arch/powerpc/net/bpf_jit_comp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* bpf_jit_comp.c: BPF JIT compiler
   3  *
   4  * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
   5  *
   6  * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
   7  * Ported to ppc32 by Denis Kirjanov <kda@linux-powerpc.org>
   8  */
   9 #include <linux/moduleloader.h>
  10 #include <asm/cacheflush.h>
  11 #include <asm/asm-compat.h>
  12 #include <linux/netdevice.h>
  13 #include <linux/filter.h>
  14 #include <linux/if_vlan.h>
  15
  16 #include "bpf_jit32.h"
  17
  18 static inline void bpf_flush_icache(void *start, void *end)
  19 {
  20         smp_wmb();
  21         flush_icache_range((unsigned long)start, (unsigned long)end);
  22 }
  23
  24 static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image,
  25                                    struct codegen_context *ctx)
  26 {
  27         int i;
  28         const struct sock_filter *filter = fp->insns;
  29
  30         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  31                 /* Make stackframe */
  32                 if (ctx->seen & SEEN_DATAREF) {
  33                         /* If we call any helpers (for loads), save LR */
  34                         EMIT(PPC_INST_MFLR | __PPC_RT(R0));
  35                         PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
  36
  37                         /* Back up non-volatile regs. */
  38                         PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
  39                         PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  40                 }
  41                 if (ctx->seen & SEEN_MEM) {
  42                         /*
  43                          * Conditionally save regs r15-r31 as some will be used
  44                          * for M[] data.
  45                          */
  46                         for (i = r_M; i < (r_M+16); i++) {
  47                                 if (ctx->seen & (1 << (i-r_M)))
  48                                         PPC_BPF_STL(i, 1, -(REG_SZ*(32-i)));
  49                         }
  50                 }
  51                 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
  52         }
  53
  54         if (ctx->seen & SEEN_DATAREF) {
  55                 /*
  56                  * If this filter needs to access skb data,
  57                  * prepare r_D and r_HL:
  58                  *  r_HL = skb->len - skb->data_len
  59                  *  r_D  = skb->data
  60                  */
  61                 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
  62                                                          data_len));
  63                 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
  64                 PPC_SUB(r_HL, r_HL, r_scratch1);
  65                 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
  66         }
  67
  68         if (ctx->seen & SEEN_XREG) {
  69                 /*
  70                  * TODO: Could also detect whether first instr. sets X and
  71                  * avoid this (as below, with A).
  72                  */
  73                 PPC_LI(r_X, 0);
  74         }
  75
  76         /* make sure we dont leak kernel information to user */
  77         if (bpf_needs_clear_a(&filter[0]))
  78                 PPC_LI(r_A, 0);
  79 }
  80
  81 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
  82 {
  83         int i;
  84
  85         if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
  86                 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
  87                 if (ctx->seen & SEEN_DATAREF) {
  88                         PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
  89                         PPC_MTLR(0);
  90                         PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
  91                         PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
  92                 }
  93                 if (ctx->seen & SEEN_MEM) {
  94                         /* Restore any saved non-vol registers */
  95                         for (i = r_M; i < (r_M+16); i++) {
  96                                 if (ctx->seen & (1 << (i-r_M)))
  97                                         PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
  98                         }
  99                 }
 100         }
 101         /* The RETs have left a return value in R3. */
 102
 103         PPC_BLR();
 104 }
 105
 106 #define CHOOSE_LOAD_FUNC(K, func) \
 107         ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 108
 109 /* Assemble the body code between the prologue & epilogue. */
 110 static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 111                               struct codegen_context *ctx,
 112                               unsigned int *addrs)
 113 {
 114         const struct sock_filter *filter = fp->insns;
 115         int flen = fp->len;
 116         u8 *func;
 117         unsigned int true_cond;
 118         int i;
 119
 120         /* Start of epilogue code */
 121         unsigned int exit_addr = addrs[flen];
 122
 123         for (i = 0; i < flen; i++) {
 124                 unsigned int K = filter[i].k;
 125                 u16 code = bpf_anc_helper(&filter[i]);
 126
 127                 /*
 128                  * addrs[] maps a BPF bytecode address into a real offset from
 129                  * the start of the body code.
 130                  */
 131                 addrs[i] = ctx->idx * 4;
 132
 133                 switch (code) {
 134                         /*** ALU ops ***/
 135                 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
 136                         ctx->seen |= SEEN_XREG;
 137                         PPC_ADD(r_A, r_A, r_X);
 138                         break;
 139                 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
 140                         if (!K)
 141                                 break;
 142                         PPC_ADDI(r_A, r_A, IMM_L(K));
 143                         if (K >= 32768)
 144                                 PPC_ADDIS(r_A, r_A, IMM_HA(K));
 145                         break;
 146                 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
 147                         ctx->seen |= SEEN_XREG;
 148                         PPC_SUB(r_A, r_A, r_X);
 149                         break;
 150                 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
 151                         if (!K)
 152                                 break;
 153                         PPC_ADDI(r_A, r_A, IMM_L(-K));
 154                         if (K >= 32768)
 155                                 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
 156                         break;
 157                 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
 158                         ctx->seen |= SEEN_XREG;
 159                         PPC_MULW(r_A, r_A, r_X);
 160                         break;
 161                 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
 162                         if (K < 32768)
 163                                 PPC_MULI(r_A, r_A, K);
 164                         else {
 165                                 PPC_LI32(r_scratch1, K);
 166                                 PPC_MULW(r_A, r_A, r_scratch1);
 167                         }
 168                         break;
 169                 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
 170                 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
 171                         ctx->seen |= SEEN_XREG;
 172                         PPC_CMPWI(r_X, 0);
 173                         if (ctx->pc_ret0 != -1) {
 174                                 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
 175                         } else {
 176                                 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
 177                                 PPC_LI(r_ret, 0);
 178                                 PPC_JMP(exit_addr);
 179                         }
 180                         if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
 181                                 PPC_DIVWU(r_scratch1, r_A, r_X);
 182                                 PPC_MULW(r_scratch1, r_X, r_scratch1);
 183                                 PPC_SUB(r_A, r_A, r_scratch1);
 184                         } else {
 185                                 PPC_DIVWU(r_A, r_A, r_X);
 186                         }
 187                         break;
 188                 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
 189                         PPC_LI32(r_scratch2, K);
 190                         PPC_DIVWU(r_scratch1, r_A, r_scratch2);
 191                         PPC_MULW(r_scratch1, r_scratch2, r_scratch1);
 192                         PPC_SUB(r_A, r_A, r_scratch1);
 193                         break;
 194                 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
 195                         if (K == 1)
 196                                 break;
 197                         PPC_LI32(r_scratch1, K);
 198                         PPC_DIVWU(r_A, r_A, r_scratch1);
 199                         break;
 200                 case BPF_ALU | BPF_AND | BPF_X:
 201                         ctx->seen |= SEEN_XREG;
 202                         PPC_AND(r_A, r_A, r_X);
 203                         break;
 204                 case BPF_ALU | BPF_AND | BPF_K:
 205                         if (!IMM_H(K))
 206                                 PPC_ANDI(r_A, r_A, K);
 207                         else {
 208                                 PPC_LI32(r_scratch1, K);
 209                                 PPC_AND(r_A, r_A, r_scratch1);
 210                         }
 211                         break;
 212                 case BPF_ALU | BPF_OR | BPF_X:
 213                         ctx->seen |= SEEN_XREG;
 214                         PPC_OR(r_A, r_A, r_X);
 215                         break;
 216                 case BPF_ALU | BPF_OR | BPF_K:
 217                         if (IMM_L(K))
 218                                 PPC_ORI(r_A, r_A, IMM_L(K));
 219                         if (K >= 65536)
 220                                 PPC_ORIS(r_A, r_A, IMM_H(K));
 221                         break;
 222                 case BPF_ANC | SKF_AD_ALU_XOR_X:
 223                 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
 224                         ctx->seen |= SEEN_XREG;
 225                         PPC_XOR(r_A, r_A, r_X);
 226                         break;
 227                 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
 228                         if (IMM_L(K))
 229                                 PPC_XORI(r_A, r_A, IMM_L(K));
 230                         if (K >= 65536)
 231                                 PPC_XORIS(r_A, r_A, IMM_H(K));
 232                         break;
 233                 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
 234                         ctx->seen |= SEEN_XREG;
 235                         PPC_SLW(r_A, r_A, r_X);
 236                         break;
 237                 case BPF_ALU | BPF_LSH | BPF_K:
 238                         if (K == 0)
 239                                 break;
 240                         else
 241                                 PPC_SLWI(r_A, r_A, K);
 242                         break;
 243                 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
 244                         ctx->seen |= SEEN_XREG;
 245                         PPC_SRW(r_A, r_A, r_X);
 246                         break;
 247                 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
 248                         if (K == 0)
 249                                 break;
 250                         else
 251                                 PPC_SRWI(r_A, r_A, K);
 252                         break;
 253                 case BPF_ALU | BPF_NEG:
 254                         PPC_NEG(r_A, r_A);
 255                         break;
 256                 case BPF_RET | BPF_K:
 257                         PPC_LI32(r_ret, K);
 258                         if (!K) {
 259                                 if (ctx->pc_ret0 == -1)
 260                                         ctx->pc_ret0 = i;
 261                         }
 262                         /*
 263                          * If this isn't the very last instruction, branch to
 264                          * the epilogue if we've stuff to clean up.  Otherwise,
 265                          * if there's nothing to tidy, just return.  If we /are/
 266                          * the last instruction, we're about to fall through to
 267                          * the epilogue to return.
 268                          */
 269                         if (i != flen - 1) {
 270                                 /*
 271                                  * Note: 'seen' is properly valid only on pass
 272                                  * #2.  Both parts of this conditional are the
 273                                  * same instruction size though, meaning the
 274                                  * first pass will still correctly determine the
 275                                  * code size/addresses.
 276                                  */
 277                                 if (ctx->seen)
 278                                         PPC_JMP(exit_addr);
 279                                 else
 280                                         PPC_BLR();
 281                         }
 282                         break;
 283                 case BPF_RET | BPF_A:
 284                         PPC_MR(r_ret, r_A);
 285                         if (i != flen - 1) {
 286                                 if (ctx->seen)
 287                                         PPC_JMP(exit_addr);
 288                                 else
 289                                         PPC_BLR();
 290                         }
 291                         break;
 292                 case BPF_MISC | BPF_TAX: /* X = A */
 293                         PPC_MR(r_X, r_A);
 294                         break;
 295                 case BPF_MISC | BPF_TXA: /* A = X */
 296                         ctx->seen |= SEEN_XREG;
 297                         PPC_MR(r_A, r_X);
 298                         break;
 299
 300                         /*** Constant loads/M[] access ***/
 301                 case BPF_LD | BPF_IMM: /* A = K */
 302                         PPC_LI32(r_A, K);
 303                         break;
 304                 case BPF_LDX | BPF_IMM: /* X = K */
 305                         PPC_LI32(r_X, K);
 306                         break;
 307                 case BPF_LD | BPF_MEM: /* A = mem[K] */
 308                         PPC_MR(r_A, r_M + (K & 0xf));
 309                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 310                         break;
 311                 case BPF_LDX | BPF_MEM: /* X = mem[K] */
 312                         PPC_MR(r_X, r_M + (K & 0xf));
 313                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 314                         break;
 315                 case BPF_ST: /* mem[K] = A */
 316                         PPC_MR(r_M + (K & 0xf), r_A);
 317                         ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
 318                         break;
 319                 case BPF_STX: /* mem[K] = X */
 320                         PPC_MR(r_M + (K & 0xf), r_X);
 321                         ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
 322                         break;
 323                 case BPF_LD | BPF_W | BPF_LEN: /*       A = skb->len; */
 324                         BUILD_BUG_ON(sizeof_field(struct sk_buff, len) != 4);
 325                         PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
 326                         break;
 327                 case BPF_LDX | BPF_W | BPF_ABS: /* A = *((u32 *)(seccomp_data + K)); */
 328                         PPC_LWZ_OFFS(r_A, r_skb, K);
 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(sizeof_field(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(sizeof_field(struct net_device,
 344                                                 ifindex) != 4);
 345                         BUILD_BUG_ON(sizeof_field(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(sizeof_field(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(sizeof_field(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                         BUILD_BUG_ON(sizeof_field(struct sk_buff, vlan_tci) != 2);
 379
 380                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 381                                                           vlan_tci));
 382                         break;
 383                 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
 384                         PPC_LBZ_OFFS(r_A, r_skb, PKT_VLAN_PRESENT_OFFSET());
 385                         if (PKT_VLAN_PRESENT_BIT)
 386                                 PPC_SRWI(r_A, r_A, PKT_VLAN_PRESENT_BIT);
 387                         if (PKT_VLAN_PRESENT_BIT < 7)
 388                                 PPC_ANDI(r_A, r_A, 1);
 389                         break;
 390                 case BPF_ANC | SKF_AD_QUEUE:
 391                         BUILD_BUG_ON(sizeof_field(struct sk_buff,
 392                                                   queue_mapping) != 2);
 393                         PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
 394                                                           queue_mapping));
 395                         break;
 396                 case BPF_ANC | SKF_AD_PKTTYPE:
 397                         PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
 398                         PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
 399                         PPC_SRWI(r_A, r_A, 5);
 400                         break;
 401                 case BPF_ANC | SKF_AD_CPU:
 402                         PPC_BPF_LOAD_CPU(r_A);
 403                         break;
 404                         /*** Absolute loads from packet header/data ***/
 405                 case BPF_LD | BPF_W | BPF_ABS:
 406                         func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 407                         goto common_load;
 408                 case BPF_LD | BPF_H | BPF_ABS:
 409                         func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 410                         goto common_load;
 411                 case BPF_LD | BPF_B | BPF_ABS:
 412                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 413                 common_load:
 414                         /* Load from [K]. */
 415                         ctx->seen |= SEEN_DATAREF;
 416                         PPC_FUNC_ADDR(r_scratch1, func);
 417                         PPC_MTLR(r_scratch1);
 418                         PPC_LI32(r_addr, K);
 419                         PPC_BLRL();
 420                         /*
 421                          * Helper returns 'lt' condition on error, and an
 422                          * appropriate return value in r3
 423                          */
 424                         PPC_BCC(COND_LT, exit_addr);
 425                         break;
 426
 427                         /*** Indirect loads from packet header/data ***/
 428                 case BPF_LD | BPF_W | BPF_IND:
 429                         func = sk_load_word;
 430                         goto common_load_ind;
 431                 case BPF_LD | BPF_H | BPF_IND:
 432                         func = sk_load_half;
 433                         goto common_load_ind;
 434                 case BPF_LD | BPF_B | BPF_IND:
 435                         func = sk_load_byte;
 436                 common_load_ind:
 437                         /*
 438                          * Load from [X + K].  Negative offsets are tested for
 439                          * in the helper functions.
 440                          */
 441                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
 442                         PPC_FUNC_ADDR(r_scratch1, func);
 443                         PPC_MTLR(r_scratch1);
 444                         PPC_ADDI(r_addr, r_X, IMM_L(K));
 445                         if (K >= 32768)
 446                                 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
 447                         PPC_BLRL();
 448                         /* If error, cr0.LT set */
 449                         PPC_BCC(COND_LT, exit_addr);
 450                         break;
 451
 452                 case BPF_LDX | BPF_B | BPF_MSH:
 453                         func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 454                         goto common_load;
 455                         break;
 456
 457                         /*** Jump and branches ***/
 458                 case BPF_JMP | BPF_JA:
 459                         if (K != 0)
 460                                 PPC_JMP(addrs[i + 1 + K]);
 461                         break;
 462
 463                 case BPF_JMP | BPF_JGT | BPF_K:
 464                 case BPF_JMP | BPF_JGT | BPF_X:
 465                         true_cond = COND_GT;
 466                         goto cond_branch;
 467                 case BPF_JMP | BPF_JGE | BPF_K:
 468                 case BPF_JMP | BPF_JGE | BPF_X:
 469                         true_cond = COND_GE;
 470                         goto cond_branch;
 471                 case BPF_JMP | BPF_JEQ | BPF_K:
 472                 case BPF_JMP | BPF_JEQ | BPF_X:
 473                         true_cond = COND_EQ;
 474                         goto cond_branch;
 475                 case BPF_JMP | BPF_JSET | BPF_K:
 476                 case BPF_JMP | BPF_JSET | BPF_X:
 477                         true_cond = COND_NE;
 478                         /* Fall through */
 479                 cond_branch:
 480                         /* same targets, can avoid doing the test :) */
 481                         if (filter[i].jt == filter[i].jf) {
 482                                 if (filter[i].jt > 0)
 483                                         PPC_JMP(addrs[i + 1 + filter[i].jt]);
 484                                 break;
 485                         }
 486
 487                         switch (code) {
 488                         case BPF_JMP | BPF_JGT | BPF_X:
 489                         case BPF_JMP | BPF_JGE | BPF_X:
 490                         case BPF_JMP | BPF_JEQ | BPF_X:
 491                                 ctx->seen |= SEEN_XREG;
 492                                 PPC_CMPLW(r_A, r_X);
 493                                 break;
 494                         case BPF_JMP | BPF_JSET | BPF_X:
 495                                 ctx->seen |= SEEN_XREG;
 496                                 PPC_AND_DOT(r_scratch1, r_A, r_X);
 497                                 break;
 498                         case BPF_JMP | BPF_JEQ | BPF_K:
 499                         case BPF_JMP | BPF_JGT | BPF_K:
 500                         case BPF_JMP | BPF_JGE | BPF_K:
 501                                 if (K < 32768)
 502                                         PPC_CMPLWI(r_A, K);
 503                                 else {
 504                                         PPC_LI32(r_scratch1, K);
 505                                         PPC_CMPLW(r_A, r_scratch1);
 506                                 }
 507                                 break;
 508                         case BPF_JMP | BPF_JSET | BPF_K:
 509                                 if (K < 32768)
 510                                         /* PPC_ANDI is /only/ dot-form */
 511                                         PPC_ANDI(r_scratch1, r_A, K);
 512                                 else {
 513                                         PPC_LI32(r_scratch1, K);
 514                                         PPC_AND_DOT(r_scratch1, r_A,
 515                                                     r_scratch1);
 516                                 }
 517                                 break;
 518                         }
 519                         /* Sometimes branches are constructed "backward", with
 520                          * the false path being the branch and true path being
 521                          * a fallthrough to the next instruction.
 522                          */
 523                         if (filter[i].jt == 0)
 524                                 /* Swap the sense of the branch */
 525                                 PPC_BCC(true_cond ^ COND_CMP_TRUE,
 526                                         addrs[i + 1 + filter[i].jf]);
 527                         else {
 528                                 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
 529                                 if (filter[i].jf != 0)
 530                                         PPC_JMP(addrs[i + 1 + filter[i].jf]);
 531                         }
 532                         break;
 533                 default:
 534                         /* The filter contains something cruel & unusual.
 535                          * We don't handle it, but also there shouldn't be
 536                          * anything missing from our list.
 537                          */
 538                         if (printk_ratelimit())
 539                                 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
 540                                        filter[i].code, i);
 541                         return -ENOTSUPP;
 542                 }
 543
 544         }
 545         /* Set end-of-body-code address for exit. */
 546         addrs[i] = ctx->idx * 4;
 547
 548         return 0;
 549 }
 550
 551 void bpf_jit_compile(struct bpf_prog *fp)
 552 {
 553         unsigned int proglen;
 554         unsigned int alloclen;
 555         u32 *image = NULL;
 556         u32 *code_base;
 557         unsigned int *addrs;
 558         struct codegen_context cgctx;
 559         int pass;
 560         int flen = fp->len;
 561
 562         if (!bpf_jit_enable)
 563                 return;
 564
 565         addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
 566         if (addrs == NULL)
 567                 return;
 568
 569         /*
 570          * There are multiple assembly passes as the generated code will change
 571          * size as it settles down, figuring out the max branch offsets/exit
 572          * paths required.
 573          *
 574          * The range of standard conditional branches is +/- 32Kbytes.  Since
 575          * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
 576          * finish with 8 bytes/instruction.  Not feasible, so long jumps are
 577          * used, distinct from short branches.
 578          *
 579          * Current:
 580          *
 581          * For now, both branch types assemble to 2 words (short branches padded
 582          * with a NOP); this is less efficient, but assembly will always complete
 583          * after exactly 3 passes:
 584          *
 585          * First pass: No code buffer; Program is "faux-generated" -- no code
 586          * emitted but maximum size of output determined (and addrs[] filled
 587          * in).  Also, we note whether we use M[], whether we use skb data, etc.
 588          * All generation choices assumed to be 'worst-case', e.g. branches all
 589          * far (2 instructions), return path code reduction not available, etc.
 590          *
 591          * Second pass: Code buffer allocated with size determined previously.
 592          * Prologue generated to support features we have seen used.  Exit paths
 593          * determined and addrs[] is filled in again, as code may be slightly
 594          * smaller as a result.
 595          *
 596          * Third pass: Code generated 'for real', and branch destinations
 597          * determined from now-accurate addrs[] map.
 598          *
 599          * Ideal:
 600          *
 601          * If we optimise this, near branches will be shorter.  On the
 602          * first assembly pass, we should err on the side of caution and
 603          * generate the biggest code.  On subsequent passes, branches will be
 604          * generated short or long and code size will reduce.  With smaller
 605          * code, more branches may fall into the short category, and code will
 606          * reduce more.
 607          *
 608          * Finally, if we see one pass generate code the same size as the
 609          * previous pass we have converged and should now generate code for
 610          * real.  Allocating at the end will also save the memory that would
 611          * otherwise be wasted by the (small) current code shrinkage.
 612          * Preferably, we should do a small number of passes (e.g. 5) and if we
 613          * haven't converged by then, get impatient and force code to generate
 614          * as-is, even if the odd branch would be left long.  The chances of a
 615          * long jump are tiny with all but the most enormous of BPF filter
 616          * inputs, so we should usually converge on the third pass.
 617          */
 618
 619         cgctx.idx = 0;
 620         cgctx.seen = 0;
 621         cgctx.pc_ret0 = -1;
 622         /* Scouting faux-generate pass 0 */
 623         if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
 624                 /* We hit something illegal or unsupported. */
 625                 goto out;
 626
 627         /*
 628          * Pretend to build prologue, given the features we've seen.  This will
 629          * update ctgtx.idx as it pretends to output instructions, then we can
 630          * calculate total size from idx.
 631          */
 632         bpf_jit_build_prologue(fp, 0, &cgctx);
 633         bpf_jit_build_epilogue(0, &cgctx);
 634
 635         proglen = cgctx.idx * 4;
 636         alloclen = proglen + FUNCTION_DESCR_SIZE;
 637         image = module_alloc(alloclen);
 638         if (!image)
 639                 goto out;
 640
 641         code_base = image + (FUNCTION_DESCR_SIZE/4);
 642
 643         /* Code generation passes 1-2 */
 644         for (pass = 1; pass < 3; pass++) {
 645                 /* Now build the prologue, body code & epilogue for real. */
 646                 cgctx.idx = 0;
 647                 bpf_jit_build_prologue(fp, code_base, &cgctx);
 648                 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
 649                 bpf_jit_build_epilogue(code_base, &cgctx);
 650
 651                 if (bpf_jit_enable > 1)
 652                         pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
 653                                 proglen - (cgctx.idx * 4), cgctx.seen);
 654         }
 655
 656         if (bpf_jit_enable > 1)
 657                 /* Note that we output the base address of the code_base
 658                  * rather than image, since opcodes are in code_base.
 659                  */
 660                 bpf_jit_dump(flen, proglen, pass, code_base);
 661
 662         bpf_flush_icache(code_base, code_base + (proglen/4));
 663
 664 #ifdef CONFIG_PPC64
 665         /* Function descriptor nastiness: Address + TOC */
 666         ((u64 *)image)[0] = (u64)code_base;
 667         ((u64 *)image)[1] = local_paca->kernel_toc;
 668 #endif
 669
 670         fp->bpf_func = (void *)image;
 671         fp->jited = 1;
 672
 673 out:
 674         kfree(addrs);
 675         return;
 676 }
 677
 678 void bpf_jit_free(struct bpf_prog *fp)
 679 {
 680         if (fp->jited)
 681                 module_memfree(fp->bpf_func);
 682
 683         bpf_prog_unlock_free(fp);
 684 }