ld/ldwrite.c

   1 /* ldwrite.c -- write out the linked file
   2    Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2002,
   3    2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   4    Written by Steve Chamberlain sac@cygnus.com
   5
   6 This file is part of GLD, the Gnu Linker.
   7
   8 This program is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2 of the License, or
  11 (at your option) any later version.
  12
  13 This program is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with this program; if not, write to the Free Software
  20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  21
  22 #include "bfd.h"
  23 #include "sysdep.h"
  24 #include "bfdlink.h"
  25 #include "libiberty.h"
  26 #include "safe-ctype.h"
  27
  28 #include "ld.h"
  29 #include "ldexp.h"
  30 #include "ldlang.h"
  31 #include "ldwrite.h"
  32 #include "ldmisc.h"
  33 #include <ldgram.h>
  34 #include "ldmain.h"
  35
  36 /* Build link_order structures for the BFD linker.  */
  37
  38 static void
  39 build_link_order (lang_statement_union_type *statement)
  40 {
  41   switch (statement->header.type)
  42     {
  43     case lang_data_statement_enum:
  44       {
  45         asection *output_section;
  46         struct bfd_link_order *link_order;
  47         bfd_vma value;
  48         bfd_boolean big_endian = FALSE;
  49
  50         output_section = statement->data_statement.output_section;
  51         ASSERT (output_section->owner == output_bfd);
  52
  53         link_order = bfd_new_link_order (output_bfd, output_section);
  54         if (link_order == NULL)
  55           einfo (_("%P%F: bfd_new_link_order failed\n"));
  56
  57         link_order->type = bfd_data_link_order;
  58         link_order->offset = statement->data_statement.output_offset;
  59         link_order->u.data.contents = xmalloc (QUAD_SIZE);
  60
  61         value = statement->data_statement.value;
  62
  63         /* If the endianness of the output BFD is not known, then we
  64            base the endianness of the data on the first input file.
  65            By convention, the bfd_put routines for an unknown
  66            endianness are big endian, so we must swap here if the
  67            input file is little endian.  */
  68         if (bfd_big_endian (output_bfd))
  69           big_endian = TRUE;
  70         else if (bfd_little_endian (output_bfd))
  71           big_endian = FALSE;
  72         else
  73           {
  74             bfd_boolean swap;
  75
  76             swap = FALSE;
  77             if (command_line.endian == ENDIAN_BIG)
  78               big_endian = TRUE;
  79             else if (command_line.endian == ENDIAN_LITTLE)
  80               {
  81                 big_endian = FALSE;
  82                 swap = TRUE;
  83               }
  84             else if (command_line.endian == ENDIAN_UNSET)
  85               {
  86                 big_endian = TRUE;
  87                 {
  88                   LANG_FOR_EACH_INPUT_STATEMENT (s)
  89                     {
  90                       if (s->the_bfd != NULL)
  91                         {
  92                           if (bfd_little_endian (s->the_bfd))
  93                             {
  94                               big_endian = FALSE;
  95                               swap = TRUE;
  96                             }
  97                           break;
  98                         }
  99                     }
 100                 }
 101               }
 102
 103             if (swap)
 104               {
 105                 bfd_byte buffer[8];
 106
 107                 switch (statement->data_statement.type)
 108                   {
 109                   case QUAD:
 110                   case SQUAD:
 111                     if (sizeof (bfd_vma) >= QUAD_SIZE)
 112                       {
 113                         bfd_putl64 (value, buffer);
 114                         value = bfd_getb64 (buffer);
 115                         break;
 116                       }
 117                     /* Fall through.  */
 118                   case LONG:
 119                     bfd_putl32 (value, buffer);
 120                     value = bfd_getb32 (buffer);
 121                     break;
 122                   case SHORT:
 123                     bfd_putl16 (value, buffer);
 124                     value = bfd_getb16 (buffer);
 125                     break;
 126                   case BYTE:
 127                     break;
 128                   default:
 129                     abort ();
 130                   }
 131               }
 132           }
 133
 134         ASSERT (output_section->owner == output_bfd);
 135         switch (statement->data_statement.type)
 136           {
 137           case QUAD:
 138           case SQUAD:
 139             if (sizeof (bfd_vma) >= QUAD_SIZE)
 140               bfd_put_64 (output_bfd, value, link_order->u.data.contents);
 141             else
 142               {
 143                 bfd_vma high;
 144
 145                 if (statement->data_statement.type == QUAD)
 146                   high = 0;
 147                 else if ((value & 0x80000000) == 0)
 148                   high = 0;
 149                 else
 150                   high = (bfd_vma) -1;
 151                 bfd_put_32 (output_bfd, high,
 152                             (link_order->u.data.contents
 153                              + (big_endian ? 0 : 4)));
 154                 bfd_put_32 (output_bfd, value,
 155                             (link_order->u.data.contents
 156                              + (big_endian ? 4 : 0)));
 157               }
 158             link_order->size = QUAD_SIZE;
 159             break;
 160           case LONG:
 161             bfd_put_32 (output_bfd, value, link_order->u.data.contents);
 162             link_order->size = LONG_SIZE;
 163             break;
 164           case SHORT:
 165             bfd_put_16 (output_bfd, value, link_order->u.data.contents);
 166             link_order->size = SHORT_SIZE;
 167             break;
 168           case BYTE:
 169             bfd_put_8 (output_bfd, value, link_order->u.data.contents);
 170             link_order->size = BYTE_SIZE;
 171             break;
 172           default:
 173             abort ();
 174           }
 175       }
 176       break;
 177
 178     case lang_reloc_statement_enum:
 179       {
 180         lang_reloc_statement_type *rs;
 181         asection *output_section;
 182         struct bfd_link_order *link_order;
 183
 184         rs = &statement->reloc_statement;
 185
 186         output_section = rs->output_section;
 187         ASSERT (output_section->owner == output_bfd);
 188
 189         link_order = bfd_new_link_order (output_bfd, output_section);
 190         if (link_order == NULL)
 191           einfo (_("%P%F: bfd_new_link_order failed\n"));
 192
 193         link_order->offset = rs->output_offset;
 194         link_order->size = bfd_get_reloc_size (rs->howto);
 195
 196         link_order->u.reloc.p = xmalloc (sizeof (struct bfd_link_order_reloc));
 197
 198         link_order->u.reloc.p->reloc = rs->reloc;
 199         link_order->u.reloc.p->addend = rs->addend_value;
 200
 201         if (rs->name == NULL)
 202           {
 203             link_order->type = bfd_section_reloc_link_order;
 204             if (rs->section->owner == output_bfd)
 205               link_order->u.reloc.p->u.section = rs->section;
 206             else
 207               {
 208                 link_order->u.reloc.p->u.section = rs->section->output_section;
 209                 link_order->u.reloc.p->addend += rs->section->output_offset;
 210               }
 211           }
 212         else
 213           {
 214             link_order->type = bfd_symbol_reloc_link_order;
 215             link_order->u.reloc.p->u.name = rs->name;
 216           }
 217       }
 218       break;
 219
 220     case lang_input_section_enum:
 221       {
 222         /* Create a new link_order in the output section with this
 223            attached */
 224         asection *i = statement->input_section.section;
 225
 226         if (!((lang_input_statement_type *) i->owner->usrdata)->just_syms_flag
 227             && (i->flags & SEC_EXCLUDE) == 0)
 228           {
 229             asection *output_section = i->output_section;
 230
 231             ASSERT (output_section->owner == output_bfd);
 232
 233             if ((output_section->flags & SEC_HAS_CONTENTS) != 0
 234                 || ((output_section->flags & SEC_LOAD) != 0
 235                     && (output_section->flags & SEC_THREAD_LOCAL)))
 236               {
 237                 struct bfd_link_order *link_order;
 238
 239                 link_order = bfd_new_link_order (output_bfd, output_section);
 240
 241                 if (i->flags & SEC_NEVER_LOAD)
 242                   {
 243                     /* We've got a never load section inside one which
 244                        is going to be output, we'll change it into a
 245                        fill.  */
 246                     link_order->type = bfd_data_link_order;
 247                     link_order->u.data.contents = (unsigned char *) "";
 248                     link_order->u.data.size = 1;
 249                   }
 250                 else
 251                   {
 252                     link_order->type = bfd_indirect_link_order;
 253                     link_order->u.indirect.section = i;
 254                     ASSERT (i->output_section == output_section);
 255                   }
 256                 link_order->size = i->size;
 257                 link_order->offset = i->output_offset;
 258               }
 259           }
 260       }
 261       break;
 262
 263     case lang_padding_statement_enum:
 264       /* Make a new link_order with the right filler */
 265       {
 266         asection *output_section;
 267         struct bfd_link_order *link_order;
 268
 269         output_section = statement->padding_statement.output_section;
 270         ASSERT (statement->padding_statement.output_section->owner
 271                 == output_bfd);
 272         if ((output_section->flags & SEC_HAS_CONTENTS) != 0)
 273           {
 274             link_order = bfd_new_link_order (output_bfd, output_section);
 275             link_order->type = bfd_data_link_order;
 276             link_order->size = statement->padding_statement.size;
 277             link_order->offset = statement->padding_statement.output_offset;
 278             link_order->u.data.contents = statement->padding_statement.fill->data;
 279             link_order->u.data.size = statement->padding_statement.fill->size;
 280           }
 281       }
 282       break;
 283
 284     default:
 285       /* All the other ones fall through */
 286       break;
 287     }
 288 }
 289
 290 /* Return true if NAME is the name of an unsplittable section. These
 291    are the stabs strings, dwarf strings.  */
 292
 293 static bfd_boolean
 294 unsplittable_name (const char *name)
 295 {
 296   if (CONST_STRNEQ (name, ".stab"))
 297     {
 298       /* There are several stab like string sections. We pattern match on
 299          ".stab...str"  */
 300       unsigned len = strlen (name);
 301       if (strcmp (&name[len-3], "str") == 0)
 302         return TRUE;
 303     }
 304   else if (strcmp (name, "$GDB_STRINGS$") == 0)
 305     return TRUE;
 306   return FALSE;
 307 }
 308
 309 /* Wander around the input sections, make sure that
 310    we'll never try and create an output section with more relocs
 311    than will fit.. Do this by always assuming the worst case, and
 312    creating new output sections with all the right bits.  */
 313 #define TESTIT 1
 314 static asection *
 315 clone_section (bfd *abfd, asection *s, const char *name, int *count)
 316 {
 317   char *tname;
 318   char *sname;
 319   unsigned int len;
 320   asection *n;
 321   struct bfd_link_hash_entry *h;
 322
 323   /* Invent a section name from the section name and a dotted numeric
 324      suffix.   */
 325   len = strlen (name);
 326   tname = xmalloc (len + 1);
 327   memcpy (tname, name, len + 1);
 328   /* Remove a dotted number suffix, from a previous split link. */
 329   while (len && ISDIGIT (tname[len-1]))
 330     len--;
 331   if (len > 1 && tname[len-1] == '.')
 332     /* It was a dotted number. */
 333     tname[len-1] = 0;
 334
 335   /* We want to use the whole of the original section name for the
 336      split name, but coff can be restricted to 8 character names.  */
 337   if (bfd_family_coff (abfd) && strlen (tname) > 5)
 338     {
 339       /* Some section names cannot be truncated, as the name is
 340          used to locate some other section.  */
 341       if (CONST_STRNEQ (name, ".stab")
 342           || strcmp (name, "$GDB_SYMBOLS$") == 0)
 343         {
 344           einfo (_ ("%F%P: cannot create split section name for %s\n"), name);
 345           /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 346           return NULL;
 347         }
 348       tname[5] = 0;
 349     }
 350
 351   if ((sname = bfd_get_unique_section_name (abfd, tname, count)) == NULL
 352       || (n = bfd_make_section_anyway (abfd, sname)) == NULL
 353       || (h = bfd_link_hash_lookup (link_info.hash,
 354                                     sname, TRUE, TRUE, FALSE)) == NULL)
 355     {
 356       einfo (_("%F%P: clone section failed: %E\n"));
 357       /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 358       return NULL;
 359     }
 360   free (tname);
 361
 362   /* Set up section symbol.  */
 363   h->type = bfd_link_hash_defined;
 364   h->u.def.value = 0;
 365   h->u.def.section = n;
 366
 367   n->flags = s->flags;
 368   n->vma = s->vma;
 369   n->user_set_vma = s->user_set_vma;
 370   n->lma = s->lma;
 371   n->size = 0;
 372   n->output_offset = s->output_offset;
 373   n->output_section = n;
 374   n->orelocation = 0;
 375   n->reloc_count = 0;
 376   n->alignment_power = s->alignment_power;
 377   return n;
 378 }
 379
 380 #if TESTING
 381 static void
 382 ds (asection *s)
 383 {
 384   struct bfd_link_order *l = s->map_head.link_order;
 385   printf ("vma %x size %x\n", s->vma, s->size);
 386   while (l)
 387     {
 388       if (l->type == bfd_indirect_link_order)
 389         {
 390           printf ("%8x %s\n", l->offset, l->u.indirect.section->owner->filename);
 391         }
 392       else
 393         {
 394           printf (_("%8x something else\n"), l->offset);
 395         }
 396       l = l->next;
 397     }
 398   printf ("\n");
 399 }
 400
 401 dump (char *s, asection *a1, asection *a2)
 402 {
 403   printf ("%s\n", s);
 404   ds (a1);
 405   ds (a2);
 406 }
 407
 408 static void
 409 sanity_check (bfd *abfd)
 410 {
 411   asection *s;
 412   for (s = abfd->sections; s; s = s->next)
 413     {
 414       struct bfd_link_order *p;
 415       bfd_vma prev = 0;
 416       for (p = s->map_head.link_order; p; p = p->next)
 417         {
 418           if (p->offset > 100000)
 419             abort ();
 420           if (p->offset < prev)
 421             abort ();
 422           prev = p->offset;
 423         }
 424     }
 425 }
 426 #else
 427 #define sanity_check(a)
 428 #define dump(a, b, c)
 429 #endif
 430
 431 static void
 432 split_sections (bfd *abfd, struct bfd_link_info *info)
 433 {
 434   asection *original_sec;
 435   int nsecs = abfd->section_count;
 436   sanity_check (abfd);
 437   /* Look through all the original sections.  */
 438   for (original_sec = abfd->sections;
 439        original_sec && nsecs;
 440        original_sec = original_sec->next, nsecs--)
 441     {
 442       int count = 0;
 443       unsigned int lines = 0;
 444       unsigned int relocs = 0;
 445       bfd_size_type sec_size = 0;
 446       struct bfd_link_order *l;
 447       struct bfd_link_order *p;
 448       bfd_vma vma = original_sec->vma;
 449       asection *cursor = original_sec;
 450
 451       /* Count up the relocations and line entries to see if anything
 452          would be too big to fit.  Accumulate section size too.  */
 453       for (l = NULL, p = cursor->map_head.link_order; p != NULL; p = l->next)
 454         {
 455           unsigned int thislines = 0;
 456           unsigned int thisrelocs = 0;
 457           bfd_size_type thissize = 0;
 458           if (p->type == bfd_indirect_link_order)
 459             {
 460               asection *sec;
 461
 462               sec = p->u.indirect.section;
 463
 464               if (info->strip == strip_none
 465                   || info->strip == strip_some)
 466                 thislines = sec->lineno_count;
 467
 468               if (info->relocatable)
 469                 thisrelocs = sec->reloc_count;
 470
 471               thissize = sec->size;
 472
 473             }
 474           else if (info->relocatable
 475                    && (p->type == bfd_section_reloc_link_order
 476                        || p->type == bfd_symbol_reloc_link_order))
 477             thisrelocs++;
 478
 479           if (l != NULL
 480               && (thisrelocs + relocs >= config.split_by_reloc
 481                   || thislines + lines >= config.split_by_reloc
 482                   || (thissize + sec_size >= config.split_by_file))
 483               && !unsplittable_name (cursor->name))
 484             {
 485               /* Create a new section and put this link order and the
 486                  following link orders into it.  */
 487               bfd_vma shift_offset;
 488               asection *n;
 489
 490               n = clone_section (abfd, cursor, original_sec->name, &count);
 491
 492               /* Attach the link orders to the new section and snip
 493                  them off from the old section.  */
 494               n->map_head.link_order = p;
 495               n->map_tail.link_order = cursor->map_tail.link_order;
 496               cursor->map_tail.link_order = l;
 497               l->next = NULL;
 498               l = p;
 499
 500               /* Change the size of the original section and
 501                  update the vma of the new one.  */
 502
 503               dump ("before snip", cursor, n);
 504
 505               shift_offset = p->offset;
 506               n->size = cursor->size - shift_offset;
 507               cursor->size = shift_offset;
 508
 509               vma += shift_offset;
 510               n->lma = n->vma = vma;
 511
 512               /* Run down the chain and change the output section to
 513                  the right one, update the offsets too.  */
 514               do
 515                 {
 516                   p->offset -= shift_offset;
 517                   if (p->type == bfd_indirect_link_order)
 518                     {
 519                       p->u.indirect.section->output_section = n;
 520                       p->u.indirect.section->output_offset = p->offset;
 521                     }
 522                   p = p->next;
 523                 }
 524               while (p);
 525
 526               dump ("after snip", cursor, n);
 527               cursor = n;
 528               relocs = thisrelocs;
 529               lines = thislines;
 530               sec_size = thissize;
 531             }
 532           else
 533             {
 534               l = p;
 535               relocs += thisrelocs;
 536               lines += thislines;
 537               sec_size += thissize;
 538             }
 539         }
 540     }
 541   sanity_check (abfd);
 542 }
 543
 544 /* Call BFD to write out the linked file.  */
 545
 546 void
 547 ldwrite (void)
 548 {
 549   /* Reset error indicator, which can typically something like invalid
 550      format from opening up the .o files.  */
 551   bfd_set_error (bfd_error_no_error);
 552   lang_for_each_statement (build_link_order);
 553
 554   if (config.split_by_reloc != (unsigned) -1
 555       || config.split_by_file != (bfd_size_type) -1)
 556     split_sections (output_bfd, &link_info);
 557   if (!bfd_final_link (output_bfd, &link_info))
 558     {
 559       /* If there was an error recorded, print it out.  Otherwise assume
 560          an appropriate error message like unknown symbol was printed
 561          out.  */
 562
 563       if (bfd_get_error () != bfd_error_no_error)
 564         einfo (_("%F%P: final link failed: %E\n"));
 565       else
 566         xexit (1);
 567     }
 568 }