1 /* BFD back-end for linux flavored i386 a.out binaries.
2 Copyright 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2001, 2002, 2003,
3 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012
4 Free Software Foundation, Inc.
6 This file is part of BFD, the Binary File Descriptor library.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 MA 02110-1301, USA. */
23 #define TARGET_PAGE_SIZE 4096
24 #define ZMAGIC_DISK_BLOCK_SIZE 1024
25 #define SEGMENT_SIZE TARGET_PAGE_SIZE
26 #define TEXT_START_ADDR 0x0
28 #define MACHTYPE_OK(mtype) ((mtype) == M_386 || (mtype) == M_UNKNOWN)
33 #include "aout/aout64.h"
34 #include "aout/stab_gnu.h"
36 #include "libaout.h" /* BFD a.out internal data structures */
38 #define DEFAULT_ARCH bfd_arch_i386
40 /* Do not "beautify" the CONCAT* macro args. Traditional C will not
41 remove whitespace added here, and thus will fail to concatenate
43 #define MY(OP) CONCAT2 (i386linux_,OP)
44 #define TARGETNAME "a.out-i386-linux"
46 extern const bfd_target MY(vec);
48 /* We always generate QMAGIC files in preference to ZMAGIC files. It
49 would be possible to make this a linker option, if that ever
52 static void MY_final_link_callback
53 (bfd *, file_ptr *, file_ptr *, file_ptr *);
54 static bfd_boolean i386linux_bfd_final_link
55 (bfd *, struct bfd_link_info *);
56 static bfd_boolean i386linux_write_object_contents (bfd *);
59 i386linux_bfd_final_link (bfd *abfd, struct bfd_link_info *info)
61 obj_aout_subformat (abfd) = q_magic_format;
62 return NAME(aout,final_link) (abfd, info, MY_final_link_callback);
65 #define MY_bfd_final_link i386linux_bfd_final_link
67 /* Set the machine type correctly. */
70 i386linux_write_object_contents (bfd *abfd)
72 struct external_exec exec_bytes;
73 struct internal_exec *execp = exec_hdr (abfd);
75 N_SET_MACHTYPE (*execp, M_386);
77 obj_reloc_entry_size (abfd) = RELOC_STD_SIZE;
79 WRITE_HEADERS(abfd, execp);
84 #define MY_write_object_contents i386linux_write_object_contents
86 /* Code to link against Linux a.out shared libraries. */
88 /* See if a symbol name is a reference to the global offset table. */
90 #ifndef GOT_REF_PREFIX
91 #define GOT_REF_PREFIX "__GOT_"
94 #define IS_GOT_SYM(name) (CONST_STRNEQ (name, GOT_REF_PREFIX))
96 /* See if a symbol name is a reference to the procedure linkage table. */
98 #ifndef PLT_REF_PREFIX
99 #define PLT_REF_PREFIX "__PLT_"
102 #define IS_PLT_SYM(name) (CONST_STRNEQ (name, PLT_REF_PREFIX))
104 /* This string is used to generate specialized error messages. */
107 #define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
110 /* This special symbol is a set vector that contains a list of
111 pointers to fixup tables. It will be present in any dynamically
112 linked file. The linker generated fixup table should also be added
113 to the list, and it should always appear in the second slot (the
114 first one is a dummy with a magic number that is defined in
117 #ifndef SHARABLE_CONFLICTS
118 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
121 /* We keep a list of fixups. The terminology is a bit strange, but
122 each fixup contains two 32 bit numbers. A regular fixup contains
123 an address and a pointer, and at runtime we should store the
124 address at the location pointed to by the pointer. A builtin fixup
125 contains two pointers, and we should read the address using one
126 pointer and store it at the location pointed to by the other
127 pointer. Builtin fixups come into play when we have duplicate
128 __GOT__ symbols for the same variable. The builtin fixup will copy
129 the GOT pointer from one over into the other. */
134 struct linux_link_hash_entry *h;
137 /* Nonzero if this is a jump instruction that needs to be fixed,
138 zero if this is just a pointer */
144 /* We don't need a special hash table entry structure, but we do need
145 to keep some information between linker passes, so we use a special
148 struct linux_link_hash_entry
150 struct aout_link_hash_entry root;
153 struct linux_link_hash_table
155 struct aout_link_hash_table root;
157 /* First dynamic object found in link. */
160 /* Number of fixups. */
163 /* Number of builtin fixups. */
164 size_t local_builtins;
166 /* List of fixups. */
167 struct fixup *fixup_list;
170 /* Routine to create an entry in an Linux link hash table. */
172 static struct bfd_hash_entry *
173 linux_link_hash_newfunc (struct bfd_hash_entry *entry,
174 struct bfd_hash_table *table,
177 struct linux_link_hash_entry *ret = (struct linux_link_hash_entry *) entry;
179 /* Allocate the structure if it has not already been allocated by a
181 if (ret == (struct linux_link_hash_entry *) NULL)
182 ret = ((struct linux_link_hash_entry *)
183 bfd_hash_allocate (table, sizeof (struct linux_link_hash_entry)));
185 return (struct bfd_hash_entry *) ret;
187 /* Call the allocation method of the superclass. */
188 ret = ((struct linux_link_hash_entry *)
189 NAME(aout,link_hash_newfunc) ((struct bfd_hash_entry *) ret,
193 /* Set local fields; there aren't any. */
196 return (struct bfd_hash_entry *) ret;
199 /* Create a Linux link hash table. */
201 static struct bfd_link_hash_table *
202 linux_link_hash_table_create (bfd *abfd)
204 struct linux_link_hash_table *ret;
205 bfd_size_type amt = sizeof (struct linux_link_hash_table);
207 ret = (struct linux_link_hash_table *) bfd_alloc (abfd, amt);
208 if (ret == (struct linux_link_hash_table *) NULL)
209 return (struct bfd_link_hash_table *) NULL;
210 if (!NAME(aout,link_hash_table_init) (&ret->root, abfd,
211 linux_link_hash_newfunc,
212 sizeof (struct linux_link_hash_entry)))
215 return (struct bfd_link_hash_table *) NULL;
219 ret->fixup_count = 0;
220 ret->local_builtins = 0;
221 ret->fixup_list = NULL;
223 return &ret->root.root;
226 /* Look up an entry in a Linux link hash table. */
228 #define linux_link_hash_lookup(table, string, create, copy, follow) \
229 ((struct linux_link_hash_entry *) \
230 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
233 /* Traverse a Linux link hash table. */
235 #define linux_link_hash_traverse(table, func, info) \
236 (aout_link_hash_traverse \
238 (bfd_boolean (*) (struct aout_link_hash_entry *, void *)) (func), \
241 /* Get the Linux link hash table from the info structure. This is
244 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
246 /* Store the information for a new fixup. */
248 static struct fixup *
249 new_fixup (struct bfd_link_info *info,
250 struct linux_link_hash_entry *h,
256 f = (struct fixup *) bfd_hash_allocate (&info->hash->table,
257 sizeof (struct fixup));
260 f->next = linux_hash_table (info)->fixup_list;
261 linux_hash_table (info)->fixup_list = f;
264 f->builtin = builtin;
266 ++linux_hash_table (info)->fixup_count;
270 /* We come here once we realize that we are going to link to a shared
271 library. We need to create a special section that contains the
272 fixup table, and we ultimately need to add a pointer to this into
273 the set vector for SHARABLE_CONFLICTS. At this point we do not
274 know the size of the section, but that's OK - we just need to
275 create it for now. */
278 linux_link_create_dynamic_sections (bfd *abfd,
279 struct bfd_link_info *info ATTRIBUTE_UNUSED)
284 /* Note that we set the SEC_IN_MEMORY flag. */
285 flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY;
287 /* We choose to use the name ".linux-dynamic" for the fixup table.
289 s = bfd_make_section_with_flags (abfd, ".linux-dynamic", flags);
291 || ! bfd_set_section_alignment (abfd, s, 2))
299 /* Function to add a single symbol to the linker hash table. This is
300 a wrapper around _bfd_generic_link_add_one_symbol which handles the
301 tweaking needed for dynamic linking support. */
304 linux_add_one_symbol (struct bfd_link_info *info,
313 struct bfd_link_hash_entry **hashp)
315 struct linux_link_hash_entry *h;
318 /* Look up and see if we already have this symbol in the hash table.
319 If we do, and the defining entry is from a shared library, we
320 need to create the dynamic sections.
322 FIXME: What if abfd->xvec != info->output_bfd->xvec? We may
323 want to be able to link Linux a.out and ELF objects together,
324 but serious confusion is possible. */
328 if (! info->relocatable
329 && linux_hash_table (info)->dynobj == NULL
330 && strcmp (name, SHARABLE_CONFLICTS) == 0
331 && (flags & BSF_CONSTRUCTOR) != 0
332 && abfd->xvec == info->output_bfd->xvec)
334 if (! linux_link_create_dynamic_sections (abfd, info))
336 linux_hash_table (info)->dynobj = abfd;
340 if (bfd_is_abs_section (section)
341 && abfd->xvec == info->output_bfd->xvec)
343 h = linux_link_hash_lookup (linux_hash_table (info), name, FALSE,
346 && (h->root.root.type == bfd_link_hash_defined
347 || h->root.root.type == bfd_link_hash_defweak))
352 *hashp = (struct bfd_link_hash_entry *) h;
354 f = new_fixup (info, h, value, ! IS_PLT_SYM (name));
357 f->jump = IS_PLT_SYM (name);
363 /* Do the usual procedure for adding a symbol. */
364 if (! _bfd_generic_link_add_one_symbol (info, abfd, name, flags, section,
365 value, string, copy, collect,
369 /* Insert a pointer to our table in the set vector. The dynamic
370 linker requires this information */
375 /* Here we do our special thing to add the pointer to the
376 dynamic section in the SHARABLE_CONFLICTS set vector. */
377 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
379 BFD_ASSERT (s != NULL);
381 if (! (_bfd_generic_link_add_one_symbol
382 (info, linux_hash_table (info)->dynobj, SHARABLE_CONFLICTS,
383 BSF_GLOBAL | BSF_CONSTRUCTOR, s, (bfd_vma) 0, NULL,
384 FALSE, FALSE, NULL)))
391 /* We will crawl the hash table and come here for every global symbol.
392 We will examine each entry and see if there are indications that we
393 need to add a fixup. There are two possible cases - one is where
394 you have duplicate definitions of PLT or GOT symbols - these will
395 have already been caught and added as "builtin" fixups. If we find
396 that the corresponding non PLT/GOT symbol is also present, we
397 convert it to a regular fixup instead.
399 This function is called via linux_link_hash_traverse. */
402 linux_tally_symbols (struct linux_link_hash_entry *h, void * data)
404 struct bfd_link_info *info = (struct bfd_link_info *) data;
405 struct fixup *f, *f1;
407 struct linux_link_hash_entry *h1, *h2;
410 if (h->root.root.type == bfd_link_hash_undefined
411 && CONST_STRNEQ (h->root.root.root.string, NEEDS_SHRLIB))
417 name = h->root.root.root.string + sizeof NEEDS_SHRLIB - 1;
418 p = strrchr (name, '_');
420 alloc = (char *) bfd_malloc ((bfd_size_type) strlen (name) + 1);
422 if (p == NULL || alloc == NULL)
423 (*_bfd_error_handler) (_("Output file requires shared library `%s'\n"),
427 strcpy (alloc, name);
428 p = strrchr (alloc, '_');
430 (*_bfd_error_handler)
431 (_("Output file requires shared library `%s.so.%s'\n"),
439 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
440 is_plt = IS_PLT_SYM (h->root.root.root.string);
442 if (is_plt || IS_GOT_SYM (h->root.root.root.string))
444 /* Look up this symbol twice. Once just as a regular lookup,
445 and then again following all of the indirect links until we
446 reach a real symbol. */
447 h1 = linux_link_hash_lookup (linux_hash_table (info),
448 (h->root.root.root.string
449 + sizeof PLT_REF_PREFIX - 1),
451 /* h2 does not follow indirect symbols. */
452 h2 = linux_link_hash_lookup (linux_hash_table (info),
453 (h->root.root.root.string
454 + sizeof PLT_REF_PREFIX - 1),
455 FALSE, FALSE, FALSE);
457 /* The real symbol must exist but if it is also an ABS symbol,
458 there is no need to have a fixup. This is because they both
459 came from the same library. If on the other hand, we had to
460 use an indirect symbol to get to the real symbol, we add the
461 fixup anyway, since there are cases where these symbols come
462 from different shared libraries */
464 && (((h1->root.root.type == bfd_link_hash_defined
465 || h1->root.root.type == bfd_link_hash_defweak)
466 && ! bfd_is_abs_section (h1->root.root.u.def.section))
467 || h2->root.root.type == bfd_link_hash_indirect))
469 /* See if there is a "builtin" fixup already present
470 involving this symbol. If so, convert it to a regular
471 fixup. In the end, this relaxes some of the requirements
472 about the order of performing fixups. */
474 for (f1 = linux_hash_table (info)->fixup_list;
478 if ((f1->h != h && f1->h != h1)
479 || (! f1->builtin && ! f1->jump))
484 && bfd_is_abs_section (h->root.root.u.def.section))
486 f = new_fixup (info, h1, f1->h->root.root.u.def.value, 0);
495 && bfd_is_abs_section (h->root.root.u.def.section))
497 f = new_fixup (info, h1, h->root.root.u.def.value, 0);
500 /* FIXME: No way to return error. */
507 /* Quick and dirty way of stripping these symbols from the
509 if (bfd_is_abs_section (h->root.root.u.def.section))
510 h->root.written = TRUE;
516 /* This is called to set the size of the .linux-dynamic section is.
517 It is called by the Linux linker emulation before_allocation
518 routine. We have finished reading all of the input files, and now
519 we just scan the hash tables to find out how many additional fixups
523 bfd_i386linux_size_dynamic_sections (bfd *output_bfd,
524 struct bfd_link_info *info)
529 if (output_bfd->xvec != &MY(vec))
532 /* First find the fixups... */
533 linux_link_hash_traverse (linux_hash_table (info),
537 /* If there are builtin fixups, leave room for a marker. This is
538 used by the dynamic linker so that it knows that all that follow
539 are builtin fixups instead of regular fixups. */
540 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
544 ++linux_hash_table (info)->fixup_count;
545 ++linux_hash_table (info)->local_builtins;
550 if (linux_hash_table (info)->dynobj == NULL)
552 if (linux_hash_table (info)->fixup_count > 0)
557 /* Allocate memory for our fixup table. We will fill it in later. */
558 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
562 s->size = linux_hash_table (info)->fixup_count + 1;
564 s->contents = (bfd_byte *) bfd_zalloc (output_bfd, s->size);
565 if (s->contents == NULL)
572 /* We come here once we are ready to actually write the fixup table to
573 the output file. Scan the fixup tables and so forth and generate
574 the stuff we need. */
577 linux_finish_dynamic_link (bfd *output_bfd,
578 struct bfd_link_info *info)
580 asection *s, *os, *is;
581 bfd_byte *fixup_table;
582 struct linux_link_hash_entry *h;
584 unsigned int new_addr;
586 unsigned int fixups_written;
588 if (linux_hash_table (info)->dynobj == NULL)
591 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
593 BFD_ASSERT (s != NULL);
594 os = s->output_section;
597 #ifdef LINUX_LINK_DEBUG
598 printf ("Fixup table file offset: %x VMA: %x\n",
599 os->filepos + s->output_offset,
600 os->vma + s->output_offset);
603 fixup_table = s->contents;
604 bfd_put_32 (output_bfd,
605 (bfd_vma) linux_hash_table (info)->fixup_count, fixup_table);
608 /* Fill in fixup table. */
609 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
614 if (f->h->root.root.type != bfd_link_hash_defined
615 && f->h->root.root.type != bfd_link_hash_defweak)
617 (*_bfd_error_handler)
618 (_("Symbol %s not defined for fixups\n"),
619 f->h->root.root.root.string);
623 is = f->h->root.root.u.def.section;
624 section_offset = is->output_section->vma + is->output_offset;
625 new_addr = f->h->root.root.u.def.value + section_offset;
627 #ifdef LINUX_LINK_DEBUG
628 printf ("Fixup(%d) %s: %x %x\n",f->jump, f->h->root.root.string,
634 /* Relative address */
635 new_addr = new_addr - (f->value + 5);
636 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
638 bfd_put_32 (output_bfd, f->value + 1, fixup_table);
643 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
645 bfd_put_32 (output_bfd, f->value, fixup_table);
651 if (linux_hash_table (info)->local_builtins != 0)
653 /* Special marker so we know to switch to the other type of fixup */
654 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
656 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
659 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
664 if (f->h->root.root.type != bfd_link_hash_defined
665 && f->h->root.root.type != bfd_link_hash_defweak)
667 (*_bfd_error_handler)
668 (_("Symbol %s not defined for fixups\n"),
669 f->h->root.root.root.string);
673 is = f->h->root.root.u.def.section;
674 section_offset = is->output_section->vma + is->output_offset;
675 new_addr = f->h->root.root.u.def.value + section_offset;
677 #ifdef LINUX_LINK_DEBUG
678 printf ("Fixup(B) %s: %x %x\n", f->h->root.root.string,
682 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
684 bfd_put_32 (output_bfd, f->value, fixup_table);
690 if (linux_hash_table (info)->fixup_count != fixups_written)
692 (*_bfd_error_handler) (_("Warning: fixup count mismatch\n"));
693 while (linux_hash_table (info)->fixup_count > fixups_written)
695 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
697 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
703 h = linux_link_hash_lookup (linux_hash_table (info),
704 "__BUILTIN_FIXUPS__",
705 FALSE, FALSE, FALSE);
708 && (h->root.root.type == bfd_link_hash_defined
709 || h->root.root.type == bfd_link_hash_defweak))
711 is = h->root.root.u.def.section;
712 section_offset = is->output_section->vma + is->output_offset;
713 new_addr = h->root.root.u.def.value + section_offset;
715 #ifdef LINUX_LINK_DEBUG
716 printf ("Builtin fixup table at %x\n", new_addr);
719 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
722 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
724 if (bfd_seek (output_bfd, (file_ptr) (os->filepos + s->output_offset),
728 if (bfd_bwrite (s->contents, s->size, output_bfd) != s->size)
734 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
735 #define MY_add_one_symbol linux_add_one_symbol
736 #define MY_finish_dynamic_link linux_finish_dynamic_link
738 #define MY_zmagic_contiguous 1
740 #include "aout-target.h"