ld/ldwrite.c

   1 /* ldwrite.c -- write out the linked file
   2    Copyright (C) 1991-2021 Free Software Foundation, Inc.
   3    Written by Steve Chamberlain sac@cygnus.com
   4
   5    This file is part of the GNU Binutils.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #include "sysdep.h"
  23 #include "bfd.h"
  24 #include "bfdlink.h"
  25 #include "libiberty.h"
  26 #include "ctf-api.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
  50         output_section = statement->data_statement.output_section;
  51         ASSERT (output_section->owner == link_info.output_bfd);
  52
  53         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
  54               || ((output_section->flags & SEC_LOAD) != 0
  55                   && (output_section->flags & SEC_THREAD_LOCAL))))
  56           break;
  57
  58         link_order = bfd_new_link_order (link_info.output_bfd, output_section);
  59         if (link_order == NULL)
  60           einfo (_("%F%P: bfd_new_link_order failed\n"));
  61
  62         link_order->type = bfd_data_link_order;
  63         link_order->offset = statement->data_statement.output_offset;
  64         link_order->u.data.contents = (bfd_byte *) xmalloc (QUAD_SIZE);
  65
  66         value = statement->data_statement.value;
  67
  68         /* By convention, the bfd_put routines for an unknown
  69            endianness are big endian, so we must swap here if the
  70            input is little endian.  */
  71         if (!bfd_big_endian (link_info.output_bfd)
  72             && !bfd_little_endian (link_info.output_bfd)
  73             && !link_info.big_endian)
  74           {
  75             bfd_byte buffer[8];
  76
  77             switch (statement->data_statement.type)
  78               {
  79               case QUAD:
  80               case SQUAD:
  81                 if (sizeof (bfd_vma) >= QUAD_SIZE)
  82                   {
  83                     bfd_putl64 (value, buffer);
  84                     value = bfd_getb64 (buffer);
  85                     break;
  86                   }
  87                 /* Fall through.  */
  88               case LONG:
  89                 bfd_putl32 (value, buffer);
  90                 value = bfd_getb32 (buffer);
  91                 break;
  92               case SHORT:
  93                 bfd_putl16 (value, buffer);
  94                 value = bfd_getb16 (buffer);
  95                 break;
  96               case BYTE:
  97                 break;
  98               default:
  99                 abort ();
 100               }
 101           }
 102
 103         ASSERT (output_section->owner == link_info.output_bfd);
 104         switch (statement->data_statement.type)
 105           {
 106           case QUAD:
 107           case SQUAD:
 108             if (sizeof (bfd_vma) >= QUAD_SIZE)
 109               bfd_put_64 (link_info.output_bfd, value,
 110                           link_order->u.data.contents);
 111             else
 112               {
 113                 bfd_vma high;
 114
 115                 if (statement->data_statement.type == QUAD)
 116                   high = 0;
 117                 else if ((value & 0x80000000) == 0)
 118                   high = 0;
 119                 else
 120                   high = (bfd_vma) -1;
 121                 bfd_put_32 (link_info.output_bfd, high,
 122                             (link_order->u.data.contents
 123                              + (link_info.big_endian ? 0 : 4)));
 124                 bfd_put_32 (link_info.output_bfd, value,
 125                             (link_order->u.data.contents
 126                              + (link_info.big_endian ? 4 : 0)));
 127               }
 128             link_order->size = QUAD_SIZE;
 129             break;
 130           case LONG:
 131             bfd_put_32 (link_info.output_bfd, value,
 132                         link_order->u.data.contents);
 133             link_order->size = LONG_SIZE;
 134             break;
 135           case SHORT:
 136             bfd_put_16 (link_info.output_bfd, value,
 137                         link_order->u.data.contents);
 138             link_order->size = SHORT_SIZE;
 139             break;
 140           case BYTE:
 141             bfd_put_8 (link_info.output_bfd, value,
 142                        link_order->u.data.contents);
 143             link_order->size = BYTE_SIZE;
 144             break;
 145           default:
 146             abort ();
 147           }
 148         link_order->u.data.size = link_order->size;
 149       }
 150       break;
 151
 152     case lang_reloc_statement_enum:
 153       {
 154         lang_reloc_statement_type *rs;
 155         asection *output_section;
 156         struct bfd_link_order *link_order;
 157
 158         rs = &statement->reloc_statement;
 159
 160         output_section = rs->output_section;
 161         ASSERT (output_section->owner == link_info.output_bfd);
 162
 163         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 164               || ((output_section->flags & SEC_LOAD) != 0
 165                   && (output_section->flags & SEC_THREAD_LOCAL))))
 166           break;
 167
 168         link_order = bfd_new_link_order (link_info.output_bfd, output_section);
 169         if (link_order == NULL)
 170           einfo (_("%F%P: bfd_new_link_order failed\n"));
 171
 172         link_order->offset = rs->output_offset;
 173         link_order->size = bfd_get_reloc_size (rs->howto);
 174
 175         link_order->u.reloc.p = (struct bfd_link_order_reloc *)
 176           xmalloc (sizeof (struct bfd_link_order_reloc));
 177
 178         link_order->u.reloc.p->reloc = rs->reloc;
 179         link_order->u.reloc.p->addend = rs->addend_value;
 180
 181         if (rs->name == NULL)
 182           {
 183             link_order->type = bfd_section_reloc_link_order;
 184             if (rs->section->owner == link_info.output_bfd)
 185               link_order->u.reloc.p->u.section = rs->section;
 186             else
 187               {
 188                 link_order->u.reloc.p->u.section = rs->section->output_section;
 189                 link_order->u.reloc.p->addend += rs->section->output_offset;
 190               }
 191           }
 192         else
 193           {
 194             link_order->type = bfd_symbol_reloc_link_order;
 195             link_order->u.reloc.p->u.name = rs->name;
 196           }
 197       }
 198       break;
 199
 200     case lang_input_section_enum:
 201       {
 202         /* Create a new link_order in the output section with this
 203            attached */
 204         asection *i = statement->input_section.section;
 205
 206         if (i->sec_info_type != SEC_INFO_TYPE_JUST_SYMS
 207             && (i->flags & SEC_EXCLUDE) == 0)
 208           {
 209             asection *output_section = i->output_section;
 210             struct bfd_link_order *link_order;
 211
 212             ASSERT (output_section->owner == link_info.output_bfd);
 213
 214             if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 215                   || ((output_section->flags & SEC_LOAD) != 0
 216                       && (output_section->flags & SEC_THREAD_LOCAL))))
 217               break;
 218
 219             link_order = bfd_new_link_order (link_info.output_bfd,
 220                                              output_section);
 221             if (link_order == NULL)
 222               einfo (_("%F%P: bfd_new_link_order failed\n"));
 223
 224             if ((i->flags & SEC_NEVER_LOAD) != 0
 225                 && (i->flags & SEC_DEBUGGING) == 0)
 226               {
 227                 /* We've got a never load section inside one which is
 228                    going to be output, we'll change it into a fill.  */
 229                 link_order->type = bfd_data_link_order;
 230                 link_order->u.data.contents = (unsigned char *) "";
 231                 link_order->u.data.size = 1;
 232               }
 233             else
 234               {
 235                 link_order->type = bfd_indirect_link_order;
 236                 link_order->u.indirect.section = i;
 237                 ASSERT (i->output_section == output_section);
 238               }
 239             link_order->size = i->size;
 240             link_order->offset = i->output_offset;
 241           }
 242       }
 243       break;
 244
 245     case lang_padding_statement_enum:
 246       /* Make a new link_order with the right filler */
 247       {
 248         asection *output_section;
 249         struct bfd_link_order *link_order;
 250
 251         output_section = statement->padding_statement.output_section;
 252         ASSERT (statement->padding_statement.output_section->owner
 253                 == link_info.output_bfd);
 254
 255         if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
 256               || ((output_section->flags & SEC_LOAD) != 0
 257                   && (output_section->flags & SEC_THREAD_LOCAL))))
 258           break;
 259
 260         link_order = bfd_new_link_order (link_info.output_bfd,
 261                                          output_section);
 262         if (link_order == NULL)
 263           einfo (_("%F%P: bfd_new_link_order failed\n"));
 264         link_order->type = bfd_data_link_order;
 265         link_order->size = statement->padding_statement.size;
 266         link_order->offset = statement->padding_statement.output_offset;
 267         link_order->u.data.contents = statement->padding_statement.fill->data;
 268         link_order->u.data.size = statement->padding_statement.fill->size;
 269       }
 270       break;
 271
 272     default:
 273       /* All the other ones fall through */
 274       break;
 275     }
 276 }
 277
 278 /* Return true if NAME is the name of an unsplittable section. These
 279    are the stabs strings, dwarf strings.  */
 280
 281 static bfd_boolean
 282 unsplittable_name (const char *name)
 283 {
 284   if (CONST_STRNEQ (name, ".stab"))
 285     {
 286       /* There are several stab like string sections. We pattern match on
 287          ".stab...str"  */
 288       unsigned len = strlen (name);
 289       if (strcmp (&name[len-3], "str") == 0)
 290         return TRUE;
 291     }
 292   else if (strcmp (name, "$GDB_STRINGS$") == 0)
 293     return TRUE;
 294   return FALSE;
 295 }
 296
 297 /* Wander around the input sections, make sure that
 298    we'll never try and create an output section with more relocs
 299    than will fit.. Do this by always assuming the worst case, and
 300    creating new output sections with all the right bits.  */
 301 #define TESTIT 1
 302 static asection *
 303 clone_section (bfd *abfd, asection *s, const char *name, int *count)
 304 {
 305   char *tname;
 306   char *sname;
 307   unsigned int len;
 308   asection *n;
 309   struct bfd_link_hash_entry *h;
 310
 311   /* Invent a section name from the section name and a dotted numeric
 312      suffix.   */
 313   len = strlen (name);
 314   tname = (char *) xmalloc (len + 1);
 315   memcpy (tname, name, len + 1);
 316   /* Remove a dotted number suffix, from a previous split link. */
 317   while (len && ISDIGIT (tname[len-1]))
 318     len--;
 319   if (len > 1 && tname[len-1] == '.')
 320     /* It was a dotted number. */
 321     tname[len-1] = 0;
 322
 323   /* We want to use the whole of the original section name for the
 324      split name, but coff can be restricted to 8 character names.  */
 325   if (bfd_family_coff (abfd) && strlen (tname) > 5)
 326     {
 327       /* Some section names cannot be truncated, as the name is
 328          used to locate some other section.  */
 329       if (CONST_STRNEQ (name, ".stab")
 330           || strcmp (name, "$GDB_SYMBOLS$") == 0)
 331         {
 332           einfo (_ ("%F%P: cannot create split section name for %s\n"), name);
 333           /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 334           return NULL;
 335         }
 336       tname[5] = 0;
 337     }
 338
 339   if ((sname = bfd_get_unique_section_name (abfd, tname, count)) == NULL
 340       || (n = bfd_make_section_anyway (abfd, sname)) == NULL
 341       || (h = bfd_link_hash_lookup (link_info.hash,
 342                                     sname, TRUE, TRUE, FALSE)) == NULL)
 343     {
 344       einfo (_("%F%P: clone section failed: %E\n"));
 345       /* Silence gcc warnings.  einfo exits, so we never reach here.  */
 346       return NULL;
 347     }
 348   free (tname);
 349
 350   /* Set up section symbol.  */
 351   h->type = bfd_link_hash_defined;
 352   h->u.def.value = 0;
 353   h->u.def.section = n;
 354
 355   n->flags = s->flags;
 356   n->vma = s->vma;
 357   n->user_set_vma = s->user_set_vma;
 358   n->lma = s->lma;
 359   n->size = 0;
 360   n->output_offset = s->output_offset;
 361   n->output_section = n;
 362   n->orelocation = 0;
 363   n->reloc_count = 0;
 364   n->alignment_power = s->alignment_power;
 365
 366   bfd_copy_private_section_data (abfd, s, abfd, n);
 367
 368   return n;
 369 }
 370
 371 #if TESTING
 372 static void
 373 ds (asection *s)
 374 {
 375   struct bfd_link_order *l = s->map_head.link_order;
 376   printf ("vma %x size %x\n", s->vma, s->size);
 377   while (l)
 378     {
 379       if (l->type == bfd_indirect_link_order)
 380         printf ("%8x %s\n", l->offset, l->u.indirect.section->owner->filename);
 381       else
 382         printf (_("%8x something else\n"), l->offset);
 383       l = l->next;
 384     }
 385   printf ("\n");
 386 }
 387
 388 dump (char *s, asection *a1, asection *a2)
 389 {
 390   printf ("%s\n", s);
 391   ds (a1);
 392   ds (a2);
 393 }
 394
 395 static void
 396 sanity_check (bfd *abfd)
 397 {
 398   asection *s;
 399   for (s = abfd->sections; s; s = s->next)
 400     {
 401       struct bfd_link_order *p;
 402       bfd_vma prev = 0;
 403       for (p = s->map_head.link_order; p; p = p->next)
 404         {
 405           if (p->offset > 100000)
 406             abort ();
 407           if (p->offset < prev)
 408             abort ();
 409           prev = p->offset;
 410         }
 411     }
 412 }
 413 #else
 414 #define sanity_check(a)
 415 #define dump(a, b, c)
 416 #endif
 417
 418 static void
 419 split_sections (bfd *abfd, struct bfd_link_info *info)
 420 {
 421   asection *original_sec;
 422   int nsecs = abfd->section_count;
 423   sanity_check (abfd);
 424   /* Look through all the original sections.  */
 425   for (original_sec = abfd->sections;
 426        original_sec && nsecs;
 427        original_sec = original_sec->next, nsecs--)
 428     {
 429       int count = 0;
 430       unsigned int lines = 0;
 431       unsigned int relocs = 0;
 432       bfd_size_type sec_size = 0;
 433       struct bfd_link_order *l;
 434       struct bfd_link_order *p;
 435       bfd_vma vma = original_sec->vma;
 436       asection *cursor = original_sec;
 437
 438       /* Count up the relocations and line entries to see if anything
 439          would be too big to fit.  Accumulate section size too.  */
 440       for (l = NULL, p = cursor->map_head.link_order; p != NULL; p = l->next)
 441         {
 442           unsigned int thislines = 0;
 443           unsigned int thisrelocs = 0;
 444           bfd_size_type thissize = 0;
 445           if (p->type == bfd_indirect_link_order)
 446             {
 447               asection *sec;
 448
 449               sec = p->u.indirect.section;
 450
 451               if (info->strip == strip_none
 452                   || info->strip == strip_some)
 453                 thislines = sec->lineno_count;
 454
 455               if (bfd_link_relocatable (info))
 456                 thisrelocs = sec->reloc_count;
 457
 458               thissize = sec->size;
 459
 460             }
 461           else if (bfd_link_relocatable (info)
 462                    && (p->type == bfd_section_reloc_link_order
 463                        || p->type == bfd_symbol_reloc_link_order))
 464             thisrelocs++;
 465
 466           if (l != NULL
 467               && (thisrelocs + relocs >= config.split_by_reloc
 468                   || thislines + lines >= config.split_by_reloc
 469                   || (thissize + sec_size >= config.split_by_file))
 470               && !unsplittable_name (cursor->name))
 471             {
 472               /* Create a new section and put this link order and the
 473                  following link orders into it.  */
 474               bfd_vma shift_offset;
 475               asection *n;
 476
 477               n = clone_section (abfd, cursor, original_sec->name, &count);
 478
 479               /* Attach the link orders to the new section and snip
 480                  them off from the old section.  */
 481               n->map_head.link_order = p;
 482               n->map_tail.link_order = cursor->map_tail.link_order;
 483               cursor->map_tail.link_order = l;
 484               l->next = NULL;
 485               l = p;
 486
 487               /* Change the size of the original section and
 488                  update the vma of the new one.  */
 489
 490               dump ("before snip", cursor, n);
 491
 492               shift_offset = p->offset;
 493               n->size = cursor->size - shift_offset;
 494               cursor->size = shift_offset;
 495
 496               vma += shift_offset;
 497               n->lma = n->vma = vma;
 498
 499               /* Run down the chain and change the output section to
 500                  the right one, update the offsets too.  */
 501               do
 502                 {
 503                   p->offset -= shift_offset;
 504                   if (p->type == bfd_indirect_link_order)
 505                     {
 506                       p->u.indirect.section->output_section = n;
 507                       p->u.indirect.section->output_offset = p->offset;
 508                     }
 509                   p = p->next;
 510                 }
 511               while (p);
 512
 513               dump ("after snip", cursor, n);
 514               cursor = n;
 515               relocs = thisrelocs;
 516               lines = thislines;
 517               sec_size = thissize;
 518             }
 519           else
 520             {
 521               l = p;
 522               relocs += thisrelocs;
 523               lines += thislines;
 524               sec_size += thissize;
 525             }
 526         }
 527     }
 528   sanity_check (abfd);
 529 }
 530
 531 /* Call BFD to write out the linked file.  */
 532
 533 void
 534 ldwrite (void)
 535 {
 536   /* Reset error indicator, which can typically something like invalid
 537      format from opening up the .o files.  */
 538   bfd_set_error (bfd_error_no_error);
 539   lang_clear_os_map ();
 540   lang_for_each_statement (build_link_order);
 541
 542   if (config.split_by_reloc != (unsigned) -1
 543       || config.split_by_file != (bfd_size_type) -1)
 544     split_sections (link_info.output_bfd, &link_info);
 545   if (!bfd_final_link (link_info.output_bfd, &link_info))
 546     {
 547       /* If there was an error recorded, print it out.  Otherwise assume
 548          an appropriate error message like unknown symbol was printed
 549          out.  */
 550
 551       if (bfd_get_error () != bfd_error_no_error)
 552         einfo (_("%F%P: final link failed: %E\n"));
 553       else
 554         xexit (1);
 555     }
 556 }