arch/powerpc/net/bpf_jit_comp.c

   1 /* bpf_jit_comp.c: BPF JIT compiler for PPC64
   2  *
   3  * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
   4  *
   5  * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; version 2
  10  * of the License.
  11  */
  12 #include <linux/moduleloader.h>
  13 #include <asm/cacheflush.h>
  14 #include <linux/netdevice.h>
  15 #include <linux/filter.h>
  16 #include <linux/if_vlan.h>
  17
  18 #include "bpf_jit.h"
  19
  20 #ifndef __BIG_ENDIAN
  21 /* There are endianness assumptions herein. */
  22 #error "Little-endian PPC not supported in BPF compiler"
  23 #endif
  24
  25 int bpf_jit_enable __read_mostly;
  26
  27
  28 static inline void bpf_flush_icache(void *start, void *end)
  29 {
  30         smp_wmb();
  31         flush_icache_range((unsigned long)start, (unsigned long)end);
  32 }
  33
  34 static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image,
  35                                    struct codegen_context *ctx)
  36 {
  37         int i;
  38         const struct sock_filter *filter = fp->insns;
  39
  40         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  41                 /* Make stackframe */
  42                 if (ctx->seen & SEEN_DATAREF) {
  43                         /* If we call any helpers (for loads), save LR */
  44                         EMIT(PPC_INST_MFLR | __PPC_RT(R0));
  45                         PPC_STD(0, 1, 16);
  46
  47                         /* Back up non-volatile regs. */
  48                         PPC_STD(r_D, 1, -(8*(32-r_D)));
  49                         PPC_STD(r_HL, 1, -(8*(32-r_HL)));
  50                 }
  51                 if (ctx->seen & SEEN_MEM) {
  52                         /*
  53                          * Conditionally save regs r15-r31 as some will be used
  54                          * for M[] data.
  55                          */
  56                         for (i = r_M; i < (r_M+16); i++) {
  57                                 if (ctx->seen & (1 << (i-r_M)))
  58                                         PPC_STD(i, 1, -(8*(32-i)));
  59                         }
  60                 }
  61                 EMIT(PPC_INST_STDU | __PPC_RS(R1) | __PPC_RA(R1) |
  62                      (-BPF_PPC_STACKFRAME & 0xfffc));
  63         }
  64
  65         if (ctx->seen & SEEN_DATAREF) {
  66                 /*
  67                  * If this filter needs to access skb data,
  68                  * prepare r_D and r_HL:
  69                  *  r_HL = skb->len - skb->data_len
  70                  *  r_D  = skb->data
  71                  */
  72                 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
  73                                                          data_len));
  74                 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
  75                 PPC_SUB(r_HL, r_HL, r_scratch1);
  76                 PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  77         }
  78
  79         if (ctx->seen & SEEN_XREG) {
  80                 /*
  81                  * TODO: Could also detect whether first instr. sets X and
  82                  * avoid this (as below, with A).
  83                  */
  84                 PPC_LI(r_X, 0);
  85         }
  86
  87         switch (filter[0].code) {
  88         case BPF_S_RET_K:
  89         case BPF_S_LD_W_LEN:
  90         case BPF_S_ANC_PROTOCOL:
  91         case BPF_S_ANC_IFINDEX:
  92         case BPF_S_ANC_MARK:
  93         case BPF_S_ANC_RXHASH:
  94         case BPF_S_ANC_VLAN_TAG:
  95         case BPF_S_ANC_VLAN_TAG_PRESENT:
  96         case BPF_S_ANC_CPU:
  97         case BPF_S_ANC_QUEUE:
  98         case BPF_S_LD_W_ABS:
  99         case BPF_S_LD_H_ABS:
 100         case BPF_S_LD_B_ABS:
 101                 /* first instruction sets A register (or is RET 'constant') */
 102                 break;
 103         default:
 104                 /* make sure we dont leak kernel information to user */
 105                 PPC_LI(r_A, 0);
 106         }
 107 }
 108
 109 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 110 {
 111         int i;
 112
 113         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
 114                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
 115                 if (ctx->seen & SEEN_DATAREF) {
 116                         PPC_LD(0, 1, 16);
 117                         PPC_MTLR(0);
 118                         PPC_LD(r_D, 1, -(8*(32-r_D)));
 119                         PPC_LD(r_HL, 1, -(8*(32-r_HL)));
 120                 }
 121                 if (ctx->seen & SEEN_MEM) {
 122                         /* Restore any saved non-vol registers */
 123                         for (i = r_M; i < (r_M+16); i++) {
 124                                 if (ctx->seen & (1 << (i-r_M)))
 125                                         PPC_LD(i, 1, -(8*(32-i)));
 126                         }
 127                 }
 128         }
 129         /* The RETs have left a return value in R3. */
 130
 131         PPC_BLR();
 132 }
 133
 134 #define CHOOSE_LOAD_FUNC(K, func) \
 135         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 136
 137 /* Assemble the body code between the prologue & epilogue. */
 138 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
 139                               struct codegen_context *ctx,
 140                               unsigned int *addrs)
 141 {
 142         const struct sock_filter *filter = fp->insns;
 143         int flen = fp->len;
 144         u8 *func;
 145         unsigned int true_cond;
 146         int i;
 147
 148         /* Start of epilogue code */
 149         unsigned int exit_addr = addrs[flen];
 150
 151         for (i = 0; i < flen; i++) {
 152                 unsigned int K = filter[i].k;
 153
 154                 /*
 155                  * addrs[] maps a BPF bytecode address into a real offset from
 156                  * the start of the body code.
 157                  */
 158                 addrs[i] = ctx->idx * 4;
 159
 160                 switch (filter[i].code) {
 161                         /*** ALU ops ***/
 162                 case BPF_S_ALU_ADD_X: /* A += X; */
 163                         ctx->seen |= SEEN_XREG;
 164                         PPC_ADD(r_A, r_A, r_X);
 165                         break;
 166                 case BPF_S_ALU_ADD_K: /* A += K; */
 167                         if (!K)
 168                                 break;
 169                         PPC_ADDI(r_A, r_A, IMM_L(K));
 170                         if (K >= 32768)
 171                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 172                         break;
 173                 case BPF_S_ALU_SUB_X: /* A -= X; */
 174                         ctx->seen |= SEEN_XREG;
 175                         PPC_SUB(r_A, r_A, r_X);
 176                         break;
 177                 case BPF_S_ALU_SUB_K: /* A -= K */
 178                         if (!K)
 179                                 break;
 180                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 181                         if (K >= 32768)
 182                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 183                         break;
 184                 case BPF_S_ALU_MUL_X: /* A *= X; */
 185                         ctx->seen |= SEEN_XREG;
 186                         PPC_MUL(r_A, r_A, r_X);
 187                         break;
 188                 case BPF_S_ALU_MUL_K: /* A *= K */
 189                         if (K < 32768)
 190                                 PPC_MULI(r_A, r_A, K);
 191                         else {
 192                                 PPC_LI32(r_scratch1, K);
 193                                 PPC_MUL(r_A, r_A, r_scratch1);
 194                         }
 195                         break;
 196                 case BPF_S_ALU_DIV_X: /* A /= X; */
 197                         ctx->seen |= SEEN_XREG;
 198                         PPC_CMPWI(r_X, 0);
 199                         if (ctx->pc_ret0 != -1) {
 200                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 201                         } else {
 202                                 /*
 203                                  * Exit, returning 0; first pass hits here
 204                                  * (longer worst-case code size).
 205                                  */
 206                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 207                                 PPC_LI(r_ret, 0);
 208                                 PPC_JMP(exit_addr);
 209                         }
 210                         PPC_DIVWU(r_A, r_A, r_X);
 211                         break;
 212                 case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
 213                         PPC_LI32(r_scratch1, K);
 214                         /* Top 32 bits of 64bit result -> A */
 215                         PPC_MULHWU(r_A, r_A, r_scratch1);
 216                         break;
 217                 case BPF_S_ALU_AND_X:
 218                         ctx->seen |= SEEN_XREG;
 219                         PPC_AND(r_A, r_A, r_X);
 220                         break;
 221                 case BPF_S_ALU_AND_K:
 222                         if (!IMM_H(K))
 223                                 PPC_ANDI(r_A, r_A, K);
 224                         else {
 225                                 PPC_LI32(r_scratch1, K);
 226                                 PPC_AND(r_A, r_A, r_scratch1);
 227                         }
 228                         break;
 229                 case BPF_S_ALU_OR_X:
 230                         ctx->seen |= SEEN_XREG;
 231                         PPC_OR(r_A, r_A, r_X);
 232                         break;
 233                 case BPF_S_ALU_OR_K:
 234                         if (IMM_L(K))
 235                                 PPC_ORI(r_A, r_A, IMM_L(K));
 236                         if (K >= 65536)
 237                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 238                         break;
 239                 case BPF_S_ANC_ALU_XOR_X:
 240                 case BPF_S_ALU_XOR_X: /* A ^= X */
 241                         ctx->seen |= SEEN_XREG;
 242                         PPC_XOR(r_A, r_A, r_X);
 243                         break;
 244                 case BPF_S_ALU_XOR_K: /* A ^= K */
 245                         if (IMM_L(K))
 246                                 PPC_XORI(r_A, r_A, IMM_L(K));
 247                         if (K >= 65536)
 248                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 249                         break;
 250                 case BPF_S_ALU_LSH_X: /* A <<= X; */
 251                         ctx->seen |= SEEN_XREG;
 252                         PPC_SLW(r_A, r_A, r_X);
 253                         break;
 254                 case BPF_S_ALU_LSH_K:
 255                         if (K == 0)
 256                                 break;
 257                         else
 258                                 PPC_SLWI(r_A, r_A, K);
 259                         break;
 260                 case BPF_S_ALU_RSH_X: /* A >>= X; */
 261                         ctx->seen |= SEEN_XREG;
 262                         PPC_SRW(r_A, r_A, r_X);
 263                         break;
 264                 case BPF_S_ALU_RSH_K: /* A >>= K; */
 265                         if (K == 0)
 266                                 break;
 267                         else
 268                                 PPC_SRWI(r_A, r_A, K);
 269                         break;
 270                 case BPF_S_ALU_NEG:
 271                         PPC_NEG(r_A, r_A);
 272                         break;
 273                 case BPF_S_RET_K:
 274                         PPC_LI32(r_ret, K);
 275                         if (!K) {
 276                                 if (ctx->pc_ret0 == -1)
 277                                         ctx->pc_ret0 = i;
 278                         }
 279                         /*
 280                          * If this isn't the very last instruction, branch to
 281                          * the epilogue if we've stuff to clean up.  Otherwise,
 282                          * if there's nothing to tidy, just return.  If we /are/
 283                          * the last instruction, we're about to fall through to
 284                          * the epilogue to return.
 285                          */
 286                         if (i != flen - 1) {
 287                                 /*
 288                                  * Note: 'seen' is properly valid only on pass
 289                                  * #2.  Both parts of this conditional are the
 290                                  * same instruction size though, meaning the
 291                                  * first pass will still correctly determine the
 292                                  * code size/addresses.
 293                                  */
 294                                 if (ctx->seen)
 295                                         PPC_JMP(exit_addr);
 296                                 else
 297                                         PPC_BLR();
 298                         }
 299                         break;
 300                 case BPF_S_RET_A:
 301                         PPC_MR(r_ret, r_A);
 302                         if (i != flen - 1) {
 303                                 if (ctx->seen)
 304                                         PPC_JMP(exit_addr);
 305                                 else
 306                                         PPC_BLR();
 307                         }
 308                         break;
 309                 case BPF_S_MISC_TAX: /* X = A */
 310                         PPC_MR(r_X, r_A);
 311                         break;
 312                 case BPF_S_MISC_TXA: /* A = X */
 313                         ctx->seen |= SEEN_XREG;
 314                         PPC_MR(r_A, r_X);
 315                         break;
 316
 317                         /*** Constant loads/M[] access ***/
 318                 case BPF_S_LD_IMM: /* A = K */
 319                         PPC_LI32(r_A, K);
 320                         break;
 321                 case BPF_S_LDX_IMM: /* X = K */
 322                         PPC_LI32(r_X, K);
 323                         break;
 324                 case BPF_S_LD_MEM: /* A = mem[K] */
 325                         PPC_MR(r_A, r_M + (K & 0xf));
 326                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 327                         break;
 328                 case BPF_S_LDX_MEM: /* X = mem[K] */
 329                         PPC_MR(r_X, r_M + (K & 0xf));
 330                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 331                         break;
 332                 case BPF_S_ST: /* mem[K] = A */
 333                         PPC_MR(r_M + (K & 0xf), r_A);
 334                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 335                         break;
 336                 case BPF_S_STX: /* mem[K] = X */
 337                         PPC_MR(r_M + (K & 0xf), r_X);
 338                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 339                         break;
 340                 case BPF_S_LD_W_LEN: /* A = skb->len; */
 341                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 342                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 343                         break;
 344                 case BPF_S_LDX_W_LEN: /* X = skb->len; */
 345                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 346                         break;
 347
 348                         /*** Ancillary info loads ***/
 349
 350                         /* None of the BPF_S_ANC* codes appear to be passed by
 351                          * sk_chk_filter().  The interpreter and the x86 BPF
 352                          * compiler implement them so we do too -- they may be
 353                          * planted in future.
 354                          */
 355                 case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
 356                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 357                                                   protocol) != 2);
 358                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 359                                                           protocol));
 360                         /* ntohs is a NOP with BE loads. */
 361                         break;
 362                 case BPF_S_ANC_IFINDEX:
 363                         PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 364                                                                 dev));
 365                         PPC_CMPDI(r_scratch1, 0);
 366                         if (ctx->pc_ret0 != -1) {
 367                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 368                         } else {
 369                                 /* Exit, returning 0; first pass hits here. */
 370                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 371                                 PPC_LI(r_ret, 0);
 372                                 PPC_JMP(exit_addr);
 373                         }
 374                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 375                                                   ifindex) != 4);
 376                         PPC_LWZ_OFFS(r_A, r_scratch1,
 377                                      offsetof(struct net_device, ifindex));
 378                         break;
 379                 case BPF_S_ANC_MARK:
 380                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 381                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 382                                                           mark));
 383                         break;
 384                 case BPF_S_ANC_RXHASH:
 385                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
 386                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 387                                                           rxhash));
 388                         break;
 389                 case BPF_S_ANC_VLAN_TAG:
 390                 case BPF_S_ANC_VLAN_TAG_PRESENT:
 391                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 392                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 393                                                           vlan_tci));
 394                         if (filter[i].code == BPF_S_ANC_VLAN_TAG)
 395                                 PPC_ANDI(r_A, r_A, VLAN_VID_MASK);
 396                         else
 397                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 398                         break;
 399                 case BPF_S_ANC_QUEUE:
 400                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 401                                                   queue_mapping) != 2);
 402                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 403                                                           queue_mapping));
 404                         break;
 405                 case BPF_S_ANC_CPU:
 406 #ifdef CONFIG_SMP
 407                         /*
 408                          * PACA ptr is r13:
 409                          * raw_smp_processor_id() = local_paca->paca_index
 410                          */
 411                         BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
 412                                                   paca_index) != 2);
 413                         PPC_LHZ_OFFS(r_A, 13,
 414                                      offsetof(struct paca_struct, paca_index));
 415 #else
 416                         PPC_LI(r_A, 0);
 417 #endif
 418                         break;
 419
 420                         /*** Absolute loads from packet header/data ***/
 421                 case BPF_S_LD_W_ABS:
 422                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 423                         goto common_load;
 424                 case BPF_S_LD_H_ABS:
 425                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 426                         goto common_load;
 427                 case BPF_S_LD_B_ABS:
 428                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 429                 common_load:
 430                         /* Load from [K]. */
 431                         ctx->seen |= SEEN_DATAREF;
 432                         PPC_LI64(r_scratch1, func);
 433                         PPC_MTLR(r_scratch1);
 434                         PPC_LI32(r_addr, K);
 435                         PPC_BLRL();
 436                         /*
 437                          * Helper returns 'lt' condition on error, and an
 438                          * appropriate return value in r3
 439                          */
 440                         PPC_BCC(COND_LT, exit_addr);
 441                         break;
 442
 443                         /*** Indirect loads from packet header/data ***/
 444                 case BPF_S_LD_W_IND:
 445                         func = sk_load_word;
 446                         goto common_load_ind;
 447                 case BPF_S_LD_H_IND:
 448                         func = sk_load_half;
 449                         goto common_load_ind;
 450                 case BPF_S_LD_B_IND:
 451                         func = sk_load_byte;
 452                 common_load_ind:
 453                         /*
 454                          * Load from [X + K].  Negative offsets are tested for
 455                          * in the helper functions.
 456                          */
 457                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 458                         PPC_LI64(r_scratch1, func);
 459                         PPC_MTLR(r_scratch1);
 460                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 461                         if (K >= 32768)
 462                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 463                         PPC_BLRL();
 464                         /* If error, cr0.LT set */
 465                         PPC_BCC(COND_LT, exit_addr);
 466                         break;
 467
 468                 case BPF_S_LDX_B_MSH:
 469                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 470                         goto common_load;
 471                         break;
 472
 473                         /*** Jump and branches ***/
 474                 case BPF_S_JMP_JA:
 475                         if (K != 0)
 476                                 PPC_JMP(addrs[i + 1 + K]);
 477                         break;
 478
 479                 case BPF_S_JMP_JGT_K:
 480                 case BPF_S_JMP_JGT_X:
 481                         true_cond = COND_GT;
 482                         goto cond_branch;
 483                 case BPF_S_JMP_JGE_K:
 484                 case BPF_S_JMP_JGE_X:
 485                         true_cond = COND_GE;
 486                         goto cond_branch;
 487                 case BPF_S_JMP_JEQ_K:
 488                 case BPF_S_JMP_JEQ_X:
 489                         true_cond = COND_EQ;
 490                         goto cond_branch;
 491                 case BPF_S_JMP_JSET_K:
 492                 case BPF_S_JMP_JSET_X:
 493                         true_cond = COND_NE;
 494                         /* Fall through */
 495                 cond_branch:
 496                         /* same targets, can avoid doing the test :) */
 497                         if (filter[i].jt == filter[i].jf) {
 498                                 if (filter[i].jt > 0)
 499                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 500                                 break;
 501                         }
 502
 503                         switch (filter[i].code) {
 504                         case BPF_S_JMP_JGT_X:
 505                         case BPF_S_JMP_JGE_X:
 506                         case BPF_S_JMP_JEQ_X:
 507                                 ctx->seen |= SEEN_XREG;
 508                                 PPC_CMPLW(r_A, r_X);
 509                                 break;
 510                         case BPF_S_JMP_JSET_X:
 511                                 ctx->seen |= SEEN_XREG;
 512                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 513                                 break;
 514                         case BPF_S_JMP_JEQ_K:
 515                         case BPF_S_JMP_JGT_K:
 516                         case BPF_S_JMP_JGE_K:
 517                                 if (K < 32768)
 518                                         PPC_CMPLWI(r_A, K);
 519                                 else {
 520                                         PPC_LI32(r_scratch1, K);
 521                                         PPC_CMPLW(r_A, r_scratch1);
 522                                 }
 523                                 break;
 524                         case BPF_S_JMP_JSET_K:
 525                                 if (K < 32768)
 526                                         /* PPC_ANDI is /only/ dot-form */
 527                                         PPC_ANDI(r_scratch1, r_A, K);
 528                                 else {
 529                                         PPC_LI32(r_scratch1, K);
 530                                         PPC_AND_DOT(r_scratch1, r_A,
 531                                                     r_scratch1);
 532                                 }
 533                                 break;
 534                         }
 535                         /* Sometimes branches are constructed "backward", with
 536                          * the false path being the branch and true path being
 537                          * a fallthrough to the next instruction.
 538                          */
 539                         if (filter[i].jt == 0)
 540                                 /* Swap the sense of the branch */
 541                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 542                                         addrs[i + 1 + filter[i].jf]);
 543                         else {
 544                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 545                                 if (filter[i].jf != 0)
 546                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 547                         }
 548                         break;
 549                 default:
 550                         /* The filter contains something cruel & unusual.
 551                          * We don't handle it, but also there shouldn't be
 552                          * anything missing from our list.
 553                          */
 554                         if (printk_ratelimit())
 555                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 556                                        filter[i].code, i);
 557                         return -ENOTSUPP;
 558                 }
 559
 560         }
 561         /* Set end-of-body-code address for exit. */
 562         addrs[i] = ctx->idx * 4;
 563
 564         return 0;
 565 }
 566
 567 void bpf_jit_compile(struct sk_filter *fp)
 568 {
 569         unsigned int proglen;
 570         unsigned int alloclen;
 571         u32 *image = NULL;
 572         u32 *code_base;
 573         unsigned int *addrs;
 574         struct codegen_context cgctx;
 575         int pass;
 576         int flen = fp->len;
 577
 578         if (!bpf_jit_enable)
 579                 return;
 580
 581         addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
 582         if (addrs == NULL)
 583                 return;
 584
 585         /*
 586          * There are multiple assembly passes as the generated code will change
 587          * size as it settles down, figuring out the max branch offsets/exit
 588          * paths required.
 589          *
 590          * The range of standard conditional branches is +/- 32Kbytes.  Since
 591          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 592          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 593          * used, distinct from short branches.
 594          *
 595          * Current:
 596          *
 597          * For now, both branch types assemble to 2 words (short branches padded
 598          * with a NOP); this is less efficient, but assembly will always complete
 599          * after exactly 3 passes:
 600          *
 601          * First pass: No code buffer; Program is "faux-generated" -- no code
 602          * emitted but maximum size of output determined (and addrs[] filled
 603          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 604          * All generation choices assumed to be 'worst-case', e.g. branches all
 605          * far (2 instructions), return path code reduction not available, etc.
 606          *
 607          * Second pass: Code buffer allocated with size determined previously.
 608          * Prologue generated to support features we have seen used.  Exit paths
 609          * determined and addrs[] is filled in again, as code may be slightly
 610          * smaller as a result.
 611          *
 612          * Third pass: Code generated 'for real', and branch destinations
 613          * determined from now-accurate addrs[] map.
 614          *
 615          * Ideal:
 616          *
 617          * If we optimise this, near branches will be shorter.  On the
 618          * first assembly pass, we should err on the side of caution and
 619          * generate the biggest code.  On subsequent passes, branches will be
 620          * generated short or long and code size will reduce.  With smaller
 621          * code, more branches may fall into the short category, and code will
 622          * reduce more.
 623          *
 624          * Finally, if we see one pass generate code the same size as the
 625          * previous pass we have converged and should now generate code for
 626          * real.  Allocating at the end will also save the memory that would
 627          * otherwise be wasted by the (small) current code shrinkage.
 628          * Preferably, we should do a small number of passes (e.g. 5) and if we
 629          * haven't converged by then, get impatient and force code to generate
 630          * as-is, even if the odd branch would be left long.  The chances of a
 631          * long jump are tiny with all but the most enormous of BPF filter
 632          * inputs, so we should usually converge on the third pass.
 633          */
 634
 635         cgctx.idx = 0;
 636         cgctx.seen = 0;
 637         cgctx.pc_ret0 = -1;
 638         /* Scouting faux-generate pass 0 */
 639         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 640                 /* We hit something illegal or unsupported. */
 641                 goto out;
 642
 643         /*
 644          * Pretend to build prologue, given the features we've seen.  This will
 645          * update ctgtx.idx as it pretends to output instructions, then we can
 646          * calculate total size from idx.
 647          */
 648         bpf_jit_build_prologue(fp, 0, &cgctx);
 649         bpf_jit_build_epilogue(0, &cgctx);
 650
 651         proglen = cgctx.idx * 4;
 652         alloclen = proglen + FUNCTION_DESCR_SIZE;
 653         image = module_alloc(alloclen);
 654         if (!image)
 655                 goto out;
 656
 657         code_base = image + (FUNCTION_DESCR_SIZE/4);
 658
 659         /* Code generation passes 1-2 */
 660         for (pass = 1; pass < 3; pass++) {
 661                 /* Now build the prologue, body code & epilogue for real. */
 662                 cgctx.idx = 0;
 663                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 664                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 665                 bpf_jit_build_epilogue(code_base, &cgctx);
 666
 667                 if (bpf_jit_enable > 1)
 668                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 669                                 proglen - (cgctx.idx * 4), cgctx.seen);
 670         }
 671
 672         if (bpf_jit_enable > 1)
 673                 /* Note that we output the base address of the code_base
 674                  * rather than image, since opcodes are in code_base.
 675                  */
 676                 bpf_jit_dump(flen, proglen, pass, code_base);
 677
 678         if (image) {
 679                 bpf_flush_icache(code_base, code_base + (proglen/4));
 680                 /* Function descriptor nastiness: Address + TOC */
 681                 ((u64 *)image)[0] = (u64)code_base;
 682                 ((u64 *)image)[1] = local_paca->kernel_toc;
 683                 fp->bpf_func = (void *)image;
 684         }
 685 out:
 686         kfree(addrs);
 687         return;
 688 }
 689
 690 void bpf_jit_free(struct sk_filter *fp)
 691 {
 692         if (fp->bpf_func != sk_run_filter)
 693                 module_free(NULL, fp->bpf_func);
 694 }