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 <linux/netdevice.h>
  16 #include <linux/filter.h>
  17 #include <linux/if_vlan.h>
  18
  19 #include "bpf_jit.h"
  20
  21 int bpf_jit_enable __read_mostly;
  22
  23 static inline void bpf_flush_icache(void *start, void *end)
  24 {
  25         smp_wmb();
  26         flush_icache_range((unsigned long)start, (unsigned long)end);
  27 }
  28
  29 static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image,
  30                                    struct codegen_context *ctx)
  31 {
  32         int i;
  33         const struct sock_filter *filter = fp->insns;
  34
  35         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  36                 /* Make stackframe */
  37                 if (ctx->seen & SEEN_DATAREF) {
  38                         /* If we call any helpers (for loads), save LR */
  39                         EMIT(PPC_INST_MFLR | __PPC_RT(R0));
  40                         PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
  41
  42                         /* Back up non-volatile regs. */
  43                         PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
  44                         PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  45                 }
  46                 if (ctx->seen & SEEN_MEM) {
  47                         /*
  48                          * Conditionally save regs r15-r31 as some will be used
  49                          * for M[] data.
  50                          */
  51                         for (i = r_M; i < (r_M+16); i++) {
  52                                 if (ctx->seen & (1 << (i-r_M)))
  53                                         PPC_BPF_STL(i, 1, -(REG_SZ*(32-i)));
  54                         }
  55                 }
  56                 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
  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_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  71         }
  72
  73         if (ctx->seen & SEEN_XREG) {
  74                 /*
  75                  * TODO: Could also detect whether first instr. sets X and
  76                  * avoid this (as below, with A).
  77                  */
  78                 PPC_LI(r_X, 0);
  79         }
  80
  81         switch (filter[0].code) {
  82         case BPF_RET | BPF_K:
  83         case BPF_LD | BPF_W | BPF_LEN:
  84         case BPF_LD | BPF_W | BPF_ABS:
  85         case BPF_LD | BPF_H | BPF_ABS:
  86         case BPF_LD | BPF_B | BPF_ABS:
  87                 /* first instruction sets A register (or is RET 'constant') */
  88                 break;
  89         default:
  90                 /* make sure we dont leak kernel information to user */
  91                 PPC_LI(r_A, 0);
  92         }
  93 }
  94
  95 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  96 {
  97         int i;
  98
  99         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
 100                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
 101                 if (ctx->seen & SEEN_DATAREF) {
 102                         PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
 103                         PPC_MTLR(0);
 104                         PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
 105                         PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
 106                 }
 107                 if (ctx->seen & SEEN_MEM) {
 108                         /* Restore any saved non-vol registers */
 109                         for (i = r_M; i < (r_M+16); i++) {
 110                                 if (ctx->seen & (1 << (i-r_M)))
 111                                         PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
 112                         }
 113                 }
 114         }
 115         /* The RETs have left a return value in R3. */
 116
 117         PPC_BLR();
 118 }
 119
 120 #define CHOOSE_LOAD_FUNC(K, func) \
 121         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 122
 123 /* Assemble the body code between the prologue & epilogue. */
 124 static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 125                               struct codegen_context *ctx,
 126                               unsigned int *addrs)
 127 {
 128         const struct sock_filter *filter = fp->insns;
 129         int flen = fp->len;
 130         u8 *func;
 131         unsigned int true_cond;
 132         int i;
 133
 134         /* Start of epilogue code */
 135         unsigned int exit_addr = addrs[flen];
 136
 137         for (i = 0; i < flen; i++) {
 138                 unsigned int K = filter[i].k;
 139                 u16 code = bpf_anc_helper(&filter[i]);
 140
 141                 /*
 142                  * addrs[] maps a BPF bytecode address into a real offset from
 143                  * the start of the body code.
 144                  */
 145                 addrs[i] = ctx->idx * 4;
 146
 147                 switch (code) {
 148                         /*** ALU ops ***/
 149                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 150                         ctx->seen |= SEEN_XREG;
 151                         PPC_ADD(r_A, r_A, r_X);
 152                         break;
 153                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 154                         if (!K)
 155                                 break;
 156                         PPC_ADDI(r_A, r_A, IMM_L(K));
 157                         if (K >= 32768)
 158                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 159                         break;
 160                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 161                         ctx->seen |= SEEN_XREG;
 162                         PPC_SUB(r_A, r_A, r_X);
 163                         break;
 164                 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
 165                         if (!K)
 166                                 break;
 167                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 168                         if (K >= 32768)
 169                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 170                         break;
 171                 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
 172                         ctx->seen |= SEEN_XREG;
 173                         PPC_MUL(r_A, r_A, r_X);
 174                         break;
 175                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 176                         if (K < 32768)
 177                                 PPC_MULI(r_A, r_A, K);
 178                         else {
 179                                 PPC_LI32(r_scratch1, K);
 180                                 PPC_MUL(r_A, r_A, r_scratch1);
 181                         }
 182                         break;
 183                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 184                 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
 185                         ctx->seen |= SEEN_XREG;
 186                         PPC_CMPWI(r_X, 0);
 187                         if (ctx->pc_ret0 != -1) {
 188                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 189                         } else {
 190                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 191                                 PPC_LI(r_ret, 0);
 192                                 PPC_JMP(exit_addr);
 193                         }
 194                         if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
 195                                 PPC_DIVWU(r_scratch1, r_A, r_X);
 196                                 PPC_MUL(r_scratch1, r_X, r_scratch1);
 197                                 PPC_SUB(r_A, r_A, r_scratch1);
 198                         } else {
 199                                 PPC_DIVWU(r_A, r_A, r_X);
 200                         }
 201                         break;
 202                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 203                         PPC_LI32(r_scratch2, K);
 204                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 205                         PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
 206                         PPC_SUB(r_A, r_A, r_scratch1);
 207                         break;
 208                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 209                         if (K == 1)
 210                                 break;
 211                         PPC_LI32(r_scratch1, K);
 212                         PPC_DIVWU(r_A, r_A, r_scratch1);
 213                         break;
 214                 case BPF_ALU | BPF_AND | BPF_X:
 215                         ctx->seen |= SEEN_XREG;
 216                         PPC_AND(r_A, r_A, r_X);
 217                         break;
 218                 case BPF_ALU | BPF_AND | BPF_K:
 219                         if (!IMM_H(K))
 220                                 PPC_ANDI(r_A, r_A, K);
 221                         else {
 222                                 PPC_LI32(r_scratch1, K);
 223                                 PPC_AND(r_A, r_A, r_scratch1);
 224                         }
 225                         break;
 226                 case BPF_ALU | BPF_OR | BPF_X:
 227                         ctx->seen |= SEEN_XREG;
 228                         PPC_OR(r_A, r_A, r_X);
 229                         break;
 230                 case BPF_ALU | BPF_OR | BPF_K:
 231                         if (IMM_L(K))
 232                                 PPC_ORI(r_A, r_A, IMM_L(K));
 233                         if (K >= 65536)
 234                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 235                         break;
 236                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 237                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 238                         ctx->seen |= SEEN_XREG;
 239                         PPC_XOR(r_A, r_A, r_X);
 240                         break;
 241                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 242                         if (IMM_L(K))
 243                                 PPC_XORI(r_A, r_A, IMM_L(K));
 244                         if (K >= 65536)
 245                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 246                         break;
 247                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 248                         ctx->seen |= SEEN_XREG;
 249                         PPC_SLW(r_A, r_A, r_X);
 250                         break;
 251                 case BPF_ALU | BPF_LSH | BPF_K:
 252                         if (K == 0)
 253                                 break;
 254                         else
 255                                 PPC_SLWI(r_A, r_A, K);
 256                         break;
 257                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 258                         ctx->seen |= SEEN_XREG;
 259                         PPC_SRW(r_A, r_A, r_X);
 260                         break;
 261                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 262                         if (K == 0)
 263                                 break;
 264                         else
 265                                 PPC_SRWI(r_A, r_A, K);
 266                         break;
 267                 case BPF_ALU | BPF_NEG:
 268                         PPC_NEG(r_A, r_A);
 269                         break;
 270                 case BPF_RET | BPF_K:
 271                         PPC_LI32(r_ret, K);
 272                         if (!K) {
 273                                 if (ctx->pc_ret0 == -1)
 274                                         ctx->pc_ret0 = i;
 275                         }
 276                         /*
 277                          * If this isn't the very last instruction, branch to
 278                          * the epilogue if we've stuff to clean up.  Otherwise,
 279                          * if there's nothing to tidy, just return.  If we /are/
 280                          * the last instruction, we're about to fall through to
 281                          * the epilogue to return.
 282                          */
 283                         if (i != flen - 1) {
 284                                 /*
 285                                  * Note: 'seen' is properly valid only on pass
 286                                  * #2.  Both parts of this conditional are the
 287                                  * same instruction size though, meaning the
 288                                  * first pass will still correctly determine the
 289                                  * code size/addresses.
 290                                  */
 291                                 if (ctx->seen)
 292                                         PPC_JMP(exit_addr);
 293                                 else
 294                                         PPC_BLR();
 295                         }
 296                         break;
 297                 case BPF_RET | BPF_A:
 298                         PPC_MR(r_ret, r_A);
 299                         if (i != flen - 1) {
 300                                 if (ctx->seen)
 301                                         PPC_JMP(exit_addr);
 302                                 else
 303                                         PPC_BLR();
 304                         }
 305                         break;
 306                 case BPF_MISC | BPF_TAX: /* X = A */
 307                         PPC_MR(r_X, r_A);
 308                         break;
 309                 case BPF_MISC | BPF_TXA: /* A = X */
 310                         ctx->seen |= SEEN_XREG;
 311                         PPC_MR(r_A, r_X);
 312                         break;
 313
 314                         /*** Constant loads/M[] access ***/
 315                 case BPF_LD | BPF_IMM: /* A = K */
 316                         PPC_LI32(r_A, K);
 317                         break;
 318                 case BPF_LDX | BPF_IMM: /* X = K */
 319                         PPC_LI32(r_X, K);
 320                         break;
 321                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 322                         PPC_MR(r_A, r_M + (K & 0xf));
 323                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 324                         break;
 325                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 326                         PPC_MR(r_X, r_M + (K & 0xf));
 327                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 328                         break;
 329                 case BPF_ST: /* mem[K] = A */
 330                         PPC_MR(r_M + (K & 0xf), r_A);
 331                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 332                         break;
 333                 case BPF_STX: /* mem[K] = X */
 334                         PPC_MR(r_M + (K & 0xf), r_X);
 335                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 336                         break;
 337                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 338                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 339                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 340                         break;
 341                 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
 342                         PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
 343                         break;
 344
 345                         /*** Ancillary info loads ***/
 346                 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
 347                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 348                                                   protocol) != 2);
 349                         PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 350                                                             protocol));
 351                         break;
 352                 case BPF_ANC | SKF_AD_IFINDEX:
 353                 case BPF_ANC | SKF_AD_HATYPE:
 354                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 355                                                 ifindex) != 4);
 356                         BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
 357                                                 type) != 2);
 358                         PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
 359                                                                 dev));
 360                         PPC_CMPDI(r_scratch1, 0);
 361                         if (ctx->pc_ret0 != -1) {
 362                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 363                         } else {
 364                                 /* Exit, returning 0; first pass hits here. */
 365                                 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
 366                                 PPC_LI(r_ret, 0);
 367                                 PPC_JMP(exit_addr);
 368                         }
 369                         if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
 370                                 PPC_LWZ_OFFS(r_A, r_scratch1,
 371                                      offsetof(struct net_device, ifindex));
 372                         } else {
 373                                 PPC_LHZ_OFFS(r_A, r_scratch1,
 374                                      offsetof(struct net_device, type));
 375                         }
 376
 377                         break;
 378                 case BPF_ANC | SKF_AD_MARK:
 379                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 380                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 381                                                           mark));
 382                         break;
 383                 case BPF_ANC | SKF_AD_RXHASH:
 384                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
 385                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 386                                                           hash));
 387                         break;
 388                 case BPF_ANC | SKF_AD_VLAN_TAG:
 389                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 390                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 391                         BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
 392
 393                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 394                                                           vlan_tci));
 395                         if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
 396                                 PPC_ANDI(r_A, r_A, ~VLAN_TAG_PRESENT);
 397                         } else {
 398                                 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
 399                                 PPC_SRWI(r_A, r_A, 12);
 400                         }
 401                         break;
 402                 case BPF_ANC | SKF_AD_QUEUE:
 403                         BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 404                                                   queue_mapping) != 2);
 405                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 406                                                           queue_mapping));
 407                         break;
 408                 case BPF_ANC | SKF_AD_PKTTYPE:
 409                         PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
 410                         PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
 411                         PPC_SRWI(r_A, r_A, 5);
 412                         break;
 413                 case BPF_ANC | SKF_AD_CPU:
 414                         PPC_BPF_LOAD_CPU(r_A);
 415                         break;
 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_FUNC_ADDR(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_FUNC_ADDR(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 bpf_prog *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 #ifdef CONFIG_PPC64
 677                 /* Function descriptor nastiness: Address + TOC */
 678                 ((u64 *)image)[0] = (u64)code_base;
 679                 ((u64 *)image)[1] = local_paca->kernel_toc;
 680 #endif
 681                 fp->bpf_func = (void *)image;
 682                 fp->jited = true;
 683         }
 684 out:
 685         kfree(addrs);
 686         return;
 687 }
 688
 689 void bpf_jit_free(struct bpf_prog *fp)
 690 {
 691         if (fp->jited)
 692                 module_memfree(fp->bpf_func);
 693
 694         bpf_prog_unlock_free(fp);
 695 }