kernel/bpf/core.c

   1 /*
   2  * Linux Socket Filter - Kernel level socket filtering
   3  *
   4  * Based on the design of the Berkeley Packet Filter. The new
   5  * internal format has been designed by PLUMgrid:
   6  *
   7  *      Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
   8  *
   9  * Authors:
  10  *
  11  *      Jay Schulist <[email protected]>
  12  *      Alexei Starovoitov <[email protected]>
  13  *      Daniel Borkmann <[email protected]>
  14  *
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * as published by the Free Software Foundation; either version
  18  * 2 of the License, or (at your option) any later version.
  19  *
  20  * Andi Kleen - Fix a few bad bugs and races.
  21  * Kris Katterjohn - Added many additional checks in bpf_check_classic()
  22  */
  23 #include <linux/filter.h>
  24 #include <linux/skbuff.h>
  25 #include <linux/vmalloc.h>
  26 #include <asm/unaligned.h>
  27
  28 /* Registers */
  29 #define BPF_R0  regs[BPF_REG_0]
  30 #define BPF_R1  regs[BPF_REG_1]
  31 #define BPF_R2  regs[BPF_REG_2]
  32 #define BPF_R3  regs[BPF_REG_3]
  33 #define BPF_R4  regs[BPF_REG_4]
  34 #define BPF_R5  regs[BPF_REG_5]
  35 #define BPF_R6  regs[BPF_REG_6]
  36 #define BPF_R7  regs[BPF_REG_7]
  37 #define BPF_R8  regs[BPF_REG_8]
  38 #define BPF_R9  regs[BPF_REG_9]
  39 #define BPF_R10 regs[BPF_REG_10]
  40
  41 /* Named registers */
  42 #define DST     regs[insn->dst_reg]
  43 #define SRC     regs[insn->src_reg]
  44 #define FP      regs[BPF_REG_FP]
  45 #define ARG1    regs[BPF_REG_ARG1]
  46 #define CTX     regs[BPF_REG_CTX]
  47 #define IMM     insn->imm
  48
  49 /* No hurry in this branch
  50  *
  51  * Exported for the bpf jit load helper.
  52  */
  53 void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, int k, unsigned int size)
  54 {
  55         u8 *ptr = NULL;
  56
  57         if (k >= SKF_NET_OFF)
  58                 ptr = skb_network_header(skb) + k - SKF_NET_OFF;
  59         else if (k >= SKF_LL_OFF)
  60                 ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
  61         if (ptr >= skb->head && ptr + size <= skb_tail_pointer(skb))
  62                 return ptr;
  63
  64         return NULL;
  65 }
  66
  67 struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
  68 {
  69         gfp_t gfp_flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO |
  70                           gfp_extra_flags;
  71         struct bpf_work_struct *ws;
  72         struct bpf_prog *fp;
  73
  74         size = round_up(size, PAGE_SIZE);
  75         fp = __vmalloc(size, gfp_flags, PAGE_KERNEL);
  76         if (fp == NULL)
  77                 return NULL;
  78
  79         ws = kmalloc(sizeof(*ws), GFP_KERNEL | gfp_extra_flags);
  80         if (ws == NULL) {
  81                 vfree(fp);
  82                 return NULL;
  83         }
  84
  85         fp->pages = size / PAGE_SIZE;
  86         fp->work = ws;
  87
  88         return fp;
  89 }
  90 EXPORT_SYMBOL_GPL(bpf_prog_alloc);
  91
  92 struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
  93                                   gfp_t gfp_extra_flags)
  94 {
  95         gfp_t gfp_flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO |
  96                           gfp_extra_flags;
  97         struct bpf_prog *fp;
  98
  99         BUG_ON(fp_old == NULL);
 100
 101         size = round_up(size, PAGE_SIZE);
 102         if (size <= fp_old->pages * PAGE_SIZE)
 103                 return fp_old;
 104
 105         fp = __vmalloc(size, gfp_flags, PAGE_KERNEL);
 106         if (fp != NULL) {
 107                 memcpy(fp, fp_old, fp_old->pages * PAGE_SIZE);
 108                 fp->pages = size / PAGE_SIZE;
 109
 110                 /* We keep fp->work from fp_old around in the new
 111                  * reallocated structure.
 112                  */
 113                 fp_old->work = NULL;
 114                 __bpf_prog_free(fp_old);
 115         }
 116
 117         return fp;
 118 }
 119 EXPORT_SYMBOL_GPL(bpf_prog_realloc);
 120
 121 void __bpf_prog_free(struct bpf_prog *fp)
 122 {
 123         kfree(fp->work);
 124         vfree(fp);
 125 }
 126 EXPORT_SYMBOL_GPL(__bpf_prog_free);
 127
 128 /* Base function for offset calculation. Needs to go into .text section,
 129  * therefore keeping it non-static as well; will also be used by JITs
 130  * anyway later on, so do not let the compiler omit it.
 131  */
 132 noinline u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 133 {
 134         return 0;
 135 }
 136
 137 /**
 138  *      __bpf_prog_run - run eBPF program on a given context
 139  *      @ctx: is the data we are operating on
 140  *      @insn: is the array of eBPF instructions
 141  *
 142  * Decode and execute eBPF instructions.
 143  */
 144 static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn)
 145 {
 146         u64 stack[MAX_BPF_STACK / sizeof(u64)];
 147         u64 regs[MAX_BPF_REG], tmp;
 148         static const void *jumptable[256] = {
 149                 [0 ... 255] = &&default_label,
 150                 /* Now overwrite non-defaults ... */
 151                 /* 32 bit ALU operations */
 152                 [BPF_ALU | BPF_ADD | BPF_X] = &&ALU_ADD_X,
 153                 [BPF_ALU | BPF_ADD | BPF_K] = &&ALU_ADD_K,
 154                 [BPF_ALU | BPF_SUB | BPF_X] = &&ALU_SUB_X,
 155                 [BPF_ALU | BPF_SUB | BPF_K] = &&ALU_SUB_K,
 156                 [BPF_ALU | BPF_AND | BPF_X] = &&ALU_AND_X,
 157                 [BPF_ALU | BPF_AND | BPF_K] = &&ALU_AND_K,
 158                 [BPF_ALU | BPF_OR | BPF_X]  = &&ALU_OR_X,
 159                 [BPF_ALU | BPF_OR | BPF_K]  = &&ALU_OR_K,
 160                 [BPF_ALU | BPF_LSH | BPF_X] = &&ALU_LSH_X,
 161                 [BPF_ALU | BPF_LSH | BPF_K] = &&ALU_LSH_K,
 162                 [BPF_ALU | BPF_RSH | BPF_X] = &&ALU_RSH_X,
 163                 [BPF_ALU | BPF_RSH | BPF_K] = &&ALU_RSH_K,
 164                 [BPF_ALU | BPF_XOR | BPF_X] = &&ALU_XOR_X,
 165                 [BPF_ALU | BPF_XOR | BPF_K] = &&ALU_XOR_K,
 166                 [BPF_ALU | BPF_MUL | BPF_X] = &&ALU_MUL_X,
 167                 [BPF_ALU | BPF_MUL | BPF_K] = &&ALU_MUL_K,
 168                 [BPF_ALU | BPF_MOV | BPF_X] = &&ALU_MOV_X,
 169                 [BPF_ALU | BPF_MOV | BPF_K] = &&ALU_MOV_K,
 170                 [BPF_ALU | BPF_DIV | BPF_X] = &&ALU_DIV_X,
 171                 [BPF_ALU | BPF_DIV | BPF_K] = &&ALU_DIV_K,
 172                 [BPF_ALU | BPF_MOD | BPF_X] = &&ALU_MOD_X,
 173                 [BPF_ALU | BPF_MOD | BPF_K] = &&ALU_MOD_K,
 174                 [BPF_ALU | BPF_NEG] = &&ALU_NEG,
 175                 [BPF_ALU | BPF_END | BPF_TO_BE] = &&ALU_END_TO_BE,
 176                 [BPF_ALU | BPF_END | BPF_TO_LE] = &&ALU_END_TO_LE,
 177                 /* 64 bit ALU operations */
 178                 [BPF_ALU64 | BPF_ADD | BPF_X] = &&ALU64_ADD_X,
 179                 [BPF_ALU64 | BPF_ADD | BPF_K] = &&ALU64_ADD_K,
 180                 [BPF_ALU64 | BPF_SUB | BPF_X] = &&ALU64_SUB_X,
 181                 [BPF_ALU64 | BPF_SUB | BPF_K] = &&ALU64_SUB_K,
 182                 [BPF_ALU64 | BPF_AND | BPF_X] = &&ALU64_AND_X,
 183                 [BPF_ALU64 | BPF_AND | BPF_K] = &&ALU64_AND_K,
 184                 [BPF_ALU64 | BPF_OR | BPF_X] = &&ALU64_OR_X,
 185                 [BPF_ALU64 | BPF_OR | BPF_K] = &&ALU64_OR_K,
 186                 [BPF_ALU64 | BPF_LSH | BPF_X] = &&ALU64_LSH_X,
 187                 [BPF_ALU64 | BPF_LSH | BPF_K] = &&ALU64_LSH_K,
 188                 [BPF_ALU64 | BPF_RSH | BPF_X] = &&ALU64_RSH_X,
 189                 [BPF_ALU64 | BPF_RSH | BPF_K] = &&ALU64_RSH_K,
 190                 [BPF_ALU64 | BPF_XOR | BPF_X] = &&ALU64_XOR_X,
 191                 [BPF_ALU64 | BPF_XOR | BPF_K] = &&ALU64_XOR_K,
 192                 [BPF_ALU64 | BPF_MUL | BPF_X] = &&ALU64_MUL_X,
 193                 [BPF_ALU64 | BPF_MUL | BPF_K] = &&ALU64_MUL_K,
 194                 [BPF_ALU64 | BPF_MOV | BPF_X] = &&ALU64_MOV_X,
 195                 [BPF_ALU64 | BPF_MOV | BPF_K] = &&ALU64_MOV_K,
 196                 [BPF_ALU64 | BPF_ARSH | BPF_X] = &&ALU64_ARSH_X,
 197                 [BPF_ALU64 | BPF_ARSH | BPF_K] = &&ALU64_ARSH_K,
 198                 [BPF_ALU64 | BPF_DIV | BPF_X] = &&ALU64_DIV_X,
 199                 [BPF_ALU64 | BPF_DIV | BPF_K] = &&ALU64_DIV_K,
 200                 [BPF_ALU64 | BPF_MOD | BPF_X] = &&ALU64_MOD_X,
 201                 [BPF_ALU64 | BPF_MOD | BPF_K] = &&ALU64_MOD_K,
 202                 [BPF_ALU64 | BPF_NEG] = &&ALU64_NEG,
 203                 /* Call instruction */
 204                 [BPF_JMP | BPF_CALL] = &&JMP_CALL,
 205                 /* Jumps */
 206                 [BPF_JMP | BPF_JA] = &&JMP_JA,
 207                 [BPF_JMP | BPF_JEQ | BPF_X] = &&JMP_JEQ_X,
 208                 [BPF_JMP | BPF_JEQ | BPF_K] = &&JMP_JEQ_K,
 209                 [BPF_JMP | BPF_JNE | BPF_X] = &&JMP_JNE_X,
 210                 [BPF_JMP | BPF_JNE | BPF_K] = &&JMP_JNE_K,
 211                 [BPF_JMP | BPF_JGT | BPF_X] = &&JMP_JGT_X,
 212                 [BPF_JMP | BPF_JGT | BPF_K] = &&JMP_JGT_K,
 213                 [BPF_JMP | BPF_JGE | BPF_X] = &&JMP_JGE_X,
 214                 [BPF_JMP | BPF_JGE | BPF_K] = &&JMP_JGE_K,
 215                 [BPF_JMP | BPF_JSGT | BPF_X] = &&JMP_JSGT_X,
 216                 [BPF_JMP | BPF_JSGT | BPF_K] = &&JMP_JSGT_K,
 217                 [BPF_JMP | BPF_JSGE | BPF_X] = &&JMP_JSGE_X,
 218                 [BPF_JMP | BPF_JSGE | BPF_K] = &&JMP_JSGE_K,
 219                 [BPF_JMP | BPF_JSET | BPF_X] = &&JMP_JSET_X,
 220                 [BPF_JMP | BPF_JSET | BPF_K] = &&JMP_JSET_K,
 221                 /* Program return */
 222                 [BPF_JMP | BPF_EXIT] = &&JMP_EXIT,
 223                 /* Store instructions */
 224                 [BPF_STX | BPF_MEM | BPF_B] = &&STX_MEM_B,
 225                 [BPF_STX | BPF_MEM | BPF_H] = &&STX_MEM_H,
 226                 [BPF_STX | BPF_MEM | BPF_W] = &&STX_MEM_W,
 227                 [BPF_STX | BPF_MEM | BPF_DW] = &&STX_MEM_DW,
 228                 [BPF_STX | BPF_XADD | BPF_W] = &&STX_XADD_W,
 229                 [BPF_STX | BPF_XADD | BPF_DW] = &&STX_XADD_DW,
 230                 [BPF_ST | BPF_MEM | BPF_B] = &&ST_MEM_B,
 231                 [BPF_ST | BPF_MEM | BPF_H] = &&ST_MEM_H,
 232                 [BPF_ST | BPF_MEM | BPF_W] = &&ST_MEM_W,
 233                 [BPF_ST | BPF_MEM | BPF_DW] = &&ST_MEM_DW,
 234                 /* Load instructions */
 235                 [BPF_LDX | BPF_MEM | BPF_B] = &&LDX_MEM_B,
 236                 [BPF_LDX | BPF_MEM | BPF_H] = &&LDX_MEM_H,
 237                 [BPF_LDX | BPF_MEM | BPF_W] = &&LDX_MEM_W,
 238                 [BPF_LDX | BPF_MEM | BPF_DW] = &&LDX_MEM_DW,
 239                 [BPF_LD | BPF_ABS | BPF_W] = &&LD_ABS_W,
 240                 [BPF_LD | BPF_ABS | BPF_H] = &&LD_ABS_H,
 241                 [BPF_LD | BPF_ABS | BPF_B] = &&LD_ABS_B,
 242                 [BPF_LD | BPF_IND | BPF_W] = &&LD_IND_W,
 243                 [BPF_LD | BPF_IND | BPF_H] = &&LD_IND_H,
 244                 [BPF_LD | BPF_IND | BPF_B] = &&LD_IND_B,
 245         };
 246         void *ptr;
 247         int off;
 248
 249 #define CONT     ({ insn++; goto select_insn; })
 250 #define CONT_JMP ({ insn++; goto select_insn; })
 251
 252         FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)];
 253         ARG1 = (u64) (unsigned long) ctx;
 254
 255         /* Registers used in classic BPF programs need to be reset first. */
 256         regs[BPF_REG_A] = 0;
 257         regs[BPF_REG_X] = 0;
 258
 259 select_insn:
 260         goto *jumptable[insn->code];
 261
 262         /* ALU */
 263 #define ALU(OPCODE, OP)                 \
 264         ALU64_##OPCODE##_X:             \
 265                 DST = DST OP SRC;       \
 266                 CONT;                   \
 267         ALU_##OPCODE##_X:               \
 268                 DST = (u32) DST OP (u32) SRC;   \
 269                 CONT;                   \
 270         ALU64_##OPCODE##_K:             \
 271                 DST = DST OP IMM;               \
 272                 CONT;                   \
 273         ALU_##OPCODE##_K:               \
 274                 DST = (u32) DST OP (u32) IMM;   \
 275                 CONT;
 276
 277         ALU(ADD,  +)
 278         ALU(SUB,  -)
 279         ALU(AND,  &)
 280         ALU(OR,   |)
 281         ALU(LSH, <<)
 282         ALU(RSH, >>)
 283         ALU(XOR,  ^)
 284         ALU(MUL,  *)
 285 #undef ALU
 286         ALU_NEG:
 287                 DST = (u32) -DST;
 288                 CONT;
 289         ALU64_NEG:
 290                 DST = -DST;
 291                 CONT;
 292         ALU_MOV_X:
 293                 DST = (u32) SRC;
 294                 CONT;
 295         ALU_MOV_K:
 296                 DST = (u32) IMM;
 297                 CONT;
 298         ALU64_MOV_X:
 299                 DST = SRC;
 300                 CONT;
 301         ALU64_MOV_K:
 302                 DST = IMM;
 303                 CONT;
 304         ALU64_ARSH_X:
 305                 (*(s64 *) &DST) >>= SRC;
 306                 CONT;
 307         ALU64_ARSH_K:
 308                 (*(s64 *) &DST) >>= IMM;
 309                 CONT;
 310         ALU64_MOD_X:
 311                 if (unlikely(SRC == 0))
 312                         return 0;
 313                 tmp = DST;
 314                 DST = do_div(tmp, SRC);
 315                 CONT;
 316         ALU_MOD_X:
 317                 if (unlikely(SRC == 0))
 318                         return 0;
 319                 tmp = (u32) DST;
 320                 DST = do_div(tmp, (u32) SRC);
 321                 CONT;
 322         ALU64_MOD_K:
 323                 tmp = DST;
 324                 DST = do_div(tmp, IMM);
 325                 CONT;
 326         ALU_MOD_K:
 327                 tmp = (u32) DST;
 328                 DST = do_div(tmp, (u32) IMM);
 329                 CONT;
 330         ALU64_DIV_X:
 331                 if (unlikely(SRC == 0))
 332                         return 0;
 333                 do_div(DST, SRC);
 334                 CONT;
 335         ALU_DIV_X:
 336                 if (unlikely(SRC == 0))
 337                         return 0;
 338                 tmp = (u32) DST;
 339                 do_div(tmp, (u32) SRC);
 340                 DST = (u32) tmp;
 341                 CONT;
 342         ALU64_DIV_K:
 343                 do_div(DST, IMM);
 344                 CONT;
 345         ALU_DIV_K:
 346                 tmp = (u32) DST;
 347                 do_div(tmp, (u32) IMM);
 348                 DST = (u32) tmp;
 349                 CONT;
 350         ALU_END_TO_BE:
 351                 switch (IMM) {
 352                 case 16:
 353                         DST = (__force u16) cpu_to_be16(DST);
 354                         break;
 355                 case 32:
 356                         DST = (__force u32) cpu_to_be32(DST);
 357                         break;
 358                 case 64:
 359                         DST = (__force u64) cpu_to_be64(DST);
 360                         break;
 361                 }
 362                 CONT;
 363         ALU_END_TO_LE:
 364                 switch (IMM) {
 365                 case 16:
 366                         DST = (__force u16) cpu_to_le16(DST);
 367                         break;
 368                 case 32:
 369                         DST = (__force u32) cpu_to_le32(DST);
 370                         break;
 371                 case 64:
 372                         DST = (__force u64) cpu_to_le64(DST);
 373                         break;
 374                 }
 375                 CONT;
 376
 377         /* CALL */
 378         JMP_CALL:
 379                 /* Function call scratches BPF_R1-BPF_R5 registers,
 380                  * preserves BPF_R6-BPF_R9, and stores return value
 381                  * into BPF_R0.
 382                  */
 383                 BPF_R0 = (__bpf_call_base + insn->imm)(BPF_R1, BPF_R2, BPF_R3,
 384                                                        BPF_R4, BPF_R5);
 385                 CONT;
 386
 387         /* JMP */
 388         JMP_JA:
 389                 insn += insn->off;
 390                 CONT;
 391         JMP_JEQ_X:
 392                 if (DST == SRC) {
 393                         insn += insn->off;
 394                         CONT_JMP;
 395                 }
 396                 CONT;
 397         JMP_JEQ_K:
 398                 if (DST == IMM) {
 399                         insn += insn->off;
 400                         CONT_JMP;
 401                 }
 402                 CONT;
 403         JMP_JNE_X:
 404                 if (DST != SRC) {
 405                         insn += insn->off;
 406                         CONT_JMP;
 407                 }
 408                 CONT;
 409         JMP_JNE_K:
 410                 if (DST != IMM) {
 411                         insn += insn->off;
 412                         CONT_JMP;
 413                 }
 414                 CONT;
 415         JMP_JGT_X:
 416                 if (DST > SRC) {
 417                         insn += insn->off;
 418                         CONT_JMP;
 419                 }
 420                 CONT;
 421         JMP_JGT_K:
 422                 if (DST > IMM) {
 423                         insn += insn->off;
 424                         CONT_JMP;
 425                 }
 426                 CONT;
 427         JMP_JGE_X:
 428                 if (DST >= SRC) {
 429                         insn += insn->off;
 430                         CONT_JMP;
 431                 }
 432                 CONT;
 433         JMP_JGE_K:
 434                 if (DST >= IMM) {
 435                         insn += insn->off;
 436                         CONT_JMP;
 437                 }
 438                 CONT;
 439         JMP_JSGT_X:
 440                 if (((s64) DST) > ((s64) SRC)) {
 441                         insn += insn->off;
 442                         CONT_JMP;
 443                 }
 444                 CONT;
 445         JMP_JSGT_K:
 446                 if (((s64) DST) > ((s64) IMM)) {
 447                         insn += insn->off;
 448                         CONT_JMP;
 449                 }
 450                 CONT;
 451         JMP_JSGE_X:
 452                 if (((s64) DST) >= ((s64) SRC)) {
 453                         insn += insn->off;
 454                         CONT_JMP;
 455                 }
 456                 CONT;
 457         JMP_JSGE_K:
 458                 if (((s64) DST) >= ((s64) IMM)) {
 459                         insn += insn->off;
 460                         CONT_JMP;
 461                 }
 462                 CONT;
 463         JMP_JSET_X:
 464                 if (DST & SRC) {
 465                         insn += insn->off;
 466                         CONT_JMP;
 467                 }
 468                 CONT;
 469         JMP_JSET_K:
 470                 if (DST & IMM) {
 471                         insn += insn->off;
 472                         CONT_JMP;
 473                 }
 474                 CONT;
 475         JMP_EXIT:
 476                 return BPF_R0;
 477
 478         /* STX and ST and LDX*/
 479 #define LDST(SIZEOP, SIZE)                                              \
 480         STX_MEM_##SIZEOP:                                               \
 481                 *(SIZE *)(unsigned long) (DST + insn->off) = SRC;       \
 482                 CONT;                                                   \
 483         ST_MEM_##SIZEOP:                                                \
 484                 *(SIZE *)(unsigned long) (DST + insn->off) = IMM;       \
 485                 CONT;                                                   \
 486         LDX_MEM_##SIZEOP:                                               \
 487                 DST = *(SIZE *)(unsigned long) (SRC + insn->off);       \
 488                 CONT;
 489
 490         LDST(B,   u8)
 491         LDST(H,  u16)
 492         LDST(W,  u32)
 493         LDST(DW, u64)
 494 #undef LDST
 495         STX_XADD_W: /* lock xadd *(u32 *)(dst_reg + off16) += src_reg */
 496                 atomic_add((u32) SRC, (atomic_t *)(unsigned long)
 497                            (DST + insn->off));
 498                 CONT;
 499         STX_XADD_DW: /* lock xadd *(u64 *)(dst_reg + off16) += src_reg */
 500                 atomic64_add((u64) SRC, (atomic64_t *)(unsigned long)
 501                              (DST + insn->off));
 502                 CONT;
 503         LD_ABS_W: /* BPF_R0 = ntohl(*(u32 *) (skb->data + imm32)) */
 504                 off = IMM;
 505 load_word:
 506                 /* BPF_LD + BPD_ABS and BPF_LD + BPF_IND insns are
 507                  * only appearing in the programs where ctx ==
 508                  * skb. All programs keep 'ctx' in regs[BPF_REG_CTX]
 509                  * == BPF_R6, bpf_convert_filter() saves it in BPF_R6,
 510                  * internal BPF verifier will check that BPF_R6 ==
 511                  * ctx.
 512                  *
 513                  * BPF_ABS and BPF_IND are wrappers of function calls,
 514                  * so they scratch BPF_R1-BPF_R5 registers, preserve
 515                  * BPF_R6-BPF_R9, and store return value into BPF_R0.
 516                  *
 517                  * Implicit input:
 518                  *   ctx == skb == BPF_R6 == CTX
 519                  *
 520                  * Explicit input:
 521                  *   SRC == any register
 522                  *   IMM == 32-bit immediate
 523                  *
 524                  * Output:
 525                  *   BPF_R0 - 8/16/32-bit skb data converted to cpu endianness
 526                  */
 527
 528                 ptr = bpf_load_pointer((struct sk_buff *) (unsigned long) CTX, off, 4, &tmp);
 529                 if (likely(ptr != NULL)) {
 530                         BPF_R0 = get_unaligned_be32(ptr);
 531                         CONT;
 532                 }
 533
 534                 return 0;
 535         LD_ABS_H: /* BPF_R0 = ntohs(*(u16 *) (skb->data + imm32)) */
 536                 off = IMM;
 537 load_half:
 538                 ptr = bpf_load_pointer((struct sk_buff *) (unsigned long) CTX, off, 2, &tmp);
 539                 if (likely(ptr != NULL)) {
 540                         BPF_R0 = get_unaligned_be16(ptr);
 541                         CONT;
 542                 }
 543
 544                 return 0;
 545         LD_ABS_B: /* BPF_R0 = *(u8 *) (skb->data + imm32) */
 546                 off = IMM;
 547 load_byte:
 548                 ptr = bpf_load_pointer((struct sk_buff *) (unsigned long) CTX, off, 1, &tmp);
 549                 if (likely(ptr != NULL)) {
 550                         BPF_R0 = *(u8 *)ptr;
 551                         CONT;
 552                 }
 553
 554                 return 0;
 555         LD_IND_W: /* BPF_R0 = ntohl(*(u32 *) (skb->data + src_reg + imm32)) */
 556                 off = IMM + SRC;
 557                 goto load_word;
 558         LD_IND_H: /* BPF_R0 = ntohs(*(u16 *) (skb->data + src_reg + imm32)) */
 559                 off = IMM + SRC;
 560                 goto load_half;
 561         LD_IND_B: /* BPF_R0 = *(u8 *) (skb->data + src_reg + imm32) */
 562                 off = IMM + SRC;
 563                 goto load_byte;
 564
 565         default_label:
 566                 /* If we ever reach this, we have a bug somewhere. */
 567                 WARN_RATELIMIT(1, "unknown opcode %02x\n", insn->code);
 568                 return 0;
 569 }
 570
 571 void __weak bpf_int_jit_compile(struct bpf_prog *prog)
 572 {
 573 }
 574
 575 /**
 576  *      bpf_prog_select_runtime - select execution runtime for BPF program
 577  *      @fp: bpf_prog populated with internal BPF program
 578  *
 579  * try to JIT internal BPF program, if JIT is not available select interpreter
 580  * BPF program will be executed via BPF_PROG_RUN() macro
 581  */
 582 void bpf_prog_select_runtime(struct bpf_prog *fp)
 583 {
 584         fp->bpf_func = (void *) __bpf_prog_run;
 585
 586         /* Probe if internal BPF can be JITed */
 587         bpf_int_jit_compile(fp);
 588         /* Lock whole bpf_prog as read-only */
 589         bpf_prog_lock_ro(fp);
 590 }
 591 EXPORT_SYMBOL_GPL(bpf_prog_select_runtime);
 592
 593 static void bpf_prog_free_deferred(struct work_struct *work)
 594 {
 595         struct bpf_work_struct *ws;
 596
 597         ws = container_of(work, struct bpf_work_struct, work);
 598         bpf_jit_free(ws->prog);
 599 }
 600
 601 /* Free internal BPF program */
 602 void bpf_prog_free(struct bpf_prog *fp)
 603 {
 604         struct bpf_work_struct *ws = fp->work;
 605
 606         INIT_WORK(&ws->work, bpf_prog_free_deferred);
 607         ws->prog = fp;
 608         schedule_work(&ws->work);
 609 }
 610 EXPORT_SYMBOL_GPL(bpf_prog_free);