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, 2007, 2008, 2010
   4    Free Software Foundation, Inc.
   5    Written by Steve Chamberlain sac@cygnus.com
   6
   7    This file is part of the GNU Binutils.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  22    MA 02110-1301, USA.  */
  23
  24 #include "sysdep.h"
  25 #include "bfd.h"
  26 #include "bfdlink.h"
  27 #include "libiberty.h"
  28 #include "safe-ctype.h"
  29
  30 #include "ld.h"
  31 #include "ldexp.h"
  32 #include "ldlang.h"
  33 #include "ldwrite.h"
  34 #include "ldmisc.h"
  35 #include <ldgram.h>
  36 #include "ldmain.h"
  37
  38 /* Build link_order structures for the BFD linker.  */
  39
  40 static void
  41 build_link_order (lang_statement_union_type *statement)
  42 {
  43   switch (statement->header.type)
  44     {
  45     case lang_data_statement_enum:
  46       {
  47         asection *output_section;
  48         struct bfd_link_order *link_order;
  49         bfd_vma value;
  50         bfd_boolean big_endian = FALSE;
  51
  52         output_section = statement->data_statement.output_section;
  53         ASSERT (output_section->owner == link_info.output_bfd);
  54
  55         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
  56               || ((output_section->flags & SEC_LOAD) != 0
  57                   && (output_section->flags & SEC_THREAD_LOCAL))))
  58           break;
  59
  60         link_order = bfd_new_link_order (link_info.output_bfd, output_section);
  61         if (link_order == NULL)
  62           einfo (_("%P%F: bfd_new_link_order failed\n"));
  63
  64         link_order->type = bfd_data_link_order;
  65         link_order->offset = statement->data_statement.output_offset;
  66         link_order->u.data.contents = (bfd_byte *) xmalloc (QUAD_SIZE);
  67
  68         value = statement->data_statement.value;
  69
  70         /* If the endianness of the output BFD is not known, then we
  71            base the endianness of the data on the first input file.
  72            By convention, the bfd_put routines for an unknown
  73            endianness are big endian, so we must swap here if the
  74            input file is little endian.  */
  75         if (bfd_big_endian (link_info.output_bfd))
  76           big_endian = TRUE;
  77         else if (bfd_little_endian (link_info.output_bfd))
  78           big_endian = FALSE;
  79         else
  80           {
  81             bfd_boolean swap;
  82
  83             swap = FALSE;
  84             if (command_line.endian == ENDIAN_BIG)
  85               big_endian = TRUE;
  86             else if (command_line.endian == ENDIAN_LITTLE)
  87               {
  88                 big_endian = FALSE;
  89                 swap = TRUE;
  90               }
  91             else if (command_line.endian == ENDIAN_UNSET)
  92               {
  93                 big_endian = TRUE;
  94                 {
  95                   LANG_FOR_EACH_INPUT_STATEMENT (s)
  96                     {
  97                       if (s->the_bfd != NULL)
  98                         {
  99                           if (bfd_little_endian (s->the_bfd))
 100                             {
 101                               big_endian = FALSE;
 102                               swap = TRUE;
 103                             }
 104                           break;
 105                         }
 106                     }
 107                 }
 108               }
 109
 110             if (swap)
 111               {
 112                 bfd_byte buffer[8];
 113
 114                 switch (statement->data_statement.type)
 115                   {
 116                   case QUAD:
 117                   case SQUAD:
 118                     if (sizeof (bfd_vma) >= QUAD_SIZE)
 119                       {
 120                         bfd_putl64 (value, buffer);
 121                         value = bfd_getb64 (buffer);
 122                         break;
 123                       }
 124                     /* Fall through.  */
 125                   case LONG:
 126                     bfd_putl32 (value, buffer);
 127                     value = bfd_getb32 (buffer);
 128                     break;
 129                   case SHORT:
 130                     bfd_putl16 (value, buffer);
 131                     value = bfd_getb16 (buffer);
 132                     break;
 133                   case BYTE:
 134                     break;
 135                   default:
 136                     abort ();
 137                   }
 138               }
 139           }
 140
 141         ASSERT (output_section->owner == link_info.output_bfd);
 142         switch (statement->data_statement.type)
 143           {
 144           case QUAD:
 145           case SQUAD:
 146             if (sizeof (bfd_vma) >= QUAD_SIZE)
 147               bfd_put_64 (link_info.output_bfd, value,
 148                           link_order->u.data.contents);
 149             else
 150               {
 151                 bfd_vma high;
 152
 153                 if (statement->data_statement.type == QUAD)
 154                   high = 0;
 155                 else if ((value & 0x80000000) == 0)
 156                   high = 0;
 157                 else
 158                   high = (bfd_vma) -1;
 159                 bfd_put_32 (link_info.output_bfd, high,
 160                             (link_order->u.data.contents
 161                              + (big_endian ? 0 : 4)));
 162                 bfd_put_32 (link_info.output_bfd, value,
 163                             (link_order->u.data.contents
 164                              + (big_endian ? 4 : 0)));
 165               }
 166             link_order->size = QUAD_SIZE;
 167             break;
 168           case LONG:
 169             bfd_put_32 (link_info.output_bfd, value,
 170                         link_order->u.data.contents);
 171             link_order->size = LONG_SIZE;
 172             break;
 173           case SHORT:
 174             bfd_put_16 (link_info.output_bfd, value,
 175                         link_order->u.data.contents);
 176             link_order->size = SHORT_SIZE;
 177             break;
 178           case BYTE:
 179             bfd_put_8 (link_info.output_bfd, value,
 180                        link_order->u.data.contents);
 181             link_order->size = BYTE_SIZE;
 182             break;
 183           default:
 184             abort ();
 185           }
 186         link_order->u.data.size = link_order->size;
 187       }
 188       break;
 189
 190     case lang_reloc_statement_enum:
 191       {
 192         lang_reloc_statement_type *rs;
 193         asection *output_section;
 194         struct bfd_link_order *link_order;
 195
 196         rs = &statement->reloc_statement;
 197
 198         output_section = rs->output_section;
 199         ASSERT (output_section->owner == link_info.output_bfd);
 200
 201         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 202               || ((output_section->flags & SEC_LOAD) != 0
 203                   && (output_section->flags & SEC_THREAD_LOCAL))))
 204           break;
 205
 206         link_order = bfd_new_link_order (link_info.output_bfd, output_section);
 207         if (link_order == NULL)
 208           einfo (_("%P%F: bfd_new_link_order failed\n"));
 209
 210         link_order->offset = rs->output_offset;
 211         link_order->size = bfd_get_reloc_size (rs->howto);
 212
 213         link_order->u.reloc.p = (struct bfd_link_order_reloc *)
 214             xmalloc (sizeof (struct bfd_link_order_reloc));
 215
 216         link_order->u.reloc.p->reloc = rs->reloc;
 217         link_order->u.reloc.p->addend = rs->addend_value;
 218
 219         if (rs->name == NULL)
 220           {
 221             link_order->type = bfd_section_reloc_link_order;
 222             if (rs->section->owner == link_info.output_bfd)
 223               link_order->u.reloc.p->u.section = rs->section;
 224             else
 225               {
 226                 link_order->u.reloc.p->u.section = rs->section->output_section;
 227                 link_order->u.reloc.p->addend += rs->section->output_offset;
 228               }
 229           }
 230         else
 231           {
 232             link_order->type = bfd_symbol_reloc_link_order;
 233             link_order->u.reloc.p->u.name = rs->name;
 234           }
 235       }
 236       break;
 237
 238     case lang_input_section_enum:
 239       {
 240         /* Create a new link_order in the output section with this
 241            attached */
 242         asection *i = statement->input_section.section;
 243
 244         if (!((lang_input_statement_type *) i->owner->usrdata)->flags.just_syms
 245             && (i->flags & SEC_EXCLUDE) == 0)
 246           {
 247             asection *output_section = i->output_section;
 248             struct bfd_link_order *link_order;
 249
 250             ASSERT (output_section->owner == link_info.output_bfd);
 251
 252             if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 253                   || ((output_section->flags & SEC_LOAD) != 0
 254                       && (output_section->flags & SEC_THREAD_LOCAL))))
 255               break;
 256
 257             link_order = bfd_new_link_order (link_info.output_bfd,
 258                                              output_section);
 259
 260             if ((i->flags & SEC_NEVER_LOAD) != 0
 261                 && (i->flags & SEC_DEBUGGING) == 0)
 262               {
 263                 /* We've got a never load section inside one which is
 264                    going to be output, we'll change it into a fill.  */
 265                 link_order->type = bfd_data_link_order;
 266                 link_order->u.data.contents = (unsigned char *) "";
 267                 link_order->u.data.size = 1;
 268               }
 269             else
 270               {
 271                 link_order->type = bfd_indirect_link_order;
 272                 link_order->u.indirect.section = i;
 273                 ASSERT (i->output_section == output_section);
 274               }
 275             link_order->size = i->size;
 276             link_order->offset = i->output_offset;
 277           }
 278       }
 279       break;
 280
 281     case lang_padding_statement_enum:
 282       /* Make a new link_order with the right filler */
 283       {
 284         asection *output_section;
 285         struct bfd_link_order *link_order;
 286
 287         output_section = statement->padding_statement.output_section;
 288         ASSERT (statement->padding_statement.output_section->owner
 289                 == link_info.output_bfd);
 290
 291         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 292               || ((output_section->flags & SEC_LOAD) != 0
 293                   && (output_section->flags & SEC_THREAD_LOCAL))))
 294           break;
 295
 296         link_order = bfd_new_link_order (link_info.output_bfd,
 297                                          output_section);
 298         link_order->type = bfd_data_link_order;
 299         link_order->size = statement->padding_statement.size;
 300         link_order->offset = statement->padding_statement.output_offset;
 301         link_order->u.data.contents = statement->padding_statement.fill->data;
 302         link_order->u.data.size = statement->padding_statement.fill->size;
 303       }
 304       break;
 305
 306     default:
 307       /* All the other ones fall through */
 308       break;
 309     }
 310 }
 311
 312 /* Return true if NAME is the name of an unsplittable section. These
 313    are the stabs strings, dwarf strings.  */
 314
 315 static bfd_boolean
 316 unsplittable_name (const char *name)
 317 {
 318   if (CONST_STRNEQ (name, ".stab"))
 319     {
 320       /* There are several stab like string sections. We pattern match on
 321          ".stab...str"  */
 322       unsigned len = strlen (name);
 323       if (strcmp (&name[len-3], "str") == 0)
 324         return TRUE;
 325     }
 326   else if (strcmp (name, "$GDB_STRINGS$") == 0)
 327     return TRUE;
 328   return FALSE;
 329 }
 330
 331 /* Wander around the input sections, make sure that
 332    we'll never try and create an output section with more relocs
 333    than will fit.. Do this by always assuming the worst case, and
 334    creating new output sections with all the right bits.  */
 335 #define TESTIT 1
 336 static asection *
 337 clone_section (bfd *abfd, asection *s, const char *name, int *count)
 338 {
 339   char *tname;
 340   char *sname;
 341   unsigned int len;
 342   asection *n;
 343   struct bfd_link_hash_entry *h;
 344
 345   /* Invent a section name from the section name and a dotted numeric
 346      suffix.   */
 347   len = strlen (name);
 348   tname = (char *) xmalloc (len + 1);
 349   memcpy (tname, name, len + 1);
 350   /* Remove a dotted number suffix, from a previous split link. */
 351   while (len && ISDIGIT (tname[len-1]))
 352     len--;
 353   if (len > 1 && tname[len-1] == '.')
 354     /* It was a dotted number. */
 355     tname[len-1] = 0;
 356
 357   /* We want to use the whole of the original section name for the
 358      split name, but coff can be restricted to 8 character names.  */
 359   if (bfd_family_coff (abfd) && strlen (tname) > 5)
 360     {
 361       /* Some section names cannot be truncated, as the name is
 362          used to locate some other section.  */
 363       if (CONST_STRNEQ (name, ".stab")
 364           || strcmp (name, "$GDB_SYMBOLS$") == 0)
 365         {
 366           einfo (_ ("%F%P: cannot create split section name for %s\n"), name);
 367           /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 368           return NULL;
 369         }
 370       tname[5] = 0;
 371     }
 372
 373   if ((sname = bfd_get_unique_section_name (abfd, tname, count)) == NULL
 374       || (n = bfd_make_section_anyway (abfd, sname)) == NULL
 375       || (h = bfd_link_hash_lookup (link_info.hash,
 376                                     sname, TRUE, TRUE, FALSE)) == NULL)
 377     {
 378       einfo (_("%F%P: clone section failed: %E\n"));
 379       /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 380       return NULL;
 381     }
 382   free (tname);
 383
 384   /* Set up section symbol.  */
 385   h->type = bfd_link_hash_defined;
 386   h->u.def.value = 0;
 387   h->u.def.section = n;
 388
 389   n->flags = s->flags;
 390   n->vma = s->vma;
 391   n->user_set_vma = s->user_set_vma;
 392   n->lma = s->lma;
 393   n->size = 0;
 394   n->output_offset = s->output_offset;
 395   n->output_section = n;
 396   n->orelocation = 0;
 397   n->reloc_count = 0;
 398   n->alignment_power = s->alignment_power;
 399
 400   bfd_copy_private_section_data (abfd, s, abfd, n);
 401
 402   return n;
 403 }
 404
 405 #if TESTING
 406 static void
 407 ds (asection *s)
 408 {
 409   struct bfd_link_order *l = s->map_head.link_order;
 410   printf ("vma %x size %x\n", s->vma, s->size);
 411   while (l)
 412     {
 413       if (l->type == bfd_indirect_link_order)
 414         {
 415           printf ("%8x %s\n", l->offset, l->u.indirect.section->owner->filename);
 416         }
 417       else
 418         {
 419           printf (_("%8x something else\n"), l->offset);
 420         }
 421       l = l->next;
 422     }
 423   printf ("\n");
 424 }
 425
 426 dump (char *s, asection *a1, asection *a2)
 427 {
 428   printf ("%s\n", s);
 429   ds (a1);
 430   ds (a2);
 431 }
 432
 433 static void
 434 sanity_check (bfd *abfd)
 435 {
 436   asection *s;
 437   for (s = abfd->sections; s; s = s->next)
 438     {
 439       struct bfd_link_order *p;
 440       bfd_vma prev = 0;
 441       for (p = s->map_head.link_order; p; p = p->next)
 442         {
 443           if (p->offset > 100000)
 444             abort ();
 445           if (p->offset < prev)
 446             abort ();
 447           prev = p->offset;
 448         }
 449     }
 450 }
 451 #else
 452 #define sanity_check(a)
 453 #define dump(a, b, c)
 454 #endif
 455
 456 static void
 457 split_sections (bfd *abfd, struct bfd_link_info *info)
 458 {
 459   asection *original_sec;
 460   int nsecs = abfd->section_count;
 461   sanity_check (abfd);
 462   /* Look through all the original sections.  */
 463   for (original_sec = abfd->sections;
 464        original_sec && nsecs;
 465        original_sec = original_sec->next, nsecs--)
 466     {
 467       int count = 0;
 468       unsigned int lines = 0;
 469       unsigned int relocs = 0;
 470       bfd_size_type sec_size = 0;
 471       struct bfd_link_order *l;
 472       struct bfd_link_order *p;
 473       bfd_vma vma = original_sec->vma;
 474       asection *cursor = original_sec;
 475
 476       /* Count up the relocations and line entries to see if anything
 477          would be too big to fit.  Accumulate section size too.  */
 478       for (l = NULL, p = cursor->map_head.link_order; p != NULL; p = l->next)
 479         {
 480           unsigned int thislines = 0;
 481           unsigned int thisrelocs = 0;
 482           bfd_size_type thissize = 0;
 483           if (p->type == bfd_indirect_link_order)
 484             {
 485               asection *sec;
 486
 487               sec = p->u.indirect.section;
 488
 489               if (info->strip == strip_none
 490                   || info->strip == strip_some)
 491                 thislines = sec->lineno_count;
 492
 493               if (info->relocatable)
 494                 thisrelocs = sec->reloc_count;
 495
 496               thissize = sec->size;
 497
 498             }
 499           else if (info->relocatable
 500                    && (p->type == bfd_section_reloc_link_order
 501                        || p->type == bfd_symbol_reloc_link_order))
 502             thisrelocs++;
 503
 504           if (l != NULL
 505               && (thisrelocs + relocs >= config.split_by_reloc
 506                   || thislines + lines >= config.split_by_reloc
 507                   || (thissize + sec_size >= config.split_by_file))
 508               && !unsplittable_name (cursor->name))
 509             {
 510               /* Create a new section and put this link order and the
 511                  following link orders into it.  */
 512               bfd_vma shift_offset;
 513               asection *n;
 514
 515               n = clone_section (abfd, cursor, original_sec->name, &count);
 516
 517               /* Attach the link orders to the new section and snip
 518                  them off from the old section.  */
 519               n->map_head.link_order = p;
 520               n->map_tail.link_order = cursor->map_tail.link_order;
 521               cursor->map_tail.link_order = l;
 522               l->next = NULL;
 523               l = p;
 524
 525               /* Change the size of the original section and
 526                  update the vma of the new one.  */
 527
 528               dump ("before snip", cursor, n);
 529
 530               shift_offset = p->offset;
 531               n->size = cursor->size - shift_offset;
 532               cursor->size = shift_offset;
 533
 534               vma += shift_offset;
 535               n->lma = n->vma = vma;
 536
 537               /* Run down the chain and change the output section to
 538                  the right one, update the offsets too.  */
 539               do
 540                 {
 541                   p->offset -= shift_offset;
 542                   if (p->type == bfd_indirect_link_order)
 543                     {
 544                       p->u.indirect.section->output_section = n;
 545                       p->u.indirect.section->output_offset = p->offset;
 546                     }
 547                   p = p->next;
 548                 }
 549               while (p);
 550
 551               dump ("after snip", cursor, n);
 552               cursor = n;
 553               relocs = thisrelocs;
 554               lines = thislines;
 555               sec_size = thissize;
 556             }
 557           else
 558             {
 559               l = p;
 560               relocs += thisrelocs;
 561               lines += thislines;
 562               sec_size += thissize;
 563             }
 564         }
 565     }
 566   sanity_check (abfd);
 567 }
 568
 569 /* Call BFD to write out the linked file.  */
 570
 571 void
 572 ldwrite (void)
 573 {
 574   /* Reset error indicator, which can typically something like invalid
 575      format from opening up the .o files.  */
 576   bfd_set_error (bfd_error_no_error);
 577   lang_for_each_statement (build_link_order);
 578
 579   if (config.split_by_reloc != (unsigned) -1
 580       || config.split_by_file != (bfd_size_type) -1)
 581     split_sections (link_info.output_bfd, &link_info);
 582   if (!bfd_final_link (link_info.output_bfd, &link_info))
 583     {
 584       /* If there was an error recorded, print it out.  Otherwise assume
 585          an appropriate error message like unknown symbol was printed
 586          out.  */
 587
 588       if (bfd_get_error () != bfd_error_no_error)
 589         einfo (_("%F%P: final link failed: %E\n"));
 590       else
 591         xexit (1);
 592     }
 593 }