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Commit d0003ec0 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: allow eBPF programs to use maps 



expose bpf_map_lookup_elem(), bpf_map_update_elem(), bpf_map_delete_elem()
map accessors to eBPF programs

Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ffb65f27

include/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -133,4 +133,9 @@ struct bpf_prog *bpf_prog_get(u32 ufd); 
/* verify correctness of eBPF program */

int bpf_check(struct bpf_prog *fp, union bpf_attr *attr);



/* verifier prototypes for helper functions called from eBPF programs */

extern struct bpf_func_proto bpf_map_lookup_elem_proto;

extern struct bpf_func_proto bpf_map_update_elem_proto;

extern struct bpf_func_proto bpf_map_delete_elem_proto;



#endif /* _LINUX_BPF_H */

include/uapi/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -158,6 +158,9 @@ union bpf_attr { 
 */

enum bpf_func_id {

	BPF_FUNC_unspec,

	BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(&map, &key) */

	BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */

	BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */

	__BPF_FUNC_MAX_ID,

};

kernel/bpf/Makefile

+1 −1
Original line number Diff line number Diff line 
obj-y := core.o

obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o

obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o helpers.o

ifdef CONFIG_TEST_BPF

obj-$(CONFIG_BPF_SYSCALL) += test_stub.o

endif

kernel/bpf/helpers.c

0 → 100644
+89 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

 * General Public License for more details.

 */

#include <linux/bpf.h>

#include <linux/rcupdate.h>



/* If kernel subsystem is allowing eBPF programs to call this function,

 * inside its own verifier_ops->get_func_proto() callback it should return

 * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments

 *

 * Different map implementations will rely on rcu in map methods

 * lookup/update/delete, therefore eBPF programs must run under rcu lock

 * if program is allowed to access maps, so check rcu_read_lock_held in

 * all three functions.

 */

static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)

{

	/* verifier checked that R1 contains a valid pointer to bpf_map

	 * and R2 points to a program stack and map->key_size bytes were

	 * initialized

	 */

	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;

	void *key = (void *) (unsigned long) r2;

	void *value;



	WARN_ON_ONCE(!rcu_read_lock_held());



	value = map->ops->map_lookup_elem(map, key);



	/* lookup() returns either pointer to element value or NULL

	 * which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type

	 */

	return (unsigned long) value;

}



struct bpf_func_proto bpf_map_lookup_elem_proto = {

	.func = bpf_map_lookup_elem,

	.gpl_only = false,

	.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,

	.arg1_type = ARG_CONST_MAP_PTR,

	.arg2_type = ARG_PTR_TO_MAP_KEY,

};



static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)

{

	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;

	void *key = (void *) (unsigned long) r2;

	void *value = (void *) (unsigned long) r3;



	WARN_ON_ONCE(!rcu_read_lock_held());



	return map->ops->map_update_elem(map, key, value, r4);

}



struct bpf_func_proto bpf_map_update_elem_proto = {

	.func = bpf_map_update_elem,

	.gpl_only = false,

	.ret_type = RET_INTEGER,

	.arg1_type = ARG_CONST_MAP_PTR,

	.arg2_type = ARG_PTR_TO_MAP_KEY,

	.arg3_type = ARG_PTR_TO_MAP_VALUE,

	.arg4_type = ARG_ANYTHING,

};



static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)

{

	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;

	void *key = (void *) (unsigned long) r2;



	WARN_ON_ONCE(!rcu_read_lock_held());



	return map->ops->map_delete_elem(map, key);

}



struct bpf_func_proto bpf_map_delete_elem_proto = {

	.func = bpf_map_delete_elem,

	.gpl_only = false,

	.ret_type = RET_INTEGER,

	.arg1_type = ARG_CONST_MAP_PTR,

	.arg2_type = ARG_PTR_TO_MAP_KEY,

};