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_S_RET_K:
  83         case BPF_S_LD_W_LEN:
  84         case BPF_S_ANC_PROTOCOL:
  85         case BPF_S_ANC_IFINDEX:
  86         case BPF_S_ANC_MARK:
  87         case BPF_S_ANC_RXHASH:
  88         case BPF_S_ANC_VLAN_TAG:
  89         case BPF_S_ANC_VLAN_TAG_PRESENT:
  90         case BPF_S_ANC_CPU:
  91         case BPF_S_ANC_QUEUE:
  92         case BPF_S_LD_W_ABS:
  93         case BPF_S_LD_H_ABS:
  94         case BPF_S_LD_B_ABS:
  95                 /* first instruction sets A register (or is RET 'constant') */
  96                 break;
  97         default:
  98                 /* make sure we dont leak kernel information to user */
  99                 PPC_LI(r_A, 0);
 100         }
 101 }
 102
 103 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 104 {
 105         int i;
 106
 107         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
 108                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
 109                 if (ctx->seen & SEEN_DATAREF) {
 110                         PPC_LD(0, 1, 16);
 111                         PPC_MTLR(0);
 112                         PPC_LD(r_D, 1, -(8*(32-r_D)));
 113                         PPC_LD(r_HL, 1, -(8*(32-r_HL)));
 114                 }
 115                 if (ctx->seen & SEEN_MEM) {
 116                         /* Restore any saved non-vol registers */
 117                         for (i = r_M; i < (r_M+16); i++) {
 118                                 if (ctx->seen & (1 << (i-r_M)))
 119                                         PPC_LD(i, 1, -(8*(32-i)));
 120                         }
 121                 }
 122         }
 123         /* The RETs have left a return value in R3. */
 124
 125         PPC_BLR();
 126 }
 127
 128 #define CHOOSE_LOAD_FUNC(K, func) \
 129         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 130
 131 /* Assemble the body code between the prologue & epilogue. */
 132 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
 133                               struct codegen_context *ctx,
 134                               unsigned int *addrs)
 135 {
 136         const struct sock_filter *filter = fp->insns;
 137         int flen = fp->len;
 138         u8 *func;
 139         unsigned int true_cond;
 140         int i;
 141
 142         /* Start of epilogue code */
 143         unsigned int exit_addr = addrs[flen];
 144
 145         for (i = 0; i < flen; i++) {
 146                 unsigned int K = filter[i].k;
 147
 148                 /*
 149                  * addrs[] maps a BPF bytecode address into a real offset from
 150                  * the start of the body code.
 151                  */
 152                 addrs[i] = ctx->idx * 4;
 153
 154                 switch (filter[i].code) {
 155                         /*** ALU ops ***/
 156                 case BPF_S_ALU_ADD_X: /* A += X; */
 157                         ctx->seen |= SEEN_XREG;
 158                         PPC_ADD(r_A, r_A, r_X);
 159                         break;
 160                 case BPF_S_ALU_ADD_K: /* A += K; */
 161                         if (!K)
 162                                 break;
 163                         PPC_ADDI(r_A, r_A, IMM_L(K));
 164                         if (K >= 32768)
 165                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 166                         break;
 167                 case BPF_S_ALU_SUB_X: /* A -= X; */
 168                         ctx->seen |= SEEN_XREG;
 169                         PPC_SUB(r_A, r_A, r_X);
 170                         break;
 171                 case BPF_S_ALU_SUB_K: /* A -= K */
 172                         if (!K)
 173                                 break;
 174                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 175                         if (K >= 32768)
 176                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 177                         break;
 178                 case BPF_S_ALU_MUL_X: /* A *= X; */
 179                         ctx->seen |= SEEN_XREG;
 180                         PPC_MUL(r_A, r_A, r_X);
 181                         break;
 182                 case BPF_S_ALU_MUL_K: /* A *= K */
 183                         if (K < 32768)
 184                                 PPC_MULI(r_A, r_A, K);
 185                         else {
 186                                 PPC_LI32(r_scratch1, K);
 187                                 PPC_MUL(r_A, r_A, r_scratch1);
 188                         }
 189                         break;
 190                 case BPF_S_ALU_MOD_X: /* A %= X; */
 191                         ctx->seen |= SEEN_XREG;
 192                         PPC_CMPWI(r_X, 0);
 193                         if (ctx->pc_ret0 != -1) {
 194                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 195                         } else {
 196                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 197                                 PPC_LI(r_ret, 0);
 198                                 PPC_JMP(exit_addr);
 199                         }
 200                         PPC_DIVWU(r_scratch1, r_A, r_X);
 201                         PPC_MUL(r_scratch1, r_X, r_scratch1);
 202                         PPC_SUB(r_A, r_A, r_scratch1);
 203                         break;
 204                 case BPF_S_ALU_MOD_K: /* A %= K; */
 205                         PPC_LI32(r_scratch2, K);
 206                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 207                         PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
 208                         PPC_SUB(r_A, r_A, r_scratch1);
 209                         break;
 210                 case BPF_S_ALU_DIV_X: /* A /= X; */
 211                         ctx->seen |= SEEN_XREG;
 212                         PPC_CMPWI(r_X, 0);
 213                         if (ctx->pc_ret0 != -1) {
 214                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 215                         } else {
 216                                 /*
 217                                  * Exit, returning 0; first pass hits here
 218                                  * (longer worst-case code size).
 219                                  */
 220                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 221                                 PPC_LI(r_ret, 0);
 222                                 PPC_JMP(exit_addr);
 223                         }
 224                         PPC_DIVWU(r_A, r_A, r_X);
 225                         break;
 226                 case BPF_S_ALU_DIV_K: /* A /= K */
 227                         if (K == 1)
 228                                 break;
 229                         PPC_LI32(r_scratch1, K);
 230                         PPC_DIVWU(r_A, r_A, r_scratch1);
 231                         break;
 232                 case BPF_S_ALU_AND_X:
 233                         ctx->seen |= SEEN_XREG;
 234                         PPC_AND(r_A, r_A, r_X);
 235                         break;
 236                 case BPF_S_ALU_AND_K:
 237                         if (!IMM_H(K))
 238                                 PPC_ANDI(r_A, r_A, K);
 239                         else {
 240                                 PPC_LI32(r_scratch1, K);
 241                                 PPC_AND(r_A, r_A, r_scratch1);
 242                         }
 243                         break;
 244                 case BPF_S_ALU_OR_X:
 245                         ctx->seen |= SEEN_XREG;
 246                         PPC_OR(r_A, r_A, r_X);
 247                         break;
 248                 case BPF_S_ALU_OR_K:
 249                         if (IMM_L(K))
 250                                 PPC_ORI(r_A, r_A, IMM_L(K));
 251                         if (K >= 65536)
 252                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 253                         break;
 254                 case BPF_S_ANC_ALU_XOR_X:
 255                 case BPF_S_ALU_XOR_X: /* A ^= X */
 256                         ctx->seen |= SEEN_XREG;
 257                         PPC_XOR(r_A, r_A, r_X);
 258                         break;
 259                 case BPF_S_ALU_XOR_K: /* A ^= K */
 260                         if (IMM_L(K))
 261                                 PPC_XORI(r_A, r_A, IMM_L(K));
 262                         if (K >= 65536)
 263                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 264                         break;
 265                 case BPF_S_ALU_LSH_X: /* A <<= X; */
 266                         ctx->seen |= SEEN_XREG;
 267                         PPC_SLW(r_A, r_A, r_X);
 268                         break;
 269                 case BPF_S_ALU_LSH_K:
 270                         if (K == 0)
 271                                 break;
 272                         else
 273                                 PPC_SLWI(r_A, r_A, K);
 274                         break;
 275                 case BPF_S_ALU_RSH_X: /* A >>= X; */
 276                         ctx->seen |= SEEN_XREG;
 277                         PPC_SRW(r_A, r_A, r_X);
 278                         break;
 279                 case BPF_S_ALU_RSH_K: /* A >>= K; */
 280                         if (K == 0)
 281                                 break;
 282                         else
 283                                 PPC_SRWI(r_A, r_A, K);
 284                         break;
 285                 case BPF_S_ALU_NEG:
 286                         PPC_NEG(r_A, r_A);
 287                         break;
 288                 case BPF_S_RET_K:
 289                         PPC_LI32(r_ret, K);
 290                         if (!K) {
 291                                 if (ctx->pc_ret0 == -1)
 292                                         ctx->pc_ret0 = i;
 293                         }
 294                         /*
 295                          * If this isn't the very last instruction, branch to
 296                          * the epilogue if we've stuff to clean up.  Otherwise,
 297                          * if there's nothing to tidy, just return.  If we /are/
 298                          * the last instruction, we're about to fall through to
 299                          * the epilogue to return.
 300                          */
 301                         if (i != flen - 1) {
 302                                 /*
 303                                  * Note: 'seen' is properly valid only on pass
 304                                  * #2.  Both parts of this conditional are the
 305                                  * same instruction size though, meaning the
 306                                  * first pass will still correctly determine the
 307                                  * code size/addresses.
 308                                  */
 309                                 if (ctx->seen)
 310                                         PPC_JMP(exit_addr);
 311                                 else
 312                                         PPC_BLR();
 313                         }
 314                         break;
 315                 case BPF_S_RET_A:
 316                         PPC_MR(r_ret, r_A);
 317                         if (i != flen - 1) {
 318                                 if (ctx->seen)
 319                                         PPC_JMP(exit_addr);
 320                                 else
 321                                         PPC_BLR();
 322                         }
 323                         break;
 324                 case BPF_S_MISC_TAX: /* X = A */
 325                         PPC_MR(r_X, r_A);
 326                         break;
 327                 case BPF_S_MISC_TXA: /* A = X */
 328                         ctx->seen |= SEEN_XREG;
 329                         PPC_MR(r_A, r_X);
 330                         break;
 331
 332                         /*** Constant loads/M[] access ***/
 333                 case BPF_S_LD_IMM: /* A = K */
 334                         PPC_LI32(r_A, K);
 335                         break;
 336                 case BPF_S_LDX_IMM: /* X = K */
 337                         PPC_LI32(r_X, K);
 338                         break;
 339                 case BPF_S_LD_MEM: /* A = mem[K] */
 340                         PPC_MR(r_A, r_M + (K & 0xf));
 341                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 342                         break;
 343                 case BPF_S_LDX_MEM: /* X = mem[K] */
 344                         PPC_MR(r_X, r_M + (K & 0xf));
 345                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 346                         break;
 347                 case BPF_S_ST: /* mem[K] = A */
 348                         PPC_MR(r_M + (K & 0xf), r_A);
 349                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 350                         break;
 351                 case BPF_S_STX: /* mem[K] = X */
 352                         PPC_MR(r_M + (K & 0xf), r_X);
 353                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 354                         break;
 355                 case BPF_S_LD_W_LEN: /* A = skb->len; */
 356                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 357                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 358                         break;
 359                 case BPF_S_LDX_W_LEN: /* X = skb->len; */
 360                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 361                         break;
 362
 363                         /*** Ancillary info loads ***/
 364                 case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
 365                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 366                                                   protocol) != 2);
 367                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 368                                                             protocol));
 369                         break;
 370                 case BPF_S_ANC_IFINDEX:
 371                         PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 372                                                                 dev));
 373                         PPC_CMPDI(r_scratch1, 0);
 374                         if (ctx->pc_ret0 != -1) {
 375                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 376                         } else {
 377                                 /* Exit, returning 0; first pass hits here. */
 378                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 379                                 PPC_LI(r_ret, 0);
 380                                 PPC_JMP(exit_addr);
 381                         }
 382                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 383                                                   ifindex) != 4);
 384                         PPC_LWZ_OFFS(r_A, r_scratch1,
 385                                      offsetof(struct net_device, ifindex));
 386                         break;
 387                 case BPF_S_ANC_MARK:
 388                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 389                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 390                                                           mark));
 391                         break;
 392                 case BPF_S_ANC_RXHASH:
 393                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
 394                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 395                                                           rxhash));
 396                         break;
 397                 case BPF_S_ANC_VLAN_TAG:
 398                 case BPF_S_ANC_VLAN_TAG_PRESENT:
 399                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 400                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 401                                                           vlan_tci));
 402                         if (filter[i].code == BPF_S_ANC_VLAN_TAG)
 403                                 PPC_ANDI(r_A, r_A, VLAN_VID_MASK);
 404                         else
 405                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 406                         break;
 407                 case BPF_S_ANC_QUEUE:
 408                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 409                                                   queue_mapping) != 2);
 410                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 411                                                           queue_mapping));
 412                         break;
 413                 case BPF_S_ANC_CPU:
 414 #ifdef CONFIG_SMP
 415                         /*
 416                          * PACA ptr is r13:
 417                          * raw_smp_processor_id() = local_paca->paca_index
 418                          */
 419                         BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
 420                                                   paca_index) != 2);
 421                         PPC_LHZ_OFFS(r_A, 13,
 422                                      offsetof(struct paca_struct, paca_index));
 423 #else
 424                         PPC_LI(r_A, 0);
 425 #endif
 426                         break;
 427
 428                         /*** Absolute loads from packet header/data ***/
 429                 case BPF_S_LD_W_ABS:
 430                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 431                         goto common_load;
 432                 case BPF_S_LD_H_ABS:
 433                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 434                         goto common_load;
 435                 case BPF_S_LD_B_ABS:
 436                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 437                 common_load:
 438                         /* Load from [K]. */
 439                         ctx->seen |= SEEN_DATAREF;
 440                         PPC_LI64(r_scratch1, func);
 441                         PPC_MTLR(r_scratch1);
 442                         PPC_LI32(r_addr, K);
 443                         PPC_BLRL();
 444                         /*
 445                          * Helper returns 'lt' condition on error, and an
 446                          * appropriate return value in r3
 447                          */
 448                         PPC_BCC(COND_LT, exit_addr);
 449                         break;
 450
 451                         /*** Indirect loads from packet header/data ***/
 452                 case BPF_S_LD_W_IND:
 453                         func = sk_load_word;
 454                         goto common_load_ind;
 455                 case BPF_S_LD_H_IND:
 456                         func = sk_load_half;
 457                         goto common_load_ind;
 458                 case BPF_S_LD_B_IND:
 459                         func = sk_load_byte;
 460                 common_load_ind:
 461                         /*
 462                          * Load from [X + K].  Negative offsets are tested for
 463                          * in the helper functions.
 464                          */
 465                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 466                         PPC_LI64(r_scratch1, func);
 467                         PPC_MTLR(r_scratch1);
 468                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 469                         if (K >= 32768)
 470                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 471                         PPC_BLRL();
 472                         /* If error, cr0.LT set */
 473                         PPC_BCC(COND_LT, exit_addr);
 474                         break;
 475
 476                 case BPF_S_LDX_B_MSH:
 477                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 478                         goto common_load;
 479                         break;
 480
 481                         /*** Jump and branches ***/
 482                 case BPF_S_JMP_JA:
 483                         if (K != 0)
 484                                 PPC_JMP(addrs[i + 1 + K]);
 485                         break;
 486
 487                 case BPF_S_JMP_JGT_K:
 488                 case BPF_S_JMP_JGT_X:
 489                         true_cond = COND_GT;
 490                         goto cond_branch;
 491                 case BPF_S_JMP_JGE_K:
 492                 case BPF_S_JMP_JGE_X:
 493                         true_cond = COND_GE;
 494                         goto cond_branch;
 495                 case BPF_S_JMP_JEQ_K:
 496                 case BPF_S_JMP_JEQ_X:
 497                         true_cond = COND_EQ;
 498                         goto cond_branch;
 499                 case BPF_S_JMP_JSET_K:
 500                 case BPF_S_JMP_JSET_X:
 501                         true_cond = COND_NE;
 502                         /* Fall through */
 503                 cond_branch:
 504                         /* same targets, can avoid doing the test :) */
 505                         if (filter[i].jt == filter[i].jf) {
 506                                 if (filter[i].jt > 0)
 507                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 508                                 break;
 509                         }
 510
 511                         switch (filter[i].code) {
 512                         case BPF_S_JMP_JGT_X:
 513                         case BPF_S_JMP_JGE_X:
 514                         case BPF_S_JMP_JEQ_X:
 515                                 ctx->seen |= SEEN_XREG;
 516                                 PPC_CMPLW(r_A, r_X);
 517                                 break;
 518                         case BPF_S_JMP_JSET_X:
 519                                 ctx->seen |= SEEN_XREG;
 520                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 521                                 break;
 522                         case BPF_S_JMP_JEQ_K:
 523                         case BPF_S_JMP_JGT_K:
 524                         case BPF_S_JMP_JGE_K:
 525                                 if (K < 32768)
 526                                         PPC_CMPLWI(r_A, K);
 527                                 else {
 528                                         PPC_LI32(r_scratch1, K);
 529                                         PPC_CMPLW(r_A, r_scratch1);
 530                                 }
 531                                 break;
 532                         case BPF_S_JMP_JSET_K:
 533                                 if (K < 32768)
 534                                         /* PPC_ANDI is /only/ dot-form */
 535                                         PPC_ANDI(r_scratch1, r_A, K);
 536                                 else {
 537                                         PPC_LI32(r_scratch1, K);
 538                                         PPC_AND_DOT(r_scratch1, r_A,
 539                                                     r_scratch1);
 540                                 }
 541                                 break;
 542                         }
 543                         /* Sometimes branches are constructed "backward", with
 544                          * the false path being the branch and true path being
 545                          * a fallthrough to the next instruction.
 546                          */
 547                         if (filter[i].jt == 0)
 548                                 /* Swap the sense of the branch */
 549                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 550                                         addrs[i + 1 + filter[i].jf]);
 551                         else {
 552                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 553                                 if (filter[i].jf != 0)
 554                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 555                         }
 556                         break;
 557                 default:
 558                         /* The filter contains something cruel & unusual.
 559                          * We don't handle it, but also there shouldn't be
 560                          * anything missing from our list.
 561                          */
 562                         if (printk_ratelimit())
 563                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 564                                        filter[i].code, i);
 565                         return -ENOTSUPP;
 566                 }
 567
 568         }
 569         /* Set end-of-body-code address for exit. */
 570         addrs[i] = ctx->idx * 4;
 571
 572         return 0;
 573 }
 574
 575 void bpf_jit_compile(struct sk_filter *fp)
 576 {
 577         unsigned int proglen;
 578         unsigned int alloclen;
 579         u32 *image = NULL;
 580         u32 *code_base;
 581         unsigned int *addrs;
 582         struct codegen_context cgctx;
 583         int pass;
 584         int flen = fp->len;
 585
 586         if (!bpf_jit_enable)
 587                 return;
 588
 589         addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
 590         if (addrs == NULL)
 591                 return;
 592
 593         /*
 594          * There are multiple assembly passes as the generated code will change
 595          * size as it settles down, figuring out the max branch offsets/exit
 596          * paths required.
 597          *
 598          * The range of standard conditional branches is +/- 32Kbytes.  Since
 599          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 600          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 601          * used, distinct from short branches.
 602          *
 603          * Current:
 604          *
 605          * For now, both branch types assemble to 2 words (short branches padded
 606          * with a NOP); this is less efficient, but assembly will always complete
 607          * after exactly 3 passes:
 608          *
 609          * First pass: No code buffer; Program is "faux-generated" -- no code
 610          * emitted but maximum size of output determined (and addrs[] filled
 611          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 612          * All generation choices assumed to be 'worst-case', e.g. branches all
 613          * far (2 instructions), return path code reduction not available, etc.
 614          *
 615          * Second pass: Code buffer allocated with size determined previously.
 616          * Prologue generated to support features we have seen used.  Exit paths
 617          * determined and addrs[] is filled in again, as code may be slightly
 618          * smaller as a result.
 619          *
 620          * Third pass: Code generated 'for real', and branch destinations
 621          * determined from now-accurate addrs[] map.
 622          *
 623          * Ideal:
 624          *
 625          * If we optimise this, near branches will be shorter.  On the
 626          * first assembly pass, we should err on the side of caution and
 627          * generate the biggest code.  On subsequent passes, branches will be
 628          * generated short or long and code size will reduce.  With smaller
 629          * code, more branches may fall into the short category, and code will
 630          * reduce more.
 631          *
 632          * Finally, if we see one pass generate code the same size as the
 633          * previous pass we have converged and should now generate code for
 634          * real.  Allocating at the end will also save the memory that would
 635          * otherwise be wasted by the (small) current code shrinkage.
 636          * Preferably, we should do a small number of passes (e.g. 5) and if we
 637          * haven't converged by then, get impatient and force code to generate
 638          * as-is, even if the odd branch would be left long.  The chances of a
 639          * long jump are tiny with all but the most enormous of BPF filter
 640          * inputs, so we should usually converge on the third pass.
 641          */
 642
 643         cgctx.idx = 0;
 644         cgctx.seen = 0;
 645         cgctx.pc_ret0 = -1;
 646         /* Scouting faux-generate pass 0 */
 647         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 648                 /* We hit something illegal or unsupported. */
 649                 goto out;
 650
 651         /*
 652          * Pretend to build prologue, given the features we've seen.  This will
 653          * update ctgtx.idx as it pretends to output instructions, then we can
 654          * calculate total size from idx.
 655          */
 656         bpf_jit_build_prologue(fp, 0, &cgctx);
 657         bpf_jit_build_epilogue(0, &cgctx);
 658
 659         proglen = cgctx.idx * 4;
 660         alloclen = proglen + FUNCTION_DESCR_SIZE;
 661         image = module_alloc(alloclen);
 662         if (!image)
 663                 goto out;
 664
 665         code_base = image + (FUNCTION_DESCR_SIZE/4);
 666
 667         /* Code generation passes 1-2 */
 668         for (pass = 1; pass < 3; pass++) {
 669                 /* Now build the prologue, body code & epilogue for real. */
 670                 cgctx.idx = 0;
 671                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 672                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 673                 bpf_jit_build_epilogue(code_base, &cgctx);
 674
 675                 if (bpf_jit_enable > 1)
 676                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 677                                 proglen - (cgctx.idx * 4), cgctx.seen);
 678         }
 679
 680         if (bpf_jit_enable > 1)
 681                 /* Note that we output the base address of the code_base
 682                  * rather than image, since opcodes are in code_base.
 683                  */
 684                 bpf_jit_dump(flen, proglen, pass, code_base);
 685
 686         if (image) {
 687                 bpf_flush_icache(code_base, code_base + (proglen/4));
 688                 /* Function descriptor nastiness: Address + TOC */
 689                 ((u64 *)image)[0] = (u64)code_base;
 690                 ((u64 *)image)[1] = local_paca->kernel_toc;
 691                 fp->bpf_func = (void *)image;
 692         }
 693 out:
 694         kfree(addrs);
 695         return;
 696 }
 697
 698 void bpf_jit_free(struct sk_filter *fp)
 699 {
 700         if (fp->bpf_func != sk_run_filter)
 701                 module_free(NULL, fp->bpf_func);
 702         kfree(fp);
 703 }