bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags

Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags and check them for
following APIs:

* 'map_lookup_elem()'
* 'map_update_elem()'
* 'generic_map_lookup_batch()'
* 'generic_map_update_batch()'

And, get the correct value size for these APIs.

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

Author: Asphaltt

include/linux/bpf.h

@@ -3768,14 +3768,35 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
 			   const char **linep, int *nump);
 struct bpf_prog *bpf_prog_find_from_stack(void);
 
+static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
+{
+	return false;
+}
+
 static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 allowed_flags)
 {
-	if (flags & ~allowed_flags)
+	u32 cpu;
+
+	if ((u32)flags & ~allowed_flags)
 		return -EINVAL;
 
 	if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
 		return -EINVAL;
 
+	if (!(flags & BPF_F_CPU) && flags >> 32)
+		return -EINVAL;
+
+	if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) {
+		if (!bpf_map_supports_cpu_flags(map->map_type))
+			return -EINVAL;
+		if ((flags & BPF_F_CPU) && (flags & BPF_F_ALL_CPUS))
+			return -EINVAL;
+
+		cpu = flags >> 32;
+		if ((flags & BPF_F_CPU) && cpu >= num_possible_cpus())
+			return -ERANGE;
+	}
+
 	return 0;
 }
 

include/uapi/linux/bpf.h

@@ -1372,6 +1372,8 @@ enum {
 	BPF_NOEXIST	= 1, /* create new element if it didn't exist */
 	BPF_EXIST	= 2, /* update existing element */
 	BPF_F_LOCK	= 4, /* spin_lock-ed map_lookup/map_update */
+	BPF_F_CPU	= 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
+	BPF_F_ALL_CPUS	= 16, /* update value across all CPUs for percpu maps */
 };
 
 /* flags for BPF_MAP_CREATE command */

kernel/bpf/syscall.c

@@ -133,12 +133,14 @@ bool bpf_map_write_active(const struct bpf_map *map)
 	return atomic64_read(&map->writecnt) != 0;
 }
 
-static u32 bpf_map_value_size(const struct bpf_map *map)
-{
-	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
-	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
-	    map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY ||
-	    map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
+static u32 bpf_map_value_size(const struct bpf_map *map, u64 flags)
+{
+	if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS))
+		return round_up(map->value_size, 8);
+	else if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+		 map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
+		 map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY ||
+		 map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
 		return round_up(map->value_size, 8) * num_possible_cpus();
 	else if (IS_FD_MAP(map))
 		return sizeof(u32);
@@ -1716,15 +1718,15 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
 		return -EPERM;
 
-	err = bpf_map_check_op_flags(map, attr->flags, BPF_F_LOCK);
+	err = bpf_map_check_op_flags(map, attr->flags, BPF_F_LOCK | BPF_F_CPU);
 	if (err)
 		return err;
 
 	key = __bpf_copy_key(ukey, map->key_size);
 	if (IS_ERR(key))
 		return PTR_ERR(key);
 
-	value_size = bpf_map_value_size(map);
+	value_size = bpf_map_value_size(map, attr->flags);
 
 	err = -ENOMEM;
 	value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
@@ -1791,7 +1793,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
 		goto err_put;
 	}
 
-	value_size = bpf_map_value_size(map);
+	value_size = bpf_map_value_size(map, attr->flags);
 	value = kvmemdup_bpfptr(uvalue, value_size);
 	if (IS_ERR(value)) {
 		err = PTR_ERR(value);
@@ -1987,11 +1989,12 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
 	void *key, *value;
 	int err = 0;
 
-	err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+	err = bpf_map_check_op_flags(map, attr->batch.elem_flags,
+				     BPF_F_LOCK | BPF_F_CPU | BPF_F_ALL_CPUS);
 	if (err)
 		return err;
 
-	value_size = bpf_map_value_size(map);
+	value_size = bpf_map_value_size(map, attr->batch.elem_flags);
 
 	max_count = attr->batch.count;
 	if (!max_count)
@@ -2046,11 +2049,11 @@ int generic_map_lookup_batch(struct bpf_map *map,
 	u32 value_size, cp, max_count;
 	int err;
 
-	err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+	err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK | BPF_F_CPU);
 	if (err)
 		return err;
 
-	value_size = bpf_map_value_size(map);
+	value_size = bpf_map_value_size(map, attr->batch.elem_flags);
 
 	max_count = attr->batch.count;
 	if (!max_count)
@@ -2172,7 +2175,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
 		goto err_put;
 	}
 
-	value_size = bpf_map_value_size(map);
+	value_size = bpf_map_value_size(map, 0);
 
 	err = -ENOMEM;
 	value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);

tools/include/uapi/linux/bpf.h

@@ -1372,6 +1372,8 @@ enum {
 	BPF_NOEXIST	= 1, /* create new element if it didn't exist */
 	BPF_EXIST	= 2, /* update existing element */
 	BPF_F_LOCK	= 4, /* spin_lock-ed map_lookup/map_update */
+	BPF_F_CPU	= 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
+	BPF_F_ALL_CPUS	= 16, /* update value across all CPUs for percpu maps */
 };
 
 /* flags for BPF_MAP_CREATE command */