bpf: add support for bpf_wq user type

Mostly a copy/paste from the bpf_timer API, without the initialization
and free, as they will be done in a separate patch.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-5-6c986a5a741f@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -185,7 +185,7 @@ struct bpf_map_ops {
 
 enum {
 	/* Support at most 10 fields in a BTF type */
-	BTF_FIELDS_MAX	   = 10,
+	BTF_FIELDS_MAX	   = 11,
 };
 
 enum btf_field_type {
@@ -202,6 +202,7 @@ enum btf_field_type {
 	BPF_GRAPH_NODE = BPF_RB_NODE | BPF_LIST_NODE,
 	BPF_GRAPH_ROOT = BPF_RB_ROOT | BPF_LIST_HEAD,
 	BPF_REFCOUNT   = (1 << 9),
+	BPF_WORKQUEUE  = (1 << 10),
 };
 
 typedef void (*btf_dtor_kfunc_t)(void *);
@@ -238,6 +239,7 @@ struct btf_record {
 	u32 field_mask;
 	int spin_lock_off;
 	int timer_off;
+	int wq_off;
 	int refcount_off;
 	struct btf_field fields[];
 };
@@ -312,6 +314,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
 		return "bpf_spin_lock";
 	case BPF_TIMER:
 		return "bpf_timer";
+	case BPF_WORKQUEUE:
+		return "bpf_wq";
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return "kptr";
@@ -340,6 +344,8 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 		return sizeof(struct bpf_spin_lock);
 	case BPF_TIMER:
 		return sizeof(struct bpf_timer);
+	case BPF_WORKQUEUE:
+		return sizeof(struct bpf_wq);
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 	case BPF_KPTR_PERCPU:
@@ -367,6 +373,8 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
 		return __alignof__(struct bpf_spin_lock);
 	case BPF_TIMER:
 		return __alignof__(struct bpf_timer);
+	case BPF_WORKQUEUE:
+		return __alignof__(struct bpf_wq);
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 	case BPF_KPTR_PERCPU:
@@ -406,6 +414,7 @@ static inline void bpf_obj_init_field(const struct btf_field *field, void *addr)
 		/* RB_ROOT_CACHED 0-inits, no need to do anything after memset */
 	case BPF_SPIN_LOCK:
 	case BPF_TIMER:
+	case BPF_WORKQUEUE:
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 	case BPF_KPTR_PERCPU:

include/uapi/linux/bpf.h

@@ -7306,6 +7306,10 @@ struct bpf_timer {
 	__u64 __opaque[2];
 } __attribute__((aligned(8)));
 
+struct bpf_wq {
+	__u64 __opaque[2];
+} __attribute__((aligned(8)));
+
 struct bpf_dynptr {
 	__u64 __opaque[2];
 } __attribute__((aligned(8)));

kernel/bpf/btf.c

@@ -3464,6 +3464,15 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			goto end;
 		}
 	}
+	if (field_mask & BPF_WORKQUEUE) {
+		if (!strcmp(name, "bpf_wq")) {
+			if (*seen_mask & BPF_WORKQUEUE)
+				return -E2BIG;
+			*seen_mask |= BPF_WORKQUEUE;
+			type = BPF_WORKQUEUE;
+			goto end;
+		}
+	}
 	field_mask_test_name(BPF_LIST_HEAD, "bpf_list_head");
 	field_mask_test_name(BPF_LIST_NODE, "bpf_list_node");
 	field_mask_test_name(BPF_RB_ROOT,   "bpf_rb_root");
@@ -3515,6 +3524,7 @@ static int btf_find_struct_field(const struct btf *btf,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_WORKQUEUE:
 		case BPF_LIST_NODE:
 		case BPF_RB_NODE:
 		case BPF_REFCOUNT:
@@ -3582,6 +3592,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_WORKQUEUE:
 		case BPF_LIST_NODE:
 		case BPF_RB_NODE:
 		case BPF_REFCOUNT:
@@ -3816,6 +3827,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 
 	rec->spin_lock_off = -EINVAL;
 	rec->timer_off = -EINVAL;
+	rec->wq_off = -EINVAL;
 	rec->refcount_off = -EINVAL;
 	for (i = 0; i < cnt; i++) {
 		field_type_size = btf_field_type_size(info_arr[i].type);
@@ -3846,6 +3858,11 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			/* Cache offset for faster lookup at runtime */
 			rec->timer_off = rec->fields[i].offset;
 			break;
+		case BPF_WORKQUEUE:
+			WARN_ON_ONCE(rec->wq_off >= 0);
+			/* Cache offset for faster lookup at runtime */
+			rec->wq_off = rec->fields[i].offset;
+			break;
 		case BPF_REFCOUNT:
 			WARN_ON_ONCE(rec->refcount_off >= 0);
 			/* Cache offset for faster lookup at runtime */

kernel/bpf/syscall.c

@@ -559,6 +559,7 @@ void btf_record_free(struct btf_record *rec)
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
 		case BPF_REFCOUNT:
+		case BPF_WORKQUEUE:
 			/* Nothing to release */
 			break;
 		default:
@@ -608,6 +609,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
 		case BPF_REFCOUNT:
+		case BPF_WORKQUEUE:
 			/* Nothing to acquire */
 			break;
 		default:
@@ -679,6 +681,8 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 		case BPF_TIMER:
 			bpf_timer_cancel_and_free(field_ptr);
 			break;
+		case BPF_WORKQUEUE:
+			break;
 		case BPF_KPTR_UNREF:
 			WRITE_ONCE(*(u64 *)field_ptr, 0);
 			break;
@@ -1085,7 +1089,7 @@ static int map_check_btf(struct bpf_map *map, struct bpf_token *token,
 
 	map->record = btf_parse_fields(btf, value_type,
 				       BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR | BPF_LIST_HEAD |
-				       BPF_RB_ROOT | BPF_REFCOUNT,
+				       BPF_RB_ROOT | BPF_REFCOUNT | BPF_WORKQUEUE,
 				       map->value_size);
 	if (!IS_ERR_OR_NULL(map->record)) {
 		int i;

kernel/bpf/verifier.c

@@ -1838,6 +1838,8 @@ static void mark_ptr_not_null_reg(struct bpf_reg_state *reg)
 			 */
 			if (btf_record_has_field(map->inner_map_meta->record, BPF_TIMER))
 				reg->map_uid = reg->id;
+			if (btf_record_has_field(map->inner_map_meta->record, BPF_WORKQUEUE))
+				reg->map_uid = reg->id;
 		} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
 			reg->type = PTR_TO_XDP_SOCK;
 		} else if (map->map_type == BPF_MAP_TYPE_SOCKMAP ||
@@ -18141,6 +18143,13 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		}
 	}
 
+	if (btf_record_has_field(map->record, BPF_WORKQUEUE)) {
+		if (is_tracing_prog_type(prog_type)) {
+			verbose(env, "tracing progs cannot use bpf_wq yet\n");
+			return -EINVAL;
+		}
+	}
+
 	if ((bpf_prog_is_offloaded(prog->aux) || bpf_map_is_offloaded(map)) &&
 	    !bpf_offload_prog_map_match(prog, map)) {
 		verbose(env, "offload device mismatch between prog and map\n");