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 static 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 static int dummy_ops_test_ret_function(struct bpf_dummy_ops_state *state, ...)
  16 {
  17         return 0;
  18 }
  19
  20 struct bpf_dummy_ops_test_args {
  21         u64 args[MAX_BPF_FUNC_ARGS];
  22         struct bpf_dummy_ops_state state;
  23 };
  24
  25 static struct btf *bpf_dummy_ops_btf;
  26
  27 static struct bpf_dummy_ops_test_args *
  28 dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
  29 {
  30         __u32 size_in;
  31         struct bpf_dummy_ops_test_args *args;
  32         void __user *ctx_in;
  33         void __user *u_state;
  34
  35         size_in = kattr->test.ctx_size_in;
  36         if (size_in != sizeof(u64) * nr)
  37                 return ERR_PTR(-EINVAL);
  38
  39         args = kzalloc(sizeof(*args), GFP_KERNEL);
  40         if (!args)
  41                 return ERR_PTR(-ENOMEM);
  42
  43         ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
  44         if (copy_from_user(args->args, ctx_in, size_in))
  45                 goto out;
  46
  47         /* args[0] is 0 means state argument of test_N will be NULL */
  48         u_state = u64_to_user_ptr(args->args[0]);
  49         if (u_state && copy_from_user(&args->state, u_state,
  50                                       sizeof(args->state)))
  51                 goto out;
  52
  53         return args;
  54 out:
  55         kfree(args);
  56         return ERR_PTR(-EFAULT);
  57 }
  58
  59 static int dummy_ops_copy_args(struct bpf_dummy_ops_test_args *args)
  60 {
  61         void __user *u_state;
  62
  63         u_state = u64_to_user_ptr(args->args[0]);
  64         if (u_state && copy_to_user(u_state, &args->state, sizeof(args->state)))
  65                 return -EFAULT;
  66
  67         return 0;
  68 }
  69
  70 static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
  71 {
  72         dummy_ops_test_ret_fn test = (void *)image + cfi_get_offset();
  73         struct bpf_dummy_ops_state *state = NULL;
  74
  75         /* state needs to be NULL if args[0] is 0 */
  76         if (args->args[0])
  77                 state = &args->state;
  78         return test(state, args->args[1], args->args[2],
  79                     args->args[3], args->args[4]);
  80 }
  81
  82 extern const struct bpf_link_ops bpf_struct_ops_link_lops;
  83
  84 int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
  85                             union bpf_attr __user *uattr)
  86 {
  87         const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
  88         const struct btf_type *func_proto;
  89         struct bpf_dummy_ops_test_args *args;
  90         struct bpf_tramp_links *tlinks;
  91         struct bpf_tramp_link *link = NULL;
  92         void *image = NULL;
  93         unsigned int op_idx;
  94         u32 image_off = 0;
  95         int prog_ret;
  96         s32 type_id;
  97         int err;
  98
  99         type_id = btf_find_by_name_kind(bpf_dummy_ops_btf,
 100                                         bpf_bpf_dummy_ops.name,
 101                                         BTF_KIND_STRUCT);
 102         if (type_id < 0)
 103                 return -EINVAL;
 104         if (prog->aux->attach_btf_id != type_id)
 105                 return -EOPNOTSUPP;
 106
 107         func_proto = prog->aux->attach_func_proto;
 108         args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
 109         if (IS_ERR(args))
 110                 return PTR_ERR(args);
 111
 112         tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
 113         if (!tlinks) {
 114                 err = -ENOMEM;
 115                 goto out;
 116         }
 117
 118         link = kzalloc(sizeof(*link), GFP_USER);
 119         if (!link) {
 120                 err = -ENOMEM;
 121                 goto out;
 122         }
 123         /* prog doesn't take the ownership of the reference from caller */
 124         bpf_prog_inc(prog);
 125         bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_link_lops, prog);
 126
 127         op_idx = prog->expected_attach_type;
 128         err = bpf_struct_ops_prepare_trampoline(tlinks, link,
 129                                                 &st_ops->func_models[op_idx],
 130                                                 &dummy_ops_test_ret_function,
 131                                                 &image, &image_off,
 132                                                 true);
 133         if (err < 0)
 134                 goto out;
 135
 136         arch_protect_bpf_trampoline(image, PAGE_SIZE);
 137         prog_ret = dummy_ops_call_op(image, args);
 138
 139         err = dummy_ops_copy_args(args);
 140         if (err)
 141                 goto out;
 142         if (put_user(prog_ret, &uattr->test.retval))
 143                 err = -EFAULT;
 144 out:
 145         kfree(args);
 146         bpf_struct_ops_image_free(image);
 147         if (link)
 148                 bpf_link_put(&link->link);
 149         kfree(tlinks);
 150         return err;
 151 }
 152
 153 static int bpf_dummy_init(struct btf *btf)
 154 {
 155         bpf_dummy_ops_btf = btf;
 156         return 0;
 157 }
 158
 159 static bool bpf_dummy_ops_is_valid_access(int off, int size,
 160                                           enum bpf_access_type type,
 161                                           const struct bpf_prog *prog,
 162                                           struct bpf_insn_access_aux *info)
 163 {
 164         return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
 165 }
 166
 167 static int bpf_dummy_ops_check_member(const struct btf_type *t,
 168                                       const struct btf_member *member,
 169                                       const struct bpf_prog *prog)
 170 {
 171         u32 moff = __btf_member_bit_offset(t, member) / 8;
 172
 173         switch (moff) {
 174         case offsetof(struct bpf_dummy_ops, test_sleepable):
 175                 break;
 176         default:
 177                 if (prog->sleepable)
 178                         return -EINVAL;
 179         }
 180
 181         return 0;
 182 }
 183
 184 static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
 185                                            const struct bpf_reg_state *reg,
 186                                            int off, int size)
 187 {
 188         const struct btf_type *state;
 189         const struct btf_type *t;
 190         s32 type_id;
 191
 192         type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
 193                                         BTF_KIND_STRUCT);
 194         if (type_id < 0)
 195                 return -EINVAL;
 196
 197         t = btf_type_by_id(reg->btf, reg->btf_id);
 198         state = btf_type_by_id(reg->btf, type_id);
 199         if (t != state) {
 200                 bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
 201                 return -EACCES;
 202         }
 203
 204         if (off + size > sizeof(struct bpf_dummy_ops_state)) {
 205                 bpf_log(log, "write access at off %d with size %d\n", off, size);
 206                 return -EACCES;
 207         }
 208
 209         return NOT_INIT;
 210 }
 211
 212 static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
 213         .is_valid_access = bpf_dummy_ops_is_valid_access,
 214         .btf_struct_access = bpf_dummy_ops_btf_struct_access,
 215 };
 216
 217 static int bpf_dummy_init_member(const struct btf_type *t,
 218                                  const struct btf_member *member,
 219                                  void *kdata, const void *udata)
 220 {
 221         return -EOPNOTSUPP;
 222 }
 223
 224 static int bpf_dummy_reg(void *kdata)
 225 {
 226         return -EOPNOTSUPP;
 227 }
 228
 229 static void bpf_dummy_unreg(void *kdata)
 230 {
 231 }
 232
 233 static int bpf_dummy_test_1(struct bpf_dummy_ops_state *cb)
 234 {
 235         return 0;
 236 }
 237
 238 static int bpf_dummy_test_2(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
 239                             char a3, unsigned long a4)
 240 {
 241         return 0;
 242 }
 243
 244 static int bpf_dummy_test_sleepable(struct bpf_dummy_ops_state *cb)
 245 {
 246         return 0;
 247 }
 248
 249 static struct bpf_dummy_ops __bpf_bpf_dummy_ops = {
 250         .test_1 = bpf_dummy_test_1,
 251         .test_2 = bpf_dummy_test_2,
 252         .test_sleepable = bpf_dummy_test_sleepable,
 253 };
 254
 255 static struct bpf_struct_ops bpf_bpf_dummy_ops = {
 256         .verifier_ops = &bpf_dummy_verifier_ops,
 257         .init = bpf_dummy_init,
 258         .check_member = bpf_dummy_ops_check_member,
 259         .init_member = bpf_dummy_init_member,
 260         .reg = bpf_dummy_reg,
 261         .unreg = bpf_dummy_unreg,
 262         .name = "bpf_dummy_ops",
 263         .cfi_stubs = &__bpf_bpf_dummy_ops,
 264         .owner = THIS_MODULE,
 265 };
 266
 267 static int __init bpf_dummy_struct_ops_init(void)
 268 {
 269         return register_bpf_struct_ops(&bpf_bpf_dummy_ops, bpf_dummy_ops);
 270 }
 271 late_initcall(bpf_dummy_struct_ops_init);