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Commit f1a2e44a authored by Mauricio Vasquez B's avatar Mauricio Vasquez B Committed by Alexei Starovoitov
Browse files

bpf: add queue and stack maps 



Queue/stack maps implement a FIFO/LIFO data storage for ebpf programs.
These maps support peek, pop and push operations that are exposed to eBPF
programs through the new bpf_map[peek/pop/push] helpers.  Those operations
are exposed to userspace applications through the already existing
syscalls in the following way:

BPF_MAP_LOOKUP_ELEM            -> peek
BPF_MAP_LOOKUP_AND_DELETE_ELEM -> pop
BPF_MAP_UPDATE_ELEM            -> push

Queue/stack maps are implemented using a buffer, tail and head indexes,
hence BPF_F_NO_PREALLOC is not supported.

As opposite to other maps, queue and stack do not use RCU for protecting
maps values, the bpf_map[peek/pop] have a ARG_PTR_TO_UNINIT_MAP_VALUE
argument that is a pointer to a memory zone where to save the value of a
map.  Basically the same as ARG_PTR_TO_UNINIT_MEM, but the size has not
be passed as an extra argument.

Our main motivation for implementing queue/stack maps was to keep track
of a pool of elements, like network ports in a SNAT, however we forsee
other use cases, like for exampling saving last N kernel events in a map
and then analysing from userspace.

Signed-off-by: default avatarMauricio Vasquez B <mauricio.vasquez@polito.it>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 2ea864c5

include/linux/bpf.h

+6 −0
Original line number Diff line number Diff line
@@ -39,6 +39,9 @@ struct bpf_map_ops { 
	void *(*map_lookup_elem)(struct bpf_map *map, void *key);

	int (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags);

	int (*map_delete_elem)(struct bpf_map *map, void *key);

	int (*map_push_elem)(struct bpf_map *map, void *value, u64 flags);

	int (*map_pop_elem)(struct bpf_map *map, void *value);

	int (*map_peek_elem)(struct bpf_map *map, void *value);



	/* funcs called by prog_array and perf_event_array map */

	void *(*map_fd_get_ptr)(struct bpf_map *map, struct file *map_file,
@@ -811,6 +814,9 @@ static inline int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, 
extern const struct bpf_func_proto bpf_map_lookup_elem_proto;

extern const struct bpf_func_proto bpf_map_update_elem_proto;

extern const struct bpf_func_proto bpf_map_delete_elem_proto;

extern const struct bpf_func_proto bpf_map_push_elem_proto;

extern const struct bpf_func_proto bpf_map_pop_elem_proto;

extern const struct bpf_func_proto bpf_map_peek_elem_proto;



extern const struct bpf_func_proto bpf_get_prandom_u32_proto;

extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;

include/linux/bpf_types.h

+2 −0
Original line number Diff line number Diff line
@@ -69,3 +69,5 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_XSKMAP, xsk_map_ops) 
BPF_MAP_TYPE(BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, reuseport_array_ops)

#endif

#endif

BPF_MAP_TYPE(BPF_MAP_TYPE_QUEUE, queue_map_ops)

BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)

include/uapi/linux/bpf.h

+28 −1
Original line number Diff line number Diff line
@@ -128,6 +128,8 @@ enum bpf_map_type { 
	BPF_MAP_TYPE_CGROUP_STORAGE,

	BPF_MAP_TYPE_REUSEPORT_SOCKARRAY,

	BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE,

	BPF_MAP_TYPE_QUEUE,

	BPF_MAP_TYPE_STACK,

};



enum bpf_prog_type {
@@ -462,6 +464,28 @@ union bpf_attr { 
 * 	Return

 * 		0 on success, or a negative error in case of failure.

 *

 * int bpf_map_push_elem(struct bpf_map *map, const void *value, u64 flags)

 * 	Description

 * 		Push an element *value* in *map*. *flags* is one of:

 *

 * 		**BPF_EXIST**

 * 		If the queue/stack is full, the oldest element is removed to

 * 		make room for this.

 * 	Return

 * 		0 on success, or a negative error in case of failure.

 *

 * int bpf_map_pop_elem(struct bpf_map *map, void *value)

 * 	Description

 * 		Pop an element from *map*.

 * Return

 * 		0 on success, or a negative error in case of failure.

 *

 * int bpf_map_peek_elem(struct bpf_map *map, void *value)

 * 	Description

 * 		Get an element from *map* without removing it.

 * Return

 * 		0 on success, or a negative error in case of failure.

 *

 * int bpf_probe_read(void *dst, u32 size, const void *src)

 * 	Description

 * 		For tracing programs, safely attempt to read *size* bytes from
@@ -2303,7 +2327,10 @@ union bpf_attr { 
	FN(skb_ancestor_cgroup_id),	\

	FN(sk_lookup_tcp),		\

	FN(sk_lookup_udp),		\

	FN(sk_release),

	FN(sk_release),			\

	FN(map_push_elem),		\

	FN(map_pop_elem),		\

	FN(map_peek_elem),



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

 * function eBPF program intends to call

kernel/bpf/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ obj-y := core.o 


obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o

obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o

obj-$(CONFIG_BPF_SYSCALL) += local_storage.o

obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o

obj-$(CONFIG_BPF_SYSCALL) += disasm.o

obj-$(CONFIG_BPF_SYSCALL) += btf.o

ifeq ($(CONFIG_NET),y)

kernel/bpf/core.c

+3 −0
Original line number Diff line number Diff line
@@ -1783,6 +1783,9 @@ BPF_CALL_0(bpf_user_rnd_u32) 
const struct bpf_func_proto bpf_map_lookup_elem_proto __weak;

const struct bpf_func_proto bpf_map_update_elem_proto __weak;

const struct bpf_func_proto bpf_map_delete_elem_proto __weak;

const struct bpf_func_proto bpf_map_push_elem_proto __weak;

const struct bpf_func_proto bpf_map_pop_elem_proto __weak;

const struct bpf_func_proto bpf_map_peek_elem_proto __weak;



const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;

const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;