+					     obj->btf, btf_id))
+			return -EINVAL;
 
+		/* request updating VAR's/FUNC's underlying BTF type when appending BTF type */
+		glob_sym->underlying_btf_id = 0;
+
+		obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
+		return 0;
+	}
+
+add_sym:
+	name_off = strset__add_str(linker->strtab_strs, sym_name);
+	if (name_off < 0)
+		return name_off;
+
+	dst_sym = add_new_sym(linker, &dst_sym_idx);
+	if (!dst_sym)
+		return -ENOMEM;
+
+	dst_sym->st_name = name_off;
+	dst_sym->st_info = sym->st_info;
+	dst_sym->st_other = sym->st_other;
+	dst_sym->st_shndx = dst_sec ? dst_sec->sec_idx : sym->st_shndx;
+	dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
+	dst_sym->st_size = sym->st_size;
+
+	obj->sym_map[src_sym_idx] = dst_sym_idx;
+
+	if (sym_type == STT_SECTION && dst_sym) {
+		dst_sec->sec_sym_idx = dst_sym_idx;
+		dst_sym->st_value = 0;
+	}
+
+	if (sym_bind != STB_LOCAL) {
+		glob_sym = add_glob_sym(linker);
+		if (!glob_sym)
+			return -ENOMEM;
+
+		glob_sym->sym_idx = dst_sym_idx;
+		/* we use dst_sec->id (and not dst_sec->sec_idx), because
+		 * ephemeral sections (.kconfig, .ksyms, etc) don't have
+		 * sec_idx (as they don't have corresponding ELF section), but
+		 * still have id. .extern doesn't have even ephemeral section
+		 * associated with it, so dst_sec->id == dst_sec->sec_idx == 0.
+		 */
+		glob_sym->sec_id = dst_sec ? dst_sec->id : 0;
+		glob_sym->name_off = name_off;
+		/* we will fill btf_id in during BTF merging step */
+		glob_sym->btf_id = 0;
+		glob_sym->is_extern = sym_is_extern;
+		glob_sym->is_weak = sym_bind == STB_WEAK;
 	}
 
 	return 0;
@@ -1200,7 +2014,7 @@ static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *ob
 				return err;
 			}
 		} else if (!secs_match(dst_sec, src_sec)) {
-			pr_warn("Secs %s are not compatible\n", src_sec->sec_name);
+			pr_warn("sections %s are not compatible\n", src_sec->sec_name);
 			return -1;
 		}
 
@@ -1212,7 +2026,7 @@ static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *ob
 		dst_sec->shdr->sh_info = dst_linked_sec->sec_idx;
 
 		src_sec->dst_id = dst_sec->id;
-		err = extend_sec(dst_sec, src_sec);
+		err = extend_sec(linker, dst_sec, src_sec);
 		if (err)
 			return err;
 
@@ -1265,21 +2079,6 @@ static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *ob
 	return 0;
 }
 
-static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name)
-{
-	struct src_sec *sec;
-	int i;
-
-	for (i = 1; i < obj->sec_cnt; i++) {
-		sec = &obj->secs[i];
-
-		if (strcmp(sec->sec_name, sec_name) == 0)
-			return sec;
-	}
-
-	return NULL;
-}
-
 static Elf64_Sym *find_sym_by_name(struct src_obj *obj, size_t sec_idx,
 				   int sym_type, const char *sym_name)
 {
@@ -1334,12 +2133,32 @@ static int linker_fixup_btf(struct src_obj *obj)
 				t->size = sec->shdr->sh_size;
 		} else {
 			/* BTF can have some sections that are not represented
-			 * in ELF, e.g., .kconfig and .ksyms, which are used
-			 * for special extern variables.  Here we'll
-			 * pre-create "section shells" for them to be able to
-			 * keep track of extra per-section metadata later
-			 * (e.g., BTF variables).
+			 * in ELF, e.g., .kconfig, .ksyms, .extern, which are used
+			 * for special extern variables.
+			 *
+			 * For all but one such special (ephemeral)
+			 * sections, we pre-create "section shells" to be able
+			 * to keep track of extra per-section metadata later
+			 * (e.g., those BTF extern variables).
+			 *
+			 * .extern is even more special, though, because it
+			 * contains extern variables that need to be resolved
+			 * by static linker, not libbpf and kernel. When such
+			 * externs are resolved, we are going to remove them
+			 * from .extern BTF section and might end up not
+			 * needing it at all. Each resolved extern should have
+			 * matching non-extern VAR/FUNC in other sections.
+			 *
+			 * We do support leaving some of the externs
+			 * unresolved, though, to support cases of building
+			 * libraries, which will later be linked against final
+			 * BPF applications. So if at finalization we still
+			 * see unresolved externs, we'll create .extern
+			 * section on our own.
 			 */
+			if (strcmp(sec_name, BTF_EXTERN_SEC) == 0)
+				continue;
+
 			sec = add_src_sec(obj, sec_name);
 			if (!sec)
 				return -ENOMEM;
@@ -1379,6 +2198,13 @@ static int linker_fixup_btf(struct src_obj *obj)
 static int remap_type_id(__u32 *type_id, void *ctx)
 {
 	int *id_map = ctx;
+	int new_id = id_map[*type_id];
+
+	/* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
+	if (new_id == 0 && *type_id != 0) {
+		pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id);
+		return -EINVAL;
+	}
 
 	*type_id = id_map[*type_id];
 
@@ -1389,6 +2215,7 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 {
 	const struct btf_type *t;
 	int i, j, n, start_id, id;
+	const char *name;
 
 	if (!obj->btf)
 		return 0;
@@ -1401,12 +2228,44 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 		return -ENOMEM;
 
 	for (i = 1; i <= n; i++) {
+		struct glob_sym *glob_sym = NULL;
+
 		t = btf__type_by_id(obj->btf, i);
 
 		/* DATASECs are handled specially below */
 		if (btf_kind(t) == BTF_KIND_DATASEC)
 			continue;
 
+		if (btf_is_non_static(t)) {
+			/* there should be glob_sym already */
+			name = btf__str_by_offset(obj->btf, t->name_off);
+			glob_sym = find_glob_sym(linker, name);
+
+			/* VARs without corresponding glob_sym are those that
+			 * belong to skipped/deduplicated sections (i.e.,
+			 * license and version), so just skip them
+			 */
+			if (!glob_sym)
+				continue;
+
+			/* linker_append_elf_sym() might have requested
+			 * updating underlying type ID, if extern was resolved
+			 * to strong symbol or weak got upgraded to non-weak
+			 */
+			if (glob_sym->underlying_btf_id == 0)
+				glob_sym->underlying_btf_id = -t->type;
+
+			/* globals from previous object files that match our
+			 * VAR/FUNC already have a corresponding associated
+			 * BTF type, so just make sure to use it
+			 */
+			if (glob_sym->btf_id) {
+				/* reuse existing BTF type for global var/func */
+				obj->btf_type_map[i] = glob_sym->btf_id;
+				continue;
+			}
+		}
+
 		id = btf__add_type(linker->btf, obj->btf, t);
 		if (id < 0) {
 			pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename);
@@ -1414,6 +2273,12 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 		}
 
 		obj->btf_type_map[i] = id;
+
+		/* record just appended BTF type for var/func */
+		if (glob_sym) {
+			glob_sym->btf_id = id;
+			glob_sym->underlying_btf_id = -t->type;
+		}
 	}
 
 	/* remap all the types except DATASECs */
@@ -1425,6 +2290,22 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 			return -EINVAL;
 	}
 
+	/* Rewrite VAR/FUNC underlying types (i.e., FUNC's FUNC_PROTO and VAR's
+	 * actual type), if necessary
+	 */
+	for (i = 0; i < linker->glob_sym_cnt; i++) {
+		struct glob_sym *glob_sym = &linker->glob_syms[i];
+		struct btf_type *glob_t;
+
+		if (glob_sym->underlying_btf_id >= 0)
+			continue;
+
+		glob_sym->underlying_btf_id = obj->btf_type_map[-glob_sym->underlying_btf_id];
+
+		glob_t = btf_type_by_id(linker->btf, glob_sym->btf_id);
+		glob_t->type = glob_sym->underlying_btf_id;
+	}
+
 	/* append DATASEC info */
 	for (i = 1; i < obj->sec_cnt; i++) {
 		struct src_sec *src_sec;
@@ -1452,6 +2333,42 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 		n = btf_vlen(t);
 		for (j = 0; j < n; j++, src_var++) {
 			void *sec_vars = dst_sec->sec_vars;
+			int new_id = obj->btf_type_map[src_var->type];
+			struct glob_sym *glob_sym = NULL;
+
+			t = btf_type_by_id(linker->btf, new_id);
+			if (btf_is_non_static(t)) {
+				name = btf__str_by_offset(linker->btf, t->name_off);
+				glob_sym = find_glob_sym(linker, name);
+				if (glob_sym->sec_id != dst_sec->id) {
+					pr_warn("global '%s': section mismatch %d vs %d\n",
+						name, glob_sym->sec_id, dst_sec->id);
+					return -EINVAL;
+				}
+			}
+
+			/* If there is already a member (VAR or FUNC) mapped
+			 * to the same type, don't add a duplicate entry.
+			 * This will happen when multiple object files define
+			 * the same extern VARs/FUNCs.
+			 */
+			if (glob_sym && glob_sym->var_idx >= 0) {
+				__s64 sz;
+
+				dst_var = &dst_sec->sec_vars[glob_sym->var_idx];
+				/* Because underlying BTF type might have
+				 * changed, so might its size have changed, so
+				 * re-calculate and update it in sec_var.
+				 */
+				sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
+				if (sz < 0) {
+					pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
+						name, (int)sz);
+					return -EINVAL;
+				}
+				dst_var->size = sz;
+				continue;
+			}
 
 			sec_vars = libbpf_reallocarray(sec_vars,
 						       dst_sec->sec_var_cnt + 1,
@@ -1466,6 +2383,9 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
 			dst_var->type = obj->btf_type_map[src_var->type];
 			dst_var->size = src_var->size;
 			dst_var->offset = src_sec->dst_off + src_var->offset;
+
+			if (glob_sym)
+				glob_sym->var_idx = dst_sec->sec_var_cnt - 1;
 		}
 	}
 
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c5bcdb3d4b12..283e5ad8385e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -21,7 +21,7 @@ endif
 
 BPF_GCC		?= $(shell command -v bpf-gcc;)
 SAN_CFLAGS	?=
-CFLAGS += -g -Og -rdynamic -Wall $(GENFLAGS) $(SAN_CFLAGS)		\
+CFLAGS += -g -O0 -rdynamic -Wall $(GENFLAGS) $(SAN_CFLAGS)		\
 	  -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)		\
 	  -I$(TOOLSINCDIR) -I$(APIDIR) -I$(OUTPUT)			\
 	  -Dbpf_prog_load=bpf_prog_test_load				\
@@ -205,7 +205,7 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
 		    $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
 	$(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)			       \
 		    CC=$(HOSTCC) LD=$(HOSTLD)				       \
-		    EXTRA_CFLAGS='-g -Og'				       \
+		    EXTRA_CFLAGS='-g -O0'				       \
 		    OUTPUT=$(HOST_BUILD_DIR)/bpftool/			       \
 		    prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install
 
@@ -225,7 +225,7 @@ $(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)		       \
 	   ../../../include/uapi/linux/bpf.h                                   \
 	   | $(INCLUDE_DIR) $(BUILD_DIR)/libbpf
 	$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(BUILD_DIR)/libbpf/ \
-		    EXTRA_CFLAGS='-g -Og'					       \
+		    EXTRA_CFLAGS='-g -O0'				       \
 		    DESTDIR=$(SCRATCH_DIR) prefix= all install_headers
 
 ifneq ($(BPFOBJ),$(HOST_BPFOBJ))
@@ -233,7 +233,7 @@ $(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)                \
 	   ../../../include/uapi/linux/bpf.h                                   \
 	   | $(INCLUDE_DIR) $(HOST_BUILD_DIR)/libbpf
 	$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR)                             \
-		    EXTRA_CFLAGS='-g -Og'					       \
+		    EXTRA_CFLAGS='-g -O0'				       \
 		    OUTPUT=$(HOST_BUILD_DIR)/libbpf/ CC=$(HOSTCC) LD=$(HOSTLD) \
 		    DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers
 endif
@@ -309,9 +309,15 @@ endef
 
 SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
 
-LINKED_SKELS := test_static_linked.skel.h
+LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
+		linked_vars.skel.h linked_maps.skel.h
 
 test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
+linked_funcs.skel.h-deps := linked_funcs1.o linked_funcs2.o
+linked_vars.skel.h-deps := linked_vars1.o linked_vars2.o
+linked_maps.skel.h-deps := linked_maps1.o linked_maps2.o
+
+LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
 
 # Set up extra TRUNNER_XXX "temporary" variables in the environment (relies on
 # $eval()) and pass control to DEFINE_TEST_RUNNER_RULES.
@@ -331,7 +337,7 @@ TRUNNER_TESTS_HDR := $(TRUNNER_TESTS_DIR)/tests.h
 TRUNNER_BPF_SRCS := $$(notdir $$(wildcard $(TRUNNER_BPF_PROGS_DIR)/*.c))
 TRUNNER_BPF_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.o, $$(TRUNNER_BPF_SRCS))
 TRUNNER_BPF_SKELS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.skel.h,	\
-				 $$(filter-out $(SKEL_BLACKLIST),	\
+				 $$(filter-out $(SKEL_BLACKLIST) $(LINKED_BPF_SRCS),\
 					       $$(TRUNNER_BPF_SRCS)))
 TRUNNER_BPF_SKELS_LINKED := $$(addprefix $$(TRUNNER_OUTPUT)/,$(LINKED_SKELS))
 TEST_GEN_FILES += $$(TRUNNER_BPF_OBJS)
diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst
index 65fe318d1e71..3353778c30f8 100644
--- a/tools/testing/selftests/bpf/README.rst
+++ b/tools/testing/selftests/bpf/README.rst
@@ -193,3 +193,12 @@ Without it, the error from compiling bpf selftests looks like:
   libbpf: failed to find BTF for extern 'tcp_slow_start' [25] section: -2
 
 __ https://reviews.llvm.org/D93563
+
+Clang dependencies for static linking tests
+===========================================
+
+linked_vars, linked_maps, and linked_funcs tests depend on `Clang fix`__ to
+generate valid BTF information for weak variables. Please make sure you use
+Clang that contains the fix.
+
+__ https://reviews.llvm.org/D100362
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_funcs.c b/tools/testing/selftests/bpf/prog_tests/linked_funcs.c
new file mode 100644
index 000000000000..e9916f2817ec
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_funcs.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+#include <sys/syscall.h>
+#include "linked_funcs.skel.h"
+
+void test_linked_funcs(void)
+{
+	int err;
+	struct linked_funcs *skel;
+
+	skel = linked_funcs__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->rodata->my_tid = syscall(SYS_gettid);
+	skel->bss->syscall_id = SYS_getpgid;
+
+	err = linked_funcs__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	err = linked_funcs__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	syscall(SYS_getpgid);
+
+	ASSERT_EQ(skel->bss->output_val1, 2000 + 2000, "output_val1");
+	ASSERT_EQ(skel->bss->output_ctx1, SYS_getpgid, "output_ctx1");
+	ASSERT_EQ(skel->bss->output_weak1, 42, "output_weak1");
+
+	ASSERT_EQ(skel->bss->output_val2, 2 * 1000 + 2 * (2 * 1000), "output_val2");
+	ASSERT_EQ(skel->bss->output_ctx2, SYS_getpgid, "output_ctx2");
+	/* output_weak2 should never be updated */
+	ASSERT_EQ(skel->bss->output_weak2, 0, "output_weak2");
+
+cleanup:
+	linked_funcs__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_maps.c b/tools/testing/selftests/bpf/prog_tests/linked_maps.c
new file mode 100644
index 000000000000..85dcaaaf2775
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_maps.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+#include <sys/syscall.h>
+#include "linked_maps.skel.h"
+
+void test_linked_maps(void)
+{
+	int err;
+	struct linked_maps *skel;
+
+	skel = linked_maps__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	err = linked_maps__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	syscall(SYS_getpgid);
+
+	ASSERT_EQ(skel->bss->output_first1, 2000, "output_first1");
+	ASSERT_EQ(skel->bss->output_second1, 2, "output_second1");
+	ASSERT_EQ(skel->bss->output_weak1, 2, "output_weak1");
+
+cleanup:
+	linked_maps__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_vars.c b/tools/testing/selftests/bpf/prog_tests/linked_vars.c
new file mode 100644
index 000000000000..267166abe4c1
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_vars.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+#include <sys/syscall.h>
+#include "linked_vars.skel.h"
+
+void test_linked_vars(void)
+{
+	int err;
+	struct linked_vars *skel;
+
+	skel = linked_vars__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->bss->input_bss1 = 1000;
+	skel->bss->input_bss2 = 2000;
+	skel->bss->input_bss_weak = 3000;
+
+	err = linked_vars__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	err = linked_vars__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	syscall(SYS_getpgid);
+
+	ASSERT_EQ(skel->bss->output_bss1, 1000 + 2000 + 3000, "output_bss1");
+	ASSERT_EQ(skel->bss->output_bss2, 1000 + 2000 + 3000, "output_bss2");
+	/* 10 comes from "winner" input_data_weak in first obj file */
+	ASSERT_EQ(skel->bss->output_data1, 1 + 2 + 10, "output_bss1");
+	ASSERT_EQ(skel->bss->output_data2, 1 + 2 + 10, "output_bss2");
+	/* 100 comes from "winner" input_rodata_weak in first obj file */
+	ASSERT_EQ(skel->bss->output_rodata1, 11 + 22 + 100, "output_weak1");
+	ASSERT_EQ(skel->bss->output_rodata2, 11 + 22 + 100, "output_weak2");
+
+cleanup:
+	linked_vars__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/linked_funcs1.c b/tools/testing/selftests/bpf/progs/linked_funcs1.c
new file mode 100644
index 000000000000..b964ec1390c2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_funcs1.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+/* weak and shared between two files */
+const volatile int my_tid __weak;
+long syscall_id __weak;
+
+int output_val1;
+int output_ctx1;
+int output_weak1;
+
+/* same "subprog" name in all files, but it's ok because they all are static */
+static __noinline int subprog(int x)
+{
+	/* but different formula */
+	return x * 1;
+}
+
+/* Global functions can't be void */
+int set_output_val1(int x)
+{
+	output_val1 = x + subprog(x);
+	return x;
+}
+
+/* This function can't be verified as global, as it assumes raw_tp/sys_enter
+ * context and accesses syscall id (second argument). So we mark it as
+ * __hidden, so that libbpf will mark it as static in the final object file,
+ * right before verifying it in the kernel.
+ *
+ * But we don't mark it as __hidden here, rather at extern site. __hidden is
+ * "contaminating" visibility, so it will get propagated from either extern or
+ * actual definition (including from the losing __weak definition).
+ */
+void set_output_ctx1(__u64 *ctx)
+{
+	output_ctx1 = ctx[1]; /* long id, same as in BPF_PROG below */
+}
+
+/* this weak instance should win because it's the first one */
+__weak int set_output_weak(int x)
+{
+	output_weak1 = x;
+	return x;
+}
+
+extern int set_output_val2(int x);
+
+/* here we'll force set_output_ctx2() to be __hidden in the final obj file */
+__hidden extern void set_output_ctx2(__u64 *ctx);
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler1, struct pt_regs *regs, long id)
+{
+	if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
+		return 0;
+
+	set_output_val2(1000);
+	set_output_ctx2(ctx); /* ctx definition is hidden in BPF_PROG macro */
+
+	/* keep input value the same across both files to avoid dependency on
+	 * handler call order; differentiate by output_weak1 vs output_weak2.
+	 */
+	set_output_weak(42);
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_funcs2.c b/tools/testing/selftests/bpf/progs/linked_funcs2.c
new file mode 100644
index 000000000000..575e958e60b7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_funcs2.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+/* weak and shared between both files */
+const volatile int my_tid __weak;
+long syscall_id __weak;
+
+int output_val2;
+int output_ctx2;
+int output_weak2; /* should stay zero */
+
+/* same "subprog" name in all files, but it's ok because they all are static */
+static __noinline int subprog(int x)
+{
+	/* but different formula */
+	return x * 2;
+}
+
+/* Global functions can't be void */
+int set_output_val2(int x)
+{
+	output_val2 = 2 * x + 2 * subprog(x);
+	return 2 * x;
+}
+
+/* This function can't be verified as global, as it assumes raw_tp/sys_enter
+ * context and accesses syscall id (second argument). So we mark it as
+ * __hidden, so that libbpf will mark it as static in the final object file,
+ * right before verifying it in the kernel.
+ *
+ * But we don't mark it as __hidden here, rather at extern site. __hidden is
+ * "contaminating" visibility, so it will get propagated from either extern or
+ * actual definition (including from the losing __weak definition).
+ */
+void set_output_ctx2(__u64 *ctx)
+{
+	output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
+}
+
+/* this weak instance should lose, because it will be processed second */
+__weak int set_output_weak(int x)
+{
+	output_weak2 = x;
+	return 2 * x;
+}
+
+extern int set_output_val1(int x);
+
+/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
+__hidden extern void set_output_ctx1(__u64 *ctx);
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler2, struct pt_regs *regs, long id)
+{
+	if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
+		return 0;
+
+	set_output_val1(2000);
+	set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */
+
+	/* keep input value the same across both files to avoid dependency on
+	 * handler call order; differentiate by output_weak1 vs output_weak2.
+	 */
+	set_output_weak(42);
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_maps1.c b/tools/testing/selftests/bpf/progs/linked_maps1.c
new file mode 100644
index 000000000000..52291515cc72
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_maps1.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct my_key { long x; };
+struct my_value { long x; };
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, struct my_key);
+	__type(value, struct my_value);
+	__uint(max_entries, 16);
+} map1 SEC(".maps");
+
+ /* Matches map2 definition in linked_maps2.c. Order of the attributes doesn't
+  * matter.
+  */
+typedef struct {
+	__uint(max_entries, 8);
+	__type(key, int);
+	__type(value, int);
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+} map2_t;
+
+extern map2_t map2 SEC(".maps");
+
+/* This should be the winning map definition, but we have no way of verifying,
+ * so we just make sure that it links and works without errors
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 16);
+} map_weak __weak SEC(".maps");
+
+int output_first1;
+int output_second1;
+int output_weak1;
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler_enter1)
+{
+	/* update values with key = 1 */
+	int key = 1, val = 1;
+	struct my_key key_struct = { .x = 1 };
+	struct my_value val_struct = { .x = 1000 };
+
+	bpf_map_update_elem(&map1, &key_struct, &val_struct, 0);
+	bpf_map_update_elem(&map2, &key, &val, 0);
+	bpf_map_update_elem(&map_weak, &key, &val, 0);
+
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int BPF_PROG(handler_exit1)
+{
+	/* lookup values with key = 2, set in another file */
+	int key = 2, *val;
+	struct my_key key_struct = { .x = 2 };
+	struct my_value *value_struct;
+
+	value_struct = bpf_map_lookup_elem(&map1, &key_struct);
+	if (value_struct)
+		output_first1 = value_struct->x;
+
+	val = bpf_map_lookup_elem(&map2, &key);
+	if (val)
+		output_second1 = *val;
+
+	val = bpf_map_lookup_elem(&map_weak, &key);
+	if (val)
+		output_weak1 = *val;
+	
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_maps2.c b/tools/testing/selftests/bpf/progs/linked_maps2.c
new file mode 100644
index 000000000000..0693687474ed
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_maps2.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+/* modifiers and typedefs are ignored when comparing key/value types */
+typedef struct my_key { long x; } key_type;
+typedef struct my_value { long x; } value_type;
+
+extern struct {
+	__uint(max_entries, 16);
+	__type(key, key_type);
+	__type(value, value_type);
+	__uint(type, BPF_MAP_TYPE_HASH);
+} map1 SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 8);
+} map2 SEC(".maps");
+
+/* this definition will lose, but it has to exactly match the winner */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 16);
+} map_weak __weak SEC(".maps");
+
+int output_first2;
+int output_second2;
+int output_weak2;
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler_enter2)
+{
+	/* update values with key = 2 */
+	int key = 2, val = 2;
+	key_type key_struct = { .x = 2 };
+	value_type val_struct = { .x = 2000 };
+
+	bpf_map_update_elem(&map1, &key_struct, &val_struct, 0);
+	bpf_map_update_elem(&map2, &key, &val, 0);
+	bpf_map_update_elem(&map_weak, &key, &val, 0);
+
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int BPF_PROG(handler_exit2)
+{
+	/* lookup values with key = 1, set in another file */
+	int key = 1, *val;
+	key_type key_struct = { .x = 1 };
+	value_type *value_struct;
+
+	value_struct = bpf_map_lookup_elem(&map1, &key_struct);
+	if (value_struct)
+		output_first2 = value_struct->x;
+
+	val = bpf_map_lookup_elem(&map2, &key);
+	if (val)
+		output_second2 = *val;
+
+	val = bpf_map_lookup_elem(&map_weak, &key);
+	if (val)
+		output_weak2 = *val;
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_vars1.c b/tools/testing/selftests/bpf/progs/linked_vars1.c
new file mode 100644
index 000000000000..ef9e9d0bb0ca
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_vars1.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+extern int LINUX_KERNEL_VERSION __kconfig;
+/* this weak extern will be strict due to the other file's strong extern */
+extern bool CONFIG_BPF_SYSCALL __kconfig __weak;
+extern const void bpf_link_fops __ksym __weak;
+
+int input_bss1;
+int input_data1 = 1;
+const volatile int input_rodata1 = 11;
+
+int input_bss_weak __weak;
+/* these two definitions should win */
+int input_data_weak __weak = 10;
+const volatile int input_rodata_weak __weak = 100;
+
+extern int input_bss2;
+extern int input_data2;
+extern const int input_rodata2;
+
+int output_bss1;
+int output_data1;
+int output_rodata1;
+
+long output_sink1;
+
+static __noinline int get_bss_res(void)
+{
+	/* just make sure all the relocations work against .text as well */
+	return input_bss1 + input_bss2 + input_bss_weak;
+}
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler1)
+{
+	output_bss1 = get_bss_res();
+	output_data1 = input_data1 + input_data2 + input_data_weak;
+	output_rodata1 = input_rodata1 + input_rodata2 + input_rodata_weak;
+
+	/* make sure we actually use above special externs, otherwise compiler
+	 * will optimize them out
+	 */
+	output_sink1 = LINUX_KERNEL_VERSION
+		       + CONFIG_BPF_SYSCALL
+		       + (long)&bpf_link_fops;
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_vars2.c b/tools/testing/selftests/bpf/progs/linked_vars2.c
new file mode 100644
index 000000000000..e4f5bd388a3c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_vars2.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+extern int LINUX_KERNEL_VERSION __kconfig;
+/* when an extern is defined as both strong and weak, resulting symbol will be strong */
+extern bool CONFIG_BPF_SYSCALL __kconfig;
+extern const void __start_BTF __ksym;
+
+int input_bss2;
+int input_data2 = 2;
+const volatile int input_rodata2 = 22;
+
+int input_bss_weak __weak;
+/* these two weak variables should lose */
+int input_data_weak __weak = 20;
+const volatile int input_rodata_weak __weak = 200;
+
+extern int input_bss1;
+extern int input_data1;
+extern const int input_rodata1;
+
+int output_bss2;
+int output_data2;
+int output_rodata2;
+
+int output_sink2;
+
+static __noinline int get_data_res(void)
+{
+	/* just make sure all the relocations work against .text as well */
+	return input_data1 + input_data2 + input_data_weak;
+}
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler2)
+{
+	output_bss2 = input_bss1 + input_bss2 + input_bss_weak;
+	output_data2 = get_data_res();
+	output_rodata2 = input_rodata1 + input_rodata2 + input_rodata_weak;
+
+	/* make sure we actually use above special externs, otherwise compiler
+	 * will optimize them out
+	 */
+	output_sink2 = LINUX_KERNEL_VERSION
+		       + CONFIG_BPF_SYSCALL
+		       + (long)&__start_BTF;
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";