• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /* subsegs.c - subsegments -
2    Copyright (C) 1987-2014 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
subsegs_begin(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 /*
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
subseg_change(segT seg,int subseg)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 = (segment_info_type *) xcalloc (1, sizeof (*seginfo));
67       seginfo->bfd_section = seg;
68       bfd_set_section_userdata (stdoutput, seg, seginfo);
69     }
70 }
71 
72 static void
subseg_set_rest(segT seg,subsegT subseg)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
subseg_get(const char * segname,int force_new)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
150 			      ? bfd_get_section_name (stdoutput, now_seg)
151 			      : 0);
152 
153   if (!force_new
154       && now_seg_name
155       && (now_seg_name == segname
156 	  || !strcmp (now_seg_name, segname)))
157     return now_seg;
158 
159   if (!force_new)
160     secptr = bfd_make_section_old_way (stdoutput, segname);
161   else
162     secptr = bfd_make_section_anyway (stdoutput, segname);
163 
164   seginfo = seg_info (secptr);
165   if (! seginfo)
166     {
167       secptr->output_section = secptr;
168       seginfo = (segment_info_type *) xcalloc (1, sizeof (*seginfo));
169       seginfo->bfd_section = secptr;
170       bfd_set_section_userdata (stdoutput, secptr, seginfo);
171     }
172   return secptr;
173 }
174 
175 segT
subseg_new(const char * segname,subsegT subseg)176 subseg_new (const char *segname, subsegT subseg)
177 {
178   segT secptr;
179 
180   secptr = subseg_get (segname, 0);
181   subseg_set_rest (secptr, subseg);
182   return secptr;
183 }
184 
185 /* Like subseg_new, except a new section is always created, even if
186    a section with that name already exists.  */
187 segT
subseg_force_new(const char * segname,subsegT subseg)188 subseg_force_new (const char *segname, subsegT subseg)
189 {
190   segT secptr;
191 
192   secptr = subseg_get (segname, 1);
193   subseg_set_rest (secptr, subseg);
194   return secptr;
195 }
196 
197 void
subseg_set(segT secptr,subsegT subseg)198 subseg_set (segT secptr, subsegT subseg)
199 {
200   if (! (secptr == now_seg && subseg == now_subseg))
201     subseg_set_rest (secptr, subseg);
202   mri_common_symbol = NULL;
203 }
204 
205 #ifndef obj_sec_sym_ok_for_reloc
206 #define obj_sec_sym_ok_for_reloc(SEC)	0
207 #endif
208 
209 symbolS *
section_symbol(segT sec)210 section_symbol (segT sec)
211 {
212   segment_info_type *seginfo = seg_info (sec);
213   symbolS *s;
214 
215   if (seginfo == 0)
216     abort ();
217   if (seginfo->sym)
218     return seginfo->sym;
219 
220 #ifndef EMIT_SECTION_SYMBOLS
221 #define EMIT_SECTION_SYMBOLS 1
222 #endif
223 
224   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
225     {
226       /* Here we know it won't be going into the symbol table.  */
227       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
228     }
229   else
230     {
231       segT seg;
232       s = symbol_find (sec->symbol->name);
233       /* We have to make sure it is the right symbol when we
234 	 have multiple sections with the same section name.  */
235       if (s == NULL
236 	  || ((seg = S_GET_SEGMENT (s)) != sec
237 	      && seg != undefined_section))
238 	s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
239       else if (seg == undefined_section)
240 	{
241 	  S_SET_SEGMENT (s, sec);
242 	  symbol_set_frag (s, &zero_address_frag);
243 	}
244     }
245 
246   S_CLEAR_EXTERNAL (s);
247 
248   /* Use the BFD section symbol, if possible.  */
249   if (obj_sec_sym_ok_for_reloc (sec))
250     symbol_set_bfdsym (s, sec->symbol);
251   else
252     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
253 
254   seginfo->sym = s;
255   return s;
256 }
257 
258 /* Return whether the specified segment is thought to hold text.  */
259 
260 int
subseg_text_p(segT sec)261 subseg_text_p (segT sec)
262 {
263   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
264 }
265 
266 /* Return non zero if SEC has at least one byte of data.  It is
267    possible that we'll return zero even on a non-empty section because
268    we don't know all the fragment types, and it is possible that an
269    fr_fix == 0 one still contributes data.  Think of this as
270    seg_definitely_not_empty_p.  */
271 
272 int
seg_not_empty_p(segT sec ATTRIBUTE_UNUSED)273 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
274 {
275   segment_info_type *seginfo = seg_info (sec);
276   frchainS *chain;
277   fragS *frag;
278 
279   if (!seginfo)
280     return 0;
281 
282   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
283     {
284       for (frag = chain->frch_root; frag; frag = frag->fr_next)
285 	if (frag->fr_fix)
286 	  return 1;
287       if (obstack_next_free (&chain->frch_obstack)
288 	  != chain->frch_last->fr_literal)
289 	return 1;
290     }
291   return 0;
292 }
293 
294 void
subsegs_print_statistics(FILE * file)295 subsegs_print_statistics (FILE *file)
296 {
297   frchainS *frchp;
298   asection *s;
299 
300   fprintf (file, "frag chains:\n");
301   for (s = stdoutput->sections; s; s = s->next)
302     {
303       segment_info_type *seginfo;
304 
305       /* Skip gas-internal sections.  */
306       if (segment_name (s)[0] == '*')
307 	continue;
308 
309       seginfo = seg_info (s);
310       if (!seginfo)
311 	continue;
312 
313       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
314 	{
315 	  int count = 0;
316 	  fragS *fragp;
317 
318 	  for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
319 	    count++;
320 
321 	  fprintf (file, "\n");
322 	  fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
323 		   segment_name (s), count);
324 	}
325     }
326 }
327 
328 /* end of subsegs.c */
329