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