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 /= K */
 213                         if (K == 1)
 214                                 break;
 215                         PPC_LI32(r_scratch1, K);
 216                         PPC_DIVWU(r_A, r_A, r_scratch1);
 217                         break;
 218                 case BPF_S_ALU_AND_X:
 219                         ctx->seen |= SEEN_XREG;
 220                         PPC_AND(r_A, r_A, r_X);
 221                         break;
 222                 case BPF_S_ALU_AND_K:
 223                         if (!IMM_H(K))
 224                                 PPC_ANDI(r_A, r_A, K);
 225                         else {
 226                                 PPC_LI32(r_scratch1, K);
 227                                 PPC_AND(r_A, r_A, r_scratch1);
 228                         }
 229                         break;
 230                 case BPF_S_ALU_OR_X:
 231                         ctx->seen |= SEEN_XREG;
 232                         PPC_OR(r_A, r_A, r_X);
 233                         break;
 234                 case BPF_S_ALU_OR_K:
 235                         if (IMM_L(K))
 236                                 PPC_ORI(r_A, r_A, IMM_L(K));
 237                         if (K >= 65536)
 238                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 239                         break;
 240                 case BPF_S_ANC_ALU_XOR_X:
 241                 case BPF_S_ALU_XOR_X: /* A ^= X */
 242                         ctx->seen |= SEEN_XREG;
 243                         PPC_XOR(r_A, r_A, r_X);
 244                         break;
 245                 case BPF_S_ALU_XOR_K: /* A ^= K */
 246                         if (IMM_L(K))
 247                                 PPC_XORI(r_A, r_A, IMM_L(K));
 248                         if (K >= 65536)
 249                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 250                         break;
 251                 case BPF_S_ALU_LSH_X: /* A <<= X; */
 252                         ctx->seen |= SEEN_XREG;
 253                         PPC_SLW(r_A, r_A, r_X);
 254                         break;
 255                 case BPF_S_ALU_LSH_K:
 256                         if (K == 0)
 257                                 break;
 258                         else
 259                                 PPC_SLWI(r_A, r_A, K);
 260                         break;
 261                 case BPF_S_ALU_RSH_X: /* A >>= X; */
 262                         ctx->seen |= SEEN_XREG;
 263                         PPC_SRW(r_A, r_A, r_X);
 264                         break;
 265                 case BPF_S_ALU_RSH_K: /* A >>= K; */
 266                         if (K == 0)
 267                                 break;
 268                         else
 269                                 PPC_SRWI(r_A, r_A, K);
 270                         break;
 271                 case BPF_S_ALU_NEG:
 272                         PPC_NEG(r_A, r_A);
 273                         break;
 274                 case BPF_S_RET_K:
 275                         PPC_LI32(r_ret, K);
 276                         if (!K) {
 277                                 if (ctx->pc_ret0 == -1)
 278                                         ctx->pc_ret0 = i;
 279                         }
 280                         /*
 281                          * If this isn't the very last instruction, branch to
 282                          * the epilogue if we've stuff to clean up.  Otherwise,
 283                          * if there's nothing to tidy, just return.  If we /are/
 284                          * the last instruction, we're about to fall through to
 285                          * the epilogue to return.
 286                          */
 287                         if (i != flen - 1) {
 288                                 /*
 289                                  * Note: 'seen' is properly valid only on pass
 290                                  * #2.  Both parts of this conditional are the
 291                                  * same instruction size though, meaning the
 292                                  * first pass will still correctly determine the
 293                                  * code size/addresses.
 294                                  */
 295                                 if (ctx->seen)
 296                                         PPC_JMP(exit_addr);
 297                                 else
 298                                         PPC_BLR();
 299                         }
 300                         break;
 301                 case BPF_S_RET_A:
 302                         PPC_MR(r_ret, r_A);
 303                         if (i != flen - 1) {
 304                                 if (ctx->seen)
 305                                         PPC_JMP(exit_addr);
 306                                 else
 307                                         PPC_BLR();
 308                         }
 309                         break;
 310                 case BPF_S_MISC_TAX: /* X = A */
 311                         PPC_MR(r_X, r_A);
 312                         break;
 313                 case BPF_S_MISC_TXA: /* A = X */
 314                         ctx->seen |= SEEN_XREG;
 315                         PPC_MR(r_A, r_X);
 316                         break;
 317
 318                         /*** Constant loads/M[] access ***/
 319                 case BPF_S_LD_IMM: /* A = K */
 320                         PPC_LI32(r_A, K);
 321                         break;
 322                 case BPF_S_LDX_IMM: /* X = K */
 323                         PPC_LI32(r_X, K);
 324                         break;
 325                 case BPF_S_LD_MEM: /* A = mem[K] */
 326                         PPC_MR(r_A, r_M + (K & 0xf));
 327                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 328                         break;
 329                 case BPF_S_LDX_MEM: /* X = mem[K] */
 330                         PPC_MR(r_X, r_M + (K & 0xf));
 331                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 332                         break;
 333                 case BPF_S_ST: /* mem[K] = A */
 334                         PPC_MR(r_M + (K & 0xf), r_A);
 335                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 336                         break;
 337                 case BPF_S_STX: /* mem[K] = X */
 338                         PPC_MR(r_M + (K & 0xf), r_X);
 339                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 340                         break;
 341                 case BPF_S_LD_W_LEN: /* A = skb->len; */
 342                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 343                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 344                         break;
 345                 case BPF_S_LDX_W_LEN: /* X = skb->len; */
 346                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 347                         break;
 348
 349                         /*** Ancillary info loads ***/
 350
 351                         /* None of the BPF_S_ANC* codes appear to be passed by
 352                          * sk_chk_filter().  The interpreter and the x86 BPF
 353                          * compiler implement them so we do too -- they may be
 354                          * planted in future.
 355                          */
 356                 case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
 357                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 358                                                   protocol) != 2);
 359                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 360                                                           protocol));
 361                         /* ntohs is a NOP with BE loads. */
 362                         break;
 363                 case BPF_S_ANC_IFINDEX:
 364                         PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 365                                                                 dev));
 366                         PPC_CMPDI(r_scratch1, 0);
 367                         if (ctx->pc_ret0 != -1) {
 368                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 369                         } else {
 370                                 /* Exit, returning 0; first pass hits here. */
 371                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 372                                 PPC_LI(r_ret, 0);
 373                                 PPC_JMP(exit_addr);
 374                         }
 375                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 376                                                   ifindex) != 4);
 377                         PPC_LWZ_OFFS(r_A, r_scratch1,
 378                                      offsetof(struct net_device, ifindex));
 379                         break;
 380                 case BPF_S_ANC_MARK:
 381                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 382                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 383                                                           mark));
 384                         break;
 385                 case BPF_S_ANC_RXHASH:
 386                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
 387                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 388                                                           rxhash));
 389                         break;
 390                 case BPF_S_ANC_VLAN_TAG:
 391                 case BPF_S_ANC_VLAN_TAG_PRESENT:
 392                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 393                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 394                                                           vlan_tci));
 395                         if (filter[i].code == BPF_S_ANC_VLAN_TAG)
 396                                 PPC_ANDI(r_A, r_A, VLAN_VID_MASK);
 397                         else
 398                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 399                         break;
 400                 case BPF_S_ANC_QUEUE:
 401                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 402                                                   queue_mapping) != 2);
 403                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 404                                                           queue_mapping));
 405                         break;
 406                 case BPF_S_ANC_CPU:
 407 #ifdef CONFIG_SMP
 408                         /*
 409                          * PACA ptr is r13:
 410                          * raw_smp_processor_id() = local_paca->paca_index
 411                          */
 412                         BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
 413                                                   paca_index) != 2);
 414                         PPC_LHZ_OFFS(r_A, 13,
 415                                      offsetof(struct paca_struct, paca_index));
 416 #else
 417                         PPC_LI(r_A, 0);
 418 #endif
 419                         break;
 420
 421                         /*** Absolute loads from packet header/data ***/
 422                 case BPF_S_LD_W_ABS:
 423                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 424                         goto common_load;
 425                 case BPF_S_LD_H_ABS:
 426                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 427                         goto common_load;
 428                 case BPF_S_LD_B_ABS:
 429                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 430                 common_load:
 431                         /* Load from [K]. */
 432                         ctx->seen |= SEEN_DATAREF;
 433                         PPC_LI64(r_scratch1, func);
 434                         PPC_MTLR(r_scratch1);
 435                         PPC_LI32(r_addr, K);
 436                         PPC_BLRL();
 437                         /*
 438                          * Helper returns 'lt' condition on error, and an
 439                          * appropriate return value in r3
 440                          */
 441                         PPC_BCC(COND_LT, exit_addr);
 442                         break;
 443
 444                         /*** Indirect loads from packet header/data ***/
 445                 case BPF_S_LD_W_IND:
 446                         func = sk_load_word;
 447                         goto common_load_ind;
 448                 case BPF_S_LD_H_IND:
 449                         func = sk_load_half;
 450                         goto common_load_ind;
 451                 case BPF_S_LD_B_IND:
 452                         func = sk_load_byte;
 453                 common_load_ind:
 454                         /*
 455                          * Load from [X + K].  Negative offsets are tested for
 456                          * in the helper functions.
 457                          */
 458                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 459                         PPC_LI64(r_scratch1, func);
 460                         PPC_MTLR(r_scratch1);
 461                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 462                         if (K >= 32768)
 463                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 464                         PPC_BLRL();
 465                         /* If error, cr0.LT set */
 466                         PPC_BCC(COND_LT, exit_addr);
 467                         break;
 468
 469                 case BPF_S_LDX_B_MSH:
 470                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 471                         goto common_load;
 472                         break;
 473
 474                         /*** Jump and branches ***/
 475                 case BPF_S_JMP_JA:
 476                         if (K != 0)
 477                                 PPC_JMP(addrs[i + 1 + K]);
 478                         break;
 479
 480                 case BPF_S_JMP_JGT_K:
 481                 case BPF_S_JMP_JGT_X:
 482                         true_cond = COND_GT;
 483                         goto cond_branch;
 484                 case BPF_S_JMP_JGE_K:
 485                 case BPF_S_JMP_JGE_X:
 486                         true_cond = COND_GE;
 487                         goto cond_branch;
 488                 case BPF_S_JMP_JEQ_K:
 489                 case BPF_S_JMP_JEQ_X:
 490                         true_cond = COND_EQ;
 491                         goto cond_branch;
 492                 case BPF_S_JMP_JSET_K:
 493                 case BPF_S_JMP_JSET_X:
 494                         true_cond = COND_NE;
 495                         /* Fall through */
 496                 cond_branch:
 497                         /* same targets, can avoid doing the test :) */
 498                         if (filter[i].jt == filter[i].jf) {
 499                                 if (filter[i].jt > 0)
 500                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 501                                 break;
 502                         }
 503
 504                         switch (filter[i].code) {
 505                         case BPF_S_JMP_JGT_X:
 506                         case BPF_S_JMP_JGE_X:
 507                         case BPF_S_JMP_JEQ_X:
 508                                 ctx->seen |= SEEN_XREG;
 509                                 PPC_CMPLW(r_A, r_X);
 510                                 break;
 511                         case BPF_S_JMP_JSET_X:
 512                                 ctx->seen |= SEEN_XREG;
 513                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 514                                 break;
 515                         case BPF_S_JMP_JEQ_K:
 516                         case BPF_S_JMP_JGT_K:
 517                         case BPF_S_JMP_JGE_K:
 518                                 if (K < 32768)
 519                                         PPC_CMPLWI(r_A, K);
 520                                 else {
 521                                         PPC_LI32(r_scratch1, K);
 522                                         PPC_CMPLW(r_A, r_scratch1);
 523                                 }
 524                                 break;
 525                         case BPF_S_JMP_JSET_K:
 526                                 if (K < 32768)
 527                                         /* PPC_ANDI is /only/ dot-form */
 528                                         PPC_ANDI(r_scratch1, r_A, K);
 529                                 else {
 530                                         PPC_LI32(r_scratch1, K);
 531                                         PPC_AND_DOT(r_scratch1, r_A,
 532                                                     r_scratch1);
 533                                 }
 534                                 break;
 535                         }
 536                         /* Sometimes branches are constructed "backward", with
 537                          * the false path being the branch and true path being
 538                          * a fallthrough to the next instruction.
 539                          */
 540                         if (filter[i].jt == 0)
 541                                 /* Swap the sense of the branch */
 542                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 543                                         addrs[i + 1 + filter[i].jf]);
 544                         else {
 545                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 546                                 if (filter[i].jf != 0)
 547                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 548                         }
 549                         break;
 550                 default:
 551                         /* The filter contains something cruel & unusual.
 552                          * We don't handle it, but also there shouldn't be
 553                          * anything missing from our list.
 554                          */
 555                         if (printk_ratelimit())
 556                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 557                                        filter[i].code, i);
 558                         return -ENOTSUPP;
 559                 }
 560
 561         }
 562         /* Set end-of-body-code address for exit. */
 563         addrs[i] = ctx->idx * 4;
 564
 565         return 0;
 566 }
 567
 568 void bpf_jit_compile(struct sk_filter *fp)
 569 {
 570         unsigned int proglen;
 571         unsigned int alloclen;
 572         u32 *image = NULL;
 573         u32 *code_base;
 574         unsigned int *addrs;
 575         struct codegen_context cgctx;
 576         int pass;
 577         int flen = fp->len;
 578
 579         if (!bpf_jit_enable)
 580                 return;
 581
 582         addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
 583         if (addrs == NULL)
 584                 return;
 585
 586         /*
 587          * There are multiple assembly passes as the generated code will change
 588          * size as it settles down, figuring out the max branch offsets/exit
 589          * paths required.
 590          *
 591          * The range of standard conditional branches is +/- 32Kbytes.  Since
 592          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 593          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 594          * used, distinct from short branches.
 595          *
 596          * Current:
 597          *
 598          * For now, both branch types assemble to 2 words (short branches padded
 599          * with a NOP); this is less efficient, but assembly will always complete
 600          * after exactly 3 passes:
 601          *
 602          * First pass: No code buffer; Program is "faux-generated" -- no code
 603          * emitted but maximum size of output determined (and addrs[] filled
 604          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 605          * All generation choices assumed to be 'worst-case', e.g. branches all
 606          * far (2 instructions), return path code reduction not available, etc.
 607          *
 608          * Second pass: Code buffer allocated with size determined previously.
 609          * Prologue generated to support features we have seen used.  Exit paths
 610          * determined and addrs[] is filled in again, as code may be slightly
 611          * smaller as a result.
 612          *
 613          * Third pass: Code generated 'for real', and branch destinations
 614          * determined from now-accurate addrs[] map.
 615          *
 616          * Ideal:
 617          *
 618          * If we optimise this, near branches will be shorter.  On the
 619          * first assembly pass, we should err on the side of caution and
 620          * generate the biggest code.  On subsequent passes, branches will be
 621          * generated short or long and code size will reduce.  With smaller
 622          * code, more branches may fall into the short category, and code will
 623          * reduce more.
 624          *
 625          * Finally, if we see one pass generate code the same size as the
 626          * previous pass we have converged and should now generate code for
 627          * real.  Allocating at the end will also save the memory that would
 628          * otherwise be wasted by the (small) current code shrinkage.
 629          * Preferably, we should do a small number of passes (e.g. 5) and if we
 630          * haven't converged by then, get impatient and force code to generate
 631          * as-is, even if the odd branch would be left long.  The chances of a
 632          * long jump are tiny with all but the most enormous of BPF filter
 633          * inputs, so we should usually converge on the third pass.
 634          */
 635
 636         cgctx.idx = 0;
 637         cgctx.seen = 0;
 638         cgctx.pc_ret0 = -1;
 639         /* Scouting faux-generate pass 0 */
 640         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 641                 /* We hit something illegal or unsupported. */
 642                 goto out;
 643
 644         /*
 645          * Pretend to build prologue, given the features we've seen.  This will
 646          * update ctgtx.idx as it pretends to output instructions, then we can
 647          * calculate total size from idx.
 648          */
 649         bpf_jit_build_prologue(fp, 0, &cgctx);
 650         bpf_jit_build_epilogue(0, &cgctx);
 651
 652         proglen = cgctx.idx * 4;
 653         alloclen = proglen + FUNCTION_DESCR_SIZE;
 654         image = module_alloc(max_t(unsigned int, alloclen,
 655                                    sizeof(struct work_struct)));
 656         if (!image)
 657                 goto out;
 658
 659         code_base = image + (FUNCTION_DESCR_SIZE/4);
 660
 661         /* Code generation passes 1-2 */
 662         for (pass = 1; pass < 3; pass++) {
 663                 /* Now build the prologue, body code & epilogue for real. */
 664                 cgctx.idx = 0;
 665                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 666                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 667                 bpf_jit_build_epilogue(code_base, &cgctx);
 668
 669                 if (bpf_jit_enable > 1)
 670                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 671                                 proglen - (cgctx.idx * 4), cgctx.seen);
 672         }
 673
 674         if (bpf_jit_enable > 1)
 675                 /* Note that we output the base address of the code_base
 676                  * rather than image, since opcodes are in code_base.
 677                  */
 678                 bpf_jit_dump(flen, proglen, pass, code_base);
 679
 680         if (image) {
 681                 bpf_flush_icache(code_base, code_base + (proglen/4));
 682                 /* Function descriptor nastiness: Address + TOC */
 683                 ((u64 *)image)[0] = (u64)code_base;
 684                 ((u64 *)image)[1] = local_paca->kernel_toc;
 685                 fp->bpf_func = (void *)image;
 686         }
 687 out:
 688         kfree(addrs);
 689         return;
 690 }
 691
 692 static void jit_free_defer(struct work_struct *arg)
 693 {
 694         module_free(NULL, arg);
 695 }
 696
 697 /* run from softirq, we must use a work_struct to call
 698  * module_free() from process context
 699  */
 700 void bpf_jit_free(struct sk_filter *fp)
 701 {
 702         if (fp->bpf_func != sk_run_filter) {
 703                 struct work_struct *work = (struct work_struct *)fp->bpf_func;
 704
 705                 INIT_WORK(work, jit_free_defer);
 706                 schedule_work(work);
 707         }
 708 }