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