gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright (C) 1987-2023 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
  47 void
  48 subsegs_end (struct obstack **obs)
  49 {
  50   for (; *obs; obs++)
  51     _obstack_free (*obs, NULL);
  52   _obstack_free (&frchains, NULL);
  53   bfd_set_section_userdata (bfd_abs_section_ptr, NULL);
  54   bfd_set_section_userdata (bfd_und_section_ptr, NULL);
  55 }
  56 \f
  57 static void
  58 alloc_seginfo (segT seg)
  59 {
  60   segment_info_type *seginfo;
  61
  62   seginfo = obstack_alloc (&notes, sizeof (*seginfo));
  63   memset (seginfo, 0, sizeof (*seginfo));
  64   bfd_set_section_userdata (seg, seginfo);
  65 }
  66 /*
  67  *                      subseg_change()
  68  *
  69  * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
  70  * subsegment. If we are already in the correct subsegment, change nothing.
  71  * This is used eg as a worker for subseg_set [which does make a new frag_now]
  72  * and for changing segments after we have read the source. We construct eg
  73  * fixSs even after the source file is read, so we do have to keep the
  74  * segment context correct.
  75  */
  76 void
  77 subseg_change (segT seg, int subseg)
  78 {
  79   now_seg = seg;
  80   now_subseg = subseg;
  81
  82   if (!seg_info (seg))
  83     alloc_seginfo (seg);
  84 }
  85 \f
  86 static void
  87 subseg_set_rest (segT seg, subsegT subseg)
  88 {
  89   frchainS *frcP;               /* crawl frchain chain */
  90   frchainS **lastPP;            /* address of last pointer */
  91   frchainS *newP;               /* address of new frchain */
  92   segment_info_type *seginfo;
  93
  94   mri_common_symbol = NULL;
  95
  96   if (frag_now && frchain_now)
  97     frchain_now->frch_frag_now = frag_now;
  98
  99   gas_assert (frchain_now == 0
 100           || frchain_now->frch_last == frag_now);
 101
 102   subseg_change (seg, (int) subseg);
 103
 104   seginfo = seg_info (seg);
 105
 106   /* Should the section symbol be kept?  */
 107   if (bfd_keep_unused_section_symbols (stdoutput))
 108     seg->symbol->flags |= BSF_SECTION_SYM_USED;
 109
 110   /* Attempt to find or make a frchain for that subsection.
 111      We keep the list sorted by subsection number.  */
 112   for (frcP = *(lastPP = &seginfo->frchainP);
 113        frcP != NULL;
 114        frcP = *(lastPP = &frcP->frch_next))
 115     if (frcP->frch_subseg >= subseg)
 116       break;
 117
 118   if (frcP == NULL || frcP->frch_subseg != subseg)
 119     {
 120       /* This should be the only code that creates a frchainS.  */
 121
 122       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 123       newP->frch_subseg = subseg;
 124       newP->fix_root = NULL;
 125       newP->fix_tail = NULL;
 126       obstack_begin (&newP->frch_obstack, chunksize);
 127 #if __GNUC__ >= 2
 128       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 129 #endif
 130       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 131       newP->frch_frag_now->fr_type = rs_fill;
 132       newP->frch_cfi_data = NULL;
 133
 134       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 135
 136       *lastPP = newP;
 137       newP->frch_next = frcP;
 138       frcP = newP;
 139     }
 140
 141   frchain_now = frcP;
 142   frag_now = frcP->frch_frag_now;
 143
 144   gas_assert (frchain_now->frch_last == frag_now);
 145 }
 146
 147 /*
 148  *                      subseg_set(segT, subsegT)
 149  *
 150  * If you attempt to change to the current subsegment, nothing happens.
 151  *
 152  * In:  segT, subsegT code for new subsegment.
 153  *      frag_now -> incomplete frag for current subsegment.
 154  *      If frag_now==NULL, then there is no old, incomplete frag, so
 155  *      the old frag is not closed off.
 156  *
 157  * Out: now_subseg, now_seg updated.
 158  *      Frchain_now points to the (possibly new) struct frchain for this
 159  *      sub-segment.
 160  */
 161
 162 segT
 163 subseg_get (const char *segname, int force_new)
 164 {
 165   segT secptr;
 166   const char *now_seg_name = now_seg ? bfd_section_name (now_seg) : 0;
 167
 168   if (!force_new
 169       && now_seg_name
 170       && (now_seg_name == segname
 171           || !strcmp (now_seg_name, segname)))
 172     return now_seg;
 173
 174   if (!force_new)
 175     secptr = bfd_make_section_old_way (stdoutput, segname);
 176   else
 177     secptr = bfd_make_section_anyway (stdoutput, segname);
 178
 179   if (!seg_info (secptr))
 180     {
 181       secptr->output_section = secptr;
 182       alloc_seginfo (secptr);
 183     }
 184   return secptr;
 185 }
 186
 187 segT
 188 subseg_new (const char *segname, subsegT subseg)
 189 {
 190   segT secptr;
 191
 192   secptr = subseg_get (segname, 0);
 193   subseg_set_rest (secptr, subseg);
 194   return secptr;
 195 }
 196
 197 /* Like subseg_new, except a new section is always created, even if
 198    a section with that name already exists.  */
 199 segT
 200 subseg_force_new (const char *segname, subsegT subseg)
 201 {
 202   segT secptr;
 203
 204   secptr = subseg_get (segname, 1);
 205   subseg_set_rest (secptr, subseg);
 206   return secptr;
 207 }
 208
 209 void
 210 subseg_set (segT secptr, subsegT subseg)
 211 {
 212   if (! (secptr == now_seg && subseg == now_subseg))
 213     subseg_set_rest (secptr, subseg);
 214   mri_common_symbol = NULL;
 215 }
 216
 217 #ifndef obj_sec_sym_ok_for_reloc
 218 #define obj_sec_sym_ok_for_reloc(SEC)   0
 219 #endif
 220
 221 symbolS *
 222 section_symbol (segT sec)
 223 {
 224   segment_info_type *seginfo = seg_info (sec);
 225   symbolS *s;
 226
 227   if (seginfo == 0)
 228     abort ();
 229   if (seginfo->sym)
 230     return seginfo->sym;
 231
 232 #ifndef EMIT_SECTION_SYMBOLS
 233 #define EMIT_SECTION_SYMBOLS 1
 234 #endif
 235
 236   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 237     {
 238       /* Here we know it won't be going into the symbol table.  */
 239       s = symbol_create (sec->symbol->name, sec, &zero_address_frag, 0);
 240     }
 241   else
 242     {
 243       segT seg;
 244       s = symbol_find (sec->symbol->name);
 245       /* We have to make sure it is the right symbol when we
 246          have multiple sections with the same section name.  */
 247       if (s == NULL
 248           || ((seg = S_GET_SEGMENT (s)) != sec
 249               && seg != undefined_section))
 250         s = symbol_new (sec->symbol->name, sec, &zero_address_frag, 0);
 251       else if (seg == undefined_section)
 252         {
 253           S_SET_SEGMENT (s, sec);
 254           symbol_set_frag (s, &zero_address_frag);
 255         }
 256     }
 257
 258   S_CLEAR_EXTERNAL (s);
 259
 260   /* Use the BFD section symbol, if possible.  */
 261   if (obj_sec_sym_ok_for_reloc (sec))
 262     symbol_set_bfdsym (s, sec->symbol);
 263   else
 264     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 265
 266   seginfo->sym = s;
 267   return s;
 268 }
 269
 270 /* Return whether the specified segment is thought to hold text.  */
 271
 272 int
 273 subseg_text_p (segT sec)
 274 {
 275   return (bfd_section_flags (sec) & SEC_CODE) != 0;
 276 }
 277
 278 /* Return non zero if SEC has at least one byte of data.  It is
 279    possible that we'll return zero even on a non-empty section because
 280    we don't know all the fragment types, and it is possible that an
 281    fr_fix == 0 one still contributes data.  Think of this as
 282    seg_definitely_not_empty_p.  */
 283
 284 int
 285 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 286 {
 287   segment_info_type *seginfo = seg_info (sec);
 288   frchainS *chain;
 289   fragS *frag;
 290
 291   if (!seginfo)
 292     return 0;
 293
 294   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 295     {
 296       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 297         if (frag->fr_fix)
 298           return 1;
 299       if (obstack_next_free (&chain->frch_obstack)
 300           != chain->frch_last->fr_literal)
 301         return 1;
 302     }
 303   return 0;
 304 }
 305
 306 void
 307 subsegs_print_statistics (FILE *file)
 308 {
 309   frchainS *frchp;
 310   asection *s;
 311
 312   /* PR 20897 - check to see if the output bfd was actually created.  */
 313   if (stdoutput == NULL)
 314     return;
 315
 316   fprintf (file, "frag chains:\n");
 317   for (s = stdoutput->sections; s; s = s->next)
 318     {
 319       segment_info_type *seginfo;
 320
 321       /* Skip gas-internal sections.  */
 322       if (segment_name (s)[0] == '*')
 323         continue;
 324
 325       seginfo = seg_info (s);
 326       if (!seginfo)
 327         continue;
 328
 329       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 330         {
 331           int count = 0;
 332           fragS *fragp;
 333
 334           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 335             count++;
 336
 337           fprintf (file, "\n");
 338           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 339                    segment_name (s), count);
 340         }
 341     }
 342 }
 343
 344 /* end of subsegs.c */