1 // SPDX-License-Identifier: GPL-2.0-only 2 /* bpf_jit_comp.c: BPF JIT compiler 3 * 4 * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation 5 * 6 * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com) 7 * Ported to ppc32 by Denis Kirjanov <kda@linux-powerpc.org> 8 */ 9 #include <linux/moduleloader.h> 10 #include <asm/cacheflush.h> 11 #include <asm/asm-compat.h> 12 #include <linux/netdevice.h> 13 #include <linux/filter.h> 14 #include <linux/if_vlan.h> 15 16 #include "bpf_jit32.h" 17 18 static inline void bpf_flush_icache(void *start, void *end) 19 { 20 smp_wmb(); 21 flush_icache_range((unsigned long)start, (unsigned long)end); 22 } 23 24 static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image, 25 struct codegen_context *ctx) 26 { 27 int i; 28 const struct sock_filter *filter = fp->insns; 29 30 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) { 31 /* Make stackframe */ 32 if (ctx->seen & SEEN_DATAREF) { 33 /* If we call any helpers (for loads), save LR */ 34 EMIT(PPC_INST_MFLR | __PPC_RT(R0)); 35 PPC_BPF_STL(0, 1, PPC_LR_STKOFF); 36 37 /* Back up non-volatile regs. */ 38 PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D))); 39 PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL))); 40 } 41 if (ctx->seen & SEEN_MEM) { 42 /* 43 * Conditionally save regs r15-r31 as some will be used 44 * for M[] data. 45 */ 46 for (i = r_M; i < (r_M+16); i++) { 47 if (ctx->seen & (1 << (i-r_M))) 48 PPC_BPF_STL(i, 1, -(REG_SZ*(32-i))); 49 } 50 } 51 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME); 52 } 53 54 if (ctx->seen & SEEN_DATAREF) { 55 /* 56 * If this filter needs to access skb data, 57 * prepare r_D and r_HL: 58 * r_HL = skb->len - skb->data_len 59 * r_D = skb->data 60 */ 61 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff, 62 data_len)); 63 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len)); 64 PPC_SUB(r_HL, r_HL, r_scratch1); 65 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data)); 66 } 67 68 if (ctx->seen & SEEN_XREG) { 69 /* 70 * TODO: Could also detect whether first instr. sets X and 71 * avoid this (as below, with A). 72 */ 73 PPC_LI(r_X, 0); 74 } 75 76 /* make sure we dont leak kernel information to user */ 77 if (bpf_needs_clear_a(&filter[0])) 78 PPC_LI(r_A, 0); 79 } 80 81 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) 82 { 83 int i; 84 85 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) { 86 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME); 87 if (ctx->seen & SEEN_DATAREF) { 88 PPC_BPF_LL(0, 1, PPC_LR_STKOFF); 89 PPC_MTLR(0); 90 PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D))); 91 PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL))); 92 } 93 if (ctx->seen & SEEN_MEM) { 94 /* Restore any saved non-vol registers */ 95 for (i = r_M; i < (r_M+16); i++) { 96 if (ctx->seen & (1 << (i-r_M))) 97 PPC_BPF_LL(i, 1, -(REG_SZ*(32-i))); 98 } 99 } 100 } 101 /* The RETs have left a return value in R3. */ 102 103 PPC_BLR(); 104 } 105 106 #define CHOOSE_LOAD_FUNC(K, func) \ 107 ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset) 108 109 /* Assemble the body code between the prologue & epilogue. */ 110 static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, 111 struct codegen_context *ctx, 112 unsigned int *addrs) 113 { 114 const struct sock_filter *filter = fp->insns; 115 int flen = fp->len; 116 u8 *func; 117 unsigned int true_cond; 118 int i; 119 120 /* Start of epilogue code */ 121 unsigned int exit_addr = addrs[flen]; 122 123 for (i = 0; i < flen; i++) { 124 unsigned int K = filter[i].k; 125 u16 code = bpf_anc_helper(&filter[i]); 126 127 /* 128 * addrs[] maps a BPF bytecode address into a real offset from 129 * the start of the body code. 130 */ 131 addrs[i] = ctx->idx * 4; 132 133 switch (code) { 134 /*** ALU ops ***/ 135 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */ 136 ctx->seen |= SEEN_XREG; 137 PPC_ADD(r_A, r_A, r_X); 138 break; 139 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */ 140 if (!K) 141 break; 142 PPC_ADDI(r_A, r_A, IMM_L(K)); 143 if (K >= 32768) 144 PPC_ADDIS(r_A, r_A, IMM_HA(K)); 145 break; 146 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */ 147 ctx->seen |= SEEN_XREG; 148 PPC_SUB(r_A, r_A, r_X); 149 break; 150 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */ 151 if (!K) 152 break; 153 PPC_ADDI(r_A, r_A, IMM_L(-K)); 154 if (K >= 32768) 155 PPC_ADDIS(r_A, r_A, IMM_HA(-K)); 156 break; 157 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */ 158 ctx->seen |= SEEN_XREG; 159 PPC_MULW(r_A, r_A, r_X); 160 break; 161 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */ 162 if (K < 32768) 163 PPC_MULI(r_A, r_A, K); 164 else { 165 PPC_LI32(r_scratch1, K); 166 PPC_MULW(r_A, r_A, r_scratch1); 167 } 168 break; 169 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */ 170 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */ 171 ctx->seen |= SEEN_XREG; 172 PPC_CMPWI(r_X, 0); 173 if (ctx->pc_ret0 != -1) { 174 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]); 175 } else { 176 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12); 177 PPC_LI(r_ret, 0); 178 PPC_JMP(exit_addr); 179 } 180 if (code == (BPF_ALU | BPF_MOD | BPF_X)) { 181 PPC_DIVWU(r_scratch1, r_A, r_X); 182 PPC_MULW(r_scratch1, r_X, r_scratch1); 183 PPC_SUB(r_A, r_A, r_scratch1); 184 } else { 185 PPC_DIVWU(r_A, r_A, r_X); 186 } 187 break; 188 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */ 189 PPC_LI32(r_scratch2, K); 190 PPC_DIVWU(r_scratch1, r_A, r_scratch2); 191 PPC_MULW(r_scratch1, r_scratch2, r_scratch1); 192 PPC_SUB(r_A, r_A, r_scratch1); 193 break; 194 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */ 195 if (K == 1) 196 break; 197 PPC_LI32(r_scratch1, K); 198 PPC_DIVWU(r_A, r_A, r_scratch1); 199 break; 200 case BPF_ALU | BPF_AND | BPF_X: 201 ctx->seen |= SEEN_XREG; 202 PPC_AND(r_A, r_A, r_X); 203 break; 204 case BPF_ALU | BPF_AND | BPF_K: 205 if (!IMM_H(K)) 206 PPC_ANDI(r_A, r_A, K); 207 else { 208 PPC_LI32(r_scratch1, K); 209 PPC_AND(r_A, r_A, r_scratch1); 210 } 211 break; 212 case BPF_ALU | BPF_OR | BPF_X: 213 ctx->seen |= SEEN_XREG; 214 PPC_OR(r_A, r_A, r_X); 215 break; 216 case BPF_ALU | BPF_OR | BPF_K: 217 if (IMM_L(K)) 218 PPC_ORI(r_A, r_A, IMM_L(K)); 219 if (K >= 65536) 220 PPC_ORIS(r_A, r_A, IMM_H(K)); 221 break; 222 case BPF_ANC | SKF_AD_ALU_XOR_X: 223 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */ 224 ctx->seen |= SEEN_XREG; 225 PPC_XOR(r_A, r_A, r_X); 226 break; 227 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */ 228 if (IMM_L(K)) 229 PPC_XORI(r_A, r_A, IMM_L(K)); 230 if (K >= 65536) 231 PPC_XORIS(r_A, r_A, IMM_H(K)); 232 break; 233 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */ 234 ctx->seen |= SEEN_XREG; 235 PPC_SLW(r_A, r_A, r_X); 236 break; 237 case BPF_ALU | BPF_LSH | BPF_K: 238 if (K == 0) 239 break; 240 else 241 PPC_SLWI(r_A, r_A, K); 242 break; 243 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */ 244 ctx->seen |= SEEN_XREG; 245 PPC_SRW(r_A, r_A, r_X); 246 break; 247 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */ 248 if (K == 0) 249 break; 250 else 251 PPC_SRWI(r_A, r_A, K); 252 break; 253 case BPF_ALU | BPF_NEG: 254 PPC_NEG(r_A, r_A); 255 break; 256 case BPF_RET | BPF_K: 257 PPC_LI32(r_ret, K); 258 if (!K) { 259 if (ctx->pc_ret0 == -1) 260 ctx->pc_ret0 = i; 261 } 262 /* 263 * If this isn't the very last instruction, branch to 264 * the epilogue if we've stuff to clean up. Otherwise, 265 * if there's nothing to tidy, just return. If we /are/ 266 * the last instruction, we're about to fall through to 267 * the epilogue to return. 268 */ 269 if (i != flen - 1) { 270 /* 271 * Note: 'seen' is properly valid only on pass 272 * #2. Both parts of this conditional are the 273 * same instruction size though, meaning the 274 * first pass will still correctly determine the 275 * code size/addresses. 276 */ 277 if (ctx->seen) 278 PPC_JMP(exit_addr); 279 else 280 PPC_BLR(); 281 } 282 break; 283 case BPF_RET | BPF_A: 284 PPC_MR(r_ret, r_A); 285 if (i != flen - 1) { 286 if (ctx->seen) 287 PPC_JMP(exit_addr); 288 else 289 PPC_BLR(); 290 } 291 break; 292 case BPF_MISC | BPF_TAX: /* X = A */ 293 PPC_MR(r_X, r_A); 294 break; 295 case BPF_MISC | BPF_TXA: /* A = X */ 296 ctx->seen |= SEEN_XREG; 297 PPC_MR(r_A, r_X); 298 break; 299 300 /*** Constant loads/M[] access ***/ 301 case BPF_LD | BPF_IMM: /* A = K */ 302 PPC_LI32(r_A, K); 303 break; 304 case BPF_LDX | BPF_IMM: /* X = K */ 305 PPC_LI32(r_X, K); 306 break; 307 case BPF_LD | BPF_MEM: /* A = mem[K] */ 308 PPC_MR(r_A, r_M + (K & 0xf)); 309 ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); 310 break; 311 case BPF_LDX | BPF_MEM: /* X = mem[K] */ 312 PPC_MR(r_X, r_M + (K & 0xf)); 313 ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); 314 break; 315 case BPF_ST: /* mem[K] = A */ 316 PPC_MR(r_M + (K & 0xf), r_A); 317 ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); 318 break; 319 case BPF_STX: /* mem[K] = X */ 320 PPC_MR(r_M + (K & 0xf), r_X); 321 ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf)); 322 break; 323 case BPF_LD | BPF_W | BPF_LEN: /* A = skb->len; */ 324 BUILD_BUG_ON(sizeof_field(struct sk_buff, len) != 4); 325 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len)); 326 break; 327 case BPF_LDX | BPF_W | BPF_ABS: /* A = *((u32 *)(seccomp_data + K)); */ 328 PPC_LWZ_OFFS(r_A, r_skb, K); 329 break; 330 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */ 331 PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len)); 332 break; 333 334 /*** Ancillary info loads ***/ 335 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */ 336 BUILD_BUG_ON(sizeof_field(struct sk_buff, 337 protocol) != 2); 338 PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff, 339 protocol)); 340 break; 341 case BPF_ANC | SKF_AD_IFINDEX: 342 case BPF_ANC | SKF_AD_HATYPE: 343 BUILD_BUG_ON(sizeof_field(struct net_device, 344 ifindex) != 4); 345 BUILD_BUG_ON(sizeof_field(struct net_device, 346 type) != 2); 347 PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff, 348 dev)); 349 PPC_CMPDI(r_scratch1, 0); 350 if (ctx->pc_ret0 != -1) { 351 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]); 352 } else { 353 /* Exit, returning 0; first pass hits here. */ 354 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12); 355 PPC_LI(r_ret, 0); 356 PPC_JMP(exit_addr); 357 } 358 if (code == (BPF_ANC | SKF_AD_IFINDEX)) { 359 PPC_LWZ_OFFS(r_A, r_scratch1, 360 offsetof(struct net_device, ifindex)); 361 } else { 362 PPC_LHZ_OFFS(r_A, r_scratch1, 363 offsetof(struct net_device, type)); 364 } 365 366 break; 367 case BPF_ANC | SKF_AD_MARK: 368 BUILD_BUG_ON(sizeof_field(struct sk_buff, mark) != 4); 369 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, 370 mark)); 371 break; 372 case BPF_ANC | SKF_AD_RXHASH: 373 BUILD_BUG_ON(sizeof_field(struct sk_buff, hash) != 4); 374 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, 375 hash)); 376 break; 377 case BPF_ANC | SKF_AD_VLAN_TAG: 378 BUILD_BUG_ON(sizeof_field(struct sk_buff, vlan_tci) != 2); 379 380 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, 381 vlan_tci)); 382 break; 383 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT: 384 PPC_LBZ_OFFS(r_A, r_skb, PKT_VLAN_PRESENT_OFFSET()); 385 if (PKT_VLAN_PRESENT_BIT) 386 PPC_SRWI(r_A, r_A, PKT_VLAN_PRESENT_BIT); 387 if (PKT_VLAN_PRESENT_BIT < 7) 388 PPC_ANDI(r_A, r_A, 1); 389 break; 390 case BPF_ANC | SKF_AD_QUEUE: 391 BUILD_BUG_ON(sizeof_field(struct sk_buff, 392 queue_mapping) != 2); 393 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, 394 queue_mapping)); 395 break; 396 case BPF_ANC | SKF_AD_PKTTYPE: 397 PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET()); 398 PPC_ANDI(r_A, r_A, PKT_TYPE_MAX); 399 PPC_SRWI(r_A, r_A, 5); 400 break; 401 case BPF_ANC | SKF_AD_CPU: 402 PPC_BPF_LOAD_CPU(r_A); 403 break; 404 /*** Absolute loads from packet header/data ***/ 405 case BPF_LD | BPF_W | BPF_ABS: 406 func = CHOOSE_LOAD_FUNC(K, sk_load_word); 407 goto common_load; 408 case BPF_LD | BPF_H | BPF_ABS: 409 func = CHOOSE_LOAD_FUNC(K, sk_load_half); 410 goto common_load; 411 case BPF_LD | BPF_B | BPF_ABS: 412 func = CHOOSE_LOAD_FUNC(K, sk_load_byte); 413 common_load: 414 /* Load from [K]. */ 415 ctx->seen |= SEEN_DATAREF; 416 PPC_FUNC_ADDR(r_scratch1, func); 417 PPC_MTLR(r_scratch1); 418 PPC_LI32(r_addr, K); 419 PPC_BLRL(); 420 /* 421 * Helper returns 'lt' condition on error, and an 422 * appropriate return value in r3 423 */ 424 PPC_BCC(COND_LT, exit_addr); 425 break; 426 427 /*** Indirect loads from packet header/data ***/ 428 case BPF_LD | BPF_W | BPF_IND: 429 func = sk_load_word; 430 goto common_load_ind; 431 case BPF_LD | BPF_H | BPF_IND: 432 func = sk_load_half; 433 goto common_load_ind; 434 case BPF_LD | BPF_B | BPF_IND: 435 func = sk_load_byte; 436 common_load_ind: 437 /* 438 * Load from [X + K]. Negative offsets are tested for 439 * in the helper functions. 440 */ 441 ctx->seen |= SEEN_DATAREF | SEEN_XREG; 442 PPC_FUNC_ADDR(r_scratch1, func); 443 PPC_MTLR(r_scratch1); 444 PPC_ADDI(r_addr, r_X, IMM_L(K)); 445 if (K >= 32768) 446 PPC_ADDIS(r_addr, r_addr, IMM_HA(K)); 447 PPC_BLRL(); 448 /* If error, cr0.LT set */ 449 PPC_BCC(COND_LT, exit_addr); 450 break; 451 452 case BPF_LDX | BPF_B | BPF_MSH: 453 func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh); 454 goto common_load; 455 break; 456 457 /*** Jump and branches ***/ 458 case BPF_JMP | BPF_JA: 459 if (K != 0) 460 PPC_JMP(addrs[i + 1 + K]); 461 break; 462 463 case BPF_JMP | BPF_JGT | BPF_K: 464 case BPF_JMP | BPF_JGT | BPF_X: 465 true_cond = COND_GT; 466 goto cond_branch; 467 case BPF_JMP | BPF_JGE | BPF_K: 468 case BPF_JMP | BPF_JGE | BPF_X: 469 true_cond = COND_GE; 470 goto cond_branch; 471 case BPF_JMP | BPF_JEQ | BPF_K: 472 case BPF_JMP | BPF_JEQ | BPF_X: 473 true_cond = COND_EQ; 474 goto cond_branch; 475 case BPF_JMP | BPF_JSET | BPF_K: 476 case BPF_JMP | BPF_JSET | BPF_X: 477 true_cond = COND_NE; 478 /* Fall through */ 479 cond_branch: 480 /* same targets, can avoid doing the test :) */ 481 if (filter[i].jt == filter[i].jf) { 482 if (filter[i].jt > 0) 483 PPC_JMP(addrs[i + 1 + filter[i].jt]); 484 break; 485 } 486 487 switch (code) { 488 case BPF_JMP | BPF_JGT | BPF_X: 489 case BPF_JMP | BPF_JGE | BPF_X: 490 case BPF_JMP | BPF_JEQ | BPF_X: 491 ctx->seen |= SEEN_XREG; 492 PPC_CMPLW(r_A, r_X); 493 break; 494 case BPF_JMP | BPF_JSET | BPF_X: 495 ctx->seen |= SEEN_XREG; 496 PPC_AND_DOT(r_scratch1, r_A, r_X); 497 break; 498 case BPF_JMP | BPF_JEQ | BPF_K: 499 case BPF_JMP | BPF_JGT | BPF_K: 500 case BPF_JMP | BPF_JGE | BPF_K: 501 if (K < 32768) 502 PPC_CMPLWI(r_A, K); 503 else { 504 PPC_LI32(r_scratch1, K); 505 PPC_CMPLW(r_A, r_scratch1); 506 } 507 break; 508 case BPF_JMP | BPF_JSET | BPF_K: 509 if (K < 32768) 510 /* PPC_ANDI is /only/ dot-form */ 511 PPC_ANDI(r_scratch1, r_A, K); 512 else { 513 PPC_LI32(r_scratch1, K); 514 PPC_AND_DOT(r_scratch1, r_A, 515 r_scratch1); 516 } 517 break; 518 } 519 /* Sometimes branches are constructed "backward", with 520 * the false path being the branch and true path being 521 * a fallthrough to the next instruction. 522 */ 523 if (filter[i].jt == 0) 524 /* Swap the sense of the branch */ 525 PPC_BCC(true_cond ^ COND_CMP_TRUE, 526 addrs[i + 1 + filter[i].jf]); 527 else { 528 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]); 529 if (filter[i].jf != 0) 530 PPC_JMP(addrs[i + 1 + filter[i].jf]); 531 } 532 break; 533 default: 534 /* The filter contains something cruel & unusual. 535 * We don't handle it, but also there shouldn't be 536 * anything missing from our list. 537 */ 538 if (printk_ratelimit()) 539 pr_err("BPF filter opcode %04x (@%d) unsupported\n", 540 filter[i].code, i); 541 return -ENOTSUPP; 542 } 543 544 } 545 /* Set end-of-body-code address for exit. */ 546 addrs[i] = ctx->idx * 4; 547 548 return 0; 549 } 550 551 void bpf_jit_compile(struct bpf_prog *fp) 552 { 553 unsigned int proglen; 554 unsigned int alloclen; 555 u32 *image = NULL; 556 u32 *code_base; 557 unsigned int *addrs; 558 struct codegen_context cgctx; 559 int pass; 560 int flen = fp->len; 561 562 if (!bpf_jit_enable) 563 return; 564 565 addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL); 566 if (addrs == NULL) 567 return; 568 569 /* 570 * There are multiple assembly passes as the generated code will change 571 * size as it settles down, figuring out the max branch offsets/exit 572 * paths required. 573 * 574 * The range of standard conditional branches is +/- 32Kbytes. Since 575 * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to 576 * finish with 8 bytes/instruction. Not feasible, so long jumps are 577 * used, distinct from short branches. 578 * 579 * Current: 580 * 581 * For now, both branch types assemble to 2 words (short branches padded 582 * with a NOP); this is less efficient, but assembly will always complete 583 * after exactly 3 passes: 584 * 585 * First pass: No code buffer; Program is "faux-generated" -- no code 586 * emitted but maximum size of output determined (and addrs[] filled 587 * in). Also, we note whether we use M[], whether we use skb data, etc. 588 * All generation choices assumed to be 'worst-case', e.g. branches all 589 * far (2 instructions), return path code reduction not available, etc. 590 * 591 * Second pass: Code buffer allocated with size determined previously. 592 * Prologue generated to support features we have seen used. Exit paths 593 * determined and addrs[] is filled in again, as code may be slightly 594 * smaller as a result. 595 * 596 * Third pass: Code generated 'for real', and branch destinations 597 * determined from now-accurate addrs[] map. 598 * 599 * Ideal: 600 * 601 * If we optimise this, near branches will be shorter. On the 602 * first assembly pass, we should err on the side of caution and 603 * generate the biggest code. On subsequent passes, branches will be 604 * generated short or long and code size will reduce. With smaller 605 * code, more branches may fall into the short category, and code will 606 * reduce more. 607 * 608 * Finally, if we see one pass generate code the same size as the 609 * previous pass we have converged and should now generate code for 610 * real. Allocating at the end will also save the memory that would 611 * otherwise be wasted by the (small) current code shrinkage. 612 * Preferably, we should do a small number of passes (e.g. 5) and if we 613 * haven't converged by then, get impatient and force code to generate 614 * as-is, even if the odd branch would be left long. The chances of a 615 * long jump are tiny with all but the most enormous of BPF filter 616 * inputs, so we should usually converge on the third pass. 617 */ 618 619 cgctx.idx = 0; 620 cgctx.seen = 0; 621 cgctx.pc_ret0 = -1; 622 /* Scouting faux-generate pass 0 */ 623 if (bpf_jit_build_body(fp, 0, &cgctx, addrs)) 624 /* We hit something illegal or unsupported. */ 625 goto out; 626 627 /* 628 * Pretend to build prologue, given the features we've seen. This will 629 * update ctgtx.idx as it pretends to output instructions, then we can 630 * calculate total size from idx. 631 */ 632 bpf_jit_build_prologue(fp, 0, &cgctx); 633 bpf_jit_build_epilogue(0, &cgctx); 634 635 proglen = cgctx.idx * 4; 636 alloclen = proglen + FUNCTION_DESCR_SIZE; 637 image = module_alloc(alloclen); 638 if (!image) 639 goto out; 640 641 code_base = image + (FUNCTION_DESCR_SIZE/4); 642 643 /* Code generation passes 1-2 */ 644 for (pass = 1; pass < 3; pass++) { 645 /* Now build the prologue, body code & epilogue for real. */ 646 cgctx.idx = 0; 647 bpf_jit_build_prologue(fp, code_base, &cgctx); 648 bpf_jit_build_body(fp, code_base, &cgctx, addrs); 649 bpf_jit_build_epilogue(code_base, &cgctx); 650 651 if (bpf_jit_enable > 1) 652 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass, 653 proglen - (cgctx.idx * 4), cgctx.seen); 654 } 655 656 if (bpf_jit_enable > 1) 657 /* Note that we output the base address of the code_base 658 * rather than image, since opcodes are in code_base. 659 */ 660 bpf_jit_dump(flen, proglen, pass, code_base); 661 662 bpf_flush_icache(code_base, code_base + (proglen/4)); 663 664 #ifdef CONFIG_PPC64 665 /* Function descriptor nastiness: Address + TOC */ 666 ((u64 *)image)[0] = (u64)code_base; 667 ((u64 *)image)[1] = local_paca->kernel_toc; 668 #endif 669 670 fp->bpf_func = (void *)image; 671 fp->jited = 1; 672 673 out: 674 kfree(addrs); 675 return; 676 } 677 678 void bpf_jit_free(struct bpf_prog *fp) 679 { 680 if (fp->jited) 681 module_memfree(fp->bpf_func); 682 683 bpf_prog_unlock_free(fp); 684 } 685