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 #include <linux/filter.h>
  20
  21 /* If kernel subsystem is allowing eBPF programs to call this function,
  22  * inside its own verifier_ops->get_func_proto() callback it should return
  23  * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
  24  *
  25  * Different map implementations will rely on rcu in map methods
  26  * lookup/update/delete, therefore eBPF programs must run under rcu lock
  27  * if program is allowed to access maps, so check rcu_read_lock_held in
  28  * all three functions.
  29  */
  30 BPF_CALL_2(bpf_map_lookup_elem, struct bpf_map *, map, void *, key)
  31 {
  32         WARN_ON_ONCE(!rcu_read_lock_held());
  33         return (unsigned long) map->ops->map_lookup_elem(map, key);
  34 }
  35
  36 const struct bpf_func_proto bpf_map_lookup_elem_proto = {
  37         .func           = bpf_map_lookup_elem,
  38         .gpl_only       = false,
  39         .ret_type       = RET_PTR_TO_MAP_VALUE_OR_NULL,
  40         .arg1_type      = ARG_CONST_MAP_PTR,
  41         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  42 };
  43
  44 BPF_CALL_4(bpf_map_update_elem, struct bpf_map *, map, void *, key,
  45            void *, value, u64, flags)
  46 {
  47         WARN_ON_ONCE(!rcu_read_lock_held());
  48         return map->ops->map_update_elem(map, key, value, flags);
  49 }
  50
  51 const struct bpf_func_proto bpf_map_update_elem_proto = {
  52         .func           = bpf_map_update_elem,
  53         .gpl_only       = false,
  54         .ret_type       = RET_INTEGER,
  55         .arg1_type      = ARG_CONST_MAP_PTR,
  56         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  57         .arg3_type      = ARG_PTR_TO_MAP_VALUE,
  58         .arg4_type      = ARG_ANYTHING,
  59 };
  60
  61 BPF_CALL_2(bpf_map_delete_elem, struct bpf_map *, map, void *, key)
  62 {
  63         WARN_ON_ONCE(!rcu_read_lock_held());
  64         return map->ops->map_delete_elem(map, key);
  65 }
  66
  67 const struct bpf_func_proto bpf_map_delete_elem_proto = {
  68         .func           = bpf_map_delete_elem,
  69         .gpl_only       = false,
  70         .ret_type       = RET_INTEGER,
  71         .arg1_type      = ARG_CONST_MAP_PTR,
  72         .arg2_type      = ARG_PTR_TO_MAP_KEY,
  73 };
  74
  75 const struct bpf_func_proto bpf_get_prandom_u32_proto = {
  76         .func           = bpf_user_rnd_u32,
  77         .gpl_only       = false,
  78         .ret_type       = RET_INTEGER,
  79 };
  80
  81 BPF_CALL_0(bpf_get_smp_processor_id)
  82 {
  83         return smp_processor_id();
  84 }
  85
  86 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
  87         .func           = bpf_get_smp_processor_id,
  88         .gpl_only       = false,
  89         .ret_type       = RET_INTEGER,
  90 };
  91
  92 BPF_CALL_0(bpf_ktime_get_ns)
  93 {
  94         /* NMI safe access to clock monotonic */
  95         return ktime_get_mono_fast_ns();
  96 }
  97
  98 const struct bpf_func_proto bpf_ktime_get_ns_proto = {
  99         .func           = bpf_ktime_get_ns,
 100         .gpl_only       = true,
 101         .ret_type       = RET_INTEGER,
 102 };
 103
 104 BPF_CALL_0(bpf_get_current_pid_tgid)
 105 {
 106         struct task_struct *task = current;
 107
 108         if (unlikely(!task))
 109                 return -EINVAL;
 110
 111         return (u64) task->tgid << 32 | task->pid;
 112 }
 113
 114 const struct bpf_func_proto bpf_get_current_pid_tgid_proto = {
 115         .func           = bpf_get_current_pid_tgid,
 116         .gpl_only       = false,
 117         .ret_type       = RET_INTEGER,
 118 };
 119
 120 BPF_CALL_0(bpf_get_current_uid_gid)
 121 {
 122         struct task_struct *task = current;
 123         kuid_t uid;
 124         kgid_t gid;
 125
 126         if (unlikely(!task))
 127                 return -EINVAL;
 128
 129         current_uid_gid(&uid, &gid);
 130         return (u64) from_kgid(&init_user_ns, gid) << 32 |
 131                      from_kuid(&init_user_ns, uid);
 132 }
 133
 134 const struct bpf_func_proto bpf_get_current_uid_gid_proto = {
 135         .func           = bpf_get_current_uid_gid,
 136         .gpl_only       = false,
 137         .ret_type       = RET_INTEGER,
 138 };
 139
 140 BPF_CALL_2(bpf_get_current_comm, char *, buf, u32, size)
 141 {
 142         struct task_struct *task = current;
 143
 144         if (unlikely(!task))
 145                 goto err_clear;
 146
 147         strncpy(buf, task->comm, size);
 148
 149         /* Verifier guarantees that size > 0. For task->comm exceeding
 150          * size, guarantee that buf is %NUL-terminated. Unconditionally
 151          * done here to save the size test.
 152          */
 153         buf[size - 1] = 0;
 154         return 0;
 155 err_clear:
 156         memset(buf, 0, size);
 157         return -EINVAL;
 158 }
 159
 160 const struct bpf_func_proto bpf_get_current_comm_proto = {
 161         .func           = bpf_get_current_comm,
 162         .gpl_only       = false,
 163         .ret_type       = RET_INTEGER,
 164         .arg1_type      = ARG_PTR_TO_RAW_STACK,
 165         .arg2_type      = ARG_CONST_STACK_SIZE,
 166 };