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 #include <linux/ktime.h>
  17 #include <linux/sched.h>
  18 #include <linux/uidgid.h>
  19
  20 /* If kernel subsystem is allowing eBPF programs to call this function,
  21  * inside its own verifier_ops->get_func_proto() callback it should return
  22  * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
  23  *
  24  * Different map implementations will rely on rcu in map methods
  25  * lookup/update/delete, therefore eBPF programs must run under rcu lock
  26  * if program is allowed to access maps, so check rcu_read_lock_held in
  27  * all three functions.
  28  */
  29 static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  30 {
  31         /* verifier checked that R1 contains a valid pointer to bpf_map
  32          * and R2 points to a program stack and map->key_size bytes were
  33          * initialized
  34          */
  35         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  36         void *key = (void *) (unsigned long) r2;
  37         void *value;
  38
  39         WARN_ON_ONCE(!rcu_read_lock_held());
  40
  41         value = map->ops->map_lookup_elem(map, key);
  42
  43         /* lookup() returns either pointer to element value or NULL
  44          * which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type
  45          */
  46         return (unsigned long) value;
  47 }
  48
  49 const struct bpf_func_proto bpf_map_lookup_elem_proto = {
  50         .func           = bpf_map_lookup_elem,
  51         .gpl_only       = false,
  52         .ret_type       = RET_PTR_TO_MAP_VALUE_OR_NULL,
  53         .arg1_type      = ARG_CONST_MAP_PTR,
  54         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  55 };
  56
  57 static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  58 {
  59         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  60         void *key = (void *) (unsigned long) r2;
  61         void *value = (void *) (unsigned long) r3;
  62
  63         WARN_ON_ONCE(!rcu_read_lock_held());
  64
  65         return map->ops->map_update_elem(map, key, value, r4);
  66 }
  67
  68 const struct bpf_func_proto bpf_map_update_elem_proto = {
  69         .func           = bpf_map_update_elem,
  70         .gpl_only       = false,
  71         .ret_type       = RET_INTEGER,
  72         .arg1_type      = ARG_CONST_MAP_PTR,
  73         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  74         .arg3_type      = ARG_PTR_TO_MAP_VALUE,
  75         .arg4_type      = ARG_ANYTHING,
  76 };
  77
  78 static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  79 {
  80         struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
  81         void *key = (void *) (unsigned long) r2;
  82
  83         WARN_ON_ONCE(!rcu_read_lock_held());
  84
  85         return map->ops->map_delete_elem(map, key);
  86 }
  87
  88 const struct bpf_func_proto bpf_map_delete_elem_proto = {
  89         .func           = bpf_map_delete_elem,
  90         .gpl_only       = false,
  91         .ret_type       = RET_INTEGER,
  92         .arg1_type      = ARG_CONST_MAP_PTR,
  93         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  94 };
  95
  96 static u64 bpf_get_prandom_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
  97 {
  98         return prandom_u32();
  99 }
 100
 101 const struct bpf_func_proto bpf_get_prandom_u32_proto = {
 102         .func           = bpf_get_prandom_u32,
 103         .gpl_only       = false,
 104         .ret_type       = RET_INTEGER,
 105 };
 106
 107 static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 108 {
 109         return raw_smp_processor_id();
 110 }
 111
 112 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
 113         .func           = bpf_get_smp_processor_id,
 114         .gpl_only       = false,
 115         .ret_type       = RET_INTEGER,
 116 };
 117
 118 static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 119 {
 120         /* NMI safe access to clock monotonic */
 121         return ktime_get_mono_fast_ns();
 122 }
 123
 124 const struct bpf_func_proto bpf_ktime_get_ns_proto = {
 125         .func           = bpf_ktime_get_ns,
 126         .gpl_only       = true,
 127         .ret_type       = RET_INTEGER,
 128 };
 129
 130 static u64 bpf_get_current_pid_tgid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 131 {
 132         struct task_struct *task = current;
 133
 134         if (!task)
 135                 return -EINVAL;
 136
 137         return (u64) task->tgid << 32 | task->pid;
 138 }
 139
 140 const struct bpf_func_proto bpf_get_current_pid_tgid_proto = {
 141         .func           = bpf_get_current_pid_tgid,
 142         .gpl_only       = false,
 143         .ret_type       = RET_INTEGER,
 144 };
 145
 146 static u64 bpf_get_current_uid_gid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 147 {
 148         struct task_struct *task = current;
 149         kuid_t uid;
 150         kgid_t gid;
 151
 152         if (!task)
 153                 return -EINVAL;
 154
 155         current_uid_gid(&uid, &gid);
 156         return (u64) from_kgid(&init_user_ns, gid) << 32 |
 157                 from_kuid(&init_user_ns, uid);
 158 }
 159
 160 const struct bpf_func_proto bpf_get_current_uid_gid_proto = {
 161         .func           = bpf_get_current_uid_gid,
 162         .gpl_only       = false,
 163         .ret_type       = RET_INTEGER,
 164 };
 165
 166 static u64 bpf_get_current_comm(u64 r1, u64 size, u64 r3, u64 r4, u64 r5)
 167 {
 168         struct task_struct *task = current;
 169         char *buf = (char *) (long) r1;
 170
 171         if (!task)
 172                 return -EINVAL;
 173
 174         memcpy(buf, task->comm, min_t(size_t, size, sizeof(task->comm)));
 175         return 0;
 176 }
 177
 178 const struct bpf_func_proto bpf_get_current_comm_proto = {
 179         .func           = bpf_get_current_comm,
 180         .gpl_only       = false,
 181         .ret_type       = RET_INTEGER,
 182         .arg1_type      = ARG_PTR_TO_STACK,
 183         .arg2_type      = ARG_CONST_STACK_SIZE,
 184 };