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 #include <linux/random.h>
  15 #include <linux/smp.h>
  16
  17 /* If kernel subsystem is allowing eBPF programs to call this function,
  18  * inside its own verifier_ops->get_func_proto() callback it should return
  19  * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
  20  *
  21  * Different map implementations will rely on rcu in map methods
  22  * lookup/update/delete, therefore eBPF programs must run under rcu lock
  23  * if program is allowed to access maps, so check rcu_read_lock_held in
  24  * all three functions.
  25  */
  26 static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  27 {
  28         /* verifier checked that R1 contains a valid pointer to bpf_map
  29          * and R2 points to a program stack and map->key_size bytes were
  30          * initialized
  31          */
  32         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  33         void *key = (void *) (unsigned long) r2;
  34         void *value;
  35
  36         WARN_ON_ONCE(!rcu_read_lock_held());
  37
  38         value = map->ops->map_lookup_elem(map, key);
  39
  40         /* lookup() returns either pointer to element value or NULL
  41          * which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type
  42          */
  43         return (unsigned long) value;
  44 }
  45
  46 const struct bpf_func_proto bpf_map_lookup_elem_proto = {
  47         .func = bpf_map_lookup_elem,
  48         .gpl_only = false,
  49         .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
  50         .arg1_type = ARG_CONST_MAP_PTR,
  51         .arg2_type = ARG_PTR_TO_MAP_KEY,
  52 };
  53
  54 static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  55 {
  56         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  57         void *key = (void *) (unsigned long) r2;
  58         void *value = (void *) (unsigned long) r3;
  59
  60         WARN_ON_ONCE(!rcu_read_lock_held());
  61
  62         return map->ops->map_update_elem(map, key, value, r4);
  63 }
  64
  65 const struct bpf_func_proto bpf_map_update_elem_proto = {
  66         .func = bpf_map_update_elem,
  67         .gpl_only = false,
  68         .ret_type = RET_INTEGER,
  69         .arg1_type = ARG_CONST_MAP_PTR,
  70         .arg2_type = ARG_PTR_TO_MAP_KEY,
  71         .arg3_type = ARG_PTR_TO_MAP_VALUE,
  72         .arg4_type = ARG_ANYTHING,
  73 };
  74
  75 static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  76 {
  77         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  78         void *key = (void *) (unsigned long) r2;
  79
  80         WARN_ON_ONCE(!rcu_read_lock_held());
  81
  82         return map->ops->map_delete_elem(map, key);
  83 }
  84
  85 const struct bpf_func_proto bpf_map_delete_elem_proto = {
  86         .func = bpf_map_delete_elem,
  87         .gpl_only = false,
  88         .ret_type = RET_INTEGER,
  89         .arg1_type = ARG_CONST_MAP_PTR,
  90         .arg2_type = ARG_PTR_TO_MAP_KEY,
  91 };
  92
  93 static u64 bpf_get_prandom_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  94 {
  95         return prandom_u32();
  96 }
  97
  98 const struct bpf_func_proto bpf_get_prandom_u32_proto = {
  99         .func           = bpf_get_prandom_u32,
 100         .gpl_only       = false,
 101         .ret_type       = RET_INTEGER,
 102 };
 103
 104 static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 105 {
 106         return raw_smp_processor_id();
 107 }
 108
 109 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
 110         .func           = bpf_get_smp_processor_id,
 111         .gpl_only       = false,
 112         .ret_type       = RET_INTEGER,
 113 };