gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright (C) 1987-2024 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       newP->frch_ginsn_data = NULL;
 134
 135       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 136
 137       *lastPP = newP;
 138       newP->frch_next = frcP;
 139       frcP = newP;
 140     }
 141
 142   frchain_now = frcP;
 143   frag_now = frcP->frch_frag_now;
 144
 145   gas_assert (frchain_now->frch_last == frag_now);
 146 }
 147
 148 /*
 149  *                      subseg_set(segT, subsegT)
 150  *
 151  * If you attempt to change to the current subsegment, nothing happens.
 152  *
 153  * In:  segT, subsegT code for new subsegment.
 154  *      frag_now -> incomplete frag for current subsegment.
 155  *      If frag_now==NULL, then there is no old, incomplete frag, so
 156  *      the old frag is not closed off.
 157  *
 158  * Out: now_subseg, now_seg updated.
 159  *      Frchain_now points to the (possibly new) struct frchain for this
 160  *      sub-segment.
 161  */
 162
 163 segT
 164 subseg_get (const char *segname, int force_new)
 165 {
 166   segT secptr;
 167   const char *now_seg_name = now_seg ? bfd_section_name (now_seg) : 0;
 168
 169   if (!force_new
 170       && now_seg_name
 171       && (now_seg_name == segname
 172           || !strcmp (now_seg_name, segname)))
 173     return now_seg;
 174
 175   if (!force_new)
 176     secptr = bfd_make_section_old_way (stdoutput, segname);
 177   else
 178     secptr = bfd_make_section_anyway (stdoutput, segname);
 179
 180   if (!seg_info (secptr))
 181     {
 182       secptr->output_section = secptr;
 183       alloc_seginfo (secptr);
 184     }
 185   return secptr;
 186 }
 187
 188 segT
 189 subseg_new (const char *segname, subsegT subseg)
 190 {
 191   segT secptr;
 192
 193   secptr = subseg_get (segname, 0);
 194   subseg_set_rest (secptr, subseg);
 195   return secptr;
 196 }
 197
 198 /* Like subseg_new, except a new section is always created, even if
 199    a section with that name already exists.  */
 200 segT
 201 subseg_force_new (const char *segname, subsegT subseg)
 202 {
 203   segT secptr;
 204
 205   secptr = subseg_get (segname, 1);
 206   subseg_set_rest (secptr, subseg);
 207   return secptr;
 208 }
 209
 210 void
 211 subseg_set (segT secptr, subsegT subseg)
 212 {
 213   if (! (secptr == now_seg && subseg == now_subseg))
 214     subseg_set_rest (secptr, subseg);
 215   mri_common_symbol = NULL;
 216 }
 217
 218 #ifndef obj_sec_sym_ok_for_reloc
 219 #define obj_sec_sym_ok_for_reloc(SEC)   0
 220 #endif
 221
 222 symbolS *
 223 section_symbol (segT sec)
 224 {
 225   segment_info_type *seginfo = seg_info (sec);
 226   symbolS *s;
 227
 228   if (seginfo == 0)
 229     abort ();
 230   if (seginfo->sym)
 231     return seginfo->sym;
 232
 233 #ifndef EMIT_SECTION_SYMBOLS
 234 #define EMIT_SECTION_SYMBOLS 1
 235 #endif
 236
 237   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 238     {
 239       /* Here we know it won't be going into the symbol table.  */
 240       s = symbol_create (sec->symbol->name, sec, &zero_address_frag, 0);
 241     }
 242   else
 243     {
 244       segT seg;
 245       s = symbol_find (sec->symbol->name);
 246       /* We have to make sure it is the right symbol when we
 247          have multiple sections with the same section name.  */
 248       if (s == NULL
 249           || ((seg = S_GET_SEGMENT (s)) != sec
 250               && seg != undefined_section))
 251         s = symbol_new (sec->symbol->name, sec, &zero_address_frag, 0);
 252       else if (seg == undefined_section)
 253         {
 254           S_SET_SEGMENT (s, sec);
 255           symbol_set_frag (s, &zero_address_frag);
 256         }
 257     }
 258
 259   S_CLEAR_EXTERNAL (s);
 260
 261   /* Use the BFD section symbol, if possible.  */
 262   if (obj_sec_sym_ok_for_reloc (sec))
 263     symbol_set_bfdsym (s, sec->symbol);
 264   else
 265     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 266
 267   seginfo->sym = s;
 268   return s;
 269 }
 270
 271 /* Return whether the specified segment is thought to hold text.  */
 272
 273 int
 274 subseg_text_p (segT sec)
 275 {
 276   return (bfd_section_flags (sec) & SEC_CODE) != 0;
 277 }
 278
 279 /* Return non zero if SEC has at least one byte of data.  It is
 280    possible that we'll return zero even on a non-empty section because
 281    we don't know all the fragment types, and it is possible that an
 282    fr_fix == 0 one still contributes data.  Think of this as
 283    seg_definitely_not_empty_p.  */
 284
 285 int
 286 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 287 {
 288   segment_info_type *seginfo = seg_info (sec);
 289   frchainS *chain;
 290   fragS *frag;
 291
 292   if (!seginfo)
 293     return 0;
 294
 295   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 296     {
 297       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 298         if (frag->fr_fix)
 299           return 1;
 300       if (obstack_next_free (&chain->frch_obstack)
 301           != chain->frch_last->fr_literal)
 302         return 1;
 303     }
 304   return 0;
 305 }
 306
 307 void
 308 subsegs_print_statistics (FILE *file)
 309 {
 310   frchainS *frchp;
 311   asection *s;
 312
 313   /* PR 20897 - check to see if the output bfd was actually created.  */
 314   if (stdoutput == NULL)
 315     return;
 316
 317   fprintf (file, "frag chains:\n");
 318   for (s = stdoutput->sections; s; s = s->next)
 319     {
 320       segment_info_type *seginfo;
 321
 322       /* Skip gas-internal sections.  */
 323       if (segment_name (s)[0] == '*')
 324         continue;
 325
 326       seginfo = seg_info (s);
 327       if (!seginfo)
 328         continue;
 329
 330       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 331         {
 332           int count = 0;
 333           fragS *fragp;
 334
 335           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 336             count++;
 337
 338           fprintf (file, "\n");
 339           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 340                    segment_name (s), count);
 341         }
 342     }
 343 }
 344
 345 /* end of subsegs.c */