gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright (C) 1987-2020 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   /* 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 ? bfd_section_name (now_seg) : 0;
 150
 151   if (!force_new
 152       && now_seg_name
 153       && (now_seg_name == segname
 154           || !strcmp (now_seg_name, segname)))
 155     return now_seg;
 156
 157   if (!force_new)
 158     secptr = bfd_make_section_old_way (stdoutput, segname);
 159   else
 160     secptr = bfd_make_section_anyway (stdoutput, segname);
 161
 162   seginfo = seg_info (secptr);
 163   if (! seginfo)
 164     {
 165       secptr->output_section = secptr;
 166       seginfo = XCNEW (segment_info_type);
 167       seginfo->bfd_section = secptr;
 168       bfd_set_section_userdata (secptr, seginfo);
 169     }
 170   return secptr;
 171 }
 172
 173 segT
 174 subseg_new (const char *segname, subsegT subseg)
 175 {
 176   segT secptr;
 177
 178   secptr = subseg_get (segname, 0);
 179   subseg_set_rest (secptr, subseg);
 180   return secptr;
 181 }
 182
 183 /* Like subseg_new, except a new section is always created, even if
 184    a section with that name already exists.  */
 185 segT
 186 subseg_force_new (const char *segname, subsegT subseg)
 187 {
 188   segT secptr;
 189
 190   secptr = subseg_get (segname, 1);
 191   subseg_set_rest (secptr, subseg);
 192   return secptr;
 193 }
 194
 195 void
 196 subseg_set (segT secptr, subsegT subseg)
 197 {
 198   if (! (secptr == now_seg && subseg == now_subseg))
 199     subseg_set_rest (secptr, subseg);
 200   mri_common_symbol = NULL;
 201 }
 202
 203 #ifndef obj_sec_sym_ok_for_reloc
 204 #define obj_sec_sym_ok_for_reloc(SEC)   0
 205 #endif
 206
 207 symbolS *
 208 section_symbol (segT sec)
 209 {
 210   segment_info_type *seginfo = seg_info (sec);
 211   symbolS *s;
 212
 213   if (seginfo == 0)
 214     abort ();
 215   if (seginfo->sym)
 216     return seginfo->sym;
 217
 218 #ifndef EMIT_SECTION_SYMBOLS
 219 #define EMIT_SECTION_SYMBOLS 1
 220 #endif
 221
 222   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 223     {
 224       /* Here we know it won't be going into the symbol table.  */
 225       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 226     }
 227   else
 228     {
 229       segT seg;
 230       s = symbol_find (sec->symbol->name);
 231       /* We have to make sure it is the right symbol when we
 232          have multiple sections with the same section name.  */
 233       if (s == NULL
 234           || ((seg = S_GET_SEGMENT (s)) != sec
 235               && seg != undefined_section))
 236         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 237       else if (seg == undefined_section)
 238         {
 239           S_SET_SEGMENT (s, sec);
 240           symbol_set_frag (s, &zero_address_frag);
 241         }
 242     }
 243
 244   S_CLEAR_EXTERNAL (s);
 245
 246   /* Use the BFD section symbol, if possible.  */
 247   if (obj_sec_sym_ok_for_reloc (sec))
 248     symbol_set_bfdsym (s, sec->symbol);
 249   else
 250     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 251
 252   seginfo->sym = s;
 253   return s;
 254 }
 255
 256 /* Return whether the specified segment is thought to hold text.  */
 257
 258 int
 259 subseg_text_p (segT sec)
 260 {
 261   return (bfd_section_flags (sec) & SEC_CODE) != 0;
 262 }
 263
 264 /* Return non zero if SEC has at least one byte of data.  It is
 265    possible that we'll return zero even on a non-empty section because
 266    we don't know all the fragment types, and it is possible that an
 267    fr_fix == 0 one still contributes data.  Think of this as
 268    seg_definitely_not_empty_p.  */
 269
 270 int
 271 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 272 {
 273   segment_info_type *seginfo = seg_info (sec);
 274   frchainS *chain;
 275   fragS *frag;
 276
 277   if (!seginfo)
 278     return 0;
 279
 280   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 281     {
 282       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 283         if (frag->fr_fix)
 284           return 1;
 285       if (obstack_next_free (&chain->frch_obstack)
 286           != chain->frch_last->fr_literal)
 287         return 1;
 288     }
 289   return 0;
 290 }
 291
 292 void
 293 subsegs_print_statistics (FILE *file)
 294 {
 295   frchainS *frchp;
 296   asection *s;
 297
 298   /* PR 20897 - check to see if the output bfd was actually created.  */
 299   if (stdoutput == NULL)
 300     return;
 301
 302   fprintf (file, "frag chains:\n");
 303   for (s = stdoutput->sections; s; s = s->next)
 304     {
 305       segment_info_type *seginfo;
 306
 307       /* Skip gas-internal sections.  */
 308       if (segment_name (s)[0] == '*')
 309         continue;
 310
 311       seginfo = seg_info (s);
 312       if (!seginfo)
 313         continue;
 314
 315       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 316         {
 317           int count = 0;
 318           fragS *fragp;
 319
 320           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 321             count++;
 322
 323           fprintf (file, "\n");
 324           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 325                    segment_name (s), count);
 326         }
 327     }
 328 }
 329
 330 /* end of subsegs.c */