config/elf-dynstr-gc.c

   1 /* elf_gc_dynst
   2  *
   3  * This is a program that removes unreferenced strings from the .dynstr
   4  * section in ELF shared objects. It also shrinks the .dynstr section and
   5  * relocates all symbols after it.
   6  *
   7  * This program was written and copyrighted by:
   8  *   Alexander Larsson <alla@lysator.liu.se>
   9  *
  10  *
  11  *
  12  * ***** BEGIN LICENSE BLOCK *****
  13  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  14  *
  15  * The contents of this file are subject to the Mozilla Public License Version
  16  * 1.1 (the "License"); you may not use this file except in compliance with
  17  * the License. You may obtain a copy of the License at
  18  * http://www.mozilla.org/MPL/
  19  *
  20  * Software distributed under the License is distributed on an "AS IS" basis,
  21  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  22  * for the specific language governing rights and limitations under the
  23  * License.
  24  *
  25  * The Original Code is mozilla.org Code.
  26  *
  27  * The Initial Developer of the Original Code is
  28  * Netscape Communications Corporation.
  29  * Portions created by the Initial Developer are Copyright (C) 2001
  30  * the Initial Developer. All Rights Reserved.
  31  *
  32  * Contributor(s):
  33  *
  34  * Alternatively, the contents of this file may be used under the terms of
  35  * either of the GNU General Public License Version 2 or later (the "GPL"),
  36  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  37  * in which case the provisions of the GPL or the LGPL are applicable instead
  38  * of those above. If you wish to allow use of your version of this file only
  39  * under the terms of either the GPL or the LGPL, and not to allow others to
  40  * use your version of this file under the terms of the MPL, indicate your
  41  * decision by deleting the provisions above and replace them with the notice
  42  * and other provisions required by the GPL or the LGPL. If you do not delete
  43  * the provisions above, a recipient may use your version of this file under
  44  * the terms of any one of the MPL, the GPL or the LGPL.
  45  *
  46  * ***** END LICENSE BLOCK ***** */
  47
  48
  49 #include <stdio.h>
  50 #include <unistd.h>
  51 #include <fcntl.h>
  52 #include <sys/types.h>
  53 #include <sys/stat.h>
  54 #include <sys/mman.h>
  55
  56 #include <elf.h>
  57 #include <glib.h>
  58 #include <string.h>
  59
  60
  61 Elf32_Ehdr *elf_header = NULL;
  62 #define FILE_OFFSET(offset) ((unsigned char *)(elf_header) + (offset))
  63
  64 struct dynamic_symbol {
  65   Elf32_Word old_index;
  66   Elf32_Word new_index;
  67   char *string;
  68 };
  69
  70 GHashTable *used_dynamic_symbols = NULL;
  71 /* Data is dynamic_symbols, hashes on old_index */
  72 Elf32_Word hole_index;
  73 Elf32_Word hole_end;
  74 Elf32_Word hole_len;
  75
  76 Elf32_Addr hole_addr_start;
  77 Elf32_Addr hole_addr_remap_start;
  78 Elf32_Addr hole_addr_remap_end;
  79
  80 int need_byteswap;
  81
  82 unsigned char machine_type;
  83
  84 Elf32_Word
  85 read_word(Elf32_Word w)
  86 {
  87   if (need_byteswap)
  88     w = GUINT32_SWAP_LE_BE(w);
  89   return w;
  90 }
  91
  92 Elf32_Sword
  93 read_sword(Elf32_Sword w)
  94 {
  95   if (need_byteswap)
  96     w = (Elf32_Sword)GUINT32_SWAP_LE_BE((guint32)w);
  97   return w;
  98 }
  99
 100 void
 101 write_word(Elf32_Word *ptr, Elf32_Word w)
 102 {
 103   if (need_byteswap)
 104     w = GUINT32_SWAP_LE_BE(w);
 105   *ptr = w;
 106 }
 107
 108 Elf32_Half
 109 read_half(Elf32_Half h)
 110 {
 111   if (need_byteswap)
 112     h = GUINT16_SWAP_LE_BE(h);
 113   return h;
 114 }
 115
 116 void
 117 write_half(Elf32_Half *ptr, Elf32_Half h)
 118 {
 119   if (need_byteswap)
 120     h = GUINT16_SWAP_LE_BE(h);
 121   *ptr = h;
 122 }
 123
 124 void
 125 setup_byteswapping(unsigned char ei_data)
 126 {
 127   need_byteswap = 0;
 128 #if G_BYTE_ORDER == G_BIG_ENDIAN
 129   if (ei_data == ELFDATA2LSB)
 130     need_byteswap = 1;
 131 #endif
 132 #if G_BYTE_ORDER == G_LITTLE_ENDIAN
 133   if (ei_data == ELFDATA2MSB)
 134     need_byteswap = 1;
 135 #endif
 136 }
 137
 138
 139 Elf32_Shdr *
 140 elf_find_section_num(int section_index)
 141 {
 142   Elf32_Shdr *section;
 143   Elf32_Word sectionsize;
 144
 145   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 146   sectionsize = read_half(elf_header->e_shentsize);
 147
 148   section = (Elf32_Shdr *)((char *)section + sectionsize*section_index);
 149
 150   return section;
 151 }
 152
 153 Elf32_Shdr *
 154 elf_find_section_named(char *name)
 155 {
 156   Elf32_Shdr *section;
 157   Elf32_Shdr *strtab_section;
 158   Elf32_Word sectionsize;
 159   int numsections;
 160   char *strtab;
 161   int i = 0;
 162
 163   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 164
 165   strtab_section = elf_find_section_num(read_half(elf_header->e_shstrndx));
 166
 167   strtab = (char *)FILE_OFFSET(read_word(strtab_section->sh_offset));
 168
 169   sectionsize = read_half(elf_header->e_shentsize);
 170   numsections = read_half(elf_header->e_shnum);
 171
 172   for (i=0;i<numsections;i++) {
 173     if (strcmp(&strtab[read_word(section->sh_name)], name) == 0) {
 174       return section;
 175     }
 176     section = (Elf32_Shdr *)((char *)section + sectionsize);
 177   }
 178   return NULL;
 179 }
 180
 181
 182 Elf32_Shdr *
 183 elf_find_section(Elf32_Word sh_type)
 184 {
 185   Elf32_Shdr *section;
 186   Elf32_Word sectionsize;
 187   int numsections;
 188   int i = 0;
 189
 190   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 191   sectionsize = read_half(elf_header->e_shentsize);
 192   numsections = read_half(elf_header->e_shnum);
 193
 194   for (i=0;i<numsections;i++) {
 195     if (read_word(section->sh_type) == sh_type) {
 196       return section;
 197     }
 198     section = (Elf32_Shdr *)((char *)section + sectionsize);
 199   }
 200   return NULL;
 201 }
 202
 203 Elf32_Shdr *
 204 elf_find_next_higher_section(Elf32_Word offset)
 205 {
 206   Elf32_Shdr *section;
 207   Elf32_Shdr *higher;
 208   Elf32_Word sectionsize;
 209   int numsections;
 210   int i = 0;
 211
 212   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 213   sectionsize = read_half(elf_header->e_shentsize);
 214   numsections = read_half(elf_header->e_shnum);
 215
 216   higher = NULL;
 217
 218   for (i=0;i<numsections;i++) {
 219     if (read_word(section->sh_offset) >= offset) {
 220       if (higher == NULL) {
 221         higher = section;
 222       } else if (read_word(section->sh_offset) < read_word(higher->sh_offset)) {
 223         higher = section;
 224       }
 225     }
 226
 227     section = (Elf32_Shdr *)((char *)section + sectionsize);
 228   }
 229
 230   return higher;
 231 }
 232
 233 Elf32_Word
 234 vma_to_offset(Elf32_Addr addr)
 235 {
 236   Elf32_Shdr *section;
 237   Elf32_Shdr *higher;
 238   Elf32_Word sectionsize;
 239   int numsections;
 240   int i = 0;
 241
 242   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 243   sectionsize = read_half(elf_header->e_shentsize);
 244   numsections = read_half(elf_header->e_shnum);
 245
 246   higher = NULL;
 247
 248   for (i=0;i<numsections;i++) {
 249     if ( (addr >= read_word(section->sh_addr)) &&
 250          (addr < read_word(section->sh_addr) + read_word(section->sh_size)) ) {
 251       return read_word(section->sh_offset) + (addr - read_word(section->sh_addr));
 252     }
 253
 254     section = (Elf32_Shdr *)((char *)section + sectionsize);
 255   }
 256
 257   fprintf(stderr, "Warning, unable to convert address %d (0x%x) to file offset\n",
 258          addr, addr);
 259   return 0;
 260 }
 261
 262
 263 void
 264 find_segment_addr_min_max(Elf32_Word file_offset,
 265                           Elf32_Addr *start, Elf32_Addr *end)
 266 {
 267   Elf32_Phdr *segment;
 268   Elf32_Word segmentsize;
 269   int numsegments;
 270   int i = 0;
 271
 272   segment = (Elf32_Phdr *)FILE_OFFSET(read_word(elf_header->e_phoff));
 273   segmentsize = read_half(elf_header->e_phentsize);
 274   numsegments = read_half(elf_header->e_phnum);
 275
 276   for (i=0;i<numsegments;i++) {
 277     if ((file_offset >= read_word(segment->p_offset)) &&
 278         (file_offset < read_word(segment->p_offset) + read_word(segment->p_filesz)))  {
 279       *start = read_word(segment->p_vaddr);
 280       *end = read_word(segment->p_vaddr) + read_word(segment->p_memsz);
 281       return;
 282     }
 283
 284     segment = (Elf32_Phdr *)((char *)segment + segmentsize);
 285   }
 286   fprintf(stderr, "Error: Couldn't find segment in find_segment_addr_min_max()\n");
 287 }
 288
 289 void *
 290 dynamic_find_tag(Elf32_Shdr *dynamic, Elf32_Sword d_tag)
 291 {
 292   int i;
 293   Elf32_Dyn *element;
 294
 295   element = (Elf32_Dyn *)FILE_OFFSET(read_word(dynamic->sh_offset));
 296   for (i=0; read_sword(element[i].d_tag) != DT_NULL; i++) {
 297     if (read_sword(element[i].d_tag) == d_tag) {
 298       return FILE_OFFSET(read_word(element[i].d_un.d_ptr));
 299     }
 300   }
 301
 302   return NULL;
 303 }
 304
 305 Elf32_Word
 306 fixup_offset(Elf32_Word offset)
 307 {
 308   if (offset >= hole_index) {
 309     return offset - hole_len;
 310   }
 311   return offset;
 312 }
 313
 314 Elf32_Word
 315 fixup_size(Elf32_Word offset, Elf32_Word size)
 316 {
 317   /* Note: Doesn't handle the cases where the hole and the size intersect
 318      partially. */
 319
 320   if ( (hole_index >= offset) &&
 321        (hole_index < offset + size)){
 322     return size - hole_len;
 323   }
 324
 325   return size;
 326 }
 327
 328 Elf32_Addr
 329 fixup_addr(Elf32_Addr addr)
 330 {
 331   if (addr == 0)
 332     return 0;
 333
 334   /*
 335   if ( (addr < hole_addr_remap_start) ||
 336        (addr >= hole_addr_remap_end))
 337     return addr;
 338   */
 339
 340   if (addr >= hole_addr_start) {
 341     return addr - hole_len;
 342   }
 343   return addr;
 344 }
 345
 346 Elf32_Word
 347 fixup_addr_size(Elf32_Addr addr, Elf32_Word size)
 348 {
 349   /* Note: Doesn't handle the cases where the hole and the size intersect
 350      partially. */
 351   /*
 352   if ( (addr < hole_addr_remap_start) ||
 353        (addr >= hole_addr_remap_end))
 354     return size;
 355   */
 356   if ( (hole_addr_start >= addr) &&
 357        (hole_addr_start < addr + size)){
 358     return size - hole_len;
 359   }
 360
 361   return size;
 362 }
 363
 364 void
 365 possibly_add_string(int name_idx, const char *name)
 366 {
 367   struct dynamic_symbol *dynamic_symbol;
 368   if (name_idx != 0) {
 369     dynamic_symbol = g_hash_table_lookup(used_dynamic_symbols, (gpointer) name_idx);
 370
 371     if (dynamic_symbol == NULL) {
 372
 373       dynamic_symbol = g_new(struct dynamic_symbol, 1);
 374
 375       dynamic_symbol->old_index = name_idx;
 376       dynamic_symbol->new_index = 0;
 377       dynamic_symbol->string = g_strdup(name);
 378
 379       g_hash_table_insert(used_dynamic_symbols, (gpointer)name_idx, dynamic_symbol);
 380       /*printf("added dynamic string: %s (%d)\n", dynamic_symbol->string, name_idx);*/
 381     }
 382   }
 383 }
 384
 385 Elf32_Word
 386 fixup_string(Elf32_Word old_idx)
 387 {
 388   struct dynamic_symbol *dynamic_symbol;
 389
 390   if (old_idx == 0)
 391     return 0;
 392
 393   dynamic_symbol = g_hash_table_lookup(used_dynamic_symbols, (gpointer) old_idx);
 394
 395   if (dynamic_symbol == NULL) {
 396     fprintf(stderr, "AAAAAAAAAAAARGH!? Unknown string found in fixup (index: %d)!\n", old_idx);
 397     return 0;
 398   }
 399
 400   return dynamic_symbol->new_index;
 401 }
 402
 403
 404
 405 void
 406 add_strings_from_dynsym(Elf32_Shdr *dynsym, char *strtab)
 407 {
 408   Elf32_Sym *symbol;
 409   Elf32_Sym *symbol_end;
 410   Elf32_Word entry_size;
 411
 412
 413   symbol = (Elf32_Sym *)FILE_OFFSET(read_word(dynsym->sh_offset));
 414   symbol_end = (Elf32_Sym *)FILE_OFFSET(read_word(dynsym->sh_offset) + read_word(dynsym->sh_size));
 415   entry_size = read_word(dynsym->sh_entsize);
 416
 417   while (symbol < symbol_end) {
 418     int name_idx;
 419     struct dynamic_symbol *dynamic_symbol;
 420
 421     name_idx = read_word(symbol->st_name);
 422     possibly_add_string(name_idx, &strtab[name_idx]);
 423
 424
 425     symbol = (Elf32_Sym *)((char *)symbol + entry_size);
 426   }
 427 }
 428
 429
 430 void
 431 fixup_strings_in_dynsym(Elf32_Shdr *dynsym)
 432 {
 433   Elf32_Sym *symbol;
 434   Elf32_Sym *symbol_end;
 435   Elf32_Word entry_size;
 436
 437
 438   symbol = (Elf32_Sym *)FILE_OFFSET(read_word(dynsym->sh_offset));
 439   symbol_end = (Elf32_Sym *)FILE_OFFSET(read_word(dynsym->sh_offset) + read_word(dynsym->sh_size));
 440   entry_size = read_word(dynsym->sh_entsize);
 441
 442   while (symbol < symbol_end) {
 443     struct dynamic_symbol *dynamic_symbol;
 444
 445     write_word(&symbol->st_name,
 446                fixup_string(read_word(symbol->st_name)));
 447
 448     symbol = (Elf32_Sym *)((char *)symbol + entry_size);
 449   }
 450 }
 451
 452
 453 void
 454 add_strings_from_dynamic(Elf32_Shdr *dynamic, char *strtab)
 455 {
 456   int i;
 457   int name_idx;
 458   Elf32_Dyn *element;
 459   Elf32_Word entry_size;
 460
 461   entry_size = read_word(dynamic->sh_entsize);
 462
 463
 464   element = (Elf32_Dyn *)FILE_OFFSET(read_word(dynamic->sh_offset));
 465   while (read_sword(element->d_tag) != DT_NULL) {
 466
 467     switch(read_sword(element->d_tag)) {
 468     case DT_NEEDED:
 469     case DT_SONAME:
 470     case DT_RPATH:
 471       name_idx = read_word(element->d_un.d_val);
 472       /*if (name_idx) printf("d_tag: %d\n", element->d_tag);*/
 473       possibly_add_string(name_idx, &strtab[name_idx]);
 474       break;
 475     default:
 476       ;
 477       /*printf("unhandled d_tag: %d (0x%x)\n", element->d_tag, element->d_tag);*/
 478     }
 479
 480     element = (Elf32_Dyn *)((char *)element + entry_size);
 481   }
 482
 483 }
 484
 485 void
 486 fixup_strings_in_dynamic(Elf32_Shdr *dynamic)
 487 {
 488   int i;
 489   int name_idx;
 490   Elf32_Dyn *element;
 491   Elf32_Word entry_size;
 492
 493   entry_size = read_word(dynamic->sh_entsize);
 494
 495   element = (Elf32_Dyn *)FILE_OFFSET(read_word(dynamic->sh_offset));
 496   while (read_sword(element->d_tag) != DT_NULL) {
 497
 498     switch(read_sword(element->d_tag)) {
 499     case DT_NEEDED:
 500     case DT_SONAME:
 501     case DT_RPATH:
 502       write_word(&element->d_un.d_val,
 503                  fixup_string(read_word(element->d_un.d_val)));
 504       break;
 505     default:
 506       ;
 507       /*printf("unhandled d_tag: %d (0x%x)\n", element->d_tag, element->d_tag);*/
 508     }
 509
 510     element = (Elf32_Dyn *)((char *)element + entry_size);
 511   }
 512
 513 }
 514
 515
 516 void
 517 add_strings_from_ver_d(Elf32_Shdr *ver_d, char *strtab)
 518 {
 519   Elf32_Verdaux *veraux;
 520   Elf32_Verdef *verdef;
 521   int num_aux;
 522   int name_idx;
 523   int i;
 524   int cont;
 525
 526   verdef = (Elf32_Verdef *)FILE_OFFSET(read_word(ver_d->sh_offset));
 527
 528   do {
 529     num_aux = read_half(verdef->vd_cnt);
 530     veraux = (Elf32_Verdaux *)((char *)verdef + read_word(verdef->vd_aux));
 531     for (i=0; i<num_aux; i++) {
 532       name_idx = read_word(veraux->vda_name);
 533       possibly_add_string(name_idx, &strtab[name_idx]);
 534       veraux = (Elf32_Verdaux *)((char *)veraux + read_word(veraux->vda_next));
 535     }
 536
 537     cont = read_word(verdef->vd_next) != 0;
 538     verdef = (Elf32_Verdef *)((char *)verdef + read_word(verdef->vd_next));
 539   } while (cont);
 540
 541 }
 542
 543 void
 544 fixup_strings_in_ver_d(Elf32_Shdr *ver_d)
 545 {
 546   Elf32_Verdaux *veraux;
 547   Elf32_Verdef *verdef;
 548   int num_aux;
 549   int name_idx;
 550   int i;
 551   int cont;
 552
 553   verdef = (Elf32_Verdef *)FILE_OFFSET(read_word(ver_d->sh_offset));
 554
 555   do {
 556     num_aux = read_half(verdef->vd_cnt);
 557     veraux = (Elf32_Verdaux *)((char *)verdef + read_word(verdef->vd_aux));
 558     for (i=0; i<num_aux; i++) {
 559       write_word(&veraux->vda_name,
 560                  fixup_string(read_word(veraux->vda_name)));
 561       veraux = (Elf32_Verdaux *)((char *)veraux + read_word(veraux->vda_next));
 562     }
 563
 564     cont = read_word(verdef->vd_next) != 0;
 565     verdef = (Elf32_Verdef *)((char *)verdef + read_word(verdef->vd_next));
 566   } while (cont);
 567
 568 }
 569
 570 void
 571 add_strings_from_ver_r(Elf32_Shdr *ver_r, char *strtab)
 572 {
 573   Elf32_Vernaux *veraux;
 574   Elf32_Verneed *verneed;
 575   int num_aux;
 576   int name_idx;
 577   int i;
 578   int cont;
 579
 580   verneed = (Elf32_Verneed *)FILE_OFFSET(read_word(ver_r->sh_offset));
 581
 582   do {
 583     name_idx = read_word(verneed->vn_file);
 584     possibly_add_string(name_idx, &strtab[name_idx]);
 585     num_aux = read_half(verneed->vn_cnt);
 586     veraux = (Elf32_Vernaux *)((char *)verneed + read_word(verneed->vn_aux));
 587     for (i=0; i<num_aux; i++) {
 588       name_idx = read_word(veraux->vna_name);
 589       possibly_add_string(name_idx, &strtab[name_idx]);
 590       veraux = (Elf32_Vernaux *)((char *)veraux + read_word(veraux->vna_next));
 591     }
 592
 593     cont = read_word(verneed->vn_next) != 0;
 594     verneed = (Elf32_Verneed *)((char *)verneed + read_word(verneed->vn_next));
 595   } while (cont);
 596 }
 597
 598 void
 599 fixup_strings_in_ver_r(Elf32_Shdr *ver_r)
 600 {
 601   Elf32_Vernaux *veraux;
 602   Elf32_Verneed *verneed;
 603   int num_aux;
 604   int name_idx;
 605   int i;
 606   int cont;
 607
 608   verneed = (Elf32_Verneed *)FILE_OFFSET(read_word(ver_r->sh_offset));
 609
 610   do {
 611     write_word(&verneed->vn_file,
 612                fixup_string(read_word(verneed->vn_file)));
 613     num_aux = read_half(verneed->vn_cnt);
 614     veraux = (Elf32_Vernaux *)((char *)verneed + read_word(verneed->vn_aux));
 615     for (i=0; i<num_aux; i++) {
 616       write_word(&veraux->vna_name,
 617                  fixup_string(read_word(veraux->vna_name)));
 618       veraux = (Elf32_Vernaux *)((char *)veraux + read_word(veraux->vna_next));
 619     }
 620
 621     cont = read_word(verneed->vn_next) != 0;
 622     verneed = (Elf32_Verneed *)((char *)verneed + read_word(verneed->vn_next));
 623   } while (cont);
 624 }
 625
 626 gboolean sum_size(gpointer      key,
 627                   struct dynamic_symbol *sym,
 628                   int *size)
 629 {
 630   *size += strlen(sym->string) + 1;
 631   return 1;
 632 }
 633
 634 struct index_n_dynstr {
 635   int index;
 636   unsigned char *dynstr;
 637 };
 638
 639 gboolean output_string(gpointer key,
 640                        struct dynamic_symbol *sym,
 641                        struct index_n_dynstr *x)
 642 {
 643   sym->new_index = x->index;
 644   memcpy(x->dynstr + x->index, sym->string, strlen(sym->string) + 1);
 645   x->index += strlen(sym->string) + 1;
 646   return 1;
 647 }
 648
 649
 650 unsigned char *
 651 generate_new_dynstr(Elf32_Word *size_out)
 652 {
 653   int size;
 654   unsigned char *new_dynstr;
 655   struct index_n_dynstr x;
 656
 657   size = 1; /* first a zero */
 658   g_hash_table_foreach  (used_dynamic_symbols,
 659                          (GHFunc)sum_size,
 660                          &size);
 661
 662
 663   new_dynstr = g_malloc(size);
 664
 665   new_dynstr[0] = 0;
 666   x.index = 1;
 667   x.dynstr = new_dynstr;
 668   g_hash_table_foreach  (used_dynamic_symbols,
 669                          (GHFunc)output_string,
 670                          &x);
 671
 672   *size_out = size;
 673   return new_dynstr;
 674 }
 675
 676 void
 677 remap_sections(void)
 678 {
 679   Elf32_Shdr *section;
 680   Elf32_Word sectionsize;
 681   int numsections;
 682   int i = 0;
 683
 684   section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
 685   sectionsize = read_half(elf_header->e_shentsize);
 686   numsections = read_half(elf_header->e_shnum);
 687
 688   for (i=0;i<numsections;i++) {
 689     write_word(&section->sh_size,
 690                fixup_size(read_word(section->sh_offset),
 691                           read_word(section->sh_size)));
 692     write_word(&section->sh_offset,
 693                fixup_offset(read_word(section->sh_offset)));
 694     write_word(&section->sh_addr,
 695                fixup_addr(read_word(section->sh_addr)));
 696
 697     section = (Elf32_Shdr *)((char *)section + sectionsize);
 698   }
 699 }
 700
 701
 702 void
 703 remap_segments(void)
 704 {
 705   Elf32_Phdr *segment;
 706   Elf32_Word segmentsize;
 707   Elf32_Word p_align;
 708   int numsegments;
 709   int i = 0;
 710
 711   segment = (Elf32_Phdr *)FILE_OFFSET(read_word(elf_header->e_phoff));
 712   segmentsize = read_half(elf_header->e_phentsize);
 713   numsegments = read_half(elf_header->e_phnum);
 714
 715   for (i=0;i<numsegments;i++) {
 716     write_word(&segment->p_filesz,
 717                fixup_size(read_word(segment->p_offset),
 718                           read_word(segment->p_filesz)));
 719     write_word(&segment->p_offset,
 720                fixup_offset(read_word(segment->p_offset)));
 721
 722     write_word(&segment->p_memsz,
 723                fixup_addr_size(read_word(segment->p_vaddr),
 724                                read_word(segment->p_memsz)));
 725     write_word(&segment->p_vaddr,
 726                fixup_addr(read_word(segment->p_vaddr)));
 727     write_word(&segment->p_paddr,
 728                read_word(segment->p_vaddr));
 729
 730     /* Consistancy checking: */
 731     p_align = read_word(segment->p_align);
 732     if (p_align > 1) {
 733       if ((read_word(segment->p_vaddr) - read_word(segment->p_offset))%p_align != 0) {
 734         fprintf(stderr, "Warning, creating non-aligned segment addr: %x offset: %x allign: %x\n",
 735                 read_word(segment->p_vaddr), read_word(segment->p_offset), p_align);
 736       }
 737     }
 738
 739     segment = (Elf32_Phdr *)((char *)segment + segmentsize);
 740   }
 741 }
 742
 743 void
 744 remap_elf_header(void)
 745 {
 746   write_word(&elf_header->e_phoff,
 747              fixup_offset(read_word(elf_header->e_phoff)));
 748   write_word(&elf_header->e_shoff,
 749              fixup_offset(read_word(elf_header->e_shoff)));
 750
 751   write_word(&elf_header->e_entry,
 752              fixup_addr(read_word(elf_header->e_entry)));
 753 }
 754
 755 void
 756 remap_symtab(Elf32_Shdr *symtab)
 757 {
 758   Elf32_Sym *symbol;
 759   Elf32_Sym *symbol_end;
 760   Elf32_Word entry_size;
 761
 762   symbol = (Elf32_Sym *)FILE_OFFSET(read_word(symtab->sh_offset));
 763   symbol_end = (Elf32_Sym *)FILE_OFFSET(read_word(symtab->sh_offset) +
 764                                         read_word(symtab->sh_size));
 765   entry_size = read_word(symtab->sh_entsize);
 766
 767   while (symbol < symbol_end) {
 768     write_word(&symbol->st_value,
 769                fixup_addr(read_word(symbol->st_value)));
 770     symbol = (Elf32_Sym *)((char *)symbol + entry_size);
 771   }
 772 }
 773
 774
 775 /* Ugly global variables: */
 776 Elf32_Addr got_data_start = 0;
 777 Elf32_Addr got_data_end = 0;
 778
 779
 780 void
 781 remap_rel_section(Elf32_Rel *rel, Elf32_Word size, Elf32_Word entry_size)
 782 {
 783   Elf32_Rel *rel_end;
 784   Elf32_Word offset;
 785   Elf32_Addr *addr;
 786   Elf32_Word type;
 787
 788   rel_end = (Elf32_Rel *)((char *)rel + size);
 789
 790   while (rel < rel_end) {
 791     type = ELF32_R_TYPE(read_word(rel->r_info));
 792     switch (machine_type) {
 793     case EM_386:
 794       if ((type == R_386_RELATIVE) || (type == R_386_JMP_SLOT)) {
 795         /* We need to relocate the data this is pointing to too. */
 796         offset = vma_to_offset(read_word(rel->r_offset));
 797
 798         addr =  (Elf32_Addr *)FILE_OFFSET(offset);
 799         write_word(addr,
 800                    fixup_addr(read_word(*addr)));
 801       }
 802       write_word(&rel->r_offset,
 803                  fixup_addr(read_word(rel->r_offset)));
 804       break;
 805     case EM_PPC:
 806       /* The PPC always uses RELA relocations */
 807       break;
 808     }
 809
 810
 811     rel = (Elf32_Rel *)((char *)rel + entry_size);
 812   }
 813 }
 814
 815 void
 816 remap_rela_section(Elf32_Rela *rela, Elf32_Word size, Elf32_Word entry_size)
 817 {
 818   Elf32_Rela *rela_end;
 819   Elf32_Addr *addr;
 820   Elf32_Word offset;
 821   Elf32_Word type;
 822   Elf32_Word bitmask;
 823
 824   rela_end = (Elf32_Rela *)((char *)rela + size);
 825
 826   while (rela < rela_end) {
 827     type = ELF32_R_TYPE(read_word(rela->r_info));
 828     switch (machine_type) {
 829     case EM_386:
 830       if ((type == R_386_RELATIVE) || (type == R_386_JMP_SLOT)) {
 831         /* We need to relocate the data this is pointing to too. */
 832         offset = vma_to_offset(read_word(rela->r_offset));
 833
 834         addr =  (Elf32_Addr *)FILE_OFFSET(offset);
 835         write_word(addr,
 836                    fixup_addr(read_word(*addr)));
 837       }
 838       write_word(&rela->r_offset,
 839                  fixup_addr(read_word(rela->r_offset)));
 840       break;
 841     case EM_PPC:
 842 /* Some systems do not have PowerPC relocations defined */
 843 #ifdef R_PPC_NONE
 844       switch (type) {
 845       case R_PPC_RELATIVE:
 846         write_word((Elf32_Word *)&rela->r_addend,
 847                    fixup_addr(read_word(rela->r_addend)));
 848         /* Fall through for 32bit offset fixup */
 849       case R_PPC_ADDR32:
 850       case R_PPC_GLOB_DAT:
 851       case R_PPC_JMP_SLOT:
 852         write_word(&rela->r_offset,
 853                    fixup_addr(read_word(rela->r_offset)));
 854         break;
 855       case R_PPC_NONE:
 856         break;
 857       default:
 858         fprintf(stderr, "Warning, unhandled PPC relocation type %d\n", type);
 859       }
 860 #endif
 861       break;
 862     }
 863
 864     rela = (Elf32_Rela *)((char *)rela + entry_size);
 865   }
 866 }
 867
 868 void
 869 remap_i386_got(void)
 870 {
 871   Elf32_Shdr *got_section;
 872   Elf32_Addr *got;
 873   Elf32_Addr *got_end;
 874   Elf32_Word entry_size;
 875
 876   got_section = elf_find_section_named(".got");
 877   if (got_section == NULL) {
 878     fprintf(stderr, "Warning, no .got section\n");
 879     return;
 880   }
 881
 882   got_data_start = read_word(got_section->sh_offset);
 883   got_data_end = got_data_start + read_word(got_section->sh_size);
 884
 885   got = (Elf32_Addr *)FILE_OFFSET(got_data_start);
 886   got_end = (Elf32_Addr *)FILE_OFFSET(got_data_end);
 887   entry_size = read_word(got_section->sh_entsize);
 888
 889   write_word(got,
 890              fixup_addr(read_word(*got))); /* Pointer to .dynamic */
 891 }
 892
 893 void
 894 remap_ppc_got(void)
 895 {
 896   Elf32_Shdr *got_section;
 897   Elf32_Addr *got;
 898   Elf32_Addr *got_end;
 899   Elf32_Word entry_size;
 900
 901   got_section = elf_find_section_named(".got");
 902   if (got_section == NULL) {
 903     fprintf(stderr, "Warning, no .got section\n");
 904     return;
 905   }
 906
 907   got_data_start = read_word(got_section->sh_offset);
 908   got_data_end = got_data_start + read_word(got_section->sh_size);
 909
 910   got = (Elf32_Addr *)FILE_OFFSET(got_data_start);
 911   got_end = (Elf32_Addr *)FILE_OFFSET(got_data_end);
 912   entry_size = read_word(got_section->sh_entsize);
 913
 914   /* Skip reserved part.
 915    * Note that this should really be found by finding the
 916    * _GLOBAL_OFFSET_TABLE symbol, as it could (according to
 917    * the spec) point to the middle of the got.
 918    */
 919   got = (Elf32_Addr *)((char *)got + entry_size); /* Skip blrl instruction */
 920   write_word(got,
 921              fixup_addr(read_word(*got))); /* Pointer to .dynamic */
 922 }
 923
 924
 925 Elf32_Word
 926 get_dynamic_val(Elf32_Shdr *dynamic, Elf32_Sword tag)
 927 {
 928   Elf32_Dyn *element;
 929   Elf32_Word entry_size;
 930
 931   entry_size = read_word(dynamic->sh_entsize);
 932
 933   element = (Elf32_Dyn *)FILE_OFFSET(read_word(dynamic->sh_offset));
 934   while (read_sword(element->d_tag) != DT_NULL) {
 935     if (read_sword(element->d_tag) == tag) {
 936       return read_word(element->d_un.d_val);
 937     }
 938     element = (Elf32_Dyn *)((char *)element + entry_size);
 939   }
 940   return 0;
 941 }
 942
 943 void
 944 remap_dynamic(Elf32_Shdr *dynamic, Elf32_Word new_dynstr_size)
 945 {
 946   Elf32_Dyn *element;
 947   Elf32_Word entry_size;
 948   Elf32_Word rel_size;
 949   Elf32_Word rel_entry_size;
 950   Elf32_Rel *rel;
 951   Elf32_Rela *rela;
 952   int jmprel_overlaps;
 953   Elf32_Word rel_start, rel_end, jmprel_start, jmprel_end;
 954
 955   entry_size = read_word(dynamic->sh_entsize);
 956
 957   /* Find out if REL/RELA and JMPREL overlaps: */
 958   if (get_dynamic_val(dynamic, DT_PLTREL) == DT_REL) {
 959     rel_start = get_dynamic_val(dynamic, DT_REL);
 960     rel_end = rel_start + get_dynamic_val(dynamic, DT_RELSZ);
 961   } else {
 962     rel_start = get_dynamic_val(dynamic, DT_RELA);
 963     rel_end = rel_start + get_dynamic_val(dynamic, DT_RELASZ);
 964   }
 965   jmprel_start = get_dynamic_val(dynamic, DT_JMPREL);
 966
 967   jmprel_overlaps = 0;
 968   if ((jmprel_start >= rel_start) && (jmprel_start < rel_end))
 969     jmprel_overlaps = 1;
 970
 971   element = (Elf32_Dyn *)FILE_OFFSET(read_word(dynamic->sh_offset));
 972   while (read_sword(element->d_tag) != DT_NULL) {
 973     switch(read_sword(element->d_tag)) {
 974     case DT_STRSZ:
 975       write_word(&element->d_un.d_val, new_dynstr_size);
 976       break;
 977     case DT_PLTGOT:
 978     case DT_HASH:
 979     case DT_STRTAB:
 980     case DT_INIT:
 981     case DT_FINI:
 982     case DT_VERDEF:
 983     case DT_VERNEED:
 984     case DT_VERSYM:
 985       write_word(&element->d_un.d_ptr,
 986                  fixup_addr(read_word(element->d_un.d_ptr)));
 987       break;
 988     case DT_JMPREL:
 989       rel_size = get_dynamic_val(dynamic, DT_PLTRELSZ);
 990       if (!jmprel_overlaps) {
 991         if (get_dynamic_val(dynamic, DT_PLTREL) == DT_REL) {
 992           rel_entry_size = get_dynamic_val(dynamic, DT_RELENT);
 993           rel = (Elf32_Rel *)FILE_OFFSET(vma_to_offset(read_word(element->d_un.d_ptr)));
 994           remap_rel_section(rel, rel_size, rel_entry_size);
 995         } else {
 996           rel_entry_size = get_dynamic_val(dynamic, DT_RELAENT);
 997           rela = (Elf32_Rela *)FILE_OFFSET(vma_to_offset(read_word(element->d_un.d_ptr)));
 998           remap_rela_section(rela, rel_size, rel_entry_size);
 999         }
1000       }
1001       write_word(&element->d_un.d_ptr,
1002                  fixup_addr(read_word(element->d_un.d_ptr)));
1003       break;
1004     case DT_REL:
1005       rel_size = get_dynamic_val(dynamic, DT_RELSZ);
1006       rel_entry_size = get_dynamic_val(dynamic, DT_RELENT);
1007       rel = (Elf32_Rel *)FILE_OFFSET(vma_to_offset(read_word(element->d_un.d_ptr)));
1008       remap_rel_section(rel, rel_size, rel_entry_size);
1009
1010       write_word(&element->d_un.d_ptr,
1011                  fixup_addr(read_word(element->d_un.d_ptr)));
1012       break;
1013     case DT_RELA:
1014       rel_size = get_dynamic_val(dynamic, DT_RELASZ);
1015       rel_entry_size = get_dynamic_val(dynamic, DT_RELAENT);
1016       rela = (Elf32_Rela *)FILE_OFFSET(vma_to_offset(read_word(element->d_un.d_ptr)));
1017       remap_rela_section(rela, rel_size, rel_entry_size);
1018
1019       write_word(&element->d_un.d_ptr,
1020                  fixup_addr(read_word(element->d_un.d_ptr)));
1021       break;
1022     default:
1023       /*printf("unhandled d_tag: %d (0x%x)\n", read_sword(element->d_tag), read_sword(element->d_tag));*/
1024       break;
1025     }
1026
1027     element = (Elf32_Dyn *)((char *)element + entry_size);
1028   }
1029 }
1030
1031 void
1032 align_hole(Elf32_Word *start, Elf32_Word *end)
1033 {
1034   Elf32_Word len;
1035   Elf32_Word align;
1036   Elf32_Shdr *section;
1037   Elf32_Word sectionsize;
1038   int numsections;
1039   int i = 0;
1040   int unaligned;
1041
1042   len = *end - *start;
1043   align = 0;
1044
1045   sectionsize = read_half(elf_header->e_shentsize);
1046   numsections = read_half(elf_header->e_shnum);
1047   do {
1048     section = (Elf32_Shdr *)FILE_OFFSET(read_word(elf_header->e_shoff));
1049     unaligned = 0;
1050
1051     for (i=0;i<numsections;i++) {
1052       if ( (read_word(section->sh_addralign) > 1) &&
1053            ( (read_word(section->sh_offset) - len + align)%read_word(section->sh_addralign) != 0) ) {
1054         unaligned = 1;
1055       }
1056
1057       section = (Elf32_Shdr *)((char *)section + sectionsize);
1058     }
1059
1060     if (unaligned) {
1061       align++;
1062     }
1063
1064   } while (unaligned);
1065
1066   *start += align;
1067 }
1068
1069 int
1070 main(int argc, char *argv[])
1071 {
1072   int fd;
1073   unsigned char *mapping;
1074   Elf32_Word size;
1075   struct stat statbuf;
1076   Elf32_Shdr *dynamic;
1077   Elf32_Shdr *dynsym;
1078   Elf32_Shdr *symtab;
1079   Elf32_Shdr *dynstr;
1080   Elf32_Shdr *hash;
1081   Elf32_Shdr *higher_section;
1082   Elf32_Word dynstr_index;
1083   Elf32_Shdr *ver_r;
1084   Elf32_Shdr *ver_d;
1085   char *dynstr_data;
1086   unsigned char *new_dynstr;
1087   Elf32_Word old_dynstr_size;
1088   Elf32_Word new_dynstr_size;
1089
1090   if (argc != 2) {
1091     fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
1092     return 1;
1093   }
1094
1095   fd = open(argv[1], O_RDWR);
1096   if (fd == -1) {
1097     fprintf(stderr, "Cannot open file %s\n", argv[1]);
1098     return 1;
1099   }
1100
1101   if (fstat(fd, &statbuf) == -1) {
1102     fprintf(stderr, "Cannot stat file %s\n", argv[1]);
1103     return 1;
1104   }
1105
1106   size = statbuf.st_size;
1107
1108   mapping = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
1109
1110   if (mapping == (unsigned char *)-1) {
1111     fprintf(stderr, "Cannot mmap file %s\n", argv[1]);
1112     return 1;
1113   }
1114
1115   used_dynamic_symbols = g_hash_table_new(g_direct_hash, g_direct_equal);
1116
1117   elf_header = (Elf32_Ehdr *)mapping;
1118
1119   if (strncmp((void *)elf_header, ELFMAG, SELFMAG)!=0) {
1120     fprintf(stderr, "Not an ELF file\n");
1121     return 1;
1122   }
1123
1124   if (elf_header->e_ident[EI_VERSION] != EV_CURRENT) {
1125     fprintf(stderr, "Wrong ELF file version\n");
1126     return 1;
1127   }
1128
1129   if (elf_header->e_ident[EI_CLASS] != ELFCLASS32) {
1130     fprintf(stderr, "Only 32bit ELF files supported\n");
1131     return 1;
1132   }
1133
1134   setup_byteswapping(elf_header->e_ident[EI_DATA]);
1135
1136   machine_type = read_half(elf_header->e_machine);
1137   if ( (machine_type != EM_386) &&
1138        (machine_type != EM_PPC) ) {
1139     fprintf(stderr, "Unsupported architecture. Supported are: x86, ppc\n");
1140     return 1;
1141   }
1142
1143   if (read_half(elf_header->e_type) != ET_DYN) {
1144     fprintf(stderr, "Not an ELF shared object\n");
1145     return 1;
1146   }
1147
1148   dynamic = elf_find_section(SHT_DYNAMIC);
1149   dynsym = elf_find_section(SHT_DYNSYM);
1150   symtab = elf_find_section(SHT_SYMTAB);
1151   dynstr_index = read_word(dynsym->sh_link);
1152   dynstr = elf_find_section_num(dynstr_index);
1153   dynstr_data = (char *)FILE_OFFSET(read_word(dynstr->sh_offset));
1154   old_dynstr_size = read_word(dynstr->sh_size);
1155   ver_d = elf_find_section(SHT_GNU_verdef);
1156   ver_r = elf_find_section(SHT_GNU_verneed);
1157   hash = elf_find_section(SHT_HASH);
1158
1159   /* Generate hash table with all used strings: */
1160
1161   add_strings_from_dynsym(dynsym, dynstr_data);
1162   add_strings_from_dynamic(dynamic, dynstr_data);
1163   if (ver_d && (read_word(ver_d->sh_link) == dynstr_index))
1164     add_strings_from_ver_d(ver_d, dynstr_data);
1165   if (ver_r && (read_word(ver_r->sh_link) == dynstr_index))
1166     add_strings_from_ver_r(ver_r, dynstr_data);
1167
1168   /* Generate new dynstr section from the used strings hashtable: */
1169
1170   new_dynstr = generate_new_dynstr(&new_dynstr_size);
1171   /*
1172   printf("New dynstr size: %d\n", new_dynstr_size);
1173   printf("Old dynstr size: %d\n", old_dynstr_size);
1174   */
1175
1176   if (new_dynstr_size >= old_dynstr_size) {
1177     fprintf(stderr, "Couldn't GC any strings, exiting.\n");
1178     return 0;
1179   }
1180
1181   /* Fixup all references: */
1182   fixup_strings_in_dynsym(dynsym);
1183   fixup_strings_in_dynamic(dynamic);
1184   if (ver_d && (read_word(ver_d->sh_link) == dynstr_index))
1185     fixup_strings_in_ver_d(ver_d);
1186   if (ver_r && (read_word(ver_r->sh_link) == dynstr_index))
1187     fixup_strings_in_ver_r(ver_r);
1188
1189   /* Copy over the new dynstr: */
1190   memcpy(dynstr_data, new_dynstr, new_dynstr_size);
1191   memset(dynstr_data + new_dynstr_size, ' ', old_dynstr_size-new_dynstr_size);
1192
1193   /* Compact the dynstr section and the file: */
1194
1195   /* 1. Set up the data for the fixup_offset() function: */
1196   hole_index = read_word(dynstr->sh_offset) + new_dynstr_size;
1197   higher_section = elf_find_next_higher_section(hole_index);
1198   hole_end = read_word(higher_section->sh_offset);
1199
1200   align_hole(&hole_index, &hole_end);
1201   hole_len = hole_end - hole_index;
1202
1203   hole_addr_start = hole_index; /* TODO: Fix this to something better */
1204
1205   find_segment_addr_min_max(read_word(dynstr->sh_offset),
1206                             &hole_addr_remap_start, &hole_addr_remap_end);
1207
1208   /*
1209   printf("Hole remap: 0x%lx - 0x%lx\n", hole_addr_remap_start, hole_addr_remap_end);
1210
1211   printf("hole: %lu - %lu (%lu bytes)\n", hole_index, hole_end, hole_len);
1212   printf("hole: 0x%lx - 0x%lx (0x%lx bytes)\n", hole_index, hole_end, hole_len);
1213   */
1214
1215   /* 2. Change all section and segment sizes and offsets: */
1216   remap_symtab(dynsym);
1217   if (symtab)
1218     remap_symtab(symtab);
1219
1220   if (machine_type == EM_386)
1221     remap_i386_got();
1222   if (machine_type == EM_PPC)
1223     remap_ppc_got();
1224
1225   remap_dynamic(dynamic, new_dynstr_size);
1226   remap_sections(); /* After this line the section headers are wrong */
1227   remap_segments();
1228   remap_elf_header();
1229
1230   /* 3. Do the real compacting. */
1231
1232   memmove(mapping + hole_index,
1233           mapping + hole_index + hole_len,
1234           size - (hole_index + hole_len));
1235
1236   munmap(mapping, size);
1237
1238   ftruncate(fd, size - hole_len);
1239   close(fd);
1240
1241   return 0;
1242 }
1243
1244
1245