arch/powerpc/net/bpf_jit_comp.c

   1 /* bpf_jit_comp.c: BPF JIT compiler
   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  * Ported to ppc32 by Denis Kirjanov <kda@linux-powerpc.org>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License
  10  * as published by the Free Software Foundation; version 2
  11  * of the License.
  12  */
  13 #include <linux/moduleloader.h>
  14 #include <asm/cacheflush.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/filter.h>
  17 #include <linux/if_vlan.h>
  18
  19 #include "bpf_jit32.h"
  20
  21 static inline void bpf_flush_icache(void *start, void *end)
  22 {
  23         smp_wmb();
  24         flush_icache_range((unsigned long)start, (unsigned long)end);
  25 }
  26
  27 static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image,
  28                                    struct codegen_context *ctx)
  29 {
  30         int i;
  31         const struct sock_filter *filter = fp->insns;
  32
  33         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  34                 /* Make stackframe */
  35                 if (ctx->seen & SEEN_DATAREF) {
  36                         /* If we call any helpers (for loads), save LR */
  37                         EMIT(PPC_INST_MFLR | __PPC_RT(R0));
  38                         PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
  39
  40                         /* Back up non-volatile regs. */
  41                         PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
  42                         PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  43                 }
  44                 if (ctx->seen & SEEN_MEM) {
  45                         /*
  46                          * Conditionally save regs r15-r31 as some will be used
  47                          * for M[] data.
  48                          */
  49                         for (i = r_M; i < (r_M+16); i++) {
  50                                 if (ctx->seen & (1 << (i-r_M)))
  51                                         PPC_BPF_STL(i, 1, -(REG_SZ*(32-i)));
  52                         }
  53                 }
  54                 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
  55         }
  56
  57         if (ctx->seen & SEEN_DATAREF) {
  58                 /*
  59                  * If this filter needs to access skb data,
  60                  * prepare r_D and r_HL:
  61                  *  r_HL = skb->len - skb->data_len
  62                  *  r_D  = skb->data
  63                  */
  64                 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
  65                                                          data_len));
  66                 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
  67                 PPC_SUB(r_HL, r_HL, r_scratch1);
  68                 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  69         }
  70
  71         if (ctx->seen & SEEN_XREG) {
  72                 /*
  73                  * TODO: Could also detect whether first instr. sets X and
  74                  * avoid this (as below, with A).
  75                  */
  76                 PPC_LI(r_X, 0);
  77         }
  78
  79         /* make sure we dont leak kernel information to user */
  80         if (bpf_needs_clear_a(&filter[0]))
  81                 PPC_LI(r_A, 0);
  82 }
  83
  84 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  85 {
  86         int i;
  87
  88         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  89                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
  90                 if (ctx->seen & SEEN_DATAREF) {
  91                         PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
  92                         PPC_MTLR(0);
  93                         PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
  94                         PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  95                 }
  96                 if (ctx->seen & SEEN_MEM) {
  97                         /* Restore any saved non-vol registers */
  98                         for (i = r_M; i < (r_M+16); i++) {
  99                                 if (ctx->seen & (1 << (i-r_M)))
 100                                         PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
 101                         }
 102                 }
 103         }
 104         /* The RETs have left a return value in R3. */
 105
 106         PPC_BLR();
 107 }
 108
 109 #define CHOOSE_LOAD_FUNC(K, func) \
 110         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 111
 112 /* Assemble the body code between the prologue & epilogue. */
 113 static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 114                               struct codegen_context *ctx,
 115                               unsigned int *addrs)
 116 {
 117         const struct sock_filter *filter = fp->insns;
 118         int flen = fp->len;
 119         u8 *func;
 120         unsigned int true_cond;
 121         int i;
 122
 123         /* Start of epilogue code */
 124         unsigned int exit_addr = addrs[flen];
 125
 126         for (i = 0; i < flen; i++) {
 127                 unsigned int K = filter[i].k;
 128                 u16 code = bpf_anc_helper(&filter[i]);
 129
 130                 /*
 131                  * addrs[] maps a BPF bytecode address into a real offset from
 132                  * the start of the body code.
 133                  */
 134                 addrs[i] = ctx->idx * 4;
 135
 136                 switch (code) {
 137                         /*** ALU ops ***/
 138                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 139                         ctx->seen |= SEEN_XREG;
 140                         PPC_ADD(r_A, r_A, r_X);
 141                         break;
 142                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 143                         if (!K)
 144                                 break;
 145                         PPC_ADDI(r_A, r_A, IMM_L(K));
 146                         if (K >= 32768)
 147                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 148                         break;
 149                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 150                         ctx->seen |= SEEN_XREG;
 151                         PPC_SUB(r_A, r_A, r_X);
 152                         break;
 153                 case BPF_ALU | BPF_SUB | 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_MUL | BPF_X: /* A *= X; */
 161                         ctx->seen |= SEEN_XREG;
 162                         PPC_MULW(r_A, r_A, r_X);
 163                         break;
 164                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 165                         if (K < 32768)
 166                                 PPC_MULI(r_A, r_A, K);
 167                         else {
 168                                 PPC_LI32(r_scratch1, K);
 169                                 PPC_MULW(r_A, r_A, r_scratch1);
 170                         }
 171                         break;
 172                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 173                 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
 174                         ctx->seen |= SEEN_XREG;
 175                         PPC_CMPWI(r_X, 0);
 176                         if (ctx->pc_ret0 != -1) {
 177                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 178                         } else {
 179                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 180                                 PPC_LI(r_ret, 0);
 181                                 PPC_JMP(exit_addr);
 182                         }
 183                         if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
 184                                 PPC_DIVWU(r_scratch1, r_A, r_X);
 185                                 PPC_MULW(r_scratch1, r_X, r_scratch1);
 186                                 PPC_SUB(r_A, r_A, r_scratch1);
 187                         } else {
 188                                 PPC_DIVWU(r_A, r_A, r_X);
 189                         }
 190                         break;
 191                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 192                         PPC_LI32(r_scratch2, K);
 193                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 194                         PPC_MULW(r_scratch1, r_scratch2, r_scratch1);
 195                         PPC_SUB(r_A, r_A, r_scratch1);
 196                         break;
 197                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 198                         if (K == 1)
 199                                 break;
 200                         PPC_LI32(r_scratch1, K);
 201                         PPC_DIVWU(r_A, r_A, r_scratch1);
 202                         break;
 203                 case BPF_ALU | BPF_AND | BPF_X:
 204                         ctx->seen |= SEEN_XREG;
 205                         PPC_AND(r_A, r_A, r_X);
 206                         break;
 207                 case BPF_ALU | BPF_AND | BPF_K:
 208                         if (!IMM_H(K))
 209                                 PPC_ANDI(r_A, r_A, K);
 210                         else {
 211                                 PPC_LI32(r_scratch1, K);
 212                                 PPC_AND(r_A, r_A, r_scratch1);
 213                         }
 214                         break;
 215                 case BPF_ALU | BPF_OR | BPF_X:
 216                         ctx->seen |= SEEN_XREG;
 217                         PPC_OR(r_A, r_A, r_X);
 218                         break;
 219                 case BPF_ALU | BPF_OR | BPF_K:
 220                         if (IMM_L(K))
 221                                 PPC_ORI(r_A, r_A, IMM_L(K));
 222                         if (K >= 65536)
 223                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 224                         break;
 225                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 226                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 227                         ctx->seen |= SEEN_XREG;
 228                         PPC_XOR(r_A, r_A, r_X);
 229                         break;
 230                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 231                         if (IMM_L(K))
 232                                 PPC_XORI(r_A, r_A, IMM_L(K));
 233                         if (K >= 65536)
 234                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 235                         break;
 236                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 237                         ctx->seen |= SEEN_XREG;
 238                         PPC_SLW(r_A, r_A, r_X);
 239                         break;
 240                 case BPF_ALU | BPF_LSH | BPF_K:
 241                         if (K == 0)
 242                                 break;
 243                         else
 244                                 PPC_SLWI(r_A, r_A, K);
 245                         break;
 246                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 247                         ctx->seen |= SEEN_XREG;
 248                         PPC_SRW(r_A, r_A, r_X);
 249                         break;
 250                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 251                         if (K == 0)
 252                                 break;
 253                         else
 254                                 PPC_SRWI(r_A, r_A, K);
 255                         break;
 256                 case BPF_ALU | BPF_NEG:
 257                         PPC_NEG(r_A, r_A);
 258                         break;
 259                 case BPF_RET | BPF_K:
 260                         PPC_LI32(r_ret, K);
 261                         if (!K) {
 262                                 if (ctx->pc_ret0 == -1)
 263                                         ctx->pc_ret0 = i;
 264                         }
 265                         /*
 266                          * If this isn't the very last instruction, branch to
 267                          * the epilogue if we've stuff to clean up.  Otherwise,
 268                          * if there's nothing to tidy, just return.  If we /are/
 269                          * the last instruction, we're about to fall through to
 270                          * the epilogue to return.
 271                          */
 272                         if (i != flen - 1) {
 273                                 /*
 274                                  * Note: 'seen' is properly valid only on pass
 275                                  * #2.  Both parts of this conditional are the
 276                                  * same instruction size though, meaning the
 277                                  * first pass will still correctly determine the
 278                                  * code size/addresses.
 279                                  */
 280                                 if (ctx->seen)
 281                                         PPC_JMP(exit_addr);
 282                                 else
 283                                         PPC_BLR();
 284                         }
 285                         break;
 286                 case BPF_RET | BPF_A:
 287                         PPC_MR(r_ret, r_A);
 288                         if (i != flen - 1) {
 289                                 if (ctx->seen)
 290                                         PPC_JMP(exit_addr);
 291                                 else
 292                                         PPC_BLR();
 293                         }
 294                         break;
 295                 case BPF_MISC | BPF_TAX: /* X = A */
 296                         PPC_MR(r_X, r_A);
 297                         break;
 298                 case BPF_MISC | BPF_TXA: /* A = X */
 299                         ctx->seen |= SEEN_XREG;
 300                         PPC_MR(r_A, r_X);
 301                         break;
 302
 303                         /*** Constant loads/M[] access ***/
 304                 case BPF_LD | BPF_IMM: /* A = K */
 305                         PPC_LI32(r_A, K);
 306                         break;
 307                 case BPF_LDX | BPF_IMM: /* X = K */
 308                         PPC_LI32(r_X, K);
 309                         break;
 310                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 311                         PPC_MR(r_A, r_M + (K & 0xf));
 312                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 313                         break;
 314                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 315                         PPC_MR(r_X, r_M + (K & 0xf));
 316                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 317                         break;
 318                 case BPF_ST: /* mem[K] = A */
 319                         PPC_MR(r_M + (K & 0xf), r_A);
 320                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 321                         break;
 322                 case BPF_STX: /* mem[K] = X */
 323                         PPC_MR(r_M + (K & 0xf), r_X);
 324                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 325                         break;
 326                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 327                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 328                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 329                         break;
 330                 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
 331                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 332                         break;
 333
 334                         /*** Ancillary info loads ***/
 335                 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
 336                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 337                                                   protocol) != 2);
 338                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 339                                                             protocol));
 340                         break;
 341                 case BPF_ANC | SKF_AD_IFINDEX:
 342                 case BPF_ANC | SKF_AD_HATYPE:
 343                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 344                                                 ifindex) != 4);
 345                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 346                                                 type) != 2);
 347                         PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 348                                                                 dev));
 349                         PPC_CMPDI(r_scratch1, 0);
 350                         if (ctx->pc_ret0 != -1) {
 351                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 352                         } else {
 353                                 /* Exit, returning 0; first pass hits here. */
 354                                 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
 355                                 PPC_LI(r_ret, 0);
 356                                 PPC_JMP(exit_addr);
 357                         }
 358                         if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
 359                                 PPC_LWZ_OFFS(r_A, r_scratch1,
 360                                      offsetof(struct net_device, ifindex));
 361                         } else {
 362                                 PPC_LHZ_OFFS(r_A, r_scratch1,
 363                                      offsetof(struct net_device, type));
 364                         }
 365
 366                         break;
 367                 case BPF_ANC | SKF_AD_MARK:
 368                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 369                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 370                                                           mark));
 371                         break;
 372                 case BPF_ANC | SKF_AD_RXHASH:
 373                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
 374                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 375                                                           hash));
 376                         break;
 377                 case BPF_ANC | SKF_AD_VLAN_TAG:
 378                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 379                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 380                         BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
 381
 382                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 383                                                           vlan_tci));
 384                         if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
 385                                 PPC_ANDI(r_A, r_A, ~VLAN_TAG_PRESENT);
 386                         } else {
 387                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 388                                 PPC_SRWI(r_A, r_A, 12);
 389                         }
 390                         break;
 391                 case BPF_ANC | SKF_AD_QUEUE:
 392                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 393                                                   queue_mapping) != 2);
 394                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 395                                                           queue_mapping));
 396                         break;
 397                 case BPF_ANC | SKF_AD_PKTTYPE:
 398                         PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
 399                         PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
 400                         PPC_SRWI(r_A, r_A, 5);
 401                         break;
 402                 case BPF_ANC | SKF_AD_CPU:
 403                         PPC_BPF_LOAD_CPU(r_A);
 404                         break;
 405                         /*** Absolute loads from packet header/data ***/
 406                 case BPF_LD | BPF_W | BPF_ABS:
 407                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 408                         goto common_load;
 409                 case BPF_LD | BPF_H | BPF_ABS:
 410                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 411                         goto common_load;
 412                 case BPF_LD | BPF_B | BPF_ABS:
 413                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 414                 common_load:
 415                         /* Load from [K]. */
 416                         ctx->seen |= SEEN_DATAREF;
 417                         PPC_FUNC_ADDR(r_scratch1, func);
 418                         PPC_MTLR(r_scratch1);
 419                         PPC_LI32(r_addr, K);
 420                         PPC_BLRL();
 421                         /*
 422                          * Helper returns 'lt' condition on error, and an
 423                          * appropriate return value in r3
 424                          */
 425                         PPC_BCC(COND_LT, exit_addr);
 426                         break;
 427
 428                         /*** Indirect loads from packet header/data ***/
 429                 case BPF_LD | BPF_W | BPF_IND:
 430                         func = sk_load_word;
 431                         goto common_load_ind;
 432                 case BPF_LD | BPF_H | BPF_IND:
 433                         func = sk_load_half;
 434                         goto common_load_ind;
 435                 case BPF_LD | BPF_B | BPF_IND:
 436                         func = sk_load_byte;
 437                 common_load_ind:
 438                         /*
 439                          * Load from [X + K].  Negative offsets are tested for
 440                          * in the helper functions.
 441                          */
 442                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 443                         PPC_FUNC_ADDR(r_scratch1, func);
 444                         PPC_MTLR(r_scratch1);
 445                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 446                         if (K >= 32768)
 447                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 448                         PPC_BLRL();
 449                         /* If error, cr0.LT set */
 450                         PPC_BCC(COND_LT, exit_addr);
 451                         break;
 452
 453                 case BPF_LDX | BPF_B | BPF_MSH:
 454                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 455                         goto common_load;
 456                         break;
 457
 458                         /*** Jump and branches ***/
 459                 case BPF_JMP | BPF_JA:
 460                         if (K != 0)
 461                                 PPC_JMP(addrs[i + 1 + K]);
 462                         break;
 463
 464                 case BPF_JMP | BPF_JGT | BPF_K:
 465                 case BPF_JMP | BPF_JGT | BPF_X:
 466                         true_cond = COND_GT;
 467                         goto cond_branch;
 468                 case BPF_JMP | BPF_JGE | BPF_K:
 469                 case BPF_JMP | BPF_JGE | BPF_X:
 470                         true_cond = COND_GE;
 471                         goto cond_branch;
 472                 case BPF_JMP | BPF_JEQ | BPF_K:
 473                 case BPF_JMP | BPF_JEQ | BPF_X:
 474                         true_cond = COND_EQ;
 475                         goto cond_branch;
 476                 case BPF_JMP | BPF_JSET | BPF_K:
 477                 case BPF_JMP | BPF_JSET | BPF_X:
 478                         true_cond = COND_NE;
 479                         /* Fall through */
 480                 cond_branch:
 481                         /* same targets, can avoid doing the test :) */
 482                         if (filter[i].jt == filter[i].jf) {
 483                                 if (filter[i].jt > 0)
 484                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 485                                 break;
 486                         }
 487
 488                         switch (code) {
 489                         case BPF_JMP | BPF_JGT | BPF_X:
 490                         case BPF_JMP | BPF_JGE | BPF_X:
 491                         case BPF_JMP | BPF_JEQ | BPF_X:
 492                                 ctx->seen |= SEEN_XREG;
 493                                 PPC_CMPLW(r_A, r_X);
 494                                 break;
 495                         case BPF_JMP | BPF_JSET | BPF_X:
 496                                 ctx->seen |= SEEN_XREG;
 497                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 498                                 break;
 499                         case BPF_JMP | BPF_JEQ | BPF_K:
 500                         case BPF_JMP | BPF_JGT | BPF_K:
 501                         case BPF_JMP | BPF_JGE | BPF_K:
 502                                 if (K < 32768)
 503                                         PPC_CMPLWI(r_A, K);
 504                                 else {
 505                                         PPC_LI32(r_scratch1, K);
 506                                         PPC_CMPLW(r_A, r_scratch1);
 507                                 }
 508                                 break;
 509                         case BPF_JMP | BPF_JSET | BPF_K:
 510                                 if (K < 32768)
 511                                         /* PPC_ANDI is /only/ dot-form */
 512                                         PPC_ANDI(r_scratch1, r_A, K);
 513                                 else {
 514                                         PPC_LI32(r_scratch1, K);
 515                                         PPC_AND_DOT(r_scratch1, r_A,
 516                                                     r_scratch1);
 517                                 }
 518                                 break;
 519                         }
 520                         /* Sometimes branches are constructed "backward", with
 521                          * the false path being the branch and true path being
 522                          * a fallthrough to the next instruction.
 523                          */
 524                         if (filter[i].jt == 0)
 525                                 /* Swap the sense of the branch */
 526                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 527                                         addrs[i + 1 + filter[i].jf]);
 528                         else {
 529                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 530                                 if (filter[i].jf != 0)
 531                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 532                         }
 533                         break;
 534                 default:
 535                         /* The filter contains something cruel & unusual.
 536                          * We don't handle it, but also there shouldn't be
 537                          * anything missing from our list.
 538                          */
 539                         if (printk_ratelimit())
 540                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 541                                        filter[i].code, i);
 542                         return -ENOTSUPP;
 543                 }
 544
 545         }
 546         /* Set end-of-body-code address for exit. */
 547         addrs[i] = ctx->idx * 4;
 548
 549         return 0;
 550 }
 551
 552 void bpf_jit_compile(struct bpf_prog *fp)
 553 {
 554         unsigned int proglen;
 555         unsigned int alloclen;
 556         u32 *image = NULL;
 557         u32 *code_base;
 558         unsigned int *addrs;
 559         struct codegen_context cgctx;
 560         int pass;
 561         int flen = fp->len;
 562
 563         if (!bpf_jit_enable)
 564                 return;
 565
 566         addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
 567         if (addrs == NULL)
 568                 return;
 569
 570         /*
 571          * There are multiple assembly passes as the generated code will change
 572          * size as it settles down, figuring out the max branch offsets/exit
 573          * paths required.
 574          *
 575          * The range of standard conditional branches is +/- 32Kbytes.  Since
 576          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 577          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 578          * used, distinct from short branches.
 579          *
 580          * Current:
 581          *
 582          * For now, both branch types assemble to 2 words (short branches padded
 583          * with a NOP); this is less efficient, but assembly will always complete
 584          * after exactly 3 passes:
 585          *
 586          * First pass: No code buffer; Program is "faux-generated" -- no code
 587          * emitted but maximum size of output determined (and addrs[] filled
 588          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 589          * All generation choices assumed to be 'worst-case', e.g. branches all
 590          * far (2 instructions), return path code reduction not available, etc.
 591          *
 592          * Second pass: Code buffer allocated with size determined previously.
 593          * Prologue generated to support features we have seen used.  Exit paths
 594          * determined and addrs[] is filled in again, as code may be slightly
 595          * smaller as a result.
 596          *
 597          * Third pass: Code generated 'for real', and branch destinations
 598          * determined from now-accurate addrs[] map.
 599          *
 600          * Ideal:
 601          *
 602          * If we optimise this, near branches will be shorter.  On the
 603          * first assembly pass, we should err on the side of caution and
 604          * generate the biggest code.  On subsequent passes, branches will be
 605          * generated short or long and code size will reduce.  With smaller
 606          * code, more branches may fall into the short category, and code will
 607          * reduce more.
 608          *
 609          * Finally, if we see one pass generate code the same size as the
 610          * previous pass we have converged and should now generate code for
 611          * real.  Allocating at the end will also save the memory that would
 612          * otherwise be wasted by the (small) current code shrinkage.
 613          * Preferably, we should do a small number of passes (e.g. 5) and if we
 614          * haven't converged by then, get impatient and force code to generate
 615          * as-is, even if the odd branch would be left long.  The chances of a
 616          * long jump are tiny with all but the most enormous of BPF filter
 617          * inputs, so we should usually converge on the third pass.
 618          */
 619
 620         cgctx.idx = 0;
 621         cgctx.seen = 0;
 622         cgctx.pc_ret0 = -1;
 623         /* Scouting faux-generate pass 0 */
 624         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 625                 /* We hit something illegal or unsupported. */
 626                 goto out;
 627
 628         /*
 629          * Pretend to build prologue, given the features we've seen.  This will
 630          * update ctgtx.idx as it pretends to output instructions, then we can
 631          * calculate total size from idx.
 632          */
 633         bpf_jit_build_prologue(fp, 0, &cgctx);
 634         bpf_jit_build_epilogue(0, &cgctx);
 635
 636         proglen = cgctx.idx * 4;
 637         alloclen = proglen + FUNCTION_DESCR_SIZE;
 638         image = module_alloc(alloclen);
 639         if (!image)
 640                 goto out;
 641
 642         code_base = image + (FUNCTION_DESCR_SIZE/4);
 643
 644         /* Code generation passes 1-2 */
 645         for (pass = 1; pass < 3; pass++) {
 646                 /* Now build the prologue, body code & epilogue for real. */
 647                 cgctx.idx = 0;
 648                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 649                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 650                 bpf_jit_build_epilogue(code_base, &cgctx);
 651
 652                 if (bpf_jit_enable > 1)
 653                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 654                                 proglen - (cgctx.idx * 4), cgctx.seen);
 655         }
 656
 657         if (bpf_jit_enable > 1)
 658                 /* Note that we output the base address of the code_base
 659                  * rather than image, since opcodes are in code_base.
 660                  */
 661                 bpf_jit_dump(flen, proglen, pass, code_base);
 662
 663         bpf_flush_icache(code_base, code_base + (proglen/4));
 664
 665 #ifdef CONFIG_PPC64
 666         /* Function descriptor nastiness: Address + TOC */
 667         ((u64 *)image)[0] = (u64)code_base;
 668         ((u64 *)image)[1] = local_paca->kernel_toc;
 669 #endif
 670
 671         fp->bpf_func = (void *)image;
 672         fp->jited = 1;
 673
 674 out:
 675         kfree(addrs);
 676         return;
 677 }
 678
 679 void bpf_jit_free(struct bpf_prog *fp)
 680 {
 681         if (fp->jited)
 682                 module_memfree(fp->bpf_func);
 683
 684         bpf_prog_unlock_free(fp);
 685 }