gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright (C) 1987-2021 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 (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   /* Should the section symbol be kept?  */
  93   if (bfd_keep_unused_section_symbols (stdoutput))
  94     seg->symbol->flags |= BSF_SECTION_SYM_USED;
  95
  96   /* Attempt to find or make a frchain for that subsection.
  97      We keep the list sorted by subsection number.  */
  98   for (frcP = *(lastPP = &seginfo->frchainP);
  99        frcP != NULL;
 100        frcP = *(lastPP = &frcP->frch_next))
 101     if (frcP->frch_subseg >= subseg)
 102       break;
 103
 104   if (frcP == NULL || frcP->frch_subseg != subseg)
 105     {
 106       /* This should be the only code that creates a frchainS.  */
 107
 108       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 109       newP->frch_subseg = subseg;
 110       newP->fix_root = NULL;
 111       newP->fix_tail = NULL;
 112       obstack_begin (&newP->frch_obstack, chunksize);
 113 #if __GNUC__ >= 2
 114       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 115 #endif
 116       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 117       newP->frch_frag_now->fr_type = rs_fill;
 118       newP->frch_cfi_data = NULL;
 119
 120       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 121
 122       *lastPP = newP;
 123       newP->frch_next = frcP;
 124       frcP = newP;
 125     }
 126
 127   frchain_now = frcP;
 128   frag_now = frcP->frch_frag_now;
 129
 130   gas_assert (frchain_now->frch_last == frag_now);
 131 }
 132
 133 /*
 134  *                      subseg_set(segT, subsegT)
 135  *
 136  * If you attempt to change to the current subsegment, nothing happens.
 137  *
 138  * In:  segT, subsegT code for new subsegment.
 139  *      frag_now -> incomplete frag for current subsegment.
 140  *      If frag_now==NULL, then there is no old, incomplete frag, so
 141  *      the old frag is not closed off.
 142  *
 143  * Out: now_subseg, now_seg updated.
 144  *      Frchain_now points to the (possibly new) struct frchain for this
 145  *      sub-segment.
 146  */
 147
 148 segT
 149 subseg_get (const char *segname, int force_new)
 150 {
 151   segT secptr;
 152   segment_info_type *seginfo;
 153   const char *now_seg_name = now_seg ? bfd_section_name (now_seg) : 0;
 154
 155   if (!force_new
 156       && now_seg_name
 157       && (now_seg_name == segname
 158           || !strcmp (now_seg_name, segname)))
 159     return now_seg;
 160
 161   if (!force_new)
 162     secptr = bfd_make_section_old_way (stdoutput, segname);
 163   else
 164     secptr = bfd_make_section_anyway (stdoutput, segname);
 165
 166   seginfo = seg_info (secptr);
 167   if (! seginfo)
 168     {
 169       secptr->output_section = secptr;
 170       seginfo = XCNEW (segment_info_type);
 171       seginfo->bfd_section = secptr;
 172       bfd_set_section_userdata (secptr, seginfo);
 173     }
 174   return secptr;
 175 }
 176
 177 segT
 178 subseg_new (const char *segname, subsegT subseg)
 179 {
 180   segT secptr;
 181
 182   secptr = subseg_get (segname, 0);
 183   subseg_set_rest (secptr, subseg);
 184   return secptr;
 185 }
 186
 187 /* Like subseg_new, except a new section is always created, even if
 188    a section with that name already exists.  */
 189 segT
 190 subseg_force_new (const char *segname, subsegT subseg)
 191 {
 192   segT secptr;
 193
 194   secptr = subseg_get (segname, 1);
 195   subseg_set_rest (secptr, subseg);
 196   return secptr;
 197 }
 198
 199 void
 200 subseg_set (segT secptr, subsegT subseg)
 201 {
 202   if (! (secptr == now_seg && subseg == now_subseg))
 203     subseg_set_rest (secptr, subseg);
 204   mri_common_symbol = NULL;
 205 }
 206
 207 #ifndef obj_sec_sym_ok_for_reloc
 208 #define obj_sec_sym_ok_for_reloc(SEC)   0
 209 #endif
 210
 211 symbolS *
 212 section_symbol (segT sec)
 213 {
 214   segment_info_type *seginfo = seg_info (sec);
 215   symbolS *s;
 216
 217   if (seginfo == 0)
 218     abort ();
 219   if (seginfo->sym)
 220     return seginfo->sym;
 221
 222 #ifndef EMIT_SECTION_SYMBOLS
 223 #define EMIT_SECTION_SYMBOLS 1
 224 #endif
 225
 226   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 227     {
 228       /* Here we know it won't be going into the symbol table.  */
 229       s = symbol_create (sec->symbol->name, sec, &zero_address_frag, 0);
 230     }
 231   else
 232     {
 233       segT seg;
 234       s = symbol_find (sec->symbol->name);
 235       /* We have to make sure it is the right symbol when we
 236          have multiple sections with the same section name.  */
 237       if (s == NULL
 238           || ((seg = S_GET_SEGMENT (s)) != sec
 239               && seg != undefined_section))
 240         s = symbol_new (sec->symbol->name, sec, &zero_address_frag, 0);
 241       else if (seg == undefined_section)
 242         {
 243           S_SET_SEGMENT (s, sec);
 244           symbol_set_frag (s, &zero_address_frag);
 245         }
 246     }
 247
 248   S_CLEAR_EXTERNAL (s);
 249
 250   /* Use the BFD section symbol, if possible.  */
 251   if (obj_sec_sym_ok_for_reloc (sec))
 252     symbol_set_bfdsym (s, sec->symbol);
 253   else
 254     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 255
 256   seginfo->sym = s;
 257   return s;
 258 }
 259
 260 /* Return whether the specified segment is thought to hold text.  */
 261
 262 int
 263 subseg_text_p (segT sec)
 264 {
 265   return (bfd_section_flags (sec) & SEC_CODE) != 0;
 266 }
 267
 268 /* Return non zero if SEC has at least one byte of data.  It is
 269    possible that we'll return zero even on a non-empty section because
 270    we don't know all the fragment types, and it is possible that an
 271    fr_fix == 0 one still contributes data.  Think of this as
 272    seg_definitely_not_empty_p.  */
 273
 274 int
 275 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 276 {
 277   segment_info_type *seginfo = seg_info (sec);
 278   frchainS *chain;
 279   fragS *frag;
 280
 281   if (!seginfo)
 282     return 0;
 283
 284   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 285     {
 286       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 287         if (frag->fr_fix)
 288           return 1;
 289       if (obstack_next_free (&chain->frch_obstack)
 290           != chain->frch_last->fr_literal)
 291         return 1;
 292     }
 293   return 0;
 294 }
 295
 296 void
 297 subsegs_print_statistics (FILE *file)
 298 {
 299   frchainS *frchp;
 300   asection *s;
 301
 302   /* PR 20897 - check to see if the output bfd was actually created.  */
 303   if (stdoutput == NULL)
 304     return;
 305
 306   fprintf (file, "frag chains:\n");
 307   for (s = stdoutput->sections; s; s = s->next)
 308     {
 309       segment_info_type *seginfo;
 310
 311       /* Skip gas-internal sections.  */
 312       if (segment_name (s)[0] == '*')
 313         continue;
 314
 315       seginfo = seg_info (s);
 316       if (!seginfo)
 317         continue;
 318
 319       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 320         {
 321           int count = 0;
 322           fragS *fragp;
 323
 324           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 325             count++;
 326
 327           fprintf (file, "\n");
 328           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 329                    segment_name (s), count);
 330         }
 331     }
 332 }
 333
 334 /* end of subsegs.c */