1 /* ldctor.c -- constructor support routines 2 Copyright (C) 1991-2018 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 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 (_("%X%P: 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 (_("%X%P: 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 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 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 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 (_("%X%P: %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 /* See PR 20911 for a reproducer. */ 294 if (p->elements->section->owner == NULL) 295 einfo (_("%X%P: special section %s does not support reloc %s for set %s\n"), 296 bfd_get_section_name (link_info.output_bfd, p->elements->section), 297 bfd_get_reloc_code_name (p->reloc), 298 p->h->root.string); 299 else 300 einfo (_("%X%P: %s does not support reloc %s for set %s\n"), 301 bfd_get_target (p->elements->section->owner), 302 bfd_get_reloc_code_name (p->reloc), 303 p->h->root.string); 304 continue; 305 } 306 } 307 308 reloc_size = bfd_get_reloc_size (howto); 309 switch (reloc_size) 310 { 311 case 1: size = BYTE; break; 312 case 2: size = SHORT; break; 313 case 4: size = LONG; break; 314 case 8: 315 if (howto->complain_on_overflow == complain_overflow_signed) 316 size = SQUAD; 317 else 318 size = QUAD; 319 break; 320 default: 321 einfo (_("%X%P: unsupported size %d for set %s\n"), 322 bfd_get_reloc_size (howto), p->h->root.string); 323 size = LONG; 324 break; 325 } 326 327 lang_add_assignment (exp_assign (".", 328 exp_unop (ALIGN_K, 329 exp_intop (reloc_size)), 330 FALSE)); 331 lang_add_assignment (exp_assign (p->h->root.string, 332 exp_nameop (NAME, "."), 333 FALSE)); 334 lang_add_data (size, exp_intop (p->count)); 335 336 for (e = p->elements; e != NULL; e = e->next) 337 { 338 if (config.map_file != NULL) 339 { 340 int len; 341 342 if (!header_printed) 343 { 344 minfo (_("\nSet Symbol\n\n")); 345 header_printed = TRUE; 346 } 347 348 minfo ("%s", p->h->root.string); 349 len = strlen (p->h->root.string); 350 351 if (len >= 19) 352 { 353 print_nl (); 354 len = 0; 355 } 356 while (len < 20) 357 { 358 print_space (); 359 ++len; 360 } 361 362 if (e->name != NULL) 363 minfo ("%pT\n", e->name); 364 else 365 minfo ("%G\n", e->section->owner, e->section, e->value); 366 } 367 368 /* Need SEC_KEEP for --gc-sections. */ 369 if (!bfd_is_abs_section (e->section)) 370 e->section->flags |= SEC_KEEP; 371 372 if (bfd_link_relocatable (&link_info)) 373 lang_add_reloc (p->reloc, howto, e->section, e->name, 374 exp_intop (e->value)); 375 else 376 lang_add_data (size, exp_relop (e->section, e->value)); 377 } 378 379 lang_add_data (size, exp_intop (0)); 380 } 381 382 pop_stat_ptr (); 383 } 384