arch/arm/net/bpf_jit_32.c

   1 /*
   2  * Just-In-Time compiler for BPF filters on 32bit ARM
   3  *
   4  * Copyright (c) 2011 Mircea Gherzan <mgherzan@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; version 2 of the License.
   9  */
  10
  11 #include <linux/bitops.h>
  12 #include <linux/compiler.h>
  13 #include <linux/errno.h>
  14 #include <linux/filter.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/string.h>
  17 #include <linux/slab.h>
  18 #include <linux/if_vlan.h>
  19
  20 #include <asm/cacheflush.h>
  21 #include <asm/hwcap.h>
  22 #include <asm/opcodes.h>
  23
  24 #include "bpf_jit_32.h"
  25
  26 /*
  27  * ABI:
  28  *
  29  * r0   scratch register
  30  * r4   BPF register A
  31  * r5   BPF register X
  32  * r6   pointer to the skb
  33  * r7   skb->data
  34  * r8   skb_headlen(skb)
  35  */
  36
  37 #define r_scratch       ARM_R0
  38 /* r1-r3 are (also) used for the unaligned loads on the non-ARMv7 slowpath */
  39 #define r_off           ARM_R1
  40 #define r_A             ARM_R4
  41 #define r_X             ARM_R5
  42 #define r_skb           ARM_R6
  43 #define r_skb_data      ARM_R7
  44 #define r_skb_hl        ARM_R8
  45
  46 #define SCRATCH_SP_OFFSET       0
  47 #define SCRATCH_OFF(k)          (SCRATCH_SP_OFFSET + 4 * (k))
  48
  49 #define SEEN_MEM                ((1 << BPF_MEMWORDS) - 1)
  50 #define SEEN_MEM_WORD(k)        (1 << (k))
  51 #define SEEN_X                  (1 << BPF_MEMWORDS)
  52 #define SEEN_CALL               (1 << (BPF_MEMWORDS + 1))
  53 #define SEEN_SKB                (1 << (BPF_MEMWORDS + 2))
  54 #define SEEN_DATA               (1 << (BPF_MEMWORDS + 3))
  55
  56 #define FLAG_NEED_X_RESET       (1 << 0)
  57 #define FLAG_IMM_OVERFLOW       (1 << 1)
  58
  59 struct jit_ctx {
  60         const struct bpf_prog *skf;
  61         unsigned idx;
  62         unsigned prologue_bytes;
  63         int ret0_fp_idx;
  64         u32 seen;
  65         u32 flags;
  66         u32 *offsets;
  67         u32 *target;
  68 #if __LINUX_ARM_ARCH__ < 7
  69         u16 epilogue_bytes;
  70         u16 imm_count;
  71         u32 *imms;
  72 #endif
  73 };
  74
  75 int bpf_jit_enable __read_mostly;
  76
  77 static u64 jit_get_skb_b(struct sk_buff *skb, unsigned offset)
  78 {
  79         u8 ret;
  80         int err;
  81
  82         err = skb_copy_bits(skb, offset, &ret, 1);
  83
  84         return (u64)err << 32 | ret;
  85 }
  86
  87 static u64 jit_get_skb_h(struct sk_buff *skb, unsigned offset)
  88 {
  89         u16 ret;
  90         int err;
  91
  92         err = skb_copy_bits(skb, offset, &ret, 2);
  93
  94         return (u64)err << 32 | ntohs(ret);
  95 }
  96
  97 static u64 jit_get_skb_w(struct sk_buff *skb, unsigned offset)
  98 {
  99         u32 ret;
 100         int err;
 101
 102         err = skb_copy_bits(skb, offset, &ret, 4);
 103
 104         return (u64)err << 32 | ntohl(ret);
 105 }
 106
 107 /*
 108  * Wrapper that handles both OABI and EABI and assures Thumb2 interworking
 109  * (where the assembly routines like __aeabi_uidiv could cause problems).
 110  */
 111 static u32 jit_udiv(u32 dividend, u32 divisor)
 112 {
 113         return dividend / divisor;
 114 }
 115
 116 static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx)
 117 {
 118         inst |= (cond << 28);
 119         inst = __opcode_to_mem_arm(inst);
 120
 121         if (ctx->target != NULL)
 122                 ctx->target[ctx->idx] = inst;
 123
 124         ctx->idx++;
 125 }
 126
 127 /*
 128  * Emit an instruction that will be executed unconditionally.
 129  */
 130 static inline void emit(u32 inst, struct jit_ctx *ctx)
 131 {
 132         _emit(ARM_COND_AL, inst, ctx);
 133 }
 134
 135 static u16 saved_regs(struct jit_ctx *ctx)
 136 {
 137         u16 ret = 0;
 138
 139         if ((ctx->skf->len > 1) ||
 140             (ctx->skf->insns[0].code == (BPF_RET | BPF_A)))
 141                 ret |= 1 << r_A;
 142
 143 #ifdef CONFIG_FRAME_POINTER
 144         ret |= (1 << ARM_FP) | (1 << ARM_IP) | (1 << ARM_LR) | (1 << ARM_PC);
 145 #else
 146         if (ctx->seen & SEEN_CALL)
 147                 ret |= 1 << ARM_LR;
 148 #endif
 149         if (ctx->seen & (SEEN_DATA | SEEN_SKB))
 150                 ret |= 1 << r_skb;
 151         if (ctx->seen & SEEN_DATA)
 152                 ret |= (1 << r_skb_data) | (1 << r_skb_hl);
 153         if (ctx->seen & SEEN_X)
 154                 ret |= 1 << r_X;
 155
 156         return ret;
 157 }
 158
 159 static inline int mem_words_used(struct jit_ctx *ctx)
 160 {
 161         /* yes, we do waste some stack space IF there are "holes" in the set" */
 162         return fls(ctx->seen & SEEN_MEM);
 163 }
 164
 165 static void jit_fill_hole(void *area, unsigned int size)
 166 {
 167         u32 *ptr;
 168         /* We are guaranteed to have aligned memory. */
 169         for (ptr = area; size >= sizeof(u32); size -= sizeof(u32))
 170                 *ptr++ = __opcode_to_mem_arm(ARM_INST_UDF);
 171 }
 172
 173 static void build_prologue(struct jit_ctx *ctx)
 174 {
 175         u16 reg_set = saved_regs(ctx);
 176         u16 off;
 177
 178 #ifdef CONFIG_FRAME_POINTER
 179         emit(ARM_MOV_R(ARM_IP, ARM_SP), ctx);
 180         emit(ARM_PUSH(reg_set), ctx);
 181         emit(ARM_SUB_I(ARM_FP, ARM_IP, 4), ctx);
 182 #else
 183         if (reg_set)
 184                 emit(ARM_PUSH(reg_set), ctx);
 185 #endif
 186
 187         if (ctx->seen & (SEEN_DATA | SEEN_SKB))
 188                 emit(ARM_MOV_R(r_skb, ARM_R0), ctx);
 189
 190         if (ctx->seen & SEEN_DATA) {
 191                 off = offsetof(struct sk_buff, data);
 192                 emit(ARM_LDR_I(r_skb_data, r_skb, off), ctx);
 193                 /* headlen = len - data_len */
 194                 off = offsetof(struct sk_buff, len);
 195                 emit(ARM_LDR_I(r_skb_hl, r_skb, off), ctx);
 196                 off = offsetof(struct sk_buff, data_len);
 197                 emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);
 198                 emit(ARM_SUB_R(r_skb_hl, r_skb_hl, r_scratch), ctx);
 199         }
 200
 201         if (ctx->flags & FLAG_NEED_X_RESET)
 202                 emit(ARM_MOV_I(r_X, 0), ctx);
 203
 204         /* do not leak kernel data to userspace */
 205         if (bpf_needs_clear_a(&ctx->skf->insns[0]))
 206                 emit(ARM_MOV_I(r_A, 0), ctx);
 207
 208         /* stack space for the BPF_MEM words */
 209         if (ctx->seen & SEEN_MEM)
 210                 emit(ARM_SUB_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);
 211 }
 212
 213 static void build_epilogue(struct jit_ctx *ctx)
 214 {
 215         u16 reg_set = saved_regs(ctx);
 216
 217         if (ctx->seen & SEEN_MEM)
 218                 emit(ARM_ADD_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);
 219
 220         reg_set &= ~(1 << ARM_LR);
 221
 222 #ifdef CONFIG_FRAME_POINTER
 223         /* the first instruction of the prologue was: mov ip, sp */
 224         reg_set &= ~(1 << ARM_IP);
 225         reg_set |= (1 << ARM_SP);
 226         emit(ARM_LDM(ARM_SP, reg_set), ctx);
 227 #else
 228         if (reg_set) {
 229                 if (ctx->seen & SEEN_CALL)
 230                         reg_set |= 1 << ARM_PC;
 231                 emit(ARM_POP(reg_set), ctx);
 232         }
 233
 234         if (!(ctx->seen & SEEN_CALL))
 235                 emit(ARM_BX(ARM_LR), ctx);
 236 #endif
 237 }
 238
 239 static int16_t imm8m(u32 x)
 240 {
 241         u32 rot;
 242
 243         for (rot = 0; rot < 16; rot++)
 244                 if ((x & ~ror32(0xff, 2 * rot)) == 0)
 245                         return rol32(x, 2 * rot) | (rot << 8);
 246
 247         return -1;
 248 }
 249
 250 #if __LINUX_ARM_ARCH__ < 7
 251
 252 static u16 imm_offset(u32 k, struct jit_ctx *ctx)
 253 {
 254         unsigned i = 0, offset;
 255         u16 imm;
 256
 257         /* on the "fake" run we just count them (duplicates included) */
 258         if (ctx->target == NULL) {
 259                 ctx->imm_count++;
 260                 return 0;
 261         }
 262
 263         while ((i < ctx->imm_count) && ctx->imms[i]) {
 264                 if (ctx->imms[i] == k)
 265                         break;
 266                 i++;
 267         }
 268
 269         if (ctx->imms[i] == 0)
 270                 ctx->imms[i] = k;
 271
 272         /* constants go just after the epilogue */
 273         offset =  ctx->offsets[ctx->skf->len];
 274         offset += ctx->prologue_bytes;
 275         offset += ctx->epilogue_bytes;
 276         offset += i * 4;
 277
 278         ctx->target[offset / 4] = k;
 279
 280         /* PC in ARM mode == address of the instruction + 8 */
 281         imm = offset - (8 + ctx->idx * 4);
 282
 283         if (imm & ~0xfff) {
 284                 /*
 285                  * literal pool is too far, signal it into flags. we
 286                  * can only detect it on the second pass unfortunately.
 287                  */
 288                 ctx->flags |= FLAG_IMM_OVERFLOW;
 289                 return 0;
 290         }
 291
 292         return imm;
 293 }
 294
 295 #endif /* __LINUX_ARM_ARCH__ */
 296
 297 /*
 298  * Move an immediate that's not an imm8m to a core register.
 299  */
 300 static inline void emit_mov_i_no8m(int rd, u32 val, struct jit_ctx *ctx)
 301 {
 302 #if __LINUX_ARM_ARCH__ < 7
 303         emit(ARM_LDR_I(rd, ARM_PC, imm_offset(val, ctx)), ctx);
 304 #else
 305         emit(ARM_MOVW(rd, val & 0xffff), ctx);
 306         if (val > 0xffff)
 307                 emit(ARM_MOVT(rd, val >> 16), ctx);
 308 #endif
 309 }
 310
 311 static inline void emit_mov_i(int rd, u32 val, struct jit_ctx *ctx)
 312 {
 313         int imm12 = imm8m(val);
 314
 315         if (imm12 >= 0)
 316                 emit(ARM_MOV_I(rd, imm12), ctx);
 317         else
 318                 emit_mov_i_no8m(rd, val, ctx);
 319 }
 320
 321 #if __LINUX_ARM_ARCH__ < 6
 322
 323 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
 324 {
 325         _emit(cond, ARM_LDRB_I(ARM_R3, r_addr, 1), ctx);
 326         _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
 327         _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 3), ctx);
 328         _emit(cond, ARM_LSL_I(ARM_R3, ARM_R3, 16), ctx);
 329         _emit(cond, ARM_LDRB_I(ARM_R0, r_addr, 2), ctx);
 330         _emit(cond, ARM_ORR_S(ARM_R3, ARM_R3, ARM_R1, SRTYPE_LSL, 24), ctx);
 331         _emit(cond, ARM_ORR_R(ARM_R3, ARM_R3, ARM_R2), ctx);
 332         _emit(cond, ARM_ORR_S(r_res, ARM_R3, ARM_R0, SRTYPE_LSL, 8), ctx);
 333 }
 334
 335 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
 336 {
 337         _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
 338         _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 1), ctx);
 339         _emit(cond, ARM_ORR_S(r_res, ARM_R2, ARM_R1, SRTYPE_LSL, 8), ctx);
 340 }
 341
 342 static inline void emit_swap16(u8 r_dst, u8 r_src, struct jit_ctx *ctx)
 343 {
 344         /* r_dst = (r_src << 8) | (r_src >> 8) */
 345         emit(ARM_LSL_I(ARM_R1, r_src, 8), ctx);
 346         emit(ARM_ORR_S(r_dst, ARM_R1, r_src, SRTYPE_LSR, 8), ctx);
 347
 348         /*
 349          * we need to mask out the bits set in r_dst[23:16] due to
 350          * the first shift instruction.
 351          *
 352          * note that 0x8ff is the encoded immediate 0x00ff0000.
 353          */
 354         emit(ARM_BIC_I(r_dst, r_dst, 0x8ff), ctx);
 355 }
 356
 357 #else  /* ARMv6+ */
 358
 359 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
 360 {
 361         _emit(cond, ARM_LDR_I(r_res, r_addr, 0), ctx);
 362 #ifdef __LITTLE_ENDIAN
 363         _emit(cond, ARM_REV(r_res, r_res), ctx);
 364 #endif
 365 }
 366
 367 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
 368 {
 369         _emit(cond, ARM_LDRH_I(r_res, r_addr, 0), ctx);
 370 #ifdef __LITTLE_ENDIAN
 371         _emit(cond, ARM_REV16(r_res, r_res), ctx);
 372 #endif
 373 }
 374
 375 static inline void emit_swap16(u8 r_dst __maybe_unused,
 376                                u8 r_src __maybe_unused,
 377                                struct jit_ctx *ctx __maybe_unused)
 378 {
 379 #ifdef __LITTLE_ENDIAN
 380         emit(ARM_REV16(r_dst, r_src), ctx);
 381 #endif
 382 }
 383
 384 #endif /* __LINUX_ARM_ARCH__ < 6 */
 385
 386
 387 /* Compute the immediate value for a PC-relative branch. */
 388 static inline u32 b_imm(unsigned tgt, struct jit_ctx *ctx)
 389 {
 390         u32 imm;
 391
 392         if (ctx->target == NULL)
 393                 return 0;
 394         /*
 395          * BPF allows only forward jumps and the offset of the target is
 396          * still the one computed during the first pass.
 397          */
 398         imm  = ctx->offsets[tgt] + ctx->prologue_bytes - (ctx->idx * 4 + 8);
 399
 400         return imm >> 2;
 401 }
 402
 403 #define OP_IMM3(op, r1, r2, imm_val, ctx)                               \
 404         do {                                                            \
 405                 imm12 = imm8m(imm_val);                                 \
 406                 if (imm12 < 0) {                                        \
 407                         emit_mov_i_no8m(r_scratch, imm_val, ctx);       \
 408                         emit(op ## _R((r1), (r2), r_scratch), ctx);     \
 409                 } else {                                                \
 410                         emit(op ## _I((r1), (r2), imm12), ctx);         \
 411                 }                                                       \
 412         } while (0)
 413
 414 static inline void emit_err_ret(u8 cond, struct jit_ctx *ctx)
 415 {
 416         if (ctx->ret0_fp_idx >= 0) {
 417                 _emit(cond, ARM_B(b_imm(ctx->ret0_fp_idx, ctx)), ctx);
 418                 /* NOP to keep the size constant between passes */
 419                 emit(ARM_MOV_R(ARM_R0, ARM_R0), ctx);
 420         } else {
 421                 _emit(cond, ARM_MOV_I(ARM_R0, 0), ctx);
 422                 _emit(cond, ARM_B(b_imm(ctx->skf->len, ctx)), ctx);
 423         }
 424 }
 425
 426 static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
 427 {
 428 #if __LINUX_ARM_ARCH__ < 5
 429         emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx);
 430
 431         if (elf_hwcap & HWCAP_THUMB)
 432                 emit(ARM_BX(tgt_reg), ctx);
 433         else
 434                 emit(ARM_MOV_R(ARM_PC, tgt_reg), ctx);
 435 #else
 436         emit(ARM_BLX_R(tgt_reg), ctx);
 437 #endif
 438 }
 439
 440 static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx)
 441 {
 442 #if __LINUX_ARM_ARCH__ == 7
 443         if (elf_hwcap & HWCAP_IDIVA) {
 444                 emit(ARM_UDIV(rd, rm, rn), ctx);
 445                 return;
 446         }
 447 #endif
 448
 449         /*
 450          * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4
 451          * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into
 452          * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm
 453          * before using it as a source for ARM_R1.
 454          *
 455          * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is
 456          * ARM_R5 (r_X) so there is no particular register overlap
 457          * issues.
 458          */
 459         if (rn != ARM_R1)
 460                 emit(ARM_MOV_R(ARM_R1, rn), ctx);
 461         if (rm != ARM_R0)
 462                 emit(ARM_MOV_R(ARM_R0, rm), ctx);
 463
 464         ctx->seen |= SEEN_CALL;
 465         emit_mov_i(ARM_R3, (u32)jit_udiv, ctx);
 466         emit_blx_r(ARM_R3, ctx);
 467
 468         if (rd != ARM_R0)
 469                 emit(ARM_MOV_R(rd, ARM_R0), ctx);
 470 }
 471
 472 static inline void update_on_xread(struct jit_ctx *ctx)
 473 {
 474         if (!(ctx->seen & SEEN_X))
 475                 ctx->flags |= FLAG_NEED_X_RESET;
 476
 477         ctx->seen |= SEEN_X;
 478 }
 479
 480 static int build_body(struct jit_ctx *ctx)
 481 {
 482         void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w};
 483         const struct bpf_prog *prog = ctx->skf;
 484         const struct sock_filter *inst;
 485         unsigned i, load_order, off, condt;
 486         int imm12;
 487         u32 k;
 488
 489         for (i = 0; i < prog->len; i++) {
 490                 u16 code;
 491
 492                 inst = &(prog->insns[i]);
 493                 /* K as an immediate value operand */
 494                 k = inst->k;
 495                 code = bpf_anc_helper(inst);
 496
 497                 /* compute offsets only in the fake pass */
 498                 if (ctx->target == NULL)
 499                         ctx->offsets[i] = ctx->idx * 4;
 500
 501                 switch (code) {
 502                 case BPF_LD | BPF_IMM:
 503                         emit_mov_i(r_A, k, ctx);
 504                         break;
 505                 case BPF_LD | BPF_W | BPF_LEN:
 506                         ctx->seen |= SEEN_SKB;
 507                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 508                         emit(ARM_LDR_I(r_A, r_skb,
 509                                        offsetof(struct sk_buff, len)), ctx);
 510                         break;
 511                 case BPF_LD | BPF_MEM:
 512                         /* A = scratch[k] */
 513                         ctx->seen |= SEEN_MEM_WORD(k);
 514                         emit(ARM_LDR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
 515                         break;
 516                 case BPF_LD | BPF_W | BPF_ABS:
 517                         load_order = 2;
 518                         goto load;
 519                 case BPF_LD | BPF_H | BPF_ABS:
 520                         load_order = 1;
 521                         goto load;
 522                 case BPF_LD | BPF_B | BPF_ABS:
 523                         load_order = 0;
 524 load:
 525                         /* the interpreter will deal with the negative K */
 526                         if ((int)k < 0)
 527                                 return -ENOTSUPP;
 528                         emit_mov_i(r_off, k, ctx);
 529 load_common:
 530                         ctx->seen |= SEEN_DATA | SEEN_CALL;
 531
 532                         if (load_order > 0) {
 533                                 emit(ARM_SUB_I(r_scratch, r_skb_hl,
 534                                                1 << load_order), ctx);
 535                                 emit(ARM_CMP_R(r_scratch, r_off), ctx);
 536                                 condt = ARM_COND_HS;
 537                         } else {
 538                                 emit(ARM_CMP_R(r_skb_hl, r_off), ctx);
 539                                 condt = ARM_COND_HI;
 540                         }
 541
 542                         _emit(condt, ARM_ADD_R(r_scratch, r_off, r_skb_data),
 543                               ctx);
 544
 545                         if (load_order == 0)
 546                                 _emit(condt, ARM_LDRB_I(r_A, r_scratch, 0),
 547                                       ctx);
 548                         else if (load_order == 1)
 549                                 emit_load_be16(condt, r_A, r_scratch, ctx);
 550                         else if (load_order == 2)
 551                                 emit_load_be32(condt, r_A, r_scratch, ctx);
 552
 553                         _emit(condt, ARM_B(b_imm(i + 1, ctx)), ctx);
 554
 555                         /* the slowpath */
 556                         emit_mov_i(ARM_R3, (u32)load_func[load_order], ctx);
 557                         emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
 558                         /* the offset is already in R1 */
 559                         emit_blx_r(ARM_R3, ctx);
 560                         /* check the result of skb_copy_bits */
 561                         emit(ARM_CMP_I(ARM_R1, 0), ctx);
 562                         emit_err_ret(ARM_COND_NE, ctx);
 563                         emit(ARM_MOV_R(r_A, ARM_R0), ctx);
 564                         break;
 565                 case BPF_LD | BPF_W | BPF_IND:
 566                         load_order = 2;
 567                         goto load_ind;
 568                 case BPF_LD | BPF_H | BPF_IND:
 569                         load_order = 1;
 570                         goto load_ind;
 571                 case BPF_LD | BPF_B | BPF_IND:
 572                         load_order = 0;
 573 load_ind:
 574                         OP_IMM3(ARM_ADD, r_off, r_X, k, ctx);
 575                         goto load_common;
 576                 case BPF_LDX | BPF_IMM:
 577                         ctx->seen |= SEEN_X;
 578                         emit_mov_i(r_X, k, ctx);
 579                         break;
 580                 case BPF_LDX | BPF_W | BPF_LEN:
 581                         ctx->seen |= SEEN_X | SEEN_SKB;
 582                         emit(ARM_LDR_I(r_X, r_skb,
 583                                        offsetof(struct sk_buff, len)), ctx);
 584                         break;
 585                 case BPF_LDX | BPF_MEM:
 586                         ctx->seen |= SEEN_X | SEEN_MEM_WORD(k);
 587                         emit(ARM_LDR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
 588                         break;
 589                 case BPF_LDX | BPF_B | BPF_MSH:
 590                         /* x = ((*(frame + k)) & 0xf) << 2; */
 591                         ctx->seen |= SEEN_X | SEEN_DATA | SEEN_CALL;
 592                         /* the interpreter should deal with the negative K */
 593                         if ((int)k < 0)
 594                                 return -1;
 595                         /* offset in r1: we might have to take the slow path */
 596                         emit_mov_i(r_off, k, ctx);
 597                         emit(ARM_CMP_R(r_skb_hl, r_off), ctx);
 598
 599                         /* load in r0: common with the slowpath */
 600                         _emit(ARM_COND_HI, ARM_LDRB_R(ARM_R0, r_skb_data,
 601                                                       ARM_R1), ctx);
 602                         /*
 603                          * emit_mov_i() might generate one or two instructions,
 604                          * the same holds for emit_blx_r()
 605                          */
 606                         _emit(ARM_COND_HI, ARM_B(b_imm(i + 1, ctx) - 2), ctx);
 607
 608                         emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
 609                         /* r_off is r1 */
 610                         emit_mov_i(ARM_R3, (u32)jit_get_skb_b, ctx);
 611                         emit_blx_r(ARM_R3, ctx);
 612                         /* check the return value of skb_copy_bits */
 613                         emit(ARM_CMP_I(ARM_R1, 0), ctx);
 614                         emit_err_ret(ARM_COND_NE, ctx);
 615
 616                         emit(ARM_AND_I(r_X, ARM_R0, 0x00f), ctx);
 617                         emit(ARM_LSL_I(r_X, r_X, 2), ctx);
 618                         break;
 619                 case BPF_ST:
 620                         ctx->seen |= SEEN_MEM_WORD(k);
 621                         emit(ARM_STR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
 622                         break;
 623                 case BPF_STX:
 624                         update_on_xread(ctx);
 625                         ctx->seen |= SEEN_MEM_WORD(k);
 626                         emit(ARM_STR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
 627                         break;
 628                 case BPF_ALU | BPF_ADD | BPF_K:
 629                         /* A += K */
 630                         OP_IMM3(ARM_ADD, r_A, r_A, k, ctx);
 631                         break;
 632                 case BPF_ALU | BPF_ADD | BPF_X:
 633                         update_on_xread(ctx);
 634                         emit(ARM_ADD_R(r_A, r_A, r_X), ctx);
 635                         break;
 636                 case BPF_ALU | BPF_SUB | BPF_K:
 637                         /* A -= K */
 638                         OP_IMM3(ARM_SUB, r_A, r_A, k, ctx);
 639                         break;
 640                 case BPF_ALU | BPF_SUB | BPF_X:
 641                         update_on_xread(ctx);
 642                         emit(ARM_SUB_R(r_A, r_A, r_X), ctx);
 643                         break;
 644                 case BPF_ALU | BPF_MUL | BPF_K:
 645                         /* A *= K */
 646                         emit_mov_i(r_scratch, k, ctx);
 647                         emit(ARM_MUL(r_A, r_A, r_scratch), ctx);
 648                         break;
 649                 case BPF_ALU | BPF_MUL | BPF_X:
 650                         update_on_xread(ctx);
 651                         emit(ARM_MUL(r_A, r_A, r_X), ctx);
 652                         break;
 653                 case BPF_ALU | BPF_DIV | BPF_K:
 654                         if (k == 1)
 655                                 break;
 656                         emit_mov_i(r_scratch, k, ctx);
 657                         emit_udiv(r_A, r_A, r_scratch, ctx);
 658                         break;
 659                 case BPF_ALU | BPF_DIV | BPF_X:
 660                         update_on_xread(ctx);
 661                         emit(ARM_CMP_I(r_X, 0), ctx);
 662                         emit_err_ret(ARM_COND_EQ, ctx);
 663                         emit_udiv(r_A, r_A, r_X, ctx);
 664                         break;
 665                 case BPF_ALU | BPF_OR | BPF_K:
 666                         /* A |= K */
 667                         OP_IMM3(ARM_ORR, r_A, r_A, k, ctx);
 668                         break;
 669                 case BPF_ALU | BPF_OR | BPF_X:
 670                         update_on_xread(ctx);
 671                         emit(ARM_ORR_R(r_A, r_A, r_X), ctx);
 672                         break;
 673                 case BPF_ALU | BPF_XOR | BPF_K:
 674                         /* A ^= K; */
 675                         OP_IMM3(ARM_EOR, r_A, r_A, k, ctx);
 676                         break;
 677                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 678                 case BPF_ALU | BPF_XOR | BPF_X:
 679                         /* A ^= X */
 680                         update_on_xread(ctx);
 681                         emit(ARM_EOR_R(r_A, r_A, r_X), ctx);
 682                         break;
 683                 case BPF_ALU | BPF_AND | BPF_K:
 684                         /* A &= K */
 685                         OP_IMM3(ARM_AND, r_A, r_A, k, ctx);
 686                         break;
 687                 case BPF_ALU | BPF_AND | BPF_X:
 688                         update_on_xread(ctx);
 689                         emit(ARM_AND_R(r_A, r_A, r_X), ctx);
 690                         break;
 691                 case BPF_ALU | BPF_LSH | BPF_K:
 692                         if (unlikely(k > 31))
 693                                 return -1;
 694                         emit(ARM_LSL_I(r_A, r_A, k), ctx);
 695                         break;
 696                 case BPF_ALU | BPF_LSH | BPF_X:
 697                         update_on_xread(ctx);
 698                         emit(ARM_LSL_R(r_A, r_A, r_X), ctx);
 699                         break;
 700                 case BPF_ALU | BPF_RSH | BPF_K:
 701                         if (unlikely(k > 31))
 702                                 return -1;
 703                         emit(ARM_LSR_I(r_A, r_A, k), ctx);
 704                         break;
 705                 case BPF_ALU | BPF_RSH | BPF_X:
 706                         update_on_xread(ctx);
 707                         emit(ARM_LSR_R(r_A, r_A, r_X), ctx);
 708                         break;
 709                 case BPF_ALU | BPF_NEG:
 710                         /* A = -A */
 711                         emit(ARM_RSB_I(r_A, r_A, 0), ctx);
 712                         break;
 713                 case BPF_JMP | BPF_JA:
 714                         /* pc += K */
 715                         emit(ARM_B(b_imm(i + k + 1, ctx)), ctx);
 716                         break;
 717                 case BPF_JMP | BPF_JEQ | BPF_K:
 718                         /* pc += (A == K) ? pc->jt : pc->jf */
 719                         condt  = ARM_COND_EQ;
 720                         goto cmp_imm;
 721                 case BPF_JMP | BPF_JGT | BPF_K:
 722                         /* pc += (A > K) ? pc->jt : pc->jf */
 723                         condt  = ARM_COND_HI;
 724                         goto cmp_imm;
 725                 case BPF_JMP | BPF_JGE | BPF_K:
 726                         /* pc += (A >= K) ? pc->jt : pc->jf */
 727                         condt  = ARM_COND_HS;
 728 cmp_imm:
 729                         imm12 = imm8m(k);
 730                         if (imm12 < 0) {
 731                                 emit_mov_i_no8m(r_scratch, k, ctx);
 732                                 emit(ARM_CMP_R(r_A, r_scratch), ctx);
 733                         } else {
 734                                 emit(ARM_CMP_I(r_A, imm12), ctx);
 735                         }
 736 cond_jump:
 737                         if (inst->jt)
 738                                 _emit(condt, ARM_B(b_imm(i + inst->jt + 1,
 739                                                    ctx)), ctx);
 740                         if (inst->jf)
 741                                 _emit(condt ^ 1, ARM_B(b_imm(i + inst->jf + 1,
 742                                                              ctx)), ctx);
 743                         break;
 744                 case BPF_JMP | BPF_JEQ | BPF_X:
 745                         /* pc += (A == X) ? pc->jt : pc->jf */
 746                         condt   = ARM_COND_EQ;
 747                         goto cmp_x;
 748                 case BPF_JMP | BPF_JGT | BPF_X:
 749                         /* pc += (A > X) ? pc->jt : pc->jf */
 750                         condt   = ARM_COND_HI;
 751                         goto cmp_x;
 752                 case BPF_JMP | BPF_JGE | BPF_X:
 753                         /* pc += (A >= X) ? pc->jt : pc->jf */
 754                         condt   = ARM_COND_CS;
 755 cmp_x:
 756                         update_on_xread(ctx);
 757                         emit(ARM_CMP_R(r_A, r_X), ctx);
 758                         goto cond_jump;
 759                 case BPF_JMP | BPF_JSET | BPF_K:
 760                         /* pc += (A & K) ? pc->jt : pc->jf */
 761                         condt  = ARM_COND_NE;
 762                         /* not set iff all zeroes iff Z==1 iff EQ */
 763
 764                         imm12 = imm8m(k);
 765                         if (imm12 < 0) {
 766                                 emit_mov_i_no8m(r_scratch, k, ctx);
 767                                 emit(ARM_TST_R(r_A, r_scratch), ctx);
 768                         } else {
 769                                 emit(ARM_TST_I(r_A, imm12), ctx);
 770                         }
 771                         goto cond_jump;
 772                 case BPF_JMP | BPF_JSET | BPF_X:
 773                         /* pc += (A & X) ? pc->jt : pc->jf */
 774                         update_on_xread(ctx);
 775                         condt  = ARM_COND_NE;
 776                         emit(ARM_TST_R(r_A, r_X), ctx);
 777                         goto cond_jump;
 778                 case BPF_RET | BPF_A:
 779                         emit(ARM_MOV_R(ARM_R0, r_A), ctx);
 780                         goto b_epilogue;
 781                 case BPF_RET | BPF_K:
 782                         if ((k == 0) && (ctx->ret0_fp_idx < 0))
 783                                 ctx->ret0_fp_idx = i;
 784                         emit_mov_i(ARM_R0, k, ctx);
 785 b_epilogue:
 786                         if (i != ctx->skf->len - 1)
 787                                 emit(ARM_B(b_imm(prog->len, ctx)), ctx);
 788                         break;
 789                 case BPF_MISC | BPF_TAX:
 790                         /* X = A */
 791                         ctx->seen |= SEEN_X;
 792                         emit(ARM_MOV_R(r_X, r_A), ctx);
 793                         break;
 794                 case BPF_MISC | BPF_TXA:
 795                         /* A = X */
 796                         update_on_xread(ctx);
 797                         emit(ARM_MOV_R(r_A, r_X), ctx);
 798                         break;
 799                 case BPF_ANC | SKF_AD_PROTOCOL:
 800                         /* A = ntohs(skb->protocol) */
 801                         ctx->seen |= SEEN_SKB;
 802                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 803                                                   protocol) != 2);
 804                         off = offsetof(struct sk_buff, protocol);
 805                         emit(ARM_LDRH_I(r_scratch, r_skb, off), ctx);
 806                         emit_swap16(r_A, r_scratch, ctx);
 807                         break;
 808                 case BPF_ANC | SKF_AD_CPU:
 809                         /* r_scratch = current_thread_info() */
 810                         OP_IMM3(ARM_BIC, r_scratch, ARM_SP, THREAD_SIZE - 1, ctx);
 811                         /* A = current_thread_info()->cpu */
 812                         BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info, cpu) != 4);
 813                         off = offsetof(struct thread_info, cpu);
 814                         emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
 815                         break;
 816                 case BPF_ANC | SKF_AD_IFINDEX:
 817                         /* A = skb->dev->ifindex */
 818                         ctx->seen |= SEEN_SKB;
 819                         off = offsetof(struct sk_buff, dev);
 820                         emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);
 821
 822                         emit(ARM_CMP_I(r_scratch, 0), ctx);
 823                         emit_err_ret(ARM_COND_EQ, ctx);
 824
 825                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 826                                                   ifindex) != 4);
 827                         off = offsetof(struct net_device, ifindex);
 828                         emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
 829                         break;
 830                 case BPF_ANC | SKF_AD_MARK:
 831                         ctx->seen |= SEEN_SKB;
 832                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 833                         off = offsetof(struct sk_buff, mark);
 834                         emit(ARM_LDR_I(r_A, r_skb, off), ctx);
 835                         break;
 836                 case BPF_ANC | SKF_AD_RXHASH:
 837                         ctx->seen |= SEEN_SKB;
 838                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
 839                         off = offsetof(struct sk_buff, hash);
 840                         emit(ARM_LDR_I(r_A, r_skb, off), ctx);
 841                         break;
 842                 case BPF_ANC | SKF_AD_VLAN_TAG:
 843                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 844                         ctx->seen |= SEEN_SKB;
 845                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 846                         off = offsetof(struct sk_buff, vlan_tci);
 847                         emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
 848                         if (code == (BPF_ANC | SKF_AD_VLAN_TAG))
 849                                 OP_IMM3(ARM_AND, r_A, r_A, VLAN_VID_MASK, ctx);
 850                         else
 851                                 OP_IMM3(ARM_AND, r_A, r_A, VLAN_TAG_PRESENT, ctx);
 852                         break;
 853                 case BPF_ANC | SKF_AD_QUEUE:
 854                         ctx->seen |= SEEN_SKB;
 855                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 856                                                   queue_mapping) != 2);
 857                         BUILD_BUG_ON(offsetof(struct sk_buff,
 858                                               queue_mapping) > 0xff);
 859                         off = offsetof(struct sk_buff, queue_mapping);
 860                         emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
 861                         break;
 862                 default:
 863                         return -1;
 864                 }
 865
 866                 if (ctx->flags & FLAG_IMM_OVERFLOW)
 867                         /*
 868                          * this instruction generated an overflow when
 869                          * trying to access the literal pool, so
 870                          * delegate this filter to the kernel interpreter.
 871                          */
 872                         return -1;
 873         }
 874
 875         /* compute offsets only during the first pass */
 876         if (ctx->target == NULL)
 877                 ctx->offsets[i] = ctx->idx * 4;
 878
 879         return 0;
 880 }
 881
 882
 883 void bpf_jit_compile(struct bpf_prog *fp)
 884 {
 885         struct bpf_binary_header *header;
 886         struct jit_ctx ctx;
 887         unsigned tmp_idx;
 888         unsigned alloc_size;
 889         u8 *target_ptr;
 890
 891         if (!bpf_jit_enable)
 892                 return;
 893
 894         memset(&ctx, 0, sizeof(ctx));
 895         ctx.skf         = fp;
 896         ctx.ret0_fp_idx = -1;
 897
 898         ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
 899         if (ctx.offsets == NULL)
 900                 return;
 901
 902         /* fake pass to fill in the ctx->seen */
 903         if (unlikely(build_body(&ctx)))
 904                 goto out;
 905
 906         tmp_idx = ctx.idx;
 907         build_prologue(&ctx);
 908         ctx.prologue_bytes = (ctx.idx - tmp_idx) * 4;
 909
 910 #if __LINUX_ARM_ARCH__ < 7
 911         tmp_idx = ctx.idx;
 912         build_epilogue(&ctx);
 913         ctx.epilogue_bytes = (ctx.idx - tmp_idx) * 4;
 914
 915         ctx.idx += ctx.imm_count;
 916         if (ctx.imm_count) {
 917                 ctx.imms = kzalloc(4 * ctx.imm_count, GFP_KERNEL);
 918                 if (ctx.imms == NULL)
 919                         goto out;
 920         }
 921 #else
 922         /* there's nothing after the epilogue on ARMv7 */
 923         build_epilogue(&ctx);
 924 #endif
 925         alloc_size = 4 * ctx.idx;
 926         header = bpf_jit_binary_alloc(alloc_size, &target_ptr,
 927                                       4, jit_fill_hole);
 928         if (header == NULL)
 929                 goto out;
 930
 931         ctx.target = (u32 *) target_ptr;
 932         ctx.idx = 0;
 933
 934         build_prologue(&ctx);
 935         if (build_body(&ctx) < 0) {
 936 #if __LINUX_ARM_ARCH__ < 7
 937                 if (ctx.imm_count)
 938                         kfree(ctx.imms);
 939 #endif
 940                 bpf_jit_binary_free(header);
 941                 goto out;
 942         }
 943         build_epilogue(&ctx);
 944
 945         flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx));
 946
 947 #if __LINUX_ARM_ARCH__ < 7
 948         if (ctx.imm_count)
 949                 kfree(ctx.imms);
 950 #endif
 951
 952         if (bpf_jit_enable > 1)
 953                 /* there are 2 passes here */
 954                 bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
 955
 956         set_memory_ro((unsigned long)header, header->pages);
 957         fp->bpf_func = (void *)ctx.target;
 958         fp->jited = true;
 959 out:
 960         kfree(ctx.offsets);
 961         return;
 962 }
 963
 964 void bpf_jit_free(struct bpf_prog *fp)
 965 {
 966         unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
 967         struct bpf_binary_header *header = (void *)addr;
 968
 969         if (!fp->jited)
 970                 goto free_filter;
 971
 972         set_memory_rw(addr, header->pages);
 973         bpf_jit_binary_free(header);
 974
 975 free_filter:
 976         bpf_prog_unlock_free(fp);
 977 }