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 inline int call_neg_helper(struct sk_buff *skb, int offset, void *ret, 78 unsigned int size) 79 { 80 void *ptr = bpf_internal_load_pointer_neg_helper(skb, offset, size); 81 82 if (!ptr) 83 return -EFAULT; 84 memcpy(ret, ptr, size); 85 return 0; 86 } 87 88 static u64 jit_get_skb_b(struct sk_buff *skb, int offset) 89 { 90 u8 ret; 91 int err; 92 93 if (offset < 0) 94 err = call_neg_helper(skb, offset, &ret, 1); 95 else 96 err = skb_copy_bits(skb, offset, &ret, 1); 97 98 return (u64)err << 32 | ret; 99 } 100 101 static u64 jit_get_skb_h(struct sk_buff *skb, int offset) 102 { 103 u16 ret; 104 int err; 105 106 if (offset < 0) 107 err = call_neg_helper(skb, offset, &ret, 2); 108 else 109 err = skb_copy_bits(skb, offset, &ret, 2); 110 111 return (u64)err << 32 | ntohs(ret); 112 } 113 114 static u64 jit_get_skb_w(struct sk_buff *skb, int offset) 115 { 116 u32 ret; 117 int err; 118 119 if (offset < 0) 120 err = call_neg_helper(skb, offset, &ret, 4); 121 else 122 err = skb_copy_bits(skb, offset, &ret, 4); 123 124 return (u64)err << 32 | ntohl(ret); 125 } 126 127 /* 128 * Wrapper that handles both OABI and EABI and assures Thumb2 interworking 129 * (where the assembly routines like __aeabi_uidiv could cause problems). 130 */ 131 static u32 jit_udiv(u32 dividend, u32 divisor) 132 { 133 return dividend / divisor; 134 } 135 136 static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx) 137 { 138 inst |= (cond << 28); 139 inst = __opcode_to_mem_arm(inst); 140 141 if (ctx->target != NULL) 142 ctx->target[ctx->idx] = inst; 143 144 ctx->idx++; 145 } 146 147 /* 148 * Emit an instruction that will be executed unconditionally. 149 */ 150 static inline void emit(u32 inst, struct jit_ctx *ctx) 151 { 152 _emit(ARM_COND_AL, inst, ctx); 153 } 154 155 static u16 saved_regs(struct jit_ctx *ctx) 156 { 157 u16 ret = 0; 158 159 if ((ctx->skf->len > 1) || 160 (ctx->skf->insns[0].code == (BPF_RET | BPF_A))) 161 ret |= 1 << r_A; 162 163 #ifdef CONFIG_FRAME_POINTER 164 ret |= (1 << ARM_FP) | (1 << ARM_IP) | (1 << ARM_LR) | (1 << ARM_PC); 165 #else 166 if (ctx->seen & SEEN_CALL) 167 ret |= 1 << ARM_LR; 168 #endif 169 if (ctx->seen & (SEEN_DATA | SEEN_SKB)) 170 ret |= 1 << r_skb; 171 if (ctx->seen & SEEN_DATA) 172 ret |= (1 << r_skb_data) | (1 << r_skb_hl); 173 if (ctx->seen & SEEN_X) 174 ret |= 1 << r_X; 175 176 return ret; 177 } 178 179 static inline int mem_words_used(struct jit_ctx *ctx) 180 { 181 /* yes, we do waste some stack space IF there are "holes" in the set" */ 182 return fls(ctx->seen & SEEN_MEM); 183 } 184 185 static inline bool is_load_to_a(u16 inst) 186 { 187 switch (inst) { 188 case BPF_LD | BPF_W | BPF_LEN: 189 case BPF_LD | BPF_W | BPF_ABS: 190 case BPF_LD | BPF_H | BPF_ABS: 191 case BPF_LD | BPF_B | BPF_ABS: 192 return true; 193 default: 194 return false; 195 } 196 } 197 198 static void jit_fill_hole(void *area, unsigned int size) 199 { 200 u32 *ptr; 201 /* We are guaranteed to have aligned memory. */ 202 for (ptr = area; size >= sizeof(u32); size -= sizeof(u32)) 203 *ptr++ = __opcode_to_mem_arm(ARM_INST_UDF); 204 } 205 206 static void build_prologue(struct jit_ctx *ctx) 207 { 208 u16 reg_set = saved_regs(ctx); 209 u16 first_inst = ctx->skf->insns[0].code; 210 u16 off; 211 212 #ifdef CONFIG_FRAME_POINTER 213 emit(ARM_MOV_R(ARM_IP, ARM_SP), ctx); 214 emit(ARM_PUSH(reg_set), ctx); 215 emit(ARM_SUB_I(ARM_FP, ARM_IP, 4), ctx); 216 #else 217 if (reg_set) 218 emit(ARM_PUSH(reg_set), ctx); 219 #endif 220 221 if (ctx->seen & (SEEN_DATA | SEEN_SKB)) 222 emit(ARM_MOV_R(r_skb, ARM_R0), ctx); 223 224 if (ctx->seen & SEEN_DATA) { 225 off = offsetof(struct sk_buff, data); 226 emit(ARM_LDR_I(r_skb_data, r_skb, off), ctx); 227 /* headlen = len - data_len */ 228 off = offsetof(struct sk_buff, len); 229 emit(ARM_LDR_I(r_skb_hl, r_skb, off), ctx); 230 off = offsetof(struct sk_buff, data_len); 231 emit(ARM_LDR_I(r_scratch, r_skb, off), ctx); 232 emit(ARM_SUB_R(r_skb_hl, r_skb_hl, r_scratch), ctx); 233 } 234 235 if (ctx->flags & FLAG_NEED_X_RESET) 236 emit(ARM_MOV_I(r_X, 0), ctx); 237 238 /* do not leak kernel data to userspace */ 239 if ((first_inst != (BPF_RET | BPF_K)) && !(is_load_to_a(first_inst))) 240 emit(ARM_MOV_I(r_A, 0), ctx); 241 242 /* stack space for the BPF_MEM words */ 243 if (ctx->seen & SEEN_MEM) 244 emit(ARM_SUB_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx); 245 } 246 247 static void build_epilogue(struct jit_ctx *ctx) 248 { 249 u16 reg_set = saved_regs(ctx); 250 251 if (ctx->seen & SEEN_MEM) 252 emit(ARM_ADD_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx); 253 254 reg_set &= ~(1 << ARM_LR); 255 256 #ifdef CONFIG_FRAME_POINTER 257 /* the first instruction of the prologue was: mov ip, sp */ 258 reg_set &= ~(1 << ARM_IP); 259 reg_set |= (1 << ARM_SP); 260 emit(ARM_LDM(ARM_SP, reg_set), ctx); 261 #else 262 if (reg_set) { 263 if (ctx->seen & SEEN_CALL) 264 reg_set |= 1 << ARM_PC; 265 emit(ARM_POP(reg_set), ctx); 266 } 267 268 if (!(ctx->seen & SEEN_CALL)) 269 emit(ARM_BX(ARM_LR), ctx); 270 #endif 271 } 272 273 static int16_t imm8m(u32 x) 274 { 275 u32 rot; 276 277 for (rot = 0; rot < 16; rot++) 278 if ((x & ~ror32(0xff, 2 * rot)) == 0) 279 return rol32(x, 2 * rot) | (rot << 8); 280 281 return -1; 282 } 283 284 #if __LINUX_ARM_ARCH__ < 7 285 286 static u16 imm_offset(u32 k, struct jit_ctx *ctx) 287 { 288 unsigned i = 0, offset; 289 u16 imm; 290 291 /* on the "fake" run we just count them (duplicates included) */ 292 if (ctx->target == NULL) { 293 ctx->imm_count++; 294 return 0; 295 } 296 297 while ((i < ctx->imm_count) && ctx->imms[i]) { 298 if (ctx->imms[i] == k) 299 break; 300 i++; 301 } 302 303 if (ctx->imms[i] == 0) 304 ctx->imms[i] = k; 305 306 /* constants go just after the epilogue */ 307 offset = ctx->offsets[ctx->skf->len]; 308 offset += ctx->prologue_bytes; 309 offset += ctx->epilogue_bytes; 310 offset += i * 4; 311 312 ctx->target[offset / 4] = k; 313 314 /* PC in ARM mode == address of the instruction + 8 */ 315 imm = offset - (8 + ctx->idx * 4); 316 317 if (imm & ~0xfff) { 318 /* 319 * literal pool is too far, signal it into flags. we 320 * can only detect it on the second pass unfortunately. 321 */ 322 ctx->flags |= FLAG_IMM_OVERFLOW; 323 return 0; 324 } 325 326 return imm; 327 } 328 329 #endif /* __LINUX_ARM_ARCH__ */ 330 331 /* 332 * Move an immediate that's not an imm8m to a core register. 333 */ 334 static inline void emit_mov_i_no8m(int rd, u32 val, struct jit_ctx *ctx) 335 { 336 #if __LINUX_ARM_ARCH__ < 7 337 emit(ARM_LDR_I(rd, ARM_PC, imm_offset(val, ctx)), ctx); 338 #else 339 emit(ARM_MOVW(rd, val & 0xffff), ctx); 340 if (val > 0xffff) 341 emit(ARM_MOVT(rd, val >> 16), ctx); 342 #endif 343 } 344 345 static inline void emit_mov_i(int rd, u32 val, struct jit_ctx *ctx) 346 { 347 int imm12 = imm8m(val); 348 349 if (imm12 >= 0) 350 emit(ARM_MOV_I(rd, imm12), ctx); 351 else 352 emit_mov_i_no8m(rd, val, ctx); 353 } 354 355 #if __LINUX_ARM_ARCH__ < 6 356 357 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx) 358 { 359 _emit(cond, ARM_LDRB_I(ARM_R3, r_addr, 1), ctx); 360 _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx); 361 _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 3), ctx); 362 _emit(cond, ARM_LSL_I(ARM_R3, ARM_R3, 16), ctx); 363 _emit(cond, ARM_LDRB_I(ARM_R0, r_addr, 2), ctx); 364 _emit(cond, ARM_ORR_S(ARM_R3, ARM_R3, ARM_R1, SRTYPE_LSL, 24), ctx); 365 _emit(cond, ARM_ORR_R(ARM_R3, ARM_R3, ARM_R2), ctx); 366 _emit(cond, ARM_ORR_S(r_res, ARM_R3, ARM_R0, SRTYPE_LSL, 8), ctx); 367 } 368 369 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx) 370 { 371 _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx); 372 _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 1), ctx); 373 _emit(cond, ARM_ORR_S(r_res, ARM_R2, ARM_R1, SRTYPE_LSL, 8), ctx); 374 } 375 376 static inline void emit_swap16(u8 r_dst, u8 r_src, struct jit_ctx *ctx) 377 { 378 /* r_dst = (r_src << 8) | (r_src >> 8) */ 379 emit(ARM_LSL_I(ARM_R1, r_src, 8), ctx); 380 emit(ARM_ORR_S(r_dst, ARM_R1, r_src, SRTYPE_LSR, 8), ctx); 381 382 /* 383 * we need to mask out the bits set in r_dst[23:16] due to 384 * the first shift instruction. 385 * 386 * note that 0x8ff is the encoded immediate 0x00ff0000. 387 */ 388 emit(ARM_BIC_I(r_dst, r_dst, 0x8ff), ctx); 389 } 390 391 #else /* ARMv6+ */ 392 393 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx) 394 { 395 _emit(cond, ARM_LDR_I(r_res, r_addr, 0), ctx); 396 #ifdef __LITTLE_ENDIAN 397 _emit(cond, ARM_REV(r_res, r_res), ctx); 398 #endif 399 } 400 401 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx) 402 { 403 _emit(cond, ARM_LDRH_I(r_res, r_addr, 0), ctx); 404 #ifdef __LITTLE_ENDIAN 405 _emit(cond, ARM_REV16(r_res, r_res), ctx); 406 #endif 407 } 408 409 static inline void emit_swap16(u8 r_dst __maybe_unused, 410 u8 r_src __maybe_unused, 411 struct jit_ctx *ctx __maybe_unused) 412 { 413 #ifdef __LITTLE_ENDIAN 414 emit(ARM_REV16(r_dst, r_src), ctx); 415 #endif 416 } 417 418 #endif /* __LINUX_ARM_ARCH__ < 6 */ 419 420 421 /* Compute the immediate value for a PC-relative branch. */ 422 static inline u32 b_imm(unsigned tgt, struct jit_ctx *ctx) 423 { 424 u32 imm; 425 426 if (ctx->target == NULL) 427 return 0; 428 /* 429 * BPF allows only forward jumps and the offset of the target is 430 * still the one computed during the first pass. 431 */ 432 imm = ctx->offsets[tgt] + ctx->prologue_bytes - (ctx->idx * 4 + 8); 433 434 return imm >> 2; 435 } 436 437 #define OP_IMM3(op, r1, r2, imm_val, ctx) \ 438 do { \ 439 imm12 = imm8m(imm_val); \ 440 if (imm12 < 0) { \ 441 emit_mov_i_no8m(r_scratch, imm_val, ctx); \ 442 emit(op ## _R((r1), (r2), r_scratch), ctx); \ 443 } else { \ 444 emit(op ## _I((r1), (r2), imm12), ctx); \ 445 } \ 446 } while (0) 447 448 static inline void emit_err_ret(u8 cond, struct jit_ctx *ctx) 449 { 450 if (ctx->ret0_fp_idx >= 0) { 451 _emit(cond, ARM_B(b_imm(ctx->ret0_fp_idx, ctx)), ctx); 452 /* NOP to keep the size constant between passes */ 453 emit(ARM_MOV_R(ARM_R0, ARM_R0), ctx); 454 } else { 455 _emit(cond, ARM_MOV_I(ARM_R0, 0), ctx); 456 _emit(cond, ARM_B(b_imm(ctx->skf->len, ctx)), ctx); 457 } 458 } 459 460 static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx) 461 { 462 #if __LINUX_ARM_ARCH__ < 5 463 emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx); 464 465 if (elf_hwcap & HWCAP_THUMB) 466 emit(ARM_BX(tgt_reg), ctx); 467 else 468 emit(ARM_MOV_R(ARM_PC, tgt_reg), ctx); 469 #else 470 emit(ARM_BLX_R(tgt_reg), ctx); 471 #endif 472 } 473 474 static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx) 475 { 476 #if __LINUX_ARM_ARCH__ == 7 477 if (elf_hwcap & HWCAP_IDIVA) { 478 emit(ARM_UDIV(rd, rm, rn), ctx); 479 return; 480 } 481 #endif 482 483 /* 484 * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4 485 * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into 486 * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm 487 * before using it as a source for ARM_R1. 488 * 489 * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is 490 * ARM_R5 (r_X) so there is no particular register overlap 491 * issues. 492 */ 493 if (rn != ARM_R1) 494 emit(ARM_MOV_R(ARM_R1, rn), ctx); 495 if (rm != ARM_R0) 496 emit(ARM_MOV_R(ARM_R0, rm), ctx); 497 498 ctx->seen |= SEEN_CALL; 499 emit_mov_i(ARM_R3, (u32)jit_udiv, ctx); 500 emit_blx_r(ARM_R3, ctx); 501 502 if (rd != ARM_R0) 503 emit(ARM_MOV_R(rd, ARM_R0), ctx); 504 } 505 506 static inline void update_on_xread(struct jit_ctx *ctx) 507 { 508 if (!(ctx->seen & SEEN_X)) 509 ctx->flags |= FLAG_NEED_X_RESET; 510 511 ctx->seen |= SEEN_X; 512 } 513 514 static int build_body(struct jit_ctx *ctx) 515 { 516 void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w}; 517 const struct bpf_prog *prog = ctx->skf; 518 const struct sock_filter *inst; 519 unsigned i, load_order, off, condt; 520 int imm12; 521 u32 k; 522 523 for (i = 0; i < prog->len; i++) { 524 u16 code; 525 526 inst = &(prog->insns[i]); 527 /* K as an immediate value operand */ 528 k = inst->k; 529 code = bpf_anc_helper(inst); 530 531 /* compute offsets only in the fake pass */ 532 if (ctx->target == NULL) 533 ctx->offsets[i] = ctx->idx * 4; 534 535 switch (code) { 536 case BPF_LD | BPF_IMM: 537 emit_mov_i(r_A, k, ctx); 538 break; 539 case BPF_LD | BPF_W | BPF_LEN: 540 ctx->seen |= SEEN_SKB; 541 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4); 542 emit(ARM_LDR_I(r_A, r_skb, 543 offsetof(struct sk_buff, len)), ctx); 544 break; 545 case BPF_LD | BPF_MEM: 546 /* A = scratch[k] */ 547 ctx->seen |= SEEN_MEM_WORD(k); 548 emit(ARM_LDR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx); 549 break; 550 case BPF_LD | BPF_W | BPF_ABS: 551 load_order = 2; 552 goto load; 553 case BPF_LD | BPF_H | BPF_ABS: 554 load_order = 1; 555 goto load; 556 case BPF_LD | BPF_B | BPF_ABS: 557 load_order = 0; 558 load: 559 emit_mov_i(r_off, k, ctx); 560 load_common: 561 ctx->seen |= SEEN_DATA | SEEN_CALL; 562 563 if (load_order > 0) { 564 emit(ARM_SUB_I(r_scratch, r_skb_hl, 565 1 << load_order), ctx); 566 emit(ARM_CMP_R(r_scratch, r_off), ctx); 567 condt = ARM_COND_GE; 568 } else { 569 emit(ARM_CMP_R(r_skb_hl, r_off), ctx); 570 condt = ARM_COND_HI; 571 } 572 573 /* 574 * test for negative offset, only if we are 575 * currently scheduled to take the fast 576 * path. this will update the flags so that 577 * the slowpath instruction are ignored if the 578 * offset is negative. 579 * 580 * for loard_order == 0 the HI condition will 581 * make loads at offset 0 take the slow path too. 582 */ 583 _emit(condt, ARM_CMP_I(r_off, 0), ctx); 584 585 _emit(condt, ARM_ADD_R(r_scratch, r_off, r_skb_data), 586 ctx); 587 588 if (load_order == 0) 589 _emit(condt, ARM_LDRB_I(r_A, r_scratch, 0), 590 ctx); 591 else if (load_order == 1) 592 emit_load_be16(condt, r_A, r_scratch, ctx); 593 else if (load_order == 2) 594 emit_load_be32(condt, r_A, r_scratch, ctx); 595 596 _emit(condt, ARM_B(b_imm(i + 1, ctx)), ctx); 597 598 /* the slowpath */ 599 emit_mov_i(ARM_R3, (u32)load_func[load_order], ctx); 600 emit(ARM_MOV_R(ARM_R0, r_skb), ctx); 601 /* the offset is already in R1 */ 602 emit_blx_r(ARM_R3, ctx); 603 /* check the result of skb_copy_bits */ 604 emit(ARM_CMP_I(ARM_R1, 0), ctx); 605 emit_err_ret(ARM_COND_NE, ctx); 606 emit(ARM_MOV_R(r_A, ARM_R0), ctx); 607 break; 608 case BPF_LD | BPF_W | BPF_IND: 609 load_order = 2; 610 goto load_ind; 611 case BPF_LD | BPF_H | BPF_IND: 612 load_order = 1; 613 goto load_ind; 614 case BPF_LD | BPF_B | BPF_IND: 615 load_order = 0; 616 load_ind: 617 OP_IMM3(ARM_ADD, r_off, r_X, k, ctx); 618 goto load_common; 619 case BPF_LDX | BPF_IMM: 620 ctx->seen |= SEEN_X; 621 emit_mov_i(r_X, k, ctx); 622 break; 623 case BPF_LDX | BPF_W | BPF_LEN: 624 ctx->seen |= SEEN_X | SEEN_SKB; 625 emit(ARM_LDR_I(r_X, r_skb, 626 offsetof(struct sk_buff, len)), ctx); 627 break; 628 case BPF_LDX | BPF_MEM: 629 ctx->seen |= SEEN_X | SEEN_MEM_WORD(k); 630 emit(ARM_LDR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx); 631 break; 632 case BPF_LDX | BPF_B | BPF_MSH: 633 /* x = ((*(frame + k)) & 0xf) << 2; */ 634 ctx->seen |= SEEN_X | SEEN_DATA | SEEN_CALL; 635 /* the interpreter should deal with the negative K */ 636 if ((int)k < 0) 637 return -1; 638 /* offset in r1: we might have to take the slow path */ 639 emit_mov_i(r_off, k, ctx); 640 emit(ARM_CMP_R(r_skb_hl, r_off), ctx); 641 642 /* load in r0: common with the slowpath */ 643 _emit(ARM_COND_HI, ARM_LDRB_R(ARM_R0, r_skb_data, 644 ARM_R1), ctx); 645 /* 646 * emit_mov_i() might generate one or two instructions, 647 * the same holds for emit_blx_r() 648 */ 649 _emit(ARM_COND_HI, ARM_B(b_imm(i + 1, ctx) - 2), ctx); 650 651 emit(ARM_MOV_R(ARM_R0, r_skb), ctx); 652 /* r_off is r1 */ 653 emit_mov_i(ARM_R3, (u32)jit_get_skb_b, ctx); 654 emit_blx_r(ARM_R3, ctx); 655 /* check the return value of skb_copy_bits */ 656 emit(ARM_CMP_I(ARM_R1, 0), ctx); 657 emit_err_ret(ARM_COND_NE, ctx); 658 659 emit(ARM_AND_I(r_X, ARM_R0, 0x00f), ctx); 660 emit(ARM_LSL_I(r_X, r_X, 2), ctx); 661 break; 662 case BPF_ST: 663 ctx->seen |= SEEN_MEM_WORD(k); 664 emit(ARM_STR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx); 665 break; 666 case BPF_STX: 667 update_on_xread(ctx); 668 ctx->seen |= SEEN_MEM_WORD(k); 669 emit(ARM_STR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx); 670 break; 671 case BPF_ALU | BPF_ADD | BPF_K: 672 /* A += K */ 673 OP_IMM3(ARM_ADD, r_A, r_A, k, ctx); 674 break; 675 case BPF_ALU | BPF_ADD | BPF_X: 676 update_on_xread(ctx); 677 emit(ARM_ADD_R(r_A, r_A, r_X), ctx); 678 break; 679 case BPF_ALU | BPF_SUB | BPF_K: 680 /* A -= K */ 681 OP_IMM3(ARM_SUB, r_A, r_A, k, ctx); 682 break; 683 case BPF_ALU | BPF_SUB | BPF_X: 684 update_on_xread(ctx); 685 emit(ARM_SUB_R(r_A, r_A, r_X), ctx); 686 break; 687 case BPF_ALU | BPF_MUL | BPF_K: 688 /* A *= K */ 689 emit_mov_i(r_scratch, k, ctx); 690 emit(ARM_MUL(r_A, r_A, r_scratch), ctx); 691 break; 692 case BPF_ALU | BPF_MUL | BPF_X: 693 update_on_xread(ctx); 694 emit(ARM_MUL(r_A, r_A, r_X), ctx); 695 break; 696 case BPF_ALU | BPF_DIV | BPF_K: 697 if (k == 1) 698 break; 699 emit_mov_i(r_scratch, k, ctx); 700 emit_udiv(r_A, r_A, r_scratch, ctx); 701 break; 702 case BPF_ALU | BPF_DIV | BPF_X: 703 update_on_xread(ctx); 704 emit(ARM_CMP_I(r_X, 0), ctx); 705 emit_err_ret(ARM_COND_EQ, ctx); 706 emit_udiv(r_A, r_A, r_X, ctx); 707 break; 708 case BPF_ALU | BPF_OR | BPF_K: 709 /* A |= K */ 710 OP_IMM3(ARM_ORR, r_A, r_A, k, ctx); 711 break; 712 case BPF_ALU | BPF_OR | BPF_X: 713 update_on_xread(ctx); 714 emit(ARM_ORR_R(r_A, r_A, r_X), ctx); 715 break; 716 case BPF_ALU | BPF_XOR | BPF_K: 717 /* A ^= K; */ 718 OP_IMM3(ARM_EOR, r_A, r_A, k, ctx); 719 break; 720 case BPF_ANC | SKF_AD_ALU_XOR_X: 721 case BPF_ALU | BPF_XOR | BPF_X: 722 /* A ^= X */ 723 update_on_xread(ctx); 724 emit(ARM_EOR_R(r_A, r_A, r_X), ctx); 725 break; 726 case BPF_ALU | BPF_AND | BPF_K: 727 /* A &= K */ 728 OP_IMM3(ARM_AND, r_A, r_A, k, ctx); 729 break; 730 case BPF_ALU | BPF_AND | BPF_X: 731 update_on_xread(ctx); 732 emit(ARM_AND_R(r_A, r_A, r_X), ctx); 733 break; 734 case BPF_ALU | BPF_LSH | BPF_K: 735 if (unlikely(k > 31)) 736 return -1; 737 emit(ARM_LSL_I(r_A, r_A, k), ctx); 738 break; 739 case BPF_ALU | BPF_LSH | BPF_X: 740 update_on_xread(ctx); 741 emit(ARM_LSL_R(r_A, r_A, r_X), ctx); 742 break; 743 case BPF_ALU | BPF_RSH | BPF_K: 744 if (unlikely(k > 31)) 745 return -1; 746 emit(ARM_LSR_I(r_A, r_A, k), ctx); 747 break; 748 case BPF_ALU | BPF_RSH | BPF_X: 749 update_on_xread(ctx); 750 emit(ARM_LSR_R(r_A, r_A, r_X), ctx); 751 break; 752 case BPF_ALU | BPF_NEG: 753 /* A = -A */ 754 emit(ARM_RSB_I(r_A, r_A, 0), ctx); 755 break; 756 case BPF_JMP | BPF_JA: 757 /* pc += K */ 758 emit(ARM_B(b_imm(i + k + 1, ctx)), ctx); 759 break; 760 case BPF_JMP | BPF_JEQ | BPF_K: 761 /* pc += (A == K) ? pc->jt : pc->jf */ 762 condt = ARM_COND_EQ; 763 goto cmp_imm; 764 case BPF_JMP | BPF_JGT | BPF_K: 765 /* pc += (A > K) ? pc->jt : pc->jf */ 766 condt = ARM_COND_HI; 767 goto cmp_imm; 768 case BPF_JMP | BPF_JGE | BPF_K: 769 /* pc += (A >= K) ? pc->jt : pc->jf */ 770 condt = ARM_COND_HS; 771 cmp_imm: 772 imm12 = imm8m(k); 773 if (imm12 < 0) { 774 emit_mov_i_no8m(r_scratch, k, ctx); 775 emit(ARM_CMP_R(r_A, r_scratch), ctx); 776 } else { 777 emit(ARM_CMP_I(r_A, imm12), ctx); 778 } 779 cond_jump: 780 if (inst->jt) 781 _emit(condt, ARM_B(b_imm(i + inst->jt + 1, 782 ctx)), ctx); 783 if (inst->jf) 784 _emit(condt ^ 1, ARM_B(b_imm(i + inst->jf + 1, 785 ctx)), ctx); 786 break; 787 case BPF_JMP | BPF_JEQ | BPF_X: 788 /* pc += (A == X) ? pc->jt : pc->jf */ 789 condt = ARM_COND_EQ; 790 goto cmp_x; 791 case BPF_JMP | BPF_JGT | BPF_X: 792 /* pc += (A > X) ? pc->jt : pc->jf */ 793 condt = ARM_COND_HI; 794 goto cmp_x; 795 case BPF_JMP | BPF_JGE | BPF_X: 796 /* pc += (A >= X) ? pc->jt : pc->jf */ 797 condt = ARM_COND_CS; 798 cmp_x: 799 update_on_xread(ctx); 800 emit(ARM_CMP_R(r_A, r_X), ctx); 801 goto cond_jump; 802 case BPF_JMP | BPF_JSET | BPF_K: 803 /* pc += (A & K) ? pc->jt : pc->jf */ 804 condt = ARM_COND_NE; 805 /* not set iff all zeroes iff Z==1 iff EQ */ 806 807 imm12 = imm8m(k); 808 if (imm12 < 0) { 809 emit_mov_i_no8m(r_scratch, k, ctx); 810 emit(ARM_TST_R(r_A, r_scratch), ctx); 811 } else { 812 emit(ARM_TST_I(r_A, imm12), ctx); 813 } 814 goto cond_jump; 815 case BPF_JMP | BPF_JSET | BPF_X: 816 /* pc += (A & X) ? pc->jt : pc->jf */ 817 update_on_xread(ctx); 818 condt = ARM_COND_NE; 819 emit(ARM_TST_R(r_A, r_X), ctx); 820 goto cond_jump; 821 case BPF_RET | BPF_A: 822 emit(ARM_MOV_R(ARM_R0, r_A), ctx); 823 goto b_epilogue; 824 case BPF_RET | BPF_K: 825 if ((k == 0) && (ctx->ret0_fp_idx < 0)) 826 ctx->ret0_fp_idx = i; 827 emit_mov_i(ARM_R0, k, ctx); 828 b_epilogue: 829 if (i != ctx->skf->len - 1) 830 emit(ARM_B(b_imm(prog->len, ctx)), ctx); 831 break; 832 case BPF_MISC | BPF_TAX: 833 /* X = A */ 834 ctx->seen |= SEEN_X; 835 emit(ARM_MOV_R(r_X, r_A), ctx); 836 break; 837 case BPF_MISC | BPF_TXA: 838 /* A = X */ 839 update_on_xread(ctx); 840 emit(ARM_MOV_R(r_A, r_X), ctx); 841 break; 842 case BPF_ANC | SKF_AD_PROTOCOL: 843 /* A = ntohs(skb->protocol) */ 844 ctx->seen |= SEEN_SKB; 845 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, 846 protocol) != 2); 847 off = offsetof(struct sk_buff, protocol); 848 emit(ARM_LDRH_I(r_scratch, r_skb, off), ctx); 849 emit_swap16(r_A, r_scratch, ctx); 850 break; 851 case BPF_ANC | SKF_AD_CPU: 852 /* r_scratch = current_thread_info() */ 853 OP_IMM3(ARM_BIC, r_scratch, ARM_SP, THREAD_SIZE - 1, ctx); 854 /* A = current_thread_info()->cpu */ 855 BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info, cpu) != 4); 856 off = offsetof(struct thread_info, cpu); 857 emit(ARM_LDR_I(r_A, r_scratch, off), ctx); 858 break; 859 case BPF_ANC | SKF_AD_IFINDEX: 860 case BPF_ANC | SKF_AD_HATYPE: 861 /* A = skb->dev->ifindex */ 862 /* A = skb->dev->type */ 863 ctx->seen |= SEEN_SKB; 864 off = offsetof(struct sk_buff, dev); 865 emit(ARM_LDR_I(r_scratch, r_skb, off), ctx); 866 867 emit(ARM_CMP_I(r_scratch, 0), ctx); 868 emit_err_ret(ARM_COND_EQ, ctx); 869 870 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, 871 ifindex) != 4); 872 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, 873 type) != 2); 874 875 if (code == (BPF_ANC | SKF_AD_IFINDEX)) { 876 off = offsetof(struct net_device, ifindex); 877 emit(ARM_LDR_I(r_A, r_scratch, off), ctx); 878 } else { 879 /* 880 * offset of field "type" in "struct 881 * net_device" is above what can be 882 * used in the ldrh rd, [rn, #imm] 883 * instruction, so load the offset in 884 * a register and use ldrh rd, [rn, rm] 885 */ 886 off = offsetof(struct net_device, type); 887 emit_mov_i(ARM_R3, off, ctx); 888 emit(ARM_LDRH_R(r_A, r_scratch, ARM_R3), ctx); 889 } 890 break; 891 case BPF_ANC | SKF_AD_MARK: 892 ctx->seen |= SEEN_SKB; 893 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4); 894 off = offsetof(struct sk_buff, mark); 895 emit(ARM_LDR_I(r_A, r_skb, off), ctx); 896 break; 897 case BPF_ANC | SKF_AD_RXHASH: 898 ctx->seen |= SEEN_SKB; 899 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4); 900 off = offsetof(struct sk_buff, hash); 901 emit(ARM_LDR_I(r_A, r_skb, off), ctx); 902 break; 903 case BPF_ANC | SKF_AD_VLAN_TAG: 904 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT: 905 ctx->seen |= SEEN_SKB; 906 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2); 907 off = offsetof(struct sk_buff, vlan_tci); 908 emit(ARM_LDRH_I(r_A, r_skb, off), ctx); 909 if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) 910 OP_IMM3(ARM_AND, r_A, r_A, ~VLAN_TAG_PRESENT, ctx); 911 else { 912 OP_IMM3(ARM_LSR, r_A, r_A, 12, ctx); 913 OP_IMM3(ARM_AND, r_A, r_A, 0x1, ctx); 914 } 915 break; 916 case BPF_ANC | SKF_AD_PKTTYPE: 917 ctx->seen |= SEEN_SKB; 918 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, 919 __pkt_type_offset[0]) != 1); 920 off = PKT_TYPE_OFFSET(); 921 emit(ARM_LDRB_I(r_A, r_skb, off), ctx); 922 emit(ARM_AND_I(r_A, r_A, PKT_TYPE_MAX), ctx); 923 #ifdef __BIG_ENDIAN_BITFIELD 924 emit(ARM_LSR_I(r_A, r_A, 5), ctx); 925 #endif 926 break; 927 case BPF_ANC | SKF_AD_QUEUE: 928 ctx->seen |= SEEN_SKB; 929 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, 930 queue_mapping) != 2); 931 BUILD_BUG_ON(offsetof(struct sk_buff, 932 queue_mapping) > 0xff); 933 off = offsetof(struct sk_buff, queue_mapping); 934 emit(ARM_LDRH_I(r_A, r_skb, off), ctx); 935 break; 936 case BPF_ANC | SKF_AD_PAY_OFFSET: 937 ctx->seen |= SEEN_SKB | SEEN_CALL; 938 939 emit(ARM_MOV_R(ARM_R0, r_skb), ctx); 940 emit_mov_i(ARM_R3, (unsigned int)skb_get_poff, ctx); 941 emit_blx_r(ARM_R3, ctx); 942 emit(ARM_MOV_R(r_A, ARM_R0), ctx); 943 break; 944 case BPF_LDX | BPF_W | BPF_ABS: 945 /* 946 * load a 32bit word from struct seccomp_data. 947 * seccomp_check_filter() will already have checked 948 * that k is 32bit aligned and lies within the 949 * struct seccomp_data. 950 */ 951 ctx->seen |= SEEN_SKB; 952 emit(ARM_LDR_I(r_A, r_skb, k), ctx); 953 break; 954 default: 955 return -1; 956 } 957 958 if (ctx->flags & FLAG_IMM_OVERFLOW) 959 /* 960 * this instruction generated an overflow when 961 * trying to access the literal pool, so 962 * delegate this filter to the kernel interpreter. 963 */ 964 return -1; 965 } 966 967 /* compute offsets only during the first pass */ 968 if (ctx->target == NULL) 969 ctx->offsets[i] = ctx->idx * 4; 970 971 return 0; 972 } 973 974 975 void bpf_jit_compile(struct bpf_prog *fp) 976 { 977 struct bpf_binary_header *header; 978 struct jit_ctx ctx; 979 unsigned tmp_idx; 980 unsigned alloc_size; 981 u8 *target_ptr; 982 983 if (!bpf_jit_enable) 984 return; 985 986 memset(&ctx, 0, sizeof(ctx)); 987 ctx.skf = fp; 988 ctx.ret0_fp_idx = -1; 989 990 ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL); 991 if (ctx.offsets == NULL) 992 return; 993 994 /* fake pass to fill in the ctx->seen */ 995 if (unlikely(build_body(&ctx))) 996 goto out; 997 998 tmp_idx = ctx.idx; 999 build_prologue(&ctx); 1000 ctx.prologue_bytes = (ctx.idx - tmp_idx) * 4; 1001 1002 #if __LINUX_ARM_ARCH__ < 7 1003 tmp_idx = ctx.idx; 1004 build_epilogue(&ctx); 1005 ctx.epilogue_bytes = (ctx.idx - tmp_idx) * 4; 1006 1007 ctx.idx += ctx.imm_count; 1008 if (ctx.imm_count) { 1009 ctx.imms = kzalloc(4 * ctx.imm_count, GFP_KERNEL); 1010 if (ctx.imms == NULL) 1011 goto out; 1012 } 1013 #else 1014 /* there's nothing after the epilogue on ARMv7 */ 1015 build_epilogue(&ctx); 1016 #endif 1017 alloc_size = 4 * ctx.idx; 1018 header = bpf_jit_binary_alloc(alloc_size, &target_ptr, 1019 4, jit_fill_hole); 1020 if (header == NULL) 1021 goto out; 1022 1023 ctx.target = (u32 *) target_ptr; 1024 ctx.idx = 0; 1025 1026 build_prologue(&ctx); 1027 if (build_body(&ctx) < 0) { 1028 #if __LINUX_ARM_ARCH__ < 7 1029 if (ctx.imm_count) 1030 kfree(ctx.imms); 1031 #endif 1032 bpf_jit_binary_free(header); 1033 goto out; 1034 } 1035 build_epilogue(&ctx); 1036 1037 flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx)); 1038 1039 #if __LINUX_ARM_ARCH__ < 7 1040 if (ctx.imm_count) 1041 kfree(ctx.imms); 1042 #endif 1043 1044 if (bpf_jit_enable > 1) 1045 /* there are 2 passes here */ 1046 bpf_jit_dump(fp->len, alloc_size, 2, ctx.target); 1047 1048 set_memory_ro((unsigned long)header, header->pages); 1049 fp->bpf_func = (void *)ctx.target; 1050 fp->jited = true; 1051 out: 1052 kfree(ctx.offsets); 1053 return; 1054 } 1055 1056 void bpf_jit_free(struct bpf_prog *fp) 1057 { 1058 unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK; 1059 struct bpf_binary_header *header = (void *)addr; 1060 1061 if (!fp->jited) 1062 goto free_filter; 1063 1064 set_memory_rw(addr, header->pages); 1065 bpf_jit_binary_free(header); 1066 1067 free_filter: 1068 bpf_prog_unlock_free(fp); 1069 } 1070