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