1/* subsegs.c - subsegments -
2   Copyright (C) 1987-2022 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
28frchainS *frchain_now;
29
30static struct obstack frchains;
31
32static fragS dummy_frag;
33
34
35void
36subsegs_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
47void
48subsegs_end (struct obstack **obs)
49{
50  for (; *obs; obs++)
51    _obstack_free (*obs, NULL);
52  _obstack_free (&frchains, NULL);
53  _obstack_free (&cond_obstack, NULL);
54  _obstack_free (&notes, NULL);
55}
56
57static void
58alloc_seginfo (segT seg)
59{
60  segment_info_type *seginfo;
61
62  seginfo = obstack_alloc (&notes, sizeof (*seginfo));
63  memset (seginfo, 0, sizeof (*seginfo));
64  seginfo->bfd_section = seg;
65  bfd_set_section_userdata (seg, seginfo);
66}
67/*
68 *			subseg_change()
69 *
70 * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
71 * subsegment. If we are already in the correct subsegment, change nothing.
72 * This is used eg as a worker for subseg_set [which does make a new frag_now]
73 * and for changing segments after we have read the source. We construct eg
74 * fixSs even after the source file is read, so we do have to keep the
75 * segment context correct.
76 */
77void
78subseg_change (segT seg, int subseg)
79{
80  now_seg = seg;
81  now_subseg = subseg;
82
83  if (!seg_info (seg))
84    alloc_seginfo (seg);
85}
86
87static void
88subseg_set_rest (segT seg, subsegT subseg)
89{
90  frchainS *frcP;		/* crawl frchain chain */
91  frchainS **lastPP;		/* address of last pointer */
92  frchainS *newP;		/* address of new frchain */
93  segment_info_type *seginfo;
94
95  mri_common_symbol = NULL;
96
97  if (frag_now && frchain_now)
98    frchain_now->frch_frag_now = frag_now;
99
100  gas_assert (frchain_now == 0
101	  || frchain_now->frch_last == frag_now);
102
103  subseg_change (seg, (int) subseg);
104
105  seginfo = seg_info (seg);
106
107  /* Should the section symbol be kept?  */
108  if (bfd_keep_unused_section_symbols (stdoutput))
109    seg->symbol->flags |= BSF_SECTION_SYM_USED;
110
111  /* Attempt to find or make a frchain for that subsection.
112     We keep the list sorted by subsection number.  */
113  for (frcP = *(lastPP = &seginfo->frchainP);
114       frcP != NULL;
115       frcP = *(lastPP = &frcP->frch_next))
116    if (frcP->frch_subseg >= subseg)
117      break;
118
119  if (frcP == NULL || frcP->frch_subseg != subseg)
120    {
121      /* This should be the only code that creates a frchainS.  */
122
123      newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
124      newP->frch_subseg = subseg;
125      newP->fix_root = NULL;
126      newP->fix_tail = NULL;
127      obstack_begin (&newP->frch_obstack, chunksize);
128#if __GNUC__ >= 2
129      obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
130#endif
131      newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
132      newP->frch_frag_now->fr_type = rs_fill;
133      newP->frch_cfi_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
163segT
164subseg_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
188segT
189subseg_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.  */
200segT
201subseg_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
210void
211subseg_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
222symbolS *
223section_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
273int
274subseg_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
285int
286seg_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
307void
308subsegs_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 */
346