gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright 1987, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GAS, the GNU Assembler.
   7
   8    GAS 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    GAS 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 GAS; 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 /* Segments & sub-segments.  */
  24
  25 #include "as.h"
  26
  27 #include "subsegs.h"
  28 #include "obstack.h"
  29
  30 frchainS *frchain_root, *frchain_now;
  31
  32 static struct obstack frchains;
  33
  34 /* Gas segment information for bfd_abs_section_ptr and
  35    bfd_und_section_ptr.  */
  36 static segment_info_type *abs_seg_info;
  37 static segment_info_type *und_seg_info;
  38
  39 static void subseg_set_rest (segT, subsegT);
  40
  41 static fragS dummy_frag;
  42
  43 static frchainS absolute_frchain;
  44 \f
  45 void
  46 subsegs_begin (void)
  47 {
  48   obstack_begin (&frchains, chunksize);
  49 #if __GNUC__ >= 2
  50   obstack_alignment_mask (&frchains) = __alignof__ (frchainS) - 1;
  51 #endif
  52
  53   frchain_root = NULL;
  54   frchain_now = NULL;           /* Warn new_subseg() that we are booting.  */
  55
  56   frag_now = &dummy_frag;
  57
  58   absolute_frchain.frch_seg = absolute_section;
  59   absolute_frchain.frch_subseg = 0;
  60   absolute_frchain.fix_root = absolute_frchain.fix_tail = 0;
  61   absolute_frchain.frch_frag_now = &zero_address_frag;
  62   absolute_frchain.frch_root = absolute_frchain.frch_last = &zero_address_frag;
  63 }
  64 \f
  65 /*
  66  *                      subseg_change()
  67  *
  68  * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
  69  * subsegment. If we are already in the correct subsegment, change nothing.
  70  * This is used eg as a worker for subseg_set [which does make a new frag_now]
  71  * and for changing segments after we have read the source. We construct eg
  72  * fixSs even after the source file is read, so we do have to keep the
  73  * segment context correct.
  74  */
  75 void
  76 subseg_change (register segT seg, register int subseg)
  77 {
  78   segment_info_type *seginfo;
  79   now_seg = seg;
  80   now_subseg = subseg;
  81
  82   if (now_seg == absolute_section)
  83     return;
  84
  85   seginfo = (segment_info_type *) bfd_get_section_userdata (stdoutput, seg);
  86   if (! seginfo)
  87     {
  88       seginfo = (segment_info_type *) xmalloc (sizeof (*seginfo));
  89       memset ((PTR) seginfo, 0, sizeof (*seginfo));
  90       seginfo->fix_root = NULL;
  91       seginfo->fix_tail = NULL;
  92       seginfo->bfd_section = seg;
  93       seginfo->sym = 0;
  94       if (seg == bfd_abs_section_ptr)
  95         abs_seg_info = seginfo;
  96       else if (seg == bfd_und_section_ptr)
  97         und_seg_info = seginfo;
  98       else
  99         bfd_set_section_userdata (stdoutput, seg, (PTR) seginfo);
 100     }
 101 }
 102 \f
 103 static void
 104 subseg_set_rest (segT seg, subsegT subseg)
 105 {
 106   register frchainS *frcP;      /* crawl frchain chain */
 107   register frchainS **lastPP;   /* address of last pointer */
 108   frchainS *newP;               /* address of new frchain */
 109
 110   mri_common_symbol = NULL;
 111
 112   if (frag_now && frchain_now)
 113     frchain_now->frch_frag_now = frag_now;
 114
 115   assert (frchain_now == 0
 116           || now_seg == undefined_section
 117           || now_seg == absolute_section
 118           || frchain_now->frch_last == frag_now);
 119
 120   subseg_change (seg, (int) subseg);
 121
 122   if (seg == absolute_section)
 123     {
 124       frchain_now = &absolute_frchain;
 125       frag_now = &zero_address_frag;
 126       return;
 127     }
 128
 129   assert (frchain_now == 0
 130           || now_seg == undefined_section
 131           || frchain_now->frch_last == frag_now);
 132
 133   /*
 134    * Attempt to find or make a frchain for that sub seg.
 135    * Crawl along chain of frchainSs, begins @ frchain_root.
 136    * If we need to make a frchainS, link it into correct
 137    * position of chain rooted in frchain_root.
 138    */
 139   for (frcP = *(lastPP = &frchain_root);
 140        frcP && frcP->frch_seg <= seg;
 141        frcP = *(lastPP = &frcP->frch_next))
 142     {
 143       if (frcP->frch_seg == seg
 144           && frcP->frch_subseg >= subseg)
 145         {
 146           break;
 147         }
 148     }
 149   /*
 150    * frcP:              Address of the 1st frchainS in correct segment with
 151    *            frch_subseg >= subseg.
 152    *            We want to either use this frchainS, or we want
 153    *            to insert a new frchainS just before it.
 154    *
 155    *            If frcP==NULL, then we are at the end of the chain
 156    *            of frchainS-s. A NULL frcP means we fell off the end
 157    *            of the chain looking for a
 158    *            frch_subseg >= subseg, so we
 159    *            must make a new frchainS.
 160    *
 161    *            If we ever maintain a pointer to
 162    *            the last frchainS in the chain, we change that pointer
 163    *            ONLY when frcP==NULL.
 164    *
 165    * lastPP:    Address of the pointer with value frcP;
 166    *            Never NULL.
 167    *            May point to frchain_root.
 168    *
 169    */
 170   if (!frcP
 171       || (frcP->frch_seg > seg
 172           || frcP->frch_subseg > subseg))       /* Kinky logic only works with 2 segments.  */
 173     {
 174       /*
 175        * This should be the only code that creates a frchainS.
 176        */
 177       segment_info_type *seginfo;
 178
 179       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 180       newP->frch_subseg = subseg;
 181       newP->frch_seg = seg;
 182       newP->fix_root = NULL;
 183       newP->fix_tail = NULL;
 184       obstack_begin (&newP->frch_obstack, chunksize);
 185 #if __GNUC__ >= 2
 186       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 187 #endif
 188       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 189       newP->frch_frag_now->fr_type = rs_fill;
 190
 191       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 192
 193       *lastPP = newP;
 194       newP->frch_next = frcP;   /* perhaps NULL */
 195
 196       seginfo = seg_info (seg);
 197       if (seginfo && seginfo->frchainP == frcP)
 198         seginfo->frchainP = newP;
 199
 200       frcP = newP;
 201     }
 202   /*
 203    * Here with frcP pointing to the frchainS for subseg.
 204    */
 205   frchain_now = frcP;
 206   frag_now = frcP->frch_frag_now;
 207
 208   assert (frchain_now->frch_last == frag_now);
 209 }
 210
 211 /*
 212  *                      subseg_set(segT, subsegT)
 213  *
 214  * If you attempt to change to the current subsegment, nothing happens.
 215  *
 216  * In:  segT, subsegT code for new subsegment.
 217  *      frag_now -> incomplete frag for current subsegment.
 218  *      If frag_now==NULL, then there is no old, incomplete frag, so
 219  *      the old frag is not closed off.
 220  *
 221  * Out: now_subseg, now_seg updated.
 222  *      Frchain_now points to the (possibly new) struct frchain for this
 223  *      sub-segment.
 224  *      Frchain_root updated if needed.
 225  */
 226
 227 segT
 228 subseg_get (const char *segname, int force_new)
 229 {
 230   segT secptr;
 231   segment_info_type *seginfo;
 232   const char *now_seg_name = (now_seg
 233                               ? bfd_get_section_name (stdoutput, now_seg)
 234                               : 0);
 235
 236   if (!force_new
 237       && now_seg_name
 238       && (now_seg_name == segname
 239           || !strcmp (now_seg_name, segname)))
 240     return now_seg;
 241
 242   if (!force_new)
 243     secptr = bfd_make_section_old_way (stdoutput, segname);
 244   else
 245     secptr = bfd_make_section_anyway (stdoutput, segname);
 246
 247 #ifdef obj_sec_set_private_data
 248   obj_sec_set_private_data (stdoutput, secptr);
 249 #endif
 250
 251   seginfo = seg_info (secptr);
 252   if (! seginfo)
 253     {
 254       /* Check whether output_section is set first because secptr may
 255          be bfd_abs_section_ptr.  */
 256       if (secptr->output_section != secptr)
 257         secptr->output_section = secptr;
 258       seginfo = (segment_info_type *) xmalloc (sizeof (*seginfo));
 259       memset ((PTR) seginfo, 0, sizeof (*seginfo));
 260       seginfo->fix_root = NULL;
 261       seginfo->fix_tail = NULL;
 262       seginfo->bfd_section = secptr;
 263       if (secptr == bfd_abs_section_ptr)
 264         abs_seg_info = seginfo;
 265       else if (secptr == bfd_und_section_ptr)
 266         und_seg_info = seginfo;
 267       else
 268         bfd_set_section_userdata (stdoutput, secptr, (PTR) seginfo);
 269       seginfo->frchainP = NULL;
 270       seginfo->lineno_list_head = seginfo->lineno_list_tail = NULL;
 271       seginfo->sym = NULL;
 272       seginfo->dot = NULL;
 273     }
 274   return secptr;
 275 }
 276
 277 segT
 278 subseg_new (const char *segname, subsegT subseg)
 279 {
 280   segT secptr;
 281   segment_info_type *seginfo;
 282
 283   secptr = subseg_get (segname, 0);
 284   subseg_set_rest (secptr, subseg);
 285   seginfo = seg_info (secptr);
 286   if (! seginfo->frchainP)
 287     seginfo->frchainP = frchain_now;
 288   return secptr;
 289 }
 290
 291 /* Like subseg_new, except a new section is always created, even if
 292    a section with that name already exists.  */
 293 segT
 294 subseg_force_new (const char *segname, subsegT subseg)
 295 {
 296   segT secptr;
 297   segment_info_type *seginfo;
 298
 299   secptr = subseg_get (segname, 1);
 300   subseg_set_rest (secptr, subseg);
 301   seginfo = seg_info (secptr);
 302   if (! seginfo->frchainP)
 303     seginfo->frchainP = frchain_now;
 304   return secptr;
 305 }
 306
 307 void
 308 subseg_set (segT secptr, subsegT subseg)
 309 {
 310   if (! (secptr == now_seg && subseg == now_subseg))
 311     subseg_set_rest (secptr, subseg);
 312   mri_common_symbol = NULL;
 313 }
 314
 315 #ifndef obj_sec_sym_ok_for_reloc
 316 #define obj_sec_sym_ok_for_reloc(SEC)   0
 317 #endif
 318
 319 /* Get the gas information we are storing for a section.  */
 320
 321 segment_info_type *
 322 seg_info (segT sec)
 323 {
 324   if (sec == bfd_abs_section_ptr)
 325     return abs_seg_info;
 326   else if (sec == bfd_und_section_ptr)
 327     return und_seg_info;
 328   else
 329     return (segment_info_type *) bfd_get_section_userdata (stdoutput, sec);
 330 }
 331
 332 symbolS *
 333 section_symbol (segT sec)
 334 {
 335   segment_info_type *seginfo = seg_info (sec);
 336   symbolS *s;
 337
 338   if (seginfo == 0)
 339     abort ();
 340   if (seginfo->sym)
 341     return seginfo->sym;
 342
 343 #ifndef EMIT_SECTION_SYMBOLS
 344 #define EMIT_SECTION_SYMBOLS 1
 345 #endif
 346
 347   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 348     {
 349       /* Here we know it won't be going into the symbol table.  */
 350       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 351     }
 352   else
 353     {
 354       segT seg;
 355       s = symbol_find (sec->symbol->name);
 356       /* We have to make sure it is the right symbol when we
 357          have multiple sections with the same section name.  */
 358       if (s == NULL
 359           || ((seg = S_GET_SEGMENT (s)) != sec
 360               && seg != undefined_section))
 361         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 362       else if (seg == undefined_section)
 363         {
 364           S_SET_SEGMENT (s, sec);
 365           symbol_set_frag (s, &zero_address_frag);
 366         }
 367     }
 368
 369   S_CLEAR_EXTERNAL (s);
 370
 371   /* Use the BFD section symbol, if possible.  */
 372   if (obj_sec_sym_ok_for_reloc (sec))
 373     symbol_set_bfdsym (s, sec->symbol);
 374   else
 375     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 376
 377   seginfo->sym = s;
 378   return s;
 379 }
 380
 381 /* Return whether the specified segment is thought to hold text.  */
 382
 383 int
 384 subseg_text_p (segT sec)
 385 {
 386   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
 387 }
 388
 389 /* Return non zero if SEC has at least one byte of data.  It is
 390    possible that we'll return zero even on a non-empty section because
 391    we don't know all the fragment types, and it is possible that an
 392    fr_fix == 0 one still contributes data.  Think of this as
 393    seg_definitely_not_empty_p.  */
 394
 395 int
 396 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 397 {
 398   segment_info_type *seginfo = seg_info (sec);
 399   frchainS *chain;
 400   fragS *frag;
 401
 402   if (!seginfo)
 403     return 0;
 404
 405   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 406     {
 407       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 408         if (frag->fr_fix)
 409           return 1;
 410       if (obstack_next_free (&chain->frch_obstack)
 411           != chain->frch_last->fr_literal)
 412         return 1;
 413     }
 414   return 0;
 415 }
 416
 417 void
 418 subsegs_print_statistics (FILE *file)
 419 {
 420   frchainS *frchp;
 421   fprintf (file, "frag chains:\n");
 422   for (frchp = frchain_root; frchp; frchp = frchp->frch_next)
 423     {
 424       int count = 0;
 425       fragS *fragp;
 426
 427       /* If frch_subseg is non-zero, it's probably been chained onto
 428          the end of a previous subsection.  Don't count it again.  */
 429       if (frchp->frch_subseg != 0)
 430         continue;
 431
 432       /* Skip gas-internal sections.  */
 433       if (segment_name (frchp->frch_seg)[0] == '*')
 434         continue;
 435
 436       for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 437         {
 438           count++;
 439         }
 440       fprintf (file, "\n");
 441       fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 442                segment_name (frchp->frch_seg), count);
 443     }
 444 }
 445
 446 /* end of subsegs.c */