net/bpf/bpf_dummy_struct_ops.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2021. Huawei Technologies Co., Ltd
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/bpf_verifier.h>
   7 #include <linux/bpf.h>
   8 #include <linux/btf.h>
   9
  10 extern struct bpf_struct_ops bpf_bpf_dummy_ops;
  11
  12 /* A common type for test_N with return value in bpf_dummy_ops */
  13 typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);
  14
  15 struct bpf_dummy_ops_test_args {
  16         u64 args[MAX_BPF_FUNC_ARGS];
  17         struct bpf_dummy_ops_state state;
  18 };
  19
  20 static struct bpf_dummy_ops_test_args *
  21 dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
  22 {
  23         __u32 size_in;
  24         struct bpf_dummy_ops_test_args *args;
  25         void __user *ctx_in;
  26         void __user *u_state;
  27
  28         size_in = kattr->test.ctx_size_in;
  29         if (size_in != sizeof(u64) * nr)
  30                 return ERR_PTR(-EINVAL);
  31
  32         args = kzalloc(sizeof(*args), GFP_KERNEL);
  33         if (!args)
  34                 return ERR_PTR(-ENOMEM);
  35
  36         ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
  37         if (copy_from_user(args->args, ctx_in, size_in))
  38                 goto out;
  39
  40         /* args[0] is 0 means state argument of test_N will be NULL */
  41         u_state = u64_to_user_ptr(args->args[0]);
  42         if (u_state && copy_from_user(&args->state, u_state,
  43                                       sizeof(args->state)))
  44                 goto out;
  45
  46         return args;
  47 out:
  48         kfree(args);
  49         return ERR_PTR(-EFAULT);
  50 }
  51
  52 static int dummy_ops_copy_args(struct bpf_dummy_ops_test_args *args)
  53 {
  54         void __user *u_state;
  55
  56         u_state = u64_to_user_ptr(args->args[0]);
  57         if (u_state && copy_to_user(u_state, &args->state, sizeof(args->state)))
  58                 return -EFAULT;
  59
  60         return 0;
  61 }
  62
  63 static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
  64 {
  65         dummy_ops_test_ret_fn test = (void *)image;
  66         struct bpf_dummy_ops_state *state = NULL;
  67
  68         /* state needs to be NULL if args[0] is 0 */
  69         if (args->args[0])
  70                 state = &args->state;
  71         return test(state, args->args[1], args->args[2],
  72                     args->args[3], args->args[4]);
  73 }
  74
  75 extern const struct bpf_link_ops bpf_struct_ops_link_lops;
  76
  77 int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
  78                             union bpf_attr __user *uattr)
  79 {
  80         const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
  81         const struct btf_type *func_proto;
  82         struct bpf_dummy_ops_test_args *args;
  83         struct bpf_tramp_links *tlinks;
  84         struct bpf_tramp_link *link = NULL;
  85         void *image = NULL;
  86         unsigned int op_idx;
  87         int prog_ret;
  88         int err;
  89
  90         if (prog->aux->attach_btf_id != st_ops->type_id)
  91                 return -EOPNOTSUPP;
  92
  93         func_proto = prog->aux->attach_func_proto;
  94         args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
  95         if (IS_ERR(args))
  96                 return PTR_ERR(args);
  97
  98         tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
  99         if (!tlinks) {
 100                 err = -ENOMEM;
 101                 goto out;
 102         }
 103
 104         image = bpf_jit_alloc_exec(PAGE_SIZE);
 105         if (!image) {
 106                 err = -ENOMEM;
 107                 goto out;
 108         }
 109         set_vm_flush_reset_perms(image);
 110
 111         link = kzalloc(sizeof(*link), GFP_USER);
 112         if (!link) {
 113                 err = -ENOMEM;
 114                 goto out;
 115         }
 116         /* prog doesn't take the ownership of the reference from caller */
 117         bpf_prog_inc(prog);
 118         bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_link_lops, prog);
 119
 120         op_idx = prog->expected_attach_type;
 121         err = bpf_struct_ops_prepare_trampoline(tlinks, link,
 122                                                 &st_ops->func_models[op_idx],
 123                                                 image, image + PAGE_SIZE);
 124         if (err < 0)
 125                 goto out;
 126
 127         set_memory_rox((long)image, 1);
 128         prog_ret = dummy_ops_call_op(image, args);
 129
 130         err = dummy_ops_copy_args(args);
 131         if (err)
 132                 goto out;
 133         if (put_user(prog_ret, &uattr->test.retval))
 134                 err = -EFAULT;
 135 out:
 136         kfree(args);
 137         bpf_jit_free_exec(image);
 138         if (link)
 139                 bpf_link_put(&link->link);
 140         kfree(tlinks);
 141         return err;
 142 }
 143
 144 static int bpf_dummy_init(struct btf *btf)
 145 {
 146         return 0;
 147 }
 148
 149 static bool bpf_dummy_ops_is_valid_access(int off, int size,
 150                                           enum bpf_access_type type,
 151                                           const struct bpf_prog *prog,
 152                                           struct bpf_insn_access_aux *info)
 153 {
 154         return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
 155 }
 156
 157 static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
 158                                            const struct bpf_reg_state *reg,
 159                                            int off, int size, enum bpf_access_type atype,
 160                                            u32 *next_btf_id,
 161                                            enum bpf_type_flag *flag)
 162 {
 163         const struct btf_type *state;
 164         const struct btf_type *t;
 165         s32 type_id;
 166         int err;
 167
 168         type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
 169                                         BTF_KIND_STRUCT);
 170         if (type_id < 0)
 171                 return -EINVAL;
 172
 173         t = btf_type_by_id(reg->btf, reg->btf_id);
 174         state = btf_type_by_id(reg->btf, type_id);
 175         if (t != state) {
 176                 bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
 177                 return -EACCES;
 178         }
 179
 180         err = btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 181         if (err < 0)
 182                 return err;
 183
 184         return atype == BPF_READ ? err : NOT_INIT;
 185 }
 186
 187 static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
 188         .is_valid_access = bpf_dummy_ops_is_valid_access,
 189         .btf_struct_access = bpf_dummy_ops_btf_struct_access,
 190 };
 191
 192 static int bpf_dummy_init_member(const struct btf_type *t,
 193                                  const struct btf_member *member,
 194                                  void *kdata, const void *udata)
 195 {
 196         return -EOPNOTSUPP;
 197 }
 198
 199 static int bpf_dummy_reg(void *kdata)
 200 {
 201         return -EOPNOTSUPP;
 202 }
 203
 204 static void bpf_dummy_unreg(void *kdata)
 205 {
 206 }
 207
 208 struct bpf_struct_ops bpf_bpf_dummy_ops = {
 209         .verifier_ops = &bpf_dummy_verifier_ops,
 210         .init = bpf_dummy_init,
 211         .init_member = bpf_dummy_init_member,
 212         .reg = bpf_dummy_reg,
 213         .unreg = bpf_dummy_unreg,
 214         .name = "bpf_dummy_ops",
 215 };