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
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
57 static void
58 alloc_seginfo (segT seg)
59 {
60 segment_info_type *seginfo;
61
62 seginfo = obstack_alloc (¬es, 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 */
77 void
78 subseg_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
87 static void
88 subseg_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
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 */