arch/powerpc/net/bpf_jit_comp.c

   1 /* bpf_jit_comp.c: BPF JIT compiler
   2  *
   3  * Copyright 2011 Matt Evans <[email protected]>, IBM Corporation
   4  *
   5  * Based on the x86 BPF compiler, by Eric Dumazet ([email protected])
   6  * Ported to ppc32 by Denis Kirjanov <[email protected]>
   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 <asm/asm-compat.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/filter.h>
  18 #include <linux/if_vlan.h>
  19
  20 #include "bpf_jit32.h"
  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 bpf_prog *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_BPF_STL(0, 1, PPC_LR_STKOFF);
  40
  41                         /* Back up non-volatile regs. */
  42                         PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
  43                         PPC_BPF_STL(r_HL, 1, -(REG_SZ*(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_BPF_STL(i, 1, -(REG_SZ*(32-i)));
  53                         }
  54                 }
  55                 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
  56         }
  57
  58         if (ctx->seen & SEEN_DATAREF) {
  59                 /*
  60                  * If this filter needs to access skb data,
  61                  * prepare r_D and r_HL:
  62                  *  r_HL = skb->len - skb->data_len
  63                  *  r_D  = skb->data
  64                  */
  65                 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
  66                                                          data_len));
  67                 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
  68                 PPC_SUB(r_HL, r_HL, r_scratch1);
  69                 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  70         }
  71
  72         if (ctx->seen & SEEN_XREG) {
  73                 /*
  74                  * TODO: Could also detect whether first instr. sets X and
  75                  * avoid this (as below, with A).
  76                  */
  77                 PPC_LI(r_X, 0);
  78         }
  79
  80         /* make sure we dont leak kernel information to user */
  81         if (bpf_needs_clear_a(&filter[0]))
  82                 PPC_LI(r_A, 0);
  83 }
  84
  85 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  86 {
  87         int i;
  88
  89         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  90                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
  91                 if (ctx->seen & SEEN_DATAREF) {
  92                         PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
  93                         PPC_MTLR(0);
  94                         PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
  95                         PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  96                 }
  97                 if (ctx->seen & SEEN_MEM) {
  98                         /* Restore any saved non-vol registers */
  99                         for (i = r_M; i < (r_M+16); i++) {
 100                                 if (ctx->seen & (1 << (i-r_M)))
 101                                         PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
 102                         }
 103                 }
 104         }
 105         /* The RETs have left a return value in R3. */
 106
 107         PPC_BLR();
 108 }
 109
 110 #define CHOOSE_LOAD_FUNC(K, func) \
 111         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 112
 113 /* Assemble the body code between the prologue & epilogue. */
 114 static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 115                               struct codegen_context *ctx,
 116                               unsigned int *addrs)
 117 {
 118         const struct sock_filter *filter = fp->insns;
 119         int flen = fp->len;
 120         u8 *func;
 121         unsigned int true_cond;
 122         int i;
 123
 124         /* Start of epilogue code */
 125         unsigned int exit_addr = addrs[flen];
 126
 127         for (i = 0; i < flen; i++) {
 128                 unsigned int K = filter[i].k;
 129                 u16 code = bpf_anc_helper(&filter[i]);
 130
 131                 /*
 132                  * addrs[] maps a BPF bytecode address into a real offset from
 133                  * the start of the body code.
 134                  */
 135                 addrs[i] = ctx->idx * 4;
 136
 137                 switch (code) {
 138                         /*** ALU ops ***/
 139                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 140                         ctx->seen |= SEEN_XREG;
 141                         PPC_ADD(r_A, r_A, r_X);
 142                         break;
 143                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 144                         if (!K)
 145                                 break;
 146                         PPC_ADDI(r_A, r_A, IMM_L(K));
 147                         if (K >= 32768)
 148                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 149                         break;
 150                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 151                         ctx->seen |= SEEN_XREG;
 152                         PPC_SUB(r_A, r_A, r_X);
 153                         break;
 154                 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
 155                         if (!K)
 156                                 break;
 157                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 158                         if (K >= 32768)
 159                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 160                         break;
 161                 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
 162                         ctx->seen |= SEEN_XREG;
 163                         PPC_MULW(r_A, r_A, r_X);
 164                         break;
 165                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 166                         if (K < 32768)
 167                                 PPC_MULI(r_A, r_A, K);
 168                         else {
 169                                 PPC_LI32(r_scratch1, K);
 170                                 PPC_MULW(r_A, r_A, r_scratch1);
 171                         }
 172                         break;
 173                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 174                 case BPF_ALU | BPF_DIV | 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                         if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
 185                                 PPC_DIVWU(r_scratch1, r_A, r_X);
 186                                 PPC_MULW(r_scratch1, r_X, r_scratch1);
 187                                 PPC_SUB(r_A, r_A, r_scratch1);
 188                         } else {
 189                                 PPC_DIVWU(r_A, r_A, r_X);
 190                         }
 191                         break;
 192                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 193                         PPC_LI32(r_scratch2, K);
 194                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 195                         PPC_MULW(r_scratch1, r_scratch2, r_scratch1);
 196                         PPC_SUB(r_A, r_A, r_scratch1);
 197                         break;
 198                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 199                         if (K == 1)
 200                                 break;
 201                         PPC_LI32(r_scratch1, K);
 202                         PPC_DIVWU(r_A, r_A, r_scratch1);
 203                         break;
 204                 case BPF_ALU | BPF_AND | BPF_X:
 205                         ctx->seen |= SEEN_XREG;
 206                         PPC_AND(r_A, r_A, r_X);
 207                         break;
 208                 case BPF_ALU | BPF_AND | BPF_K:
 209                         if (!IMM_H(K))
 210                                 PPC_ANDI(r_A, r_A, K);
 211                         else {
 212                                 PPC_LI32(r_scratch1, K);
 213                                 PPC_AND(r_A, r_A, r_scratch1);
 214                         }
 215                         break;
 216                 case BPF_ALU | BPF_OR | BPF_X:
 217                         ctx->seen |= SEEN_XREG;
 218                         PPC_OR(r_A, r_A, r_X);
 219                         break;
 220                 case BPF_ALU | BPF_OR | BPF_K:
 221                         if (IMM_L(K))
 222                                 PPC_ORI(r_A, r_A, IMM_L(K));
 223                         if (K >= 65536)
 224                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 225                         break;
 226                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 227                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 228                         ctx->seen |= SEEN_XREG;
 229                         PPC_XOR(r_A, r_A, r_X);
 230                         break;
 231                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 232                         if (IMM_L(K))
 233                                 PPC_XORI(r_A, r_A, IMM_L(K));
 234                         if (K >= 65536)
 235                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 236                         break;
 237                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 238                         ctx->seen |= SEEN_XREG;
 239                         PPC_SLW(r_A, r_A, r_X);
 240                         break;
 241                 case BPF_ALU | BPF_LSH | BPF_K:
 242                         if (K == 0)
 243                                 break;
 244                         else
 245                                 PPC_SLWI(r_A, r_A, K);
 246                         break;
 247                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 248                         ctx->seen |= SEEN_XREG;
 249                         PPC_SRW(r_A, r_A, r_X);
 250                         break;
 251                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 252                         if (K == 0)
 253                                 break;
 254                         else
 255                                 PPC_SRWI(r_A, r_A, K);
 256                         break;
 257                 case BPF_ALU | BPF_NEG:
 258                         PPC_NEG(r_A, r_A);
 259                         break;
 260                 case BPF_RET | BPF_K:
 261                         PPC_LI32(r_ret, K);
 262                         if (!K) {
 263                                 if (ctx->pc_ret0 == -1)
 264                                         ctx->pc_ret0 = i;
 265                         }
 266                         /*
 267                          * If this isn't the very last instruction, branch to
 268                          * the epilogue if we've stuff to clean up.  Otherwise,
 269                          * if there's nothing to tidy, just return.  If we /are/
 270                          * the last instruction, we're about to fall through to
 271                          * the epilogue to return.
 272                          */
 273                         if (i != flen - 1) {
 274                                 /*
 275                                  * Note: 'seen' is properly valid only on pass
 276                                  * #2.  Both parts of this conditional are the
 277                                  * same instruction size though, meaning the
 278                                  * first pass will still correctly determine the
 279                                  * code size/addresses.
 280                                  */
 281                                 if (ctx->seen)
 282                                         PPC_JMP(exit_addr);
 283                                 else
 284                                         PPC_BLR();
 285                         }
 286                         break;
 287                 case BPF_RET | BPF_A:
 288                         PPC_MR(r_ret, r_A);
 289                         if (i != flen - 1) {
 290                                 if (ctx->seen)
 291                                         PPC_JMP(exit_addr);
 292                                 else
 293                                         PPC_BLR();
 294                         }
 295                         break;
 296                 case BPF_MISC | BPF_TAX: /* X = A */
 297                         PPC_MR(r_X, r_A);
 298                         break;
 299                 case BPF_MISC | BPF_TXA: /* A = X */
 300                         ctx->seen |= SEEN_XREG;
 301                         PPC_MR(r_A, r_X);
 302                         break;
 303
 304                         /*** Constant loads/M[] access ***/
 305                 case BPF_LD | BPF_IMM: /* A = K */
 306                         PPC_LI32(r_A, K);
 307                         break;
 308                 case BPF_LDX | BPF_IMM: /* X = K */
 309                         PPC_LI32(r_X, K);
 310                         break;
 311                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 312                         PPC_MR(r_A, r_M + (K & 0xf));
 313                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 314                         break;
 315                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 316                         PPC_MR(r_X, r_M + (K & 0xf));
 317                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 318                         break;
 319                 case BPF_ST: /* mem[K] = A */
 320                         PPC_MR(r_M + (K & 0xf), r_A);
 321                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 322                         break;
 323                 case BPF_STX: /* mem[K] = X */
 324                         PPC_MR(r_M + (K & 0xf), r_X);
 325                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 326                         break;
 327                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 328                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 329                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 330                         break;
 331                 case BPF_LDX | BPF_W | BPF_ABS: /* A = *((u32 *)(seccomp_data + K)); */
 332                         PPC_LWZ_OFFS(r_A, r_skb, K);
 333                         break;
 334                 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
 335                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 336                         break;
 337
 338                         /*** Ancillary info loads ***/
 339                 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
 340                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 341                                                   protocol) != 2);
 342                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 343                                                             protocol));
 344                         break;
 345                 case BPF_ANC | SKF_AD_IFINDEX:
 346                 case BPF_ANC | SKF_AD_HATYPE:
 347                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 348                                                 ifindex) != 4);
 349                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 350                                                 type) != 2);
 351                         PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 352                                                                 dev));
 353                         PPC_CMPDI(r_scratch1, 0);
 354                         if (ctx->pc_ret0 != -1) {
 355                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 356                         } else {
 357                                 /* Exit, returning 0; first pass hits here. */
 358                                 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
 359                                 PPC_LI(r_ret, 0);
 360                                 PPC_JMP(exit_addr);
 361                         }
 362                         if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
 363                                 PPC_LWZ_OFFS(r_A, r_scratch1,
 364                                      offsetof(struct net_device, ifindex));
 365                         } else {
 366                                 PPC_LHZ_OFFS(r_A, r_scratch1,
 367                                      offsetof(struct net_device, type));
 368                         }
 369
 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                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 383
 384                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 385                                                           vlan_tci));
 386                         break;
 387                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 388                         PPC_LBZ_OFFS(r_A, r_skb, PKT_VLAN_PRESENT_OFFSET());
 389                         if (PKT_VLAN_PRESENT_BIT)
 390                                 PPC_SRWI(r_A, r_A, PKT_VLAN_PRESENT_BIT);
 391                         if (PKT_VLAN_PRESENT_BIT < 7)
 392                                 PPC_ANDI(r_A, r_A, 1);
 393                         break;
 394                 case BPF_ANC | SKF_AD_QUEUE:
 395                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 396                                                   queue_mapping) != 2);
 397                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 398                                                           queue_mapping));
 399                         break;
 400                 case BPF_ANC | SKF_AD_PKTTYPE:
 401                         PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
 402                         PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
 403                         PPC_SRWI(r_A, r_A, 5);
 404                         break;
 405                 case BPF_ANC | SKF_AD_CPU:
 406                         PPC_BPF_LOAD_CPU(r_A);
 407                         break;
 408                         /*** Absolute loads from packet header/data ***/
 409                 case BPF_LD | BPF_W | BPF_ABS:
 410                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 411                         goto common_load;
 412                 case BPF_LD | BPF_H | BPF_ABS:
 413                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 414                         goto common_load;
 415                 case BPF_LD | BPF_B | BPF_ABS:
 416                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 417                 common_load:
 418                         /* Load from [K]. */
 419                         ctx->seen |= SEEN_DATAREF;
 420                         PPC_FUNC_ADDR(r_scratch1, func);
 421                         PPC_MTLR(r_scratch1);
 422                         PPC_LI32(r_addr, K);
 423                         PPC_BLRL();
 424                         /*
 425                          * Helper returns 'lt' condition on error, and an
 426                          * appropriate return value in r3
 427                          */
 428                         PPC_BCC(COND_LT, exit_addr);
 429                         break;
 430
 431                         /*** Indirect loads from packet header/data ***/
 432                 case BPF_LD | BPF_W | BPF_IND:
 433                         func = sk_load_word;
 434                         goto common_load_ind;
 435                 case BPF_LD | BPF_H | BPF_IND:
 436                         func = sk_load_half;
 437                         goto common_load_ind;
 438                 case BPF_LD | BPF_B | BPF_IND:
 439                         func = sk_load_byte;
 440                 common_load_ind:
 441                         /*
 442                          * Load from [X + K].  Negative offsets are tested for
 443                          * in the helper functions.
 444                          */
 445                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 446                         PPC_FUNC_ADDR(r_scratch1, func);
 447                         PPC_MTLR(r_scratch1);
 448                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 449                         if (K >= 32768)
 450                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 451                         PPC_BLRL();
 452                         /* If error, cr0.LT set */
 453                         PPC_BCC(COND_LT, exit_addr);
 454                         break;
 455
 456                 case BPF_LDX | BPF_B | BPF_MSH:
 457                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 458                         goto common_load;
 459                         break;
 460
 461                         /*** Jump and branches ***/
 462                 case BPF_JMP | BPF_JA:
 463                         if (K != 0)
 464                                 PPC_JMP(addrs[i + 1 + K]);
 465                         break;
 466
 467                 case BPF_JMP | BPF_JGT | BPF_K:
 468                 case BPF_JMP | BPF_JGT | BPF_X:
 469                         true_cond = COND_GT;
 470                         goto cond_branch;
 471                 case BPF_JMP | BPF_JGE | BPF_K:
 472                 case BPF_JMP | BPF_JGE | BPF_X:
 473                         true_cond = COND_GE;
 474                         goto cond_branch;
 475                 case BPF_JMP | BPF_JEQ | BPF_K:
 476                 case BPF_JMP | BPF_JEQ | BPF_X:
 477                         true_cond = COND_EQ;
 478                         goto cond_branch;
 479                 case BPF_JMP | BPF_JSET | BPF_K:
 480                 case BPF_JMP | BPF_JSET | BPF_X:
 481                         true_cond = COND_NE;
 482                         /* Fall through */
 483                 cond_branch:
 484                         /* same targets, can avoid doing the test :) */
 485                         if (filter[i].jt == filter[i].jf) {
 486                                 if (filter[i].jt > 0)
 487                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 488                                 break;
 489                         }
 490
 491                         switch (code) {
 492                         case BPF_JMP | BPF_JGT | BPF_X:
 493                         case BPF_JMP | BPF_JGE | BPF_X:
 494                         case BPF_JMP | BPF_JEQ | BPF_X:
 495                                 ctx->seen |= SEEN_XREG;
 496                                 PPC_CMPLW(r_A, r_X);
 497                                 break;
 498                         case BPF_JMP | BPF_JSET | BPF_X:
 499                                 ctx->seen |= SEEN_XREG;
 500                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 501                                 break;
 502                         case BPF_JMP | BPF_JEQ | BPF_K:
 503                         case BPF_JMP | BPF_JGT | BPF_K:
 504                         case BPF_JMP | BPF_JGE | BPF_K:
 505                                 if (K < 32768)
 506                                         PPC_CMPLWI(r_A, K);
 507                                 else {
 508                                         PPC_LI32(r_scratch1, K);
 509                                         PPC_CMPLW(r_A, r_scratch1);
 510                                 }
 511                                 break;
 512                         case BPF_JMP | BPF_JSET | BPF_K:
 513                                 if (K < 32768)
 514                                         /* PPC_ANDI is /only/ dot-form */
 515                                         PPC_ANDI(r_scratch1, r_A, K);
 516                                 else {
 517                                         PPC_LI32(r_scratch1, K);
 518                                         PPC_AND_DOT(r_scratch1, r_A,
 519                                                     r_scratch1);
 520                                 }
 521                                 break;
 522                         }
 523                         /* Sometimes branches are constructed "backward", with
 524                          * the false path being the branch and true path being
 525                          * a fallthrough to the next instruction.
 526                          */
 527                         if (filter[i].jt == 0)
 528                                 /* Swap the sense of the branch */
 529                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 530                                         addrs[i + 1 + filter[i].jf]);
 531                         else {
 532                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 533                                 if (filter[i].jf != 0)
 534                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 535                         }
 536                         break;
 537                 default:
 538                         /* The filter contains something cruel & unusual.
 539                          * We don't handle it, but also there shouldn't be
 540                          * anything missing from our list.
 541                          */
 542                         if (printk_ratelimit())
 543                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 544                                        filter[i].code, i);
 545                         return -ENOTSUPP;
 546                 }
 547
 548         }
 549         /* Set end-of-body-code address for exit. */
 550         addrs[i] = ctx->idx * 4;
 551
 552         return 0;
 553 }
 554
 555 void bpf_jit_compile(struct bpf_prog *fp)
 556 {
 557         unsigned int proglen;
 558         unsigned int alloclen;
 559         u32 *image = NULL;
 560         u32 *code_base;
 561         unsigned int *addrs;
 562         struct codegen_context cgctx;
 563         int pass;
 564         int flen = fp->len;
 565
 566         if (!bpf_jit_enable)
 567                 return;
 568
 569         addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
 570         if (addrs == NULL)
 571                 return;
 572
 573         /*
 574          * There are multiple assembly passes as the generated code will change
 575          * size as it settles down, figuring out the max branch offsets/exit
 576          * paths required.
 577          *
 578          * The range of standard conditional branches is +/- 32Kbytes.  Since
 579          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 580          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 581          * used, distinct from short branches.
 582          *
 583          * Current:
 584          *
 585          * For now, both branch types assemble to 2 words (short branches padded
 586          * with a NOP); this is less efficient, but assembly will always complete
 587          * after exactly 3 passes:
 588          *
 589          * First pass: No code buffer; Program is "faux-generated" -- no code
 590          * emitted but maximum size of output determined (and addrs[] filled
 591          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 592          * All generation choices assumed to be 'worst-case', e.g. branches all
 593          * far (2 instructions), return path code reduction not available, etc.
 594          *
 595          * Second pass: Code buffer allocated with size determined previously.
 596          * Prologue generated to support features we have seen used.  Exit paths
 597          * determined and addrs[] is filled in again, as code may be slightly
 598          * smaller as a result.
 599          *
 600          * Third pass: Code generated 'for real', and branch destinations
 601          * determined from now-accurate addrs[] map.
 602          *
 603          * Ideal:
 604          *
 605          * If we optimise this, near branches will be shorter.  On the
 606          * first assembly pass, we should err on the side of caution and
 607          * generate the biggest code.  On subsequent passes, branches will be
 608          * generated short or long and code size will reduce.  With smaller
 609          * code, more branches may fall into the short category, and code will
 610          * reduce more.
 611          *
 612          * Finally, if we see one pass generate code the same size as the
 613          * previous pass we have converged and should now generate code for
 614          * real.  Allocating at the end will also save the memory that would
 615          * otherwise be wasted by the (small) current code shrinkage.
 616          * Preferably, we should do a small number of passes (e.g. 5) and if we
 617          * haven't converged by then, get impatient and force code to generate
 618          * as-is, even if the odd branch would be left long.  The chances of a
 619          * long jump are tiny with all but the most enormous of BPF filter
 620          * inputs, so we should usually converge on the third pass.
 621          */
 622
 623         cgctx.idx = 0;
 624         cgctx.seen = 0;
 625         cgctx.pc_ret0 = -1;
 626         /* Scouting faux-generate pass 0 */
 627         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 628                 /* We hit something illegal or unsupported. */
 629                 goto out;
 630
 631         /*
 632          * Pretend to build prologue, given the features we've seen.  This will
 633          * update ctgtx.idx as it pretends to output instructions, then we can
 634          * calculate total size from idx.
 635          */
 636         bpf_jit_build_prologue(fp, 0, &cgctx);
 637         bpf_jit_build_epilogue(0, &cgctx);
 638
 639         proglen = cgctx.idx * 4;
 640         alloclen = proglen + FUNCTION_DESCR_SIZE;
 641         image = module_alloc(alloclen);
 642         if (!image)
 643                 goto out;
 644
 645         code_base = image + (FUNCTION_DESCR_SIZE/4);
 646
 647         /* Code generation passes 1-2 */
 648         for (pass = 1; pass < 3; pass++) {
 649                 /* Now build the prologue, body code & epilogue for real. */
 650                 cgctx.idx = 0;
 651                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 652                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 653                 bpf_jit_build_epilogue(code_base, &cgctx);
 654
 655                 if (bpf_jit_enable > 1)
 656                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 657                                 proglen - (cgctx.idx * 4), cgctx.seen);
 658         }
 659
 660         if (bpf_jit_enable > 1)
 661                 /* Note that we output the base address of the code_base
 662                  * rather than image, since opcodes are in code_base.
 663                  */
 664                 bpf_jit_dump(flen, proglen, pass, code_base);
 665
 666         bpf_flush_icache(code_base, code_base + (proglen/4));
 667
 668 #ifdef CONFIG_PPC64
 669         /* Function descriptor nastiness: Address + TOC */
 670         ((u64 *)image)[0] = (u64)code_base;
 671         ((u64 *)image)[1] = local_paca->kernel_toc;
 672 #endif
 673
 674         fp->bpf_func = (void *)image;
 675         fp->jited = 1;
 676
 677 out:
 678         kfree(addrs);
 679         return;
 680 }
 681
 682 void bpf_jit_free(struct bpf_prog *fp)
 683 {
 684         if (fp->jited)
 685                 module_memfree(fp->bpf_func);
 686
 687         bpf_prog_unlock_free(fp);
 688 }