libbpf: Introduce more granular state for bpf_object

We are going to split bpf_object loading into 2 stages: preparation and
loading. This will increase flexibility when working with bpf_object
and unlock some optimizations and use cases.
This patch substitutes a boolean flag (loaded) by more finely-grained
state for bpf_object.

Signed-off-by: Mykyta Yatsenko <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: mykyta5

tools/lib/bpf/libbpf.c

@@ -670,11 +670,18 @@ struct elf_state {
 
 struct usdt_manager;
 
+enum bpf_object_state {
+	OBJ_OPEN,
+	OBJ_PREPARED,
+	OBJ_LOADED,
+};
+
 struct bpf_object {
 	char name[BPF_OBJ_NAME_LEN];
 	char license[64];
 	__u32 kern_version;
 
+	enum bpf_object_state state;
 	struct bpf_program *programs;
 	size_t nr_programs;
 	struct bpf_map *maps;
@@ -686,7 +693,6 @@ struct bpf_object {
 	int nr_extern;
 	int kconfig_map_idx;
 
-	bool loaded;
 	bool has_subcalls;
 	bool has_rodata;
 
@@ -1511,7 +1517,7 @@ static struct bpf_object *bpf_object__new(const char *path,
 	obj->kconfig_map_idx = -1;
 
 	obj->kern_version = get_kernel_version();
-	obj->loaded = false;
+	obj->state  = OBJ_OPEN;
 
 	return obj;
 }
@@ -4847,7 +4853,7 @@ static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
 
 static bool map_is_created(const struct bpf_map *map)
 {
-	return map->obj->loaded || map->reused;
+	return map->obj->state >= OBJ_PREPARED || map->reused;
 }
 
 bool bpf_map__autocreate(const struct bpf_map *map)
@@ -8550,7 +8556,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
 	if (!obj)
 		return libbpf_err(-EINVAL);
 
-	if (obj->loaded) {
+	if (obj->state >= OBJ_LOADED) {
 		pr_warn("object '%s': load can't be attempted twice\n", obj->name);
 		return libbpf_err(-EINVAL);
 	}
@@ -8602,8 +8608,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
 	btf__free(obj->btf_vmlinux);
 	obj->btf_vmlinux = NULL;
 
-	obj->loaded = true; /* doesn't matter if successfully or not */
-
+	obj->state = OBJ_LOADED; /* doesn't matter if successfully or not */
 	if (err)
 		goto out;
 
@@ -8866,7 +8871,7 @@ int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 	if (!obj)
 		return libbpf_err(-ENOENT);
 
-	if (!obj->loaded) {
+	if (obj->state < OBJ_PREPARED) {
 		pr_warn("object not yet loaded; load it first\n");
 		return libbpf_err(-ENOENT);
 	}
@@ -8945,7 +8950,7 @@ int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 	if (!obj)
 		return libbpf_err(-ENOENT);
 
-	if (!obj->loaded) {
+	if (obj->state < OBJ_LOADED) {
 		pr_warn("object not yet loaded; load it first\n");
 		return libbpf_err(-ENOENT);
 	}
@@ -9132,7 +9137,7 @@ int bpf_object__btf_fd(const struct bpf_object *obj)
 
 int bpf_object__set_kversion(struct bpf_object *obj, __u32 kern_version)
 {
-	if (obj->loaded)
+	if (obj->state >= OBJ_LOADED)
 		return libbpf_err(-EINVAL);
 
 	obj->kern_version = kern_version;
@@ -9229,7 +9234,7 @@ bool bpf_program__autoload(const struct bpf_program *prog)
 
 int bpf_program__set_autoload(struct bpf_program *prog, bool autoload)
 {
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EINVAL);
 
 	prog->autoload = autoload;
@@ -9261,7 +9266,7 @@ int bpf_program__set_insns(struct bpf_program *prog,
 {
 	struct bpf_insn *insns;
 
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	insns = libbpf_reallocarray(prog->insns, new_insn_cnt, sizeof(*insns));
@@ -9304,7 +9309,7 @@ static int last_custom_sec_def_handler_id;
 
 int bpf_program__set_type(struct bpf_program *prog, enum bpf_prog_type type)
 {
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	/* if type is not changed, do nothing */
@@ -9335,7 +9340,7 @@ enum bpf_attach_type bpf_program__expected_attach_type(const struct bpf_program
 int bpf_program__set_expected_attach_type(struct bpf_program *prog,
 					   enum bpf_attach_type type)
 {
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	prog->expected_attach_type = type;
@@ -9349,7 +9354,7 @@ __u32 bpf_program__flags(const struct bpf_program *prog)
 
 int bpf_program__set_flags(struct bpf_program *prog, __u32 flags)
 {
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	prog->prog_flags = flags;
@@ -9363,7 +9368,7 @@ __u32 bpf_program__log_level(const struct bpf_program *prog)
 
 int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level)
 {
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	prog->log_level = log_level;
@@ -9382,7 +9387,7 @@ int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log
 		return libbpf_err(-EINVAL);
 	if (prog->log_size > UINT_MAX)
 		return libbpf_err(-EINVAL);
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EBUSY);
 
 	prog->log_buf = log_buf;
@@ -13666,7 +13671,7 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
 	if (!prog || attach_prog_fd < 0)
 		return libbpf_err(-EINVAL);
 
-	if (prog->obj->loaded)
+	if (prog->obj->state >= OBJ_LOADED)
 		return libbpf_err(-EINVAL);
 
 	if (attach_prog_fd && !attach_func_name) {