kernel/bpf/helpers.c

   1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10  * General Public License for more details.
  11  */
  12 #include <linux/bpf.h>
  13 #include <linux/rcupdate.h>
  14
  15 /* If kernel subsystem is allowing eBPF programs to call this function,
  16  * inside its own verifier_ops->get_func_proto() callback it should return
  17  * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
  18  *
  19  * Different map implementations will rely on rcu in map methods
  20  * lookup/update/delete, therefore eBPF programs must run under rcu lock
  21  * if program is allowed to access maps, so check rcu_read_lock_held in
  22  * all three functions.
  23  */
  24 static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  25 {
  26         /* verifier checked that R1 contains a valid pointer to bpf_map
  27          * and R2 points to a program stack and map->key_size bytes were
  28          * initialized
  29          */
  30         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  31         void *key = (void *) (unsigned long) r2;
  32         void *value;
  33
  34         WARN_ON_ONCE(!rcu_read_lock_held());
  35
  36         value = map->ops->map_lookup_elem(map, key);
  37
  38         /* lookup() returns either pointer to element value or NULL
  39          * which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type
  40          */
  41         return (unsigned long) value;
  42 }
  43
  44 struct bpf_func_proto bpf_map_lookup_elem_proto = {
  45         .func = bpf_map_lookup_elem,
  46         .gpl_only = false,
  47         .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
  48         .arg1_type = ARG_CONST_MAP_PTR,
  49         .arg2_type = ARG_PTR_TO_MAP_KEY,
  50 };
  51
  52 static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  53 {
  54         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  55         void *key = (void *) (unsigned long) r2;
  56         void *value = (void *) (unsigned long) r3;
  57
  58         WARN_ON_ONCE(!rcu_read_lock_held());
  59
  60         return map->ops->map_update_elem(map, key, value, r4);
  61 }
  62
  63 struct bpf_func_proto bpf_map_update_elem_proto = {
  64         .func = bpf_map_update_elem,
  65         .gpl_only = false,
  66         .ret_type = RET_INTEGER,
  67         .arg1_type = ARG_CONST_MAP_PTR,
  68         .arg2_type = ARG_PTR_TO_MAP_KEY,
  69         .arg3_type = ARG_PTR_TO_MAP_VALUE,
  70         .arg4_type = ARG_ANYTHING,
  71 };
  72
  73 static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  74 {
  75         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  76         void *key = (void *) (unsigned long) r2;
  77
  78         WARN_ON_ONCE(!rcu_read_lock_held());
  79
  80         return map->ops->map_delete_elem(map, key);
  81 }
  82
  83 struct bpf_func_proto bpf_map_delete_elem_proto = {
  84         .func = bpf_map_delete_elem,
  85         .gpl_only = false,
  86         .ret_type = RET_INTEGER,
  87         .arg1_type = ARG_CONST_MAP_PTR,
  88         .arg2_type = ARG_PTR_TO_MAP_KEY,
  89 };