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 int bpf_jit_enable __read_mostly;
  21
  22 static inline void bpf_flush_icache(void *start, void *end)
  23 {
  24         smp_wmb();
  25         flush_icache_range((unsigned long)start, (unsigned long)end);
  26 }
  27
  28 static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image,
  29                                    struct codegen_context *ctx)
  30 {
  31         int i;
  32         const struct sock_filter *filter = fp->insns;
  33
  34         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  35                 /* Make stackframe */
  36                 if (ctx->seen & SEEN_DATAREF) {
  37                         /* If we call any helpers (for loads), save LR */
  38                         EMIT(PPC_INST_MFLR | __PPC_RT(R0));
  39                         PPC_STD(0, 1, 16);
  40
  41                         /* Back up non-volatile regs. */
  42                         PPC_STD(r_D, 1, -(8*(32-r_D)));
  43                         PPC_STD(r_HL, 1, -(8*(32-r_HL)));
  44                 }
  45                 if (ctx->seen & SEEN_MEM) {
  46                         /*
  47                          * Conditionally save regs r15-r31 as some will be used
  48                          * for M[] data.
  49                          */
  50                         for (i = r_M; i < (r_M+16); i++) {
  51                                 if (ctx->seen & (1 << (i-r_M)))
  52                                         PPC_STD(i, 1, -(8*(32-i)));
  53                         }
  54                 }
  55                 EMIT(PPC_INST_STDU | __PPC_RS(R1) | __PPC_RA(R1) |
  56                      (-BPF_PPC_STACKFRAME & 0xfffc));
  57         }
  58
  59         if (ctx->seen & SEEN_DATAREF) {
  60                 /*
  61                  * If this filter needs to access skb data,
  62                  * prepare r_D and r_HL:
  63                  *  r_HL = skb->len - skb->data_len
  64                  *  r_D  = skb->data
  65                  */
  66                 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
  67                                                          data_len));
  68                 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
  69                 PPC_SUB(r_HL, r_HL, r_scratch1);
  70                 PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  71         }
  72
  73         if (ctx->seen & SEEN_XREG) {
  74                 /*
  75                  * TODO: Could also detect whether first instr. sets X and
  76                  * avoid this (as below, with A).
  77                  */
  78                 PPC_LI(r_X, 0);
  79         }
  80
  81         switch (filter[0].code) {
  82         case BPF_RET | BPF_K:
  83         case BPF_LD | BPF_W | BPF_LEN:
  84         case BPF_LD | BPF_W | BPF_ABS:
  85         case BPF_LD | BPF_H | BPF_ABS:
  86         case BPF_LD | BPF_B | BPF_ABS:
  87                 /* first instruction sets A register (or is RET 'constant') */
  88                 break;
  89         default:
  90                 /* make sure we dont leak kernel information to user */
  91                 PPC_LI(r_A, 0);
  92         }
  93 }
  94
  95 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  96 {
  97         int i;
  98
  99         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
 100                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
 101                 if (ctx->seen & SEEN_DATAREF) {
 102                         PPC_LD(0, 1, 16);
 103                         PPC_MTLR(0);
 104                         PPC_LD(r_D, 1, -(8*(32-r_D)));
 105                         PPC_LD(r_HL, 1, -(8*(32-r_HL)));
 106                 }
 107                 if (ctx->seen & SEEN_MEM) {
 108                         /* Restore any saved non-vol registers */
 109                         for (i = r_M; i < (r_M+16); i++) {
 110                                 if (ctx->seen & (1 << (i-r_M)))
 111                                         PPC_LD(i, 1, -(8*(32-i)));
 112                         }
 113                 }
 114         }
 115         /* The RETs have left a return value in R3. */
 116
 117         PPC_BLR();
 118 }
 119
 120 #define CHOOSE_LOAD_FUNC(K, func) \
 121         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 122
 123 /* Assemble the body code between the prologue & epilogue. */
 124 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
 125                               struct codegen_context *ctx,
 126                               unsigned int *addrs)
 127 {
 128         const struct sock_filter *filter = fp->insns;
 129         int flen = fp->len;
 130         u8 *func;
 131         unsigned int true_cond;
 132         int i;
 133
 134         /* Start of epilogue code */
 135         unsigned int exit_addr = addrs[flen];
 136
 137         for (i = 0; i < flen; i++) {
 138                 unsigned int K = filter[i].k;
 139                 u16 code = bpf_anc_helper(&filter[i]);
 140
 141                 /*
 142                  * addrs[] maps a BPF bytecode address into a real offset from
 143                  * the start of the body code.
 144                  */
 145                 addrs[i] = ctx->idx * 4;
 146
 147                 switch (code) {
 148                         /*** ALU ops ***/
 149                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 150                         ctx->seen |= SEEN_XREG;
 151                         PPC_ADD(r_A, r_A, r_X);
 152                         break;
 153                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 154                         if (!K)
 155                                 break;
 156                         PPC_ADDI(r_A, r_A, IMM_L(K));
 157                         if (K >= 32768)
 158                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 159                         break;
 160                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 161                         ctx->seen |= SEEN_XREG;
 162                         PPC_SUB(r_A, r_A, r_X);
 163                         break;
 164                 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
 165                         if (!K)
 166                                 break;
 167                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 168                         if (K >= 32768)
 169                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 170                         break;
 171                 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
 172                         ctx->seen |= SEEN_XREG;
 173                         PPC_MUL(r_A, r_A, r_X);
 174                         break;
 175                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 176                         if (K < 32768)
 177                                 PPC_MULI(r_A, r_A, K);
 178                         else {
 179                                 PPC_LI32(r_scratch1, K);
 180                                 PPC_MUL(r_A, r_A, r_scratch1);
 181                         }
 182                         break;
 183                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 184                         ctx->seen |= SEEN_XREG;
 185                         PPC_CMPWI(r_X, 0);
 186                         if (ctx->pc_ret0 != -1) {
 187                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 188                         } else {
 189                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 190                                 PPC_LI(r_ret, 0);
 191                                 PPC_JMP(exit_addr);
 192                         }
 193                         PPC_DIVWU(r_scratch1, r_A, r_X);
 194                         PPC_MUL(r_scratch1, r_X, r_scratch1);
 195                         PPC_SUB(r_A, r_A, r_scratch1);
 196                         break;
 197                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 198                         PPC_LI32(r_scratch2, K);
 199                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 200                         PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
 201                         PPC_SUB(r_A, r_A, r_scratch1);
 202                         break;
 203                 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
 204                         ctx->seen |= SEEN_XREG;
 205                         PPC_CMPWI(r_X, 0);
 206                         if (ctx->pc_ret0 != -1) {
 207                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 208                         } else {
 209                                 /*
 210                                  * Exit, returning 0; first pass hits here
 211                                  * (longer worst-case code size).
 212                                  */
 213                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 214                                 PPC_LI(r_ret, 0);
 215                                 PPC_JMP(exit_addr);
 216                         }
 217                         PPC_DIVWU(r_A, r_A, r_X);
 218                         break;
 219                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 220                         if (K == 1)
 221                                 break;
 222                         PPC_LI32(r_scratch1, K);
 223                         PPC_DIVWU(r_A, r_A, r_scratch1);
 224                         break;
 225                 case BPF_ALU | BPF_AND | BPF_X:
 226                         ctx->seen |= SEEN_XREG;
 227                         PPC_AND(r_A, r_A, r_X);
 228                         break;
 229                 case BPF_ALU | BPF_AND | BPF_K:
 230                         if (!IMM_H(K))
 231                                 PPC_ANDI(r_A, r_A, K);
 232                         else {
 233                                 PPC_LI32(r_scratch1, K);
 234                                 PPC_AND(r_A, r_A, r_scratch1);
 235                         }
 236                         break;
 237                 case BPF_ALU | BPF_OR | BPF_X:
 238                         ctx->seen |= SEEN_XREG;
 239                         PPC_OR(r_A, r_A, r_X);
 240                         break;
 241                 case BPF_ALU | BPF_OR | BPF_K:
 242                         if (IMM_L(K))
 243                                 PPC_ORI(r_A, r_A, IMM_L(K));
 244                         if (K >= 65536)
 245                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 246                         break;
 247                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 248                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 249                         ctx->seen |= SEEN_XREG;
 250                         PPC_XOR(r_A, r_A, r_X);
 251                         break;
 252                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 253                         if (IMM_L(K))
 254                                 PPC_XORI(r_A, r_A, IMM_L(K));
 255                         if (K >= 65536)
 256                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 257                         break;
 258                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 259                         ctx->seen |= SEEN_XREG;
 260                         PPC_SLW(r_A, r_A, r_X);
 261                         break;
 262                 case BPF_ALU | BPF_LSH | BPF_K:
 263                         if (K == 0)
 264                                 break;
 265                         else
 266                                 PPC_SLWI(r_A, r_A, K);
 267                         break;
 268                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 269                         ctx->seen |= SEEN_XREG;
 270                         PPC_SRW(r_A, r_A, r_X);
 271                         break;
 272                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 273                         if (K == 0)
 274                                 break;
 275                         else
 276                                 PPC_SRWI(r_A, r_A, K);
 277                         break;
 278                 case BPF_ALU | BPF_NEG:
 279                         PPC_NEG(r_A, r_A);
 280                         break;
 281                 case BPF_RET | BPF_K:
 282                         PPC_LI32(r_ret, K);
 283                         if (!K) {
 284                                 if (ctx->pc_ret0 == -1)
 285                                         ctx->pc_ret0 = i;
 286                         }
 287                         /*
 288                          * If this isn't the very last instruction, branch to
 289                          * the epilogue if we've stuff to clean up.  Otherwise,
 290                          * if there's nothing to tidy, just return.  If we /are/
 291                          * the last instruction, we're about to fall through to
 292                          * the epilogue to return.
 293                          */
 294                         if (i != flen - 1) {
 295                                 /*
 296                                  * Note: 'seen' is properly valid only on pass
 297                                  * #2.  Both parts of this conditional are the
 298                                  * same instruction size though, meaning the
 299                                  * first pass will still correctly determine the
 300                                  * code size/addresses.
 301                                  */
 302                                 if (ctx->seen)
 303                                         PPC_JMP(exit_addr);
 304                                 else
 305                                         PPC_BLR();
 306                         }
 307                         break;
 308                 case BPF_RET | BPF_A:
 309                         PPC_MR(r_ret, r_A);
 310                         if (i != flen - 1) {
 311                                 if (ctx->seen)
 312                                         PPC_JMP(exit_addr);
 313                                 else
 314                                         PPC_BLR();
 315                         }
 316                         break;
 317                 case BPF_MISC | BPF_TAX: /* X = A */
 318                         PPC_MR(r_X, r_A);
 319                         break;
 320                 case BPF_MISC | BPF_TXA: /* A = X */
 321                         ctx->seen |= SEEN_XREG;
 322                         PPC_MR(r_A, r_X);
 323                         break;
 324
 325                         /*** Constant loads/M[] access ***/
 326                 case BPF_LD | BPF_IMM: /* A = K */
 327                         PPC_LI32(r_A, K);
 328                         break;
 329                 case BPF_LDX | BPF_IMM: /* X = K */
 330                         PPC_LI32(r_X, K);
 331                         break;
 332                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 333                         PPC_MR(r_A, r_M + (K & 0xf));
 334                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 335                         break;
 336                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 337                         PPC_MR(r_X, r_M + (K & 0xf));
 338                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 339                         break;
 340                 case BPF_ST: /* mem[K] = A */
 341                         PPC_MR(r_M + (K & 0xf), r_A);
 342                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 343                         break;
 344                 case BPF_STX: /* mem[K] = X */
 345                         PPC_MR(r_M + (K & 0xf), r_X);
 346                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 347                         break;
 348                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 349                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 350                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 351                         break;
 352                 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
 353                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 354                         break;
 355
 356                         /*** Ancillary info loads ***/
 357                 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
 358                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 359                                                   protocol) != 2);
 360                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 361                                                             protocol));
 362                         break;
 363                 case BPF_ANC | SKF_AD_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_ANC | SKF_AD_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_ANC | SKF_AD_RXHASH:
 386                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
 387                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 388                                                           hash));
 389                         break;
 390                 case BPF_ANC | SKF_AD_VLAN_TAG:
 391                 case BPF_ANC | SKF_AD_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 (code == (BPF_ANC | SKF_AD_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_ANC | SKF_AD_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_ANC | SKF_AD_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_LD | BPF_W | BPF_ABS:
 423                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 424                         goto common_load;
 425                 case BPF_LD | BPF_H | BPF_ABS:
 426                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 427                         goto common_load;
 428                 case BPF_LD | BPF_B | BPF_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_LD | BPF_W | BPF_IND:
 446                         func = sk_load_word;
 447                         goto common_load_ind;
 448                 case BPF_LD | BPF_H | BPF_IND:
 449                         func = sk_load_half;
 450                         goto common_load_ind;
 451                 case BPF_LD | BPF_B | BPF_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_LDX | BPF_B | BPF_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_JMP | BPF_JA:
 476                         if (K != 0)
 477                                 PPC_JMP(addrs[i + 1 + K]);
 478                         break;
 479
 480                 case BPF_JMP | BPF_JGT | BPF_K:
 481                 case BPF_JMP | BPF_JGT | BPF_X:
 482                         true_cond = COND_GT;
 483                         goto cond_branch;
 484                 case BPF_JMP | BPF_JGE | BPF_K:
 485                 case BPF_JMP | BPF_JGE | BPF_X:
 486                         true_cond = COND_GE;
 487                         goto cond_branch;
 488                 case BPF_JMP | BPF_JEQ | BPF_K:
 489                 case BPF_JMP | BPF_JEQ | BPF_X:
 490                         true_cond = COND_EQ;
 491                         goto cond_branch;
 492                 case BPF_JMP | BPF_JSET | BPF_K:
 493                 case BPF_JMP | BPF_JSET | BPF_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 (code) {
 505                         case BPF_JMP | BPF_JGT | BPF_X:
 506                         case BPF_JMP | BPF_JGE | BPF_X:
 507                         case BPF_JMP | BPF_JEQ | BPF_X:
 508                                 ctx->seen |= SEEN_XREG;
 509                                 PPC_CMPLW(r_A, r_X);
 510                                 break;
 511                         case BPF_JMP | BPF_JSET | BPF_X:
 512                                 ctx->seen |= SEEN_XREG;
 513                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 514                                 break;
 515                         case BPF_JMP | BPF_JEQ | BPF_K:
 516                         case BPF_JMP | BPF_JGT | BPF_K:
 517                         case BPF_JMP | BPF_JGE | BPF_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_JMP | BPF_JSET | BPF_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(alloclen);
 655         if (!image)
 656                 goto out;
 657
 658         code_base = image + (FUNCTION_DESCR_SIZE/4);
 659
 660         /* Code generation passes 1-2 */
 661         for (pass = 1; pass < 3; pass++) {
 662                 /* Now build the prologue, body code & epilogue for real. */
 663                 cgctx.idx = 0;
 664                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 665                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 666                 bpf_jit_build_epilogue(code_base, &cgctx);
 667
 668                 if (bpf_jit_enable > 1)
 669                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 670                                 proglen - (cgctx.idx * 4), cgctx.seen);
 671         }
 672
 673         if (bpf_jit_enable > 1)
 674                 /* Note that we output the base address of the code_base
 675                  * rather than image, since opcodes are in code_base.
 676                  */
 677                 bpf_jit_dump(flen, proglen, pass, code_base);
 678
 679         if (image) {
 680                 bpf_flush_icache(code_base, code_base + (proglen/4));
 681                 /* Function descriptor nastiness: Address + TOC */
 682                 ((u64 *)image)[0] = (u64)code_base;
 683                 ((u64 *)image)[1] = local_paca->kernel_toc;
 684                 fp->bpf_func = (void *)image;
 685                 fp->jited = 1;
 686         }
 687 out:
 688         kfree(addrs);
 689         return;
 690 }
 691
 692 void bpf_jit_free(struct sk_filter *fp)
 693 {
 694         if (fp->jited)
 695                 module_free(NULL, fp->bpf_func);
 696         kfree(fp);
 697 }