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         /* make sure we dont leak kernel information to user */
  82         if (bpf_needs_clear_a(&filter[0]))
  83                 PPC_LI(r_A, 0);
  84 }
  85
  86 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  87 {
  88         int i;
  89
  90         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  91                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
  92                 if (ctx->seen & SEEN_DATAREF) {
  93                         PPC_LD(0, 1, 16);
  94                         PPC_MTLR(0);
  95                         PPC_LD(r_D, 1, -(8*(32-r_D)));
  96                         PPC_LD(r_HL, 1, -(8*(32-r_HL)));
  97                 }
  98                 if (ctx->seen & SEEN_MEM) {
  99                         /* Restore any saved non-vol registers */
 100                         for (i = r_M; i < (r_M+16); i++) {
 101                                 if (ctx->seen & (1 << (i-r_M)))
 102                                         PPC_LD(i, 1, -(8*(32-i)));
 103                         }
 104                 }
 105         }
 106         /* The RETs have left a return value in R3. */
 107
 108         PPC_BLR();
 109 }
 110
 111 #define CHOOSE_LOAD_FUNC(K, func) \
 112         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 113
 114 /* Assemble the body code between the prologue & epilogue. */
 115 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
 116                               struct codegen_context *ctx,
 117                               unsigned int *addrs)
 118 {
 119         const struct sock_filter *filter = fp->insns;
 120         int flen = fp->len;
 121         u8 *func;
 122         unsigned int true_cond;
 123         int i;
 124
 125         /* Start of epilogue code */
 126         unsigned int exit_addr = addrs[flen];
 127
 128         for (i = 0; i < flen; i++) {
 129                 unsigned int K = filter[i].k;
 130                 u16 code = bpf_anc_helper(&filter[i]);
 131
 132                 /*
 133                  * addrs[] maps a BPF bytecode address into a real offset from
 134                  * the start of the body code.
 135                  */
 136                 addrs[i] = ctx->idx * 4;
 137
 138                 switch (code) {
 139                         /*** ALU ops ***/
 140                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 141                         ctx->seen |= SEEN_XREG;
 142                         PPC_ADD(r_A, r_A, r_X);
 143                         break;
 144                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 145                         if (!K)
 146                                 break;
 147                         PPC_ADDI(r_A, r_A, IMM_L(K));
 148                         if (K >= 32768)
 149                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 150                         break;
 151                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 152                         ctx->seen |= SEEN_XREG;
 153                         PPC_SUB(r_A, r_A, r_X);
 154                         break;
 155                 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
 156                         if (!K)
 157                                 break;
 158                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 159                         if (K >= 32768)
 160                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 161                         break;
 162                 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
 163                         ctx->seen |= SEEN_XREG;
 164                         PPC_MUL(r_A, r_A, r_X);
 165                         break;
 166                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 167                         if (K < 32768)
 168                                 PPC_MULI(r_A, r_A, K);
 169                         else {
 170                                 PPC_LI32(r_scratch1, K);
 171                                 PPC_MUL(r_A, r_A, r_scratch1);
 172                         }
 173                         break;
 174                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 175                         ctx->seen |= SEEN_XREG;
 176                         PPC_CMPWI(r_X, 0);
 177                         if (ctx->pc_ret0 != -1) {
 178                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 179                         } else {
 180                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 181                                 PPC_LI(r_ret, 0);
 182                                 PPC_JMP(exit_addr);
 183                         }
 184                         PPC_DIVWU(r_scratch1, r_A, r_X);
 185                         PPC_MUL(r_scratch1, r_X, r_scratch1);
 186                         PPC_SUB(r_A, r_A, r_scratch1);
 187                         break;
 188                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 189                         PPC_LI32(r_scratch2, K);
 190                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 191                         PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
 192                         PPC_SUB(r_A, r_A, r_scratch1);
 193                         break;
 194                 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
 195                         ctx->seen |= SEEN_XREG;
 196                         PPC_CMPWI(r_X, 0);
 197                         if (ctx->pc_ret0 != -1) {
 198                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 199                         } else {
 200                                 /*
 201                                  * Exit, returning 0; first pass hits here
 202                                  * (longer worst-case code size).
 203                                  */
 204                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 205                                 PPC_LI(r_ret, 0);
 206                                 PPC_JMP(exit_addr);
 207                         }
 208                         PPC_DIVWU(r_A, r_A, r_X);
 209                         break;
 210                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 211                         if (K == 1)
 212                                 break;
 213                         PPC_LI32(r_scratch1, K);
 214                         PPC_DIVWU(r_A, r_A, r_scratch1);
 215                         break;
 216                 case BPF_ALU | BPF_AND | BPF_X:
 217                         ctx->seen |= SEEN_XREG;
 218                         PPC_AND(r_A, r_A, r_X);
 219                         break;
 220                 case BPF_ALU | BPF_AND | BPF_K:
 221                         if (!IMM_H(K))
 222                                 PPC_ANDI(r_A, r_A, K);
 223                         else {
 224                                 PPC_LI32(r_scratch1, K);
 225                                 PPC_AND(r_A, r_A, r_scratch1);
 226                         }
 227                         break;
 228                 case BPF_ALU | BPF_OR | BPF_X:
 229                         ctx->seen |= SEEN_XREG;
 230                         PPC_OR(r_A, r_A, r_X);
 231                         break;
 232                 case BPF_ALU | BPF_OR | BPF_K:
 233                         if (IMM_L(K))
 234                                 PPC_ORI(r_A, r_A, IMM_L(K));
 235                         if (K >= 65536)
 236                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 237                         break;
 238                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 239                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 240                         ctx->seen |= SEEN_XREG;
 241                         PPC_XOR(r_A, r_A, r_X);
 242                         break;
 243                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 244                         if (IMM_L(K))
 245                                 PPC_XORI(r_A, r_A, IMM_L(K));
 246                         if (K >= 65536)
 247                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 248                         break;
 249                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 250                         ctx->seen |= SEEN_XREG;
 251                         PPC_SLW(r_A, r_A, r_X);
 252                         break;
 253                 case BPF_ALU | BPF_LSH | BPF_K:
 254                         if (K == 0)
 255                                 break;
 256                         else
 257                                 PPC_SLWI(r_A, r_A, K);
 258                         break;
 259                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 260                         ctx->seen |= SEEN_XREG;
 261                         PPC_SRW(r_A, r_A, r_X);
 262                         break;
 263                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 264                         if (K == 0)
 265                                 break;
 266                         else
 267                                 PPC_SRWI(r_A, r_A, K);
 268                         break;
 269                 case BPF_ALU | BPF_NEG:
 270                         PPC_NEG(r_A, r_A);
 271                         break;
 272                 case BPF_RET | BPF_K:
 273                         PPC_LI32(r_ret, K);
 274                         if (!K) {
 275                                 if (ctx->pc_ret0 == -1)
 276                                         ctx->pc_ret0 = i;
 277                         }
 278                         /*
 279                          * If this isn't the very last instruction, branch to
 280                          * the epilogue if we've stuff to clean up.  Otherwise,
 281                          * if there's nothing to tidy, just return.  If we /are/
 282                          * the last instruction, we're about to fall through to
 283                          * the epilogue to return.
 284                          */
 285                         if (i != flen - 1) {
 286                                 /*
 287                                  * Note: 'seen' is properly valid only on pass
 288                                  * #2.  Both parts of this conditional are the
 289                                  * same instruction size though, meaning the
 290                                  * first pass will still correctly determine the
 291                                  * code size/addresses.
 292                                  */
 293                                 if (ctx->seen)
 294                                         PPC_JMP(exit_addr);
 295                                 else
 296                                         PPC_BLR();
 297                         }
 298                         break;
 299                 case BPF_RET | BPF_A:
 300                         PPC_MR(r_ret, r_A);
 301                         if (i != flen - 1) {
 302                                 if (ctx->seen)
 303                                         PPC_JMP(exit_addr);
 304                                 else
 305                                         PPC_BLR();
 306                         }
 307                         break;
 308                 case BPF_MISC | BPF_TAX: /* X = A */
 309                         PPC_MR(r_X, r_A);
 310                         break;
 311                 case BPF_MISC | BPF_TXA: /* A = X */
 312                         ctx->seen |= SEEN_XREG;
 313                         PPC_MR(r_A, r_X);
 314                         break;
 315
 316                         /*** Constant loads/M[] access ***/
 317                 case BPF_LD | BPF_IMM: /* A = K */
 318                         PPC_LI32(r_A, K);
 319                         break;
 320                 case BPF_LDX | BPF_IMM: /* X = K */
 321                         PPC_LI32(r_X, K);
 322                         break;
 323                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 324                         PPC_MR(r_A, r_M + (K & 0xf));
 325                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 326                         break;
 327                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 328                         PPC_MR(r_X, r_M + (K & 0xf));
 329                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 330                         break;
 331                 case BPF_ST: /* mem[K] = A */
 332                         PPC_MR(r_M + (K & 0xf), r_A);
 333                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 334                         break;
 335                 case BPF_STX: /* mem[K] = X */
 336                         PPC_MR(r_M + (K & 0xf), r_X);
 337                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 338                         break;
 339                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 340                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 341                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 342                         break;
 343                 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
 344                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 345                         break;
 346
 347                         /*** Ancillary info loads ***/
 348                 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
 349                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 350                                                   protocol) != 2);
 351                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 352                                                             protocol));
 353                         break;
 354                 case BPF_ANC | SKF_AD_IFINDEX:
 355                         PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 356                                                                 dev));
 357                         PPC_CMPDI(r_scratch1, 0);
 358                         if (ctx->pc_ret0 != -1) {
 359                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 360                         } else {
 361                                 /* Exit, returning 0; first pass hits here. */
 362                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 363                                 PPC_LI(r_ret, 0);
 364                                 PPC_JMP(exit_addr);
 365                         }
 366                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 367                                                   ifindex) != 4);
 368                         PPC_LWZ_OFFS(r_A, r_scratch1,
 369                                      offsetof(struct net_device, ifindex));
 370                         break;
 371                 case BPF_ANC | SKF_AD_MARK:
 372                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 373                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 374                                                           mark));
 375                         break;
 376                 case BPF_ANC | SKF_AD_RXHASH:
 377                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
 378                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 379                                                           hash));
 380                         break;
 381                 case BPF_ANC | SKF_AD_VLAN_TAG:
 382                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 383                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 384                         BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
 385
 386                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 387                                                           vlan_tci));
 388                         if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
 389                                 PPC_ANDI(r_A, r_A, ~VLAN_TAG_PRESENT);
 390                         } else {
 391                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 392                                 PPC_SRWI(r_A, r_A, 12);
 393                         }
 394                         break;
 395                 case BPF_ANC | SKF_AD_QUEUE:
 396                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 397                                                   queue_mapping) != 2);
 398                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 399                                                           queue_mapping));
 400                         break;
 401                 case BPF_ANC | SKF_AD_CPU:
 402 #ifdef CONFIG_SMP
 403                         /*
 404                          * PACA ptr is r13:
 405                          * raw_smp_processor_id() = local_paca->paca_index
 406                          */
 407                         BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
 408                                                   paca_index) != 2);
 409                         PPC_LHZ_OFFS(r_A, 13,
 410                                      offsetof(struct paca_struct, paca_index));
 411 #else
 412                         PPC_LI(r_A, 0);
 413 #endif
 414                         break;
 415
 416                         /*** Absolute loads from packet header/data ***/
 417                 case BPF_LD | BPF_W | BPF_ABS:
 418                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 419                         goto common_load;
 420                 case BPF_LD | BPF_H | BPF_ABS:
 421                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 422                         goto common_load;
 423                 case BPF_LD | BPF_B | BPF_ABS:
 424                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 425                 common_load:
 426                         /* Load from [K]. */
 427                         ctx->seen |= SEEN_DATAREF;
 428                         PPC_LI64(r_scratch1, func);
 429                         PPC_MTLR(r_scratch1);
 430                         PPC_LI32(r_addr, K);
 431                         PPC_BLRL();
 432                         /*
 433                          * Helper returns 'lt' condition on error, and an
 434                          * appropriate return value in r3
 435                          */
 436                         PPC_BCC(COND_LT, exit_addr);
 437                         break;
 438
 439                         /*** Indirect loads from packet header/data ***/
 440                 case BPF_LD | BPF_W | BPF_IND:
 441                         func = sk_load_word;
 442                         goto common_load_ind;
 443                 case BPF_LD | BPF_H | BPF_IND:
 444                         func = sk_load_half;
 445                         goto common_load_ind;
 446                 case BPF_LD | BPF_B | BPF_IND:
 447                         func = sk_load_byte;
 448                 common_load_ind:
 449                         /*
 450                          * Load from [X + K].  Negative offsets are tested for
 451                          * in the helper functions.
 452                          */
 453                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 454                         PPC_LI64(r_scratch1, func);
 455                         PPC_MTLR(r_scratch1);
 456                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 457                         if (K >= 32768)
 458                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 459                         PPC_BLRL();
 460                         /* If error, cr0.LT set */
 461                         PPC_BCC(COND_LT, exit_addr);
 462                         break;
 463
 464                 case BPF_LDX | BPF_B | BPF_MSH:
 465                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 466                         goto common_load;
 467                         break;
 468
 469                         /*** Jump and branches ***/
 470                 case BPF_JMP | BPF_JA:
 471                         if (K != 0)
 472                                 PPC_JMP(addrs[i + 1 + K]);
 473                         break;
 474
 475                 case BPF_JMP | BPF_JGT | BPF_K:
 476                 case BPF_JMP | BPF_JGT | BPF_X:
 477                         true_cond = COND_GT;
 478                         goto cond_branch;
 479                 case BPF_JMP | BPF_JGE | BPF_K:
 480                 case BPF_JMP | BPF_JGE | BPF_X:
 481                         true_cond = COND_GE;
 482                         goto cond_branch;
 483                 case BPF_JMP | BPF_JEQ | BPF_K:
 484                 case BPF_JMP | BPF_JEQ | BPF_X:
 485                         true_cond = COND_EQ;
 486                         goto cond_branch;
 487                 case BPF_JMP | BPF_JSET | BPF_K:
 488                 case BPF_JMP | BPF_JSET | BPF_X:
 489                         true_cond = COND_NE;
 490                         /* Fall through */
 491                 cond_branch:
 492                         /* same targets, can avoid doing the test :) */
 493                         if (filter[i].jt == filter[i].jf) {
 494                                 if (filter[i].jt > 0)
 495                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 496                                 break;
 497                         }
 498
 499                         switch (code) {
 500                         case BPF_JMP | BPF_JGT | BPF_X:
 501                         case BPF_JMP | BPF_JGE | BPF_X:
 502                         case BPF_JMP | BPF_JEQ | BPF_X:
 503                                 ctx->seen |= SEEN_XREG;
 504                                 PPC_CMPLW(r_A, r_X);
 505                                 break;
 506                         case BPF_JMP | BPF_JSET | BPF_X:
 507                                 ctx->seen |= SEEN_XREG;
 508                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 509                                 break;
 510                         case BPF_JMP | BPF_JEQ | BPF_K:
 511                         case BPF_JMP | BPF_JGT | BPF_K:
 512                         case BPF_JMP | BPF_JGE | BPF_K:
 513                                 if (K < 32768)
 514                                         PPC_CMPLWI(r_A, K);
 515                                 else {
 516                                         PPC_LI32(r_scratch1, K);
 517                                         PPC_CMPLW(r_A, r_scratch1);
 518                                 }
 519                                 break;
 520                         case BPF_JMP | BPF_JSET | BPF_K:
 521                                 if (K < 32768)
 522                                         /* PPC_ANDI is /only/ dot-form */
 523                                         PPC_ANDI(r_scratch1, r_A, K);
 524                                 else {
 525                                         PPC_LI32(r_scratch1, K);
 526                                         PPC_AND_DOT(r_scratch1, r_A,
 527                                                     r_scratch1);
 528                                 }
 529                                 break;
 530                         }
 531                         /* Sometimes branches are constructed "backward", with
 532                          * the false path being the branch and true path being
 533                          * a fallthrough to the next instruction.
 534                          */
 535                         if (filter[i].jt == 0)
 536                                 /* Swap the sense of the branch */
 537                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 538                                         addrs[i + 1 + filter[i].jf]);
 539                         else {
 540                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 541                                 if (filter[i].jf != 0)
 542                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 543                         }
 544                         break;
 545                 default:
 546                         /* The filter contains something cruel & unusual.
 547                          * We don't handle it, but also there shouldn't be
 548                          * anything missing from our list.
 549                          */
 550                         if (printk_ratelimit())
 551                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 552                                        filter[i].code, i);
 553                         return -ENOTSUPP;
 554                 }
 555
 556         }
 557         /* Set end-of-body-code address for exit. */
 558         addrs[i] = ctx->idx * 4;
 559
 560         return 0;
 561 }
 562
 563 void bpf_jit_compile(struct sk_filter *fp)
 564 {
 565         unsigned int proglen;
 566         unsigned int alloclen;
 567         u32 *image = NULL;
 568         u32 *code_base;
 569         unsigned int *addrs;
 570         struct codegen_context cgctx;
 571         int pass;
 572         int flen = fp->len;
 573
 574         if (!bpf_jit_enable)
 575                 return;
 576
 577         addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
 578         if (addrs == NULL)
 579                 return;
 580
 581         /*
 582          * There are multiple assembly passes as the generated code will change
 583          * size as it settles down, figuring out the max branch offsets/exit
 584          * paths required.
 585          *
 586          * The range of standard conditional branches is +/- 32Kbytes.  Since
 587          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 588          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 589          * used, distinct from short branches.
 590          *
 591          * Current:
 592          *
 593          * For now, both branch types assemble to 2 words (short branches padded
 594          * with a NOP); this is less efficient, but assembly will always complete
 595          * after exactly 3 passes:
 596          *
 597          * First pass: No code buffer; Program is "faux-generated" -- no code
 598          * emitted but maximum size of output determined (and addrs[] filled
 599          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 600          * All generation choices assumed to be 'worst-case', e.g. branches all
 601          * far (2 instructions), return path code reduction not available, etc.
 602          *
 603          * Second pass: Code buffer allocated with size determined previously.
 604          * Prologue generated to support features we have seen used.  Exit paths
 605          * determined and addrs[] is filled in again, as code may be slightly
 606          * smaller as a result.
 607          *
 608          * Third pass: Code generated 'for real', and branch destinations
 609          * determined from now-accurate addrs[] map.
 610          *
 611          * Ideal:
 612          *
 613          * If we optimise this, near branches will be shorter.  On the
 614          * first assembly pass, we should err on the side of caution and
 615          * generate the biggest code.  On subsequent passes, branches will be
 616          * generated short or long and code size will reduce.  With smaller
 617          * code, more branches may fall into the short category, and code will
 618          * reduce more.
 619          *
 620          * Finally, if we see one pass generate code the same size as the
 621          * previous pass we have converged and should now generate code for
 622          * real.  Allocating at the end will also save the memory that would
 623          * otherwise be wasted by the (small) current code shrinkage.
 624          * Preferably, we should do a small number of passes (e.g. 5) and if we
 625          * haven't converged by then, get impatient and force code to generate
 626          * as-is, even if the odd branch would be left long.  The chances of a
 627          * long jump are tiny with all but the most enormous of BPF filter
 628          * inputs, so we should usually converge on the third pass.
 629          */
 630
 631         cgctx.idx = 0;
 632         cgctx.seen = 0;
 633         cgctx.pc_ret0 = -1;
 634         /* Scouting faux-generate pass 0 */
 635         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 636                 /* We hit something illegal or unsupported. */
 637                 goto out;
 638
 639         /*
 640          * Pretend to build prologue, given the features we've seen.  This will
 641          * update ctgtx.idx as it pretends to output instructions, then we can
 642          * calculate total size from idx.
 643          */
 644         bpf_jit_build_prologue(fp, 0, &cgctx);
 645         bpf_jit_build_epilogue(0, &cgctx);
 646
 647         proglen = cgctx.idx * 4;
 648         alloclen = proglen + FUNCTION_DESCR_SIZE;
 649         image = module_alloc(alloclen);
 650         if (!image)
 651                 goto out;
 652
 653         code_base = image + (FUNCTION_DESCR_SIZE/4);
 654
 655         /* Code generation passes 1-2 */
 656         for (pass = 1; pass < 3; pass++) {
 657                 /* Now build the prologue, body code & epilogue for real. */
 658                 cgctx.idx = 0;
 659                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 660                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 661                 bpf_jit_build_epilogue(code_base, &cgctx);
 662
 663                 if (bpf_jit_enable > 1)
 664                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 665                                 proglen - (cgctx.idx * 4), cgctx.seen);
 666         }
 667
 668         if (bpf_jit_enable > 1)
 669                 /* Note that we output the base address of the code_base
 670                  * rather than image, since opcodes are in code_base.
 671                  */
 672                 bpf_jit_dump(flen, proglen, pass, code_base);
 673
 674         if (image) {
 675                 bpf_flush_icache(code_base, code_base + (proglen/4));
 676                 /* Function descriptor nastiness: Address + TOC */
 677                 ((u64 *)image)[0] = (u64)code_base;
 678                 ((u64 *)image)[1] = local_paca->kernel_toc;
 679                 fp->bpf_func = (void *)image;
 680                 fp->jited = 1;
 681         }
 682 out:
 683         kfree(addrs);
 684         return;
 685 }
 686
 687 void bpf_jit_free(struct sk_filter *fp)
 688 {
 689         if (fp->jited)
 690                 module_free(NULL, fp->bpf_func);
 691         kfree(fp);
 692 }