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: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2014-11-13 17:36:49 -08:00 committed by David S. Miller
parent ffb65f27a1
commit d0003ec01c
4 changed files with 98 additions and 1 deletions

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@ -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 */

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@ -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,
};

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@ -1,5 +1,5 @@
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

89
kernel/bpf/helpers.c Normal file
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@ -0,0 +1,89 @@
/* 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,
};