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 const struct bpf_func_proto bpf_get_prandom_u32_proto = {
  97         .func           = bpf_user_rnd_u32,
  98         .gpl_only       = false,
  99         .ret_type       = RET_INTEGER,
 100 };
 101
 102 static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 103 {
 104         return raw_smp_processor_id();
 105 }
 106
 107 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
 108         .func           = bpf_get_smp_processor_id,
 109         .gpl_only       = false,
 110         .ret_type       = RET_INTEGER,
 111 };
 112
 113 static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 114 {
 115         /* NMI safe access to clock monotonic */
 116         return ktime_get_mono_fast_ns();
 117 }
 118
 119 const struct bpf_func_proto bpf_ktime_get_ns_proto = {
 120         .func           = bpf_ktime_get_ns,
 121         .gpl_only       = true,
 122         .ret_type       = RET_INTEGER,
 123 };
 124
 125 static u64 bpf_get_current_pid_tgid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 126 {
 127         struct task_struct *task = current;
 128
 129         if (!task)
 130                 return -EINVAL;
 131
 132         return (u64) task->tgid << 32 | task->pid;
 133 }
 134
 135 const struct bpf_func_proto bpf_get_current_pid_tgid_proto = {
 136         .func           = bpf_get_current_pid_tgid,
 137         .gpl_only       = false,
 138         .ret_type       = RET_INTEGER,
 139 };
 140
 141 static u64 bpf_get_current_uid_gid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 142 {
 143         struct task_struct *task = current;
 144         kuid_t uid;
 145         kgid_t gid;
 146
 147         if (!task)
 148                 return -EINVAL;
 149
 150         current_uid_gid(&uid, &gid);
 151         return (u64) from_kgid(&init_user_ns, gid) << 32 |
 152                 from_kuid(&init_user_ns, uid);
 153 }
 154
 155 const struct bpf_func_proto bpf_get_current_uid_gid_proto = {
 156         .func           = bpf_get_current_uid_gid,
 157         .gpl_only       = false,
 158         .ret_type       = RET_INTEGER,
 159 };
 160
 161 static u64 bpf_get_current_comm(u64 r1, u64 size, u64 r3, u64 r4, u64 r5)
 162 {
 163         struct task_struct *task = current;
 164         char *buf = (char *) (long) r1;
 165
 166         if (unlikely(!task))
 167                 goto err_clear;
 168
 169         strncpy(buf, task->comm, size);
 170
 171         /* Verifier guarantees that size > 0. For task->comm exceeding
 172          * size, guarantee that buf is %NUL-terminated. Unconditionally
 173          * done here to save the size test.
 174          */
 175         buf[size - 1] = 0;
 176         return 0;
 177 err_clear:
 178         memset(buf, 0, size);
 179         return -EINVAL;
 180 }
 181
 182 const struct bpf_func_proto bpf_get_current_comm_proto = {
 183         .func           = bpf_get_current_comm,
 184         .gpl_only       = false,
 185         .ret_type       = RET_INTEGER,
 186         .arg1_type      = ARG_PTR_TO_RAW_STACK,
 187         .arg2_type      = ARG_CONST_STACK_SIZE,
 188 };