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   1 /*
   2  * lzms-common.c
   3  *
   4  * Code shared between the compressor and decompressor for the LZMS compression
   5  * format.
   6  */
   7
   8 /*
   9  * Copyright (C) 2013 Eric Biggers
  10  *
  11  * This file is part of wimlib, a library for working with WIM files.
  12  *
  13  * wimlib is free software; you can redistribute it and/or modify it under the
  14  * terms of the GNU General Public License as published by the Free
  15  * Software Foundation; either version 3 of the License, or (at your option)
  16  * any later version.
  17  *
  18  * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
  19  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  20  * A PARTICULAR PURPOSE. See the GNU General Public License for more
  21  * details.
  22  *
  23  * You should have received a copy of the GNU General Public License
  24  * along with wimlib; if not, see http://www.gnu.org/licenses/.
  25  */
  26
  27 #ifdef HAVE_CONFIG_H
  28 #  include "config.h"
  29 #endif
  30
  31 #include "wimlib/endianness.h"
  32 #include "wimlib/lzms.h"
  33 #include "wimlib/util.h"
  34
  35 #include <pthread.h>
  36
  37 /***************************************************************
  38  * Constant tables initialized by lzms_compute_slots():        *
  39  ***************************************************************/
  40
  41 /* Table: position slot => position slot base value  */
  42 u32 lzms_position_slot_base[LZMS_MAX_NUM_OFFSET_SYMS + 1];
  43
  44 /* Table: position slot => number of extra position bits  */
  45 u8 lzms_extra_position_bits[LZMS_MAX_NUM_OFFSET_SYMS];
  46
  47 /* Table: log2(position) => [lower bound, upper bound] on position slot  */
  48 u16 lzms_order_to_position_slot_bounds[30][2];
  49
  50 /* Table: length slot => length slot base value  */
  51 u32 lzms_length_slot_base[LZMS_NUM_LEN_SYMS + 1];
  52
  53 /* Table: length slot => number of extra length bits  */
  54 u8 lzms_extra_length_bits[LZMS_NUM_LEN_SYMS];
  55
  56 /* Table: length (< LZMS_NUM_FAST_LENGTHS only) => length slot  */
  57 u8 lzms_length_slot_fast[LZMS_NUM_FAST_LENGTHS];
  58
  59 u32
  60 lzms_get_slot(u32 value, const u32 slot_base_tab[], unsigned num_slots)
  61 {
  62         u32 l = 0;
  63         u32 r = num_slots - 1;
  64         for (;;) {
  65                 LZMS_ASSERT(r >= l);
  66                 u32 slot = (l + r) / 2;
  67                 if (value >= slot_base_tab[slot]) {
  68                         if (value < slot_base_tab[slot + 1])
  69                                 return slot;
  70                         else
  71                                 l = slot + 1;
  72                 } else {
  73                         r = slot - 1;
  74                 }
  75         }
  76 }
  77
  78 static void
  79 lzms_decode_delta_rle_slot_bases(u32 slot_bases[],
  80                                  u8 extra_bits[],
  81                                  const u8 delta_run_lens[],
  82                                  u32 num_run_lens,
  83                                  u32 final,
  84                                  u32 expected_num_slots)
  85 {
  86         u32 order = 0;
  87         u32 delta = 1;
  88         u32 base = 0;
  89         u32 slot = 0;
  90         for (u32 i = 0; i < num_run_lens; i++) {
  91                 u8 run_len = delta_run_lens[i];
  92                 while (run_len--) {
  93                         base += delta;
  94                         if (slot > 0)
  95                                 extra_bits[slot - 1] = order;
  96                         slot_bases[slot] = base;
  97                         slot++;
  98                 }
  99                 delta <<= 1;
 100                 order++;
 101         }
 102         LZMS_ASSERT(slot == expected_num_slots);
 103
 104         slot_bases[slot] = final;
 105         extra_bits[slot - 1] = bsr32(slot_bases[slot] - slot_bases[slot - 1]);
 106 }
 107
 108 /* Initialize the global position and length slot tables.  */
 109 static void
 110 lzms_compute_slots(void)
 111 {
 112         /* If an explicit formula that maps LZMS position and length slots to
 113          * slot bases exists, then it could be used here.  But until one is
 114          * found, the following code fills in the slots using the observation
 115          * that the increase from one slot base to the next is an increasing
 116          * power of 2.  Therefore, run-length encoding of the delta of adjacent
 117          * entries can be used.  */
 118         static const u8 position_slot_delta_run_lens[] = {
 119                 9,   0,   9,   7,   10,  15,  15,  20,
 120                 20,  30,  33,  40,  42,  45,  60,  73,
 121                 80,  85,  95,  105, 6,
 122         };
 123
 124         static const u8 length_slot_delta_run_lens[] = {
 125                 27,  4,   6,   4,   5,   2,   1,   1,
 126                 1,   1,   1,   0,   0,   0,   0,   0,
 127                 1,
 128         };
 129
 130         /* Position slots  */
 131         lzms_decode_delta_rle_slot_bases(lzms_position_slot_base,
 132                                          lzms_extra_position_bits,
 133                                          position_slot_delta_run_lens,
 134                                          ARRAY_LEN(position_slot_delta_run_lens),
 135                                          0x7fffffff,
 136                                          LZMS_MAX_NUM_OFFSET_SYMS);
 137
 138         for (u32 order = 0; order < 30; order++) {
 139                 lzms_order_to_position_slot_bounds[order][0] =
 140                         lzms_get_slot(1U << order, lzms_position_slot_base,
 141                                       LZMS_MAX_NUM_OFFSET_SYMS);
 142                 lzms_order_to_position_slot_bounds[order][1] =
 143                         lzms_get_slot((1U << (order + 1)) - 1, lzms_position_slot_base,
 144                                       LZMS_MAX_NUM_OFFSET_SYMS);
 145         }
 146
 147         /* Length slots  */
 148         lzms_decode_delta_rle_slot_bases(lzms_length_slot_base,
 149                                          lzms_extra_length_bits,
 150                                          length_slot_delta_run_lens,
 151                                          ARRAY_LEN(length_slot_delta_run_lens),
 152                                          0x400108ab,
 153                                          LZMS_NUM_LEN_SYMS);
 154
 155         /* Create table mapping short lengths to length slots.  */
 156         for (u32 slot = 0, i = 0; i < LZMS_NUM_FAST_LENGTHS; i++) {
 157                 if (i >= lzms_length_slot_base[slot + 1])
 158                         slot++;
 159                 lzms_length_slot_fast[i] = slot;
 160         }
 161 }
 162
 163 /* Initialize the global position and length slot tables if not done so already.
 164  * */
 165 void
 166 lzms_init_slots(void)
 167 {
 168         static pthread_once_t once = PTHREAD_ONCE_INIT;
 169
 170         pthread_once(&once, lzms_compute_slots);
 171 }
 172
 173 static s32
 174 lzms_maybe_do_x86_translation(u8 data[restrict], s32 i, s32 num_op_bytes,
 175                               s32 * restrict closest_target_usage_p,
 176                               s32 last_target_usages[restrict],
 177                               s32 max_trans_offset, bool undo)
 178 {
 179         u16 pos;
 180
 181         if (undo) {
 182                 if (i - *closest_target_usage_p <= max_trans_offset) {
 183                         LZMS_DEBUG("Undid x86 translation at position %d "
 184                                    "(opcode 0x%02x)", i, data[i]);
 185                         le32 *p32 = (le32*)&data[i + num_op_bytes];
 186                         u32 n = le32_to_cpu(*p32);
 187                         *p32 = cpu_to_le32(n - i);
 188                 }
 189                 pos = i + le16_to_cpu(*(const le16*)&data[i + num_op_bytes]);
 190         } else {
 191                 pos = i + le16_to_cpu(*(const le16*)&data[i + num_op_bytes]);
 192
 193                 if (i - *closest_target_usage_p <= max_trans_offset) {
 194                         LZMS_DEBUG("Did x86 translation at position %d "
 195                                    "(opcode 0x%02x)", i, data[i]);
 196                         le32 *p32 = (le32*)&data[i + num_op_bytes];
 197                         u32 n = le32_to_cpu(*p32);
 198                         *p32 = cpu_to_le32(n + i);
 199                 }
 200         }
 201
 202         i += num_op_bytes + sizeof(le32) - 1;
 203
 204         if (i - last_target_usages[pos] <= LZMS_X86_MAX_GOOD_TARGET_OFFSET)
 205                 *closest_target_usage_p = i;
 206
 207         last_target_usages[pos] = i;
 208
 209         return i + 1;
 210 }
 211
 212 static s32
 213 lzms_may_x86_translate(const u8 p[restrict],
 214                        s32 *restrict max_offset_ret)
 215 {
 216         /* Switch on first byte of the opcode, assuming it is really an x86
 217          * instruction.  */
 218         *max_offset_ret = LZMS_X86_MAX_TRANSLATION_OFFSET;
 219         switch (p[0]) {
 220         case 0x48:
 221                 if (p[1] == 0x8b) {
 222                         if (p[2] == 0x5 || p[2] == 0xd) {
 223                                 /* Load relative (x86_64)  */
 224                                 return 3;
 225                         }
 226                 } else if (p[1] == 0x8d) {
 227                         if ((p[2] & 0x7) == 0x5) {
 228                                 /* Load effective address relative (x86_64)  */
 229                                 return 3;
 230                         }
 231                 }
 232                 break;
 233
 234         case 0x4c:
 235                 if (p[1] == 0x8d) {
 236                         if ((p[2] & 0x7) == 0x5) {
 237                                 /* Load effective address relative (x86_64)  */
 238                                 return 3;
 239                         }
 240                 }
 241                 break;
 242
 243         case 0xe8:
 244                 /* Call relative  */
 245                 *max_offset_ret = LZMS_X86_MAX_TRANSLATION_OFFSET / 2;
 246                 return 1;
 247
 248         case 0xe9:
 249                 /* Jump relative  */
 250                 *max_offset_ret = 0;
 251                 return 5;
 252
 253         case 0xf0:
 254                 if (p[1] == 0x83 && p[2] == 0x05) {
 255                         /* Lock add relative  */
 256                         return 3;
 257                 }
 258                 break;
 259
 260         case 0xff:
 261                 if (p[1] == 0x15) {
 262                         /* Call indirect  */
 263                         return 2;
 264                 }
 265                 break;
 266         }
 267         *max_offset_ret = 0;
 268         return 1;
 269 }
 270
 271 /*
 272  * Translate relative addresses embedded in x86 instructions into absolute
 273  * addresses (@undo == %false), or undo this translation (@undo == %true).
 274  *
 275  * @last_target_usages is a temporary array of length >= 65536.
 276  */
 277 void
 278 lzms_x86_filter(u8 data[restrict],
 279                 s32 size,
 280                 s32 last_target_usages[restrict],
 281                 bool undo)
 282 {
 283         s32 closest_target_usage = -LZMS_X86_MAX_TRANSLATION_OFFSET - 1;
 284
 285         for (s32 i = 0; i < 65536; i++)
 286                 last_target_usages[i] = -LZMS_X86_MAX_GOOD_TARGET_OFFSET - 1;
 287
 288         for (s32 i = 0; i < size - 16; ) {
 289                 s32 max_trans_offset;
 290                 s32 n;
 291
 292                 n = lzms_may_x86_translate(data + i, &max_trans_offset);
 293                 if (max_trans_offset) {
 294                         i = lzms_maybe_do_x86_translation(data, i, n,
 295                                                           &closest_target_usage,
 296                                                           last_target_usages,
 297                                                           max_trans_offset,
 298                                                           undo);
 299                 } else {
 300                         i += n;
 301                 }
 302         }
 303 }
 304
 305 static void
 306 lzms_init_lz_lru_queues(struct lzms_lz_lru_queues *lz)
 307 {
 308         /* Recent offsets for LZ matches  */
 309         for (u32 i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++)
 310                 lz->recent_offsets[i] = i + 1;
 311
 312         lz->prev_offset = 0;
 313         lz->upcoming_offset = 0;
 314 }
 315
 316 static void
 317 lzms_init_delta_lru_queues(struct lzms_delta_lru_queues *delta)
 318 {
 319         /* Recent offsets and powers for LZ matches  */
 320         for (u32 i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++) {
 321                 delta->recent_offsets[i] = i + 1;
 322                 delta->recent_powers[i] = 0;
 323         }
 324         delta->prev_offset = 0;
 325         delta->prev_power = 0;
 326         delta->upcoming_offset = 0;
 327         delta->upcoming_power = 0;
 328 }
 329
 330
 331 void
 332 lzms_init_lru_queues(struct lzms_lru_queues *lru)
 333 {
 334         lzms_init_lz_lru_queues(&lru->lz);
 335         lzms_init_delta_lru_queues(&lru->delta);
 336 }
 337
 338 void
 339 lzms_update_lz_lru_queues(struct lzms_lz_lru_queues *lz)
 340 {
 341         if (lz->prev_offset != 0) {
 342                 for (int i = LZMS_NUM_RECENT_OFFSETS - 1; i >= 0; i--)
 343                         lz->recent_offsets[i + 1] = lz->recent_offsets[i];
 344                 lz->recent_offsets[0] = lz->prev_offset;
 345         }
 346         lz->prev_offset = lz->upcoming_offset;
 347 }
 348
 349 void
 350 lzms_update_delta_lru_queues(struct lzms_delta_lru_queues *delta)
 351 {
 352         if (delta->prev_offset != 0) {
 353                 for (int i = LZMS_NUM_RECENT_OFFSETS - 1; i >= 0; i--) {
 354                         delta->recent_offsets[i + 1] = delta->recent_offsets[i];
 355                         delta->recent_powers[i + 1] = delta->recent_powers[i];
 356                 }
 357                 delta->recent_offsets[0] = delta->prev_offset;
 358                 delta->recent_powers[0] = delta->prev_power;
 359         }
 360
 361         delta->prev_offset = delta->upcoming_offset;
 362         delta->prev_power = delta->upcoming_power;
 363 }
 364
 365 void
 366 lzms_update_lru_queues(struct lzms_lru_queues *lru)
 367 {
 368         lzms_update_lz_lru_queues(&lru->lz);
 369         lzms_update_delta_lru_queues(&lru->delta);
 370 }