gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright (C) 1987-2018 Free Software Foundation, Inc.
   3
   4    This file is part of GAS, the GNU Assembler.
   5
   6    GAS is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GAS is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GAS; see the file COPYING.  If not, write to the Free
  18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  19    02110-1301, USA.  */
  20
  21 /* Segments & sub-segments.  */
  22
  23 #include "as.h"
  24
  25 #include "subsegs.h"
  26 #include "obstack.h"
  27
  28 frchainS *frchain_now;
  29
  30 static struct obstack frchains;
  31
  32 static fragS dummy_frag;
  33
  34 \f
  35 void
  36 subsegs_begin (void)
  37 {
  38   obstack_begin (&frchains, chunksize);
  39 #if __GNUC__ >= 2
  40   obstack_alignment_mask (&frchains) = __alignof__ (frchainS) - 1;
  41 #endif
  42
  43   frchain_now = NULL;           /* Warn new_subseg() that we are booting.  */
  44   frag_now = &dummy_frag;
  45 }
  46 \f
  47 /*
  48  *                      subseg_change()
  49  *
  50  * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
  51  * subsegment. If we are already in the correct subsegment, change nothing.
  52  * This is used eg as a worker for subseg_set [which does make a new frag_now]
  53  * and for changing segments after we have read the source. We construct eg
  54  * fixSs even after the source file is read, so we do have to keep the
  55  * segment context correct.
  56  */
  57 void
  58 subseg_change (segT seg, int subseg)
  59 {
  60   segment_info_type *seginfo = seg_info (seg);
  61   now_seg = seg;
  62   now_subseg = subseg;
  63
  64   if (! seginfo)
  65     {
  66       seginfo = XCNEW (segment_info_type);
  67       seginfo->bfd_section = seg;
  68       bfd_set_section_userdata (stdoutput, seg, seginfo);
  69     }
  70 }
  71 \f
  72 static void
  73 subseg_set_rest (segT seg, subsegT subseg)
  74 {
  75   frchainS *frcP;               /* crawl frchain chain */
  76   frchainS **lastPP;            /* address of last pointer */
  77   frchainS *newP;               /* address of new frchain */
  78   segment_info_type *seginfo;
  79
  80   mri_common_symbol = NULL;
  81
  82   if (frag_now && frchain_now)
  83     frchain_now->frch_frag_now = frag_now;
  84
  85   gas_assert (frchain_now == 0
  86           || frchain_now->frch_last == frag_now);
  87
  88   subseg_change (seg, (int) subseg);
  89
  90   seginfo = seg_info (seg);
  91
  92   /* Attempt to find or make a frchain for that subsection.
  93      We keep the list sorted by subsection number.  */
  94   for (frcP = *(lastPP = &seginfo->frchainP);
  95        frcP != NULL;
  96        frcP = *(lastPP = &frcP->frch_next))
  97     if (frcP->frch_subseg >= subseg)
  98       break;
  99
 100   if (frcP == NULL || frcP->frch_subseg != subseg)
 101     {
 102       /* This should be the only code that creates a frchainS.  */
 103
 104       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 105       newP->frch_subseg = subseg;
 106       newP->fix_root = NULL;
 107       newP->fix_tail = NULL;
 108       obstack_begin (&newP->frch_obstack, chunksize);
 109 #if __GNUC__ >= 2
 110       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 111 #endif
 112       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 113       newP->frch_frag_now->fr_type = rs_fill;
 114       newP->frch_cfi_data = NULL;
 115
 116       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 117
 118       *lastPP = newP;
 119       newP->frch_next = frcP;
 120       frcP = newP;
 121     }
 122
 123   frchain_now = frcP;
 124   frag_now = frcP->frch_frag_now;
 125
 126   gas_assert (frchain_now->frch_last == frag_now);
 127 }
 128
 129 /*
 130  *                      subseg_set(segT, subsegT)
 131  *
 132  * If you attempt to change to the current subsegment, nothing happens.
 133  *
 134  * In:  segT, subsegT code for new subsegment.
 135  *      frag_now -> incomplete frag for current subsegment.
 136  *      If frag_now==NULL, then there is no old, incomplete frag, so
 137  *      the old frag is not closed off.
 138  *
 139  * Out: now_subseg, now_seg updated.
 140  *      Frchain_now points to the (possibly new) struct frchain for this
 141  *      sub-segment.
 142  */
 143
 144 segT
 145 subseg_get (const char *segname, int force_new)
 146 {
 147   segT secptr;
 148   segment_info_type *seginfo;
 149   const char *now_seg_name = (now_seg
 150                               ? bfd_get_section_name (stdoutput, now_seg)
 151                               : 0);
 152
 153   if (!force_new
 154       && now_seg_name
 155       && (now_seg_name == segname
 156           || !strcmp (now_seg_name, segname)))
 157     return now_seg;
 158
 159   if (!force_new)
 160     secptr = bfd_make_section_old_way (stdoutput, segname);
 161   else
 162     secptr = bfd_make_section_anyway (stdoutput, segname);
 163
 164   seginfo = seg_info (secptr);
 165   if (! seginfo)
 166     {
 167       secptr->output_section = secptr;
 168       seginfo = XCNEW (segment_info_type);
 169       seginfo->bfd_section = secptr;
 170       bfd_set_section_userdata (stdoutput, secptr, seginfo);
 171     }
 172   return secptr;
 173 }
 174
 175 segT
 176 subseg_new (const char *segname, subsegT subseg)
 177 {
 178   segT secptr;
 179
 180   secptr = subseg_get (segname, 0);
 181   subseg_set_rest (secptr, subseg);
 182   return secptr;
 183 }
 184
 185 /* Like subseg_new, except a new section is always created, even if
 186    a section with that name already exists.  */
 187 segT
 188 subseg_force_new (const char *segname, subsegT subseg)
 189 {
 190   segT secptr;
 191
 192   secptr = subseg_get (segname, 1);
 193   subseg_set_rest (secptr, subseg);
 194   return secptr;
 195 }
 196
 197 void
 198 subseg_set (segT secptr, subsegT subseg)
 199 {
 200   if (! (secptr == now_seg && subseg == now_subseg))
 201     subseg_set_rest (secptr, subseg);
 202   mri_common_symbol = NULL;
 203 }
 204
 205 #ifndef obj_sec_sym_ok_for_reloc
 206 #define obj_sec_sym_ok_for_reloc(SEC)   0
 207 #endif
 208
 209 symbolS *
 210 section_symbol (segT sec)
 211 {
 212   segment_info_type *seginfo = seg_info (sec);
 213   symbolS *s;
 214
 215   if (seginfo == 0)
 216     abort ();
 217   if (seginfo->sym)
 218     return seginfo->sym;
 219
 220 #ifndef EMIT_SECTION_SYMBOLS
 221 #define EMIT_SECTION_SYMBOLS 1
 222 #endif
 223
 224   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 225     {
 226       /* Here we know it won't be going into the symbol table.  */
 227       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 228     }
 229   else
 230     {
 231       segT seg;
 232       s = symbol_find (sec->symbol->name);
 233       /* We have to make sure it is the right symbol when we
 234          have multiple sections with the same section name.  */
 235       if (s == NULL
 236           || ((seg = S_GET_SEGMENT (s)) != sec
 237               && seg != undefined_section))
 238         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 239       else if (seg == undefined_section)
 240         {
 241           S_SET_SEGMENT (s, sec);
 242           symbol_set_frag (s, &zero_address_frag);
 243         }
 244     }
 245
 246   S_CLEAR_EXTERNAL (s);
 247
 248   /* Use the BFD section symbol, if possible.  */
 249   if (obj_sec_sym_ok_for_reloc (sec))
 250     symbol_set_bfdsym (s, sec->symbol);
 251   else
 252     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 253
 254   seginfo->sym = s;
 255   return s;
 256 }
 257
 258 /* Return whether the specified segment is thought to hold text.  */
 259
 260 int
 261 subseg_text_p (segT sec)
 262 {
 263   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
 264 }
 265
 266 /* Return non zero if SEC has at least one byte of data.  It is
 267    possible that we'll return zero even on a non-empty section because
 268    we don't know all the fragment types, and it is possible that an
 269    fr_fix == 0 one still contributes data.  Think of this as
 270    seg_definitely_not_empty_p.  */
 271
 272 int
 273 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 274 {
 275   segment_info_type *seginfo = seg_info (sec);
 276   frchainS *chain;
 277   fragS *frag;
 278
 279   if (!seginfo)
 280     return 0;
 281
 282   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 283     {
 284       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 285         if (frag->fr_fix)
 286           return 1;
 287       if (obstack_next_free (&chain->frch_obstack)
 288           != chain->frch_last->fr_literal)
 289         return 1;
 290     }
 291   return 0;
 292 }
 293
 294 void
 295 subsegs_print_statistics (FILE *file)
 296 {
 297   frchainS *frchp;
 298   asection *s;
 299
 300   /* PR 20897 - check to see if the output bfd was actually created.  */
 301   if (stdoutput == NULL)
 302     return;
 303
 304   fprintf (file, "frag chains:\n");
 305   for (s = stdoutput->sections; s; s = s->next)
 306     {
 307       segment_info_type *seginfo;
 308
 309       /* Skip gas-internal sections.  */
 310       if (segment_name (s)[0] == '*')
 311         continue;
 312
 313       seginfo = seg_info (s);
 314       if (!seginfo)
 315         continue;
 316
 317       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 318         {
 319           int count = 0;
 320           fragS *fragp;
 321
 322           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 323             count++;
 324
 325           fprintf (file, "\n");
 326           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 327                    segment_name (s), count);
 328         }
 329     }
 330 }
 331
 332 /* end of subsegs.c */