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