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