ld/ldctor.c

   1 /* ldctor.c -- constructor support routines
   2    Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
   3    2002, 2003, 2004, 2006 Free Software Foundation, Inc.
   4    By Steve Chamberlain <sac@cygnus.com>
   5
   6 This file is part of GLD, the Gnu Linker.
   7
   8 GLD 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, or (at your option)
  11 any later version.
  12
  13 GLD 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 GLD; see the file COPYING.  If not, write to the Free
  20 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  21 02110-1301, USA.  */
  22
  23 #include "bfd.h"
  24 #include "sysdep.h"
  25 #include "bfdlink.h"
  26 #include "safe-ctype.h"
  27
  28 #include "ld.h"
  29 #include "ldexp.h"
  30 #include "ldlang.h"
  31 #include "ldmisc.h"
  32 #include <ldgram.h>
  33 #include "ldmain.h"
  34 #include "ldctor.h"
  35
  36 /* The list of statements needed to handle constructors.  These are
  37    invoked by the command CONSTRUCTORS in the linker script.  */
  38 lang_statement_list_type constructor_list;
  39
  40 /* Whether the constructors should be sorted.  Note that this is
  41    global for the entire link; we assume that there is only a single
  42    CONSTRUCTORS command in the linker script.  */
  43 bfd_boolean constructors_sorted;
  44
  45 /* The sets we have seen.  */
  46 struct set_info *sets;
  47
  48 /* Add an entry to a set.  H is the entry in the linker hash table.
  49    RELOC is the relocation to use for an entry in the set.  SECTION
  50    and VALUE are the value to add.  This is called during the first
  51    phase of the link, when we are still gathering symbols together.
  52    We just record the information now.  The ldctor_build_sets
  53    function will construct the sets.  */
  54
  55 void
  56 ldctor_add_set_entry (struct bfd_link_hash_entry *h,
  57                       bfd_reloc_code_real_type reloc,
  58                       const char *name,
  59                       asection *section,
  60                       bfd_vma value)
  61 {
  62   struct set_info *p;
  63   struct set_element *e;
  64   struct set_element **epp;
  65
  66   for (p = sets; p != NULL; p = p->next)
  67     if (p->h == h)
  68       break;
  69
  70   if (p == NULL)
  71     {
  72       p = xmalloc (sizeof (struct set_info));
  73       p->next = sets;
  74       sets = p;
  75       p->h = h;
  76       p->reloc = reloc;
  77       p->count = 0;
  78       p->elements = NULL;
  79     }
  80   else
  81     {
  82       if (p->reloc != reloc)
  83         {
  84           einfo (_("%P%X: Different relocs used in set %s\n"),
  85                  h->root.string);
  86           return;
  87         }
  88
  89       /* Don't permit a set to be constructed from different object
  90          file formats.  The same reloc may have different results.  We
  91          actually could sometimes handle this, but the case is
  92          unlikely to ever arise.  Sometimes constructor symbols are in
  93          unusual sections, such as the absolute section--this appears
  94          to be the case in Linux a.out--and in such cases we just
  95          assume everything is OK.  */
  96       if (p->elements != NULL
  97           && section->owner != NULL
  98           && p->elements->section->owner != NULL
  99           && strcmp (bfd_get_target (section->owner),
 100                      bfd_get_target (p->elements->section->owner)) != 0)
 101         {
 102           einfo (_("%P%X: Different object file formats composing set %s\n"),
 103                  h->root.string);
 104           return;
 105         }
 106     }
 107
 108   e = xmalloc (sizeof (struct set_element));
 109   e->next = NULL;
 110   e->name = name;
 111   e->section = section;
 112   e->value = value;
 113
 114   for (epp = &p->elements; *epp != NULL; epp = &(*epp)->next)
 115     ;
 116   *epp = e;
 117
 118   ++p->count;
 119 }
 120
 121 /* Get the priority of a g++ global constructor or destructor from the
 122    symbol name.  */
 123
 124 static int
 125 ctor_prio (const char *name)
 126 {
 127   /* The name will look something like _GLOBAL_$I$65535$test02__Fv.
 128      There might be extra leading underscores, and the $ characters
 129      might be something else.  The I might be a D.  */
 130
 131   while (*name == '_')
 132     ++name;
 133
 134   if (! CONST_STRNEQ (name, "GLOBAL_"))
 135     return -1;
 136
 137   name += sizeof "GLOBAL_" - 1;
 138
 139   if (name[0] != name[2])
 140     return -1;
 141   if (name[1] != 'I' && name[1] != 'D')
 142     return -1;
 143   if (! ISDIGIT (name[3]))
 144     return -1;
 145
 146   return atoi (name + 3);
 147 }
 148
 149 /* This function is used to sort constructor elements by priority.  It
 150    is called via qsort.  */
 151
 152 static int
 153 ctor_cmp (const void *p1, const void *p2)
 154 {
 155   const struct set_element * const *pe1 = p1;
 156   const struct set_element * const *pe2 = p2;
 157   const char *n1;
 158   const char *n2;
 159   int prio1;
 160   int prio2;
 161
 162   n1 = (*pe1)->name;
 163   if (n1 == NULL)
 164     n1 = "";
 165   n2 = (*pe2)->name;
 166   if (n2 == NULL)
 167     n2 = "";
 168
 169   /* We need to sort in reverse order by priority.  When two
 170      constructors have the same priority, we should maintain their
 171      current relative position.  */
 172
 173   prio1 = ctor_prio (n1);
 174   prio2 = ctor_prio (n2);
 175
 176   /* We sort in reverse order because that is what g++ expects.  */
 177   if (prio1 < prio2)
 178     return 1;
 179   else if (prio1 > prio2)
 180     return -1;
 181
 182   /* Force a stable sort.  */
 183
 184   if (pe1 < pe2)
 185     return -1;
 186   else if (pe1 > pe2)
 187     return 1;
 188   else
 189     return 0;
 190 }
 191
 192 /* This function is called after the first phase of the link and
 193    before the second phase.  At this point all set information has
 194    been gathered.  We now put the statements to build the sets
 195    themselves into constructor_list.  */
 196
 197 void
 198 ldctor_build_sets (void)
 199 {
 200   static bfd_boolean called;
 201   lang_statement_list_type *old;
 202   bfd_boolean header_printed;
 203   struct set_info *p;
 204
 205   /* The emulation code may call us directly, but we only want to do
 206      this once.  */
 207   if (called)
 208     return;
 209   called = TRUE;
 210
 211   if (constructors_sorted)
 212     {
 213       for (p = sets; p != NULL; p = p->next)
 214         {
 215           int c, i;
 216           struct set_element *e;
 217           struct set_element **array;
 218
 219           if (p->elements == NULL)
 220             continue;
 221
 222           c = 0;
 223           for (e = p->elements; e != NULL; e = e->next)
 224             ++c;
 225
 226           array = xmalloc (c * sizeof *array);
 227
 228           i = 0;
 229           for (e = p->elements; e != NULL; e = e->next)
 230             {
 231               array[i] = e;
 232               ++i;
 233             }
 234
 235           qsort (array, c, sizeof *array, ctor_cmp);
 236
 237           e = array[0];
 238           p->elements = e;
 239           for (i = 0; i < c - 1; i++)
 240             array[i]->next = array[i + 1];
 241           array[i]->next = NULL;
 242
 243           free (array);
 244         }
 245     }
 246
 247   old = stat_ptr;
 248   stat_ptr = &constructor_list;
 249
 250   lang_list_init (stat_ptr);
 251
 252   header_printed = FALSE;
 253   for (p = sets; p != NULL; p = p->next)
 254     {
 255       struct set_element *e;
 256       reloc_howto_type *howto;
 257       int reloc_size, size;
 258
 259       /* If the symbol is defined, we may have been invoked from
 260          collect, and the sets may already have been built, so we do
 261          not do anything.  */
 262       if (p->h->type == bfd_link_hash_defined
 263           || p->h->type == bfd_link_hash_defweak)
 264         continue;
 265
 266       /* For each set we build:
 267            set:
 268              .long number_of_elements
 269              .long element0
 270              ...
 271              .long elementN
 272              .long 0
 273          except that we use the right size instead of .long.  When
 274          generating relocatable output, we generate relocs instead of
 275          addresses.  */
 276       howto = bfd_reloc_type_lookup (output_bfd, p->reloc);
 277       if (howto == NULL)
 278         {
 279           if (link_info.relocatable)
 280             {
 281               einfo (_("%P%X: %s does not support reloc %s for set %s\n"),
 282                      bfd_get_target (output_bfd),
 283                      bfd_get_reloc_code_name (p->reloc),
 284                      p->h->root.string);
 285               continue;
 286             }
 287
 288           /* If this is not a relocatable link, all we need is the
 289              size, which we can get from the input BFD.  */
 290           if (p->elements->section->owner != NULL)
 291             howto = bfd_reloc_type_lookup (p->elements->section->owner,
 292                                            p->reloc);
 293           if (howto == NULL)
 294             {
 295               einfo (_("%P%X: %s does not support reloc %s for set %s\n"),
 296                      bfd_get_target (p->elements->section->owner),
 297                      bfd_get_reloc_code_name (p->reloc),
 298                      p->h->root.string);
 299               continue;
 300             }
 301         }
 302
 303       reloc_size = bfd_get_reloc_size (howto);
 304       switch (reloc_size)
 305         {
 306         case 1: size = BYTE; break;
 307         case 2: size = SHORT; break;
 308         case 4: size = LONG; break;
 309         case 8:
 310           if (howto->complain_on_overflow == complain_overflow_signed)
 311             size = SQUAD;
 312           else
 313             size = QUAD;
 314           break;
 315         default:
 316           einfo (_("%P%X: Unsupported size %d for set %s\n"),
 317                  bfd_get_reloc_size (howto), p->h->root.string);
 318           size = LONG;
 319           break;
 320         }
 321
 322       lang_add_assignment (exp_assop ('=', ".",
 323                                       exp_unop (ALIGN_K,
 324                                                 exp_intop (reloc_size))));
 325       lang_add_assignment (exp_assop ('=', p->h->root.string,
 326                                       exp_nameop (NAME, ".")));
 327       lang_add_data (size, exp_intop (p->count));
 328
 329       for (e = p->elements; e != NULL; e = e->next)
 330         {
 331           if (config.map_file != NULL)
 332             {
 333               int len;
 334
 335               if (! header_printed)
 336                 {
 337                   minfo (_("\nSet                 Symbol\n\n"));
 338                   header_printed = TRUE;
 339                 }
 340
 341               minfo ("%s", p->h->root.string);
 342               len = strlen (p->h->root.string);
 343
 344               if (len >= 19)
 345                 {
 346                   print_nl ();
 347                   len = 0;
 348                 }
 349               while (len < 20)
 350                 {
 351                   print_space ();
 352                   ++len;
 353                 }
 354
 355               if (e->name != NULL)
 356                 minfo ("%T\n", e->name);
 357               else
 358                 minfo ("%G\n", e->section->owner, e->section, e->value);
 359             }
 360
 361           /* Need SEC_KEEP for --gc-sections.  */
 362           if (! bfd_is_abs_section (e->section))
 363             e->section->flags |= SEC_KEEP;
 364
 365           if (link_info.relocatable)
 366             lang_add_reloc (p->reloc, howto, e->section, e->name,
 367                             exp_intop (e->value));
 368           else
 369             lang_add_data (size, exp_relop (e->section, e->value));
 370         }
 371
 372       lang_add_data (size, exp_intop (0));
 373     }
 374
 375   stat_ptr = old;
 376 }