1 /* ldctor.c -- constructor support routines
2 Copyright (C) 1991-2016 Free Software Foundation, Inc.
3 By Steve Chamberlain <sac@cygnus.com>
4
5 This file is part of the GNU Binutils.
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
20 MA 02110-1301, USA. */
21
22 #include "sysdep.h"
23 #include "bfd.h"
24 #include "bfdlink.h"
25 #include "safe-ctype.h"
26
27 #include "ld.h"
28 #include "ldexp.h"
29 #include "ldlang.h"
30 #include "ldmisc.h"
31 #include <ldgram.h>
32 #include "ldmain.h"
33 #include "ldctor.h"
34
35 /* The list of statements needed to handle constructors. These are
36 invoked by the command CONSTRUCTORS in the linker script. */
37 lang_statement_list_type constructor_list;
38
39 /* Whether the constructors should be sorted. Note that this is
40 global for the entire link; we assume that there is only a single
41 CONSTRUCTORS command in the linker script. */
42 bfd_boolean constructors_sorted;
43
44 /* The sets we have seen. */
45 struct set_info *sets;
46
47 /* Add an entry to a set. H is the entry in the linker hash table.
48 RELOC is the relocation to use for an entry in the set. SECTION
49 and VALUE are the value to add. This is called during the first
50 phase of the link, when we are still gathering symbols together.
51 We just record the information now. The ldctor_build_sets
52 function will construct the sets. */
53
54 void
ldctor_add_set_entry(struct bfd_link_hash_entry * h,bfd_reloc_code_real_type reloc,const char * name,asection * section,bfd_vma value)55 ldctor_add_set_entry (struct bfd_link_hash_entry *h,
56 bfd_reloc_code_real_type reloc,
57 const char *name,
58 asection *section,
59 bfd_vma value)
60 {
61 struct set_info *p;
62 struct set_element *e;
63 struct set_element **epp;
64
65 for (p = sets; p != NULL; p = p->next)
66 if (p->h == h)
67 break;
68
69 if (p == NULL)
70 {
71 p = (struct set_info *) xmalloc (sizeof (struct set_info));
72 p->next = sets;
73 sets = p;
74 p->h = h;
75 p->reloc = reloc;
76 p->count = 0;
77 p->elements = NULL;
78 }
79 else
80 {
81 if (p->reloc != reloc)
82 {
83 einfo (_("%P%X: Different relocs used in set %s\n"),
84 h->root.string);
85 return;
86 }
87
88 /* Don't permit a set to be constructed from different object
89 file formats. The same reloc may have different results. We
90 actually could sometimes handle this, but the case is
91 unlikely to ever arise. Sometimes constructor symbols are in
92 unusual sections, such as the absolute section--this appears
93 to be the case in Linux a.out--and in such cases we just
94 assume everything is OK. */
95 if (p->elements != NULL
96 && section->owner != NULL
97 && p->elements->section->owner != NULL
98 && strcmp (bfd_get_target (section->owner),
99 bfd_get_target (p->elements->section->owner)) != 0)
100 {
101 einfo (_("%P%X: Different object file formats composing set %s\n"),
102 h->root.string);
103 return;
104 }
105 }
106
107 e = (struct set_element *) xmalloc (sizeof (struct set_element));
108 e->next = NULL;
109 e->name = name;
110 e->section = section;
111 e->value = value;
112
113 for (epp = &p->elements; *epp != NULL; epp = &(*epp)->next)
114 ;
115 *epp = e;
116
117 ++p->count;
118 }
119
120 /* Get the priority of a g++ global constructor or destructor from the
121 symbol name. */
122
123 static int
ctor_prio(const char * name)124 ctor_prio (const char *name)
125 {
126 /* The name will look something like _GLOBAL_$I$65535$test02__Fv.
127 There might be extra leading underscores, and the $ characters
128 might be something else. The I might be a D. */
129
130 while (*name == '_')
131 ++name;
132
133 if (!CONST_STRNEQ (name, "GLOBAL_"))
134 return -1;
135
136 name += sizeof "GLOBAL_" - 1;
137
138 if (name[0] != name[2])
139 return -1;
140 if (name[1] != 'I' && name[1] != 'D')
141 return -1;
142 if (!ISDIGIT (name[3]))
143 return -1;
144
145 return atoi (name + 3);
146 }
147
148 /* This function is used to sort constructor elements by priority. It
149 is called via qsort. */
150
151 static int
ctor_cmp(const void * p1,const void * p2)152 ctor_cmp (const void *p1, const void *p2)
153 {
154 const struct set_element *const *pe1
155 = (const struct set_element *const *) p1;
156 const struct set_element *const *pe2
157 = (const struct set_element *const *) p2;
158 const char *n1;
159 const char *n2;
160 int prio1;
161 int prio2;
162
163 n1 = (*pe1)->name;
164 if (n1 == NULL)
165 n1 = "";
166 n2 = (*pe2)->name;
167 if (n2 == NULL)
168 n2 = "";
169
170 /* We need to sort in reverse order by priority. When two
171 constructors have the same priority, we should maintain their
172 current relative position. */
173
174 prio1 = ctor_prio (n1);
175 prio2 = ctor_prio (n2);
176
177 /* We sort in reverse order because that is what g++ expects. */
178 if (prio1 < prio2)
179 return 1;
180 else if (prio1 > prio2)
181 return -1;
182
183 /* Force a stable sort. */
184
185 if (pe1 < pe2)
186 return -1;
187 else if (pe1 > pe2)
188 return 1;
189 else
190 return 0;
191 }
192
193 /* This function is called after the first phase of the link and
194 before the second phase. At this point all set information has
195 been gathered. We now put the statements to build the sets
196 themselves into constructor_list. */
197
198 void
ldctor_build_sets(void)199 ldctor_build_sets (void)
200 {
201 static bfd_boolean called;
202 bfd_boolean header_printed;
203 struct set_info *p;
204
205 /* The emulation code may call us directly, but we only want to do
206 this once. */
207 if (called)
208 return;
209 called = TRUE;
210
211 if (constructors_sorted)
212 {
213 for (p = sets; p != NULL; p = p->next)
214 {
215 int c, i;
216 struct set_element *e;
217 struct set_element **array;
218
219 if (p->elements == NULL)
220 continue;
221
222 c = 0;
223 for (e = p->elements; e != NULL; e = e->next)
224 ++c;
225
226 array = (struct set_element **) xmalloc (c * sizeof *array);
227
228 i = 0;
229 for (e = p->elements; e != NULL; e = e->next)
230 {
231 array[i] = e;
232 ++i;
233 }
234
235 qsort (array, c, sizeof *array, ctor_cmp);
236
237 e = array[0];
238 p->elements = e;
239 for (i = 0; i < c - 1; i++)
240 array[i]->next = array[i + 1];
241 array[i]->next = NULL;
242
243 free (array);
244 }
245 }
246
247 lang_list_init (&constructor_list);
248 push_stat_ptr (&constructor_list);
249
250 header_printed = FALSE;
251 for (p = sets; p != NULL; p = p->next)
252 {
253 struct set_element *e;
254 reloc_howto_type *howto;
255 int reloc_size, size;
256
257 /* If the symbol is defined, we may have been invoked from
258 collect, and the sets may already have been built, so we do
259 not do anything. */
260 if (p->h->type == bfd_link_hash_defined
261 || p->h->type == bfd_link_hash_defweak)
262 continue;
263
264 /* For each set we build:
265 set:
266 .long number_of_elements
267 .long element0
268 ...
269 .long elementN
270 .long 0
271 except that we use the right size instead of .long. When
272 generating relocatable output, we generate relocs instead of
273 addresses. */
274 howto = bfd_reloc_type_lookup (link_info.output_bfd, p->reloc);
275 if (howto == NULL)
276 {
277 if (bfd_link_relocatable (&link_info))
278 {
279 einfo (_("%P%X: %s does not support reloc %s for set %s\n"),
280 bfd_get_target (link_info.output_bfd),
281 bfd_get_reloc_code_name (p->reloc),
282 p->h->root.string);
283 continue;
284 }
285
286 /* If this is not a relocatable link, all we need is the
287 size, which we can get from the input BFD. */
288 if (p->elements->section->owner != NULL)
289 howto = bfd_reloc_type_lookup (p->elements->section->owner,
290 p->reloc);
291 if (howto == NULL)
292 {
293 einfo (_("%P%X: %s does not support reloc %s for set %s\n"),
294 bfd_get_target (p->elements->section->owner),
295 bfd_get_reloc_code_name (p->reloc),
296 p->h->root.string);
297 continue;
298 }
299 }
300
301 reloc_size = bfd_get_reloc_size (howto);
302 switch (reloc_size)
303 {
304 case 1: size = BYTE; break;
305 case 2: size = SHORT; break;
306 case 4: size = LONG; break;
307 case 8:
308 if (howto->complain_on_overflow == complain_overflow_signed)
309 size = SQUAD;
310 else
311 size = QUAD;
312 break;
313 default:
314 einfo (_("%P%X: Unsupported size %d for set %s\n"),
315 bfd_get_reloc_size (howto), p->h->root.string);
316 size = LONG;
317 break;
318 }
319
320 lang_add_assignment (exp_assign (".",
321 exp_unop (ALIGN_K,
322 exp_intop (reloc_size)),
323 FALSE));
324 lang_add_assignment (exp_assign (p->h->root.string,
325 exp_nameop (NAME, "."),
326 FALSE));
327 lang_add_data (size, exp_intop (p->count));
328
329 for (e = p->elements; e != NULL; e = e->next)
330 {
331 if (config.map_file != NULL)
332 {
333 int len;
334
335 if (!header_printed)
336 {
337 minfo (_("\nSet Symbol\n\n"));
338 header_printed = TRUE;
339 }
340
341 minfo ("%s", p->h->root.string);
342 len = strlen (p->h->root.string);
343
344 if (len >= 19)
345 {
346 print_nl ();
347 len = 0;
348 }
349 while (len < 20)
350 {
351 print_space ();
352 ++len;
353 }
354
355 if (e->name != NULL)
356 minfo ("%T\n", e->name);
357 else
358 minfo ("%G\n", e->section->owner, e->section, e->value);
359 }
360
361 /* Need SEC_KEEP for --gc-sections. */
362 if (!bfd_is_abs_section (e->section))
363 e->section->flags |= SEC_KEEP;
364
365 if (bfd_link_relocatable (&link_info))
366 lang_add_reloc (p->reloc, howto, e->section, e->name,
367 exp_intop (e->value));
368 else
369 lang_add_data (size, exp_relop (e->section, e->value));
370 }
371
372 lang_add_data (size, exp_intop (0));
373 }
374
375 pop_stat_ptr ();
376 }
377