bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_array maps

Introduce support for the BPF_F_ALL_CPUS flag in percpu_array maps to
allow updating values for all CPUs with a single value for both
update_elem and update_batch APIs.

Introduce support for the BPF_F_CPU flag in percpu_array maps to allow:

* update value for specified CPU for both update_elem and update_batch
APIs.
* lookup value for specified CPU for both lookup_elem and lookup_batch
APIs.

The BPF_F_CPU flag is passed via:

* map_flags of lookup_elem and update_elem APIs along with embedded cpu
info.
* elem_flags of lookup_batch and update_batch APIs along with embedded
cpu info.

Signed-off-by: Leon Hwang <[email protected]>

Author: Asphaltt

include/linux/bpf.h

@@ -2762,7 +2762,7 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env,
 				   struct bpf_func_state *callee);
 
 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
-int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
+int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags);
 int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 			   u64 flags);
 int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
@@ -3831,7 +3831,12 @@ bpf_prog_update_insn_ptrs(struct bpf_prog *prog, u32 *offsets, void *image)
 
 static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
 {
-	return false;
+	switch (map_type) {
+	case BPF_MAP_TYPE_PERCPU_ARRAY:
+		return true;
+	default:
+		return false;
+	}
 }
 
 static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 allowed_flags)

kernel/bpf/arraymap.c

@@ -307,7 +307,7 @@ static void *percpu_array_map_lookup_percpu_elem(struct bpf_map *map, void *key,
 	return per_cpu_ptr(array->pptrs[index & array->index_mask], cpu);
 }
 
-int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
+int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 map_flags)
 {
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	u32 index = *(u32 *)key;
@@ -325,11 +325,18 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
 	size = array->elem_size;
 	rcu_read_lock();
 	pptr = array->pptrs[index & array->index_mask];
+	if (map_flags & BPF_F_CPU) {
+		cpu = map_flags >> 32;
+		copy_map_value(map, value, per_cpu_ptr(pptr, cpu));
+		check_and_init_map_value(map, value);
+		goto unlock;
+	}
 	for_each_possible_cpu(cpu) {
 		copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu));
 		check_and_init_map_value(map, value + off);
 		off += size;
 	}
+unlock:
 	rcu_read_unlock();
 	return 0;
 }
@@ -398,10 +405,11 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	u32 index = *(u32 *)key;
 	void __percpu *pptr;
-	int cpu, off = 0;
+	void *ptr, *val;
 	u32 size;
+	int cpu;
 
-	if (unlikely(map_flags > BPF_EXIST))
+	if (unlikely((map_flags & BPF_F_LOCK) || (u32)map_flags > BPF_F_ALL_CPUS))
 		/* unknown flags */
 		return -EINVAL;
 
@@ -422,11 +430,20 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	size = array->elem_size;
 	rcu_read_lock();
 	pptr = array->pptrs[index & array->index_mask];
+	if (map_flags & BPF_F_CPU) {
+		cpu = map_flags >> 32;
+		ptr = per_cpu_ptr(pptr, cpu);
+		copy_map_value(map, ptr, value);
+		bpf_obj_free_fields(array->map.record, ptr);
+		goto unlock;
+	}
 	for_each_possible_cpu(cpu) {
-		copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off);
-		bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu));
-		off += size;
+		ptr = per_cpu_ptr(pptr, cpu);
+		val = (map_flags & BPF_F_ALL_CPUS) ? value : value + size * cpu;
+		copy_map_value(map, ptr, val);
+		bpf_obj_free_fields(array->map.record, ptr);
 	}
+unlock:
 	rcu_read_unlock();
 	return 0;
 }

kernel/bpf/syscall.c

@@ -318,7 +318,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
 	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
 		err = bpf_percpu_hash_copy(map, key, value);
 	} else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
-		err = bpf_percpu_array_copy(map, key, value);
+		err = bpf_percpu_array_copy(map, key, value, flags);
 	} else if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) {
 		err = bpf_percpu_cgroup_storage_copy(map, key, value);
 	} else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) {