1 /* BFD back-end for linux flavored i386 a.out binaries.
2 Copyright (C) 1992-2015 Free Software Foundation, Inc.
4 This file is part of BFD, the Binary File Descriptor library.
6 This program 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 of the License, or
9 (at your option) any later version.
11 This program 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.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
19 MA 02110-1301, USA. */
21 #define TARGET_PAGE_SIZE 4096
22 #define ZMAGIC_DISK_BLOCK_SIZE 1024
23 #define SEGMENT_SIZE TARGET_PAGE_SIZE
24 #define TEXT_START_ADDR 0x0
26 #define MACHTYPE_OK(mtype) ((mtype) == M_386 || (mtype) == M_UNKNOWN)
31 #include "aout/aout64.h"
32 #include "aout/stab_gnu.h"
34 #include "libaout.h" /* BFD a.out internal data structures */
36 #define DEFAULT_ARCH bfd_arch_i386
38 /* Do not "beautify" the CONCAT* macro args. Traditional C will not
39 remove whitespace added here, and thus will fail to concatenate
41 #define MY(OP) CONCAT2 (i386_aout_linux_,OP)
42 #define TARGETNAME "a.out-i386-linux"
44 extern const bfd_target MY(vec);
46 /* We always generate QMAGIC files in preference to ZMAGIC files. It
47 would be possible to make this a linker option, if that ever
50 static void MY_final_link_callback
51 (bfd *, file_ptr *, file_ptr *, file_ptr *);
52 static bfd_boolean i386linux_bfd_final_link
53 (bfd *, struct bfd_link_info *);
54 static bfd_boolean i386linux_write_object_contents (bfd *);
57 i386linux_bfd_final_link (bfd *abfd, struct bfd_link_info *info)
59 obj_aout_subformat (abfd) = q_magic_format;
60 return NAME(aout,final_link) (abfd, info, MY_final_link_callback);
63 #define MY_bfd_final_link i386linux_bfd_final_link
65 /* Set the machine type correctly. */
68 i386linux_write_object_contents (bfd *abfd)
70 struct external_exec exec_bytes;
71 struct internal_exec *execp = exec_hdr (abfd);
73 N_SET_MACHTYPE (*execp, M_386);
75 obj_reloc_entry_size (abfd) = RELOC_STD_SIZE;
77 WRITE_HEADERS(abfd, execp);
82 #define MY_write_object_contents i386linux_write_object_contents
84 /* Code to link against Linux a.out shared libraries. */
86 /* See if a symbol name is a reference to the global offset table. */
88 #ifndef GOT_REF_PREFIX
89 #define GOT_REF_PREFIX "__GOT_"
92 #define IS_GOT_SYM(name) (CONST_STRNEQ (name, GOT_REF_PREFIX))
94 /* See if a symbol name is a reference to the procedure linkage table. */
96 #ifndef PLT_REF_PREFIX
97 #define PLT_REF_PREFIX "__PLT_"
100 #define IS_PLT_SYM(name) (CONST_STRNEQ (name, PLT_REF_PREFIX))
102 /* This string is used to generate specialized error messages. */
105 #define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
108 /* This special symbol is a set vector that contains a list of
109 pointers to fixup tables. It will be present in any dynamically
110 linked file. The linker generated fixup table should also be added
111 to the list, and it should always appear in the second slot (the
112 first one is a dummy with a magic number that is defined in
115 #ifndef SHARABLE_CONFLICTS
116 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
119 /* We keep a list of fixups. The terminology is a bit strange, but
120 each fixup contains two 32 bit numbers. A regular fixup contains
121 an address and a pointer, and at runtime we should store the
122 address at the location pointed to by the pointer. A builtin fixup
123 contains two pointers, and we should read the address using one
124 pointer and store it at the location pointed to by the other
125 pointer. Builtin fixups come into play when we have duplicate
126 __GOT__ symbols for the same variable. The builtin fixup will copy
127 the GOT pointer from one over into the other. */
132 struct linux_link_hash_entry *h;
135 /* Nonzero if this is a jump instruction that needs to be fixed,
136 zero if this is just a pointer */
142 /* We don't need a special hash table entry structure, but we do need
143 to keep some information between linker passes, so we use a special
146 struct linux_link_hash_entry
148 struct aout_link_hash_entry root;
151 struct linux_link_hash_table
153 struct aout_link_hash_table root;
155 /* First dynamic object found in link. */
158 /* Number of fixups. */
161 /* Number of builtin fixups. */
162 size_t local_builtins;
164 /* List of fixups. */
165 struct fixup *fixup_list;
168 /* Routine to create an entry in an Linux link hash table. */
170 static struct bfd_hash_entry *
171 linux_link_hash_newfunc (struct bfd_hash_entry *entry,
172 struct bfd_hash_table *table,
175 struct linux_link_hash_entry *ret = (struct linux_link_hash_entry *) entry;
177 /* Allocate the structure if it has not already been allocated by a
179 if (ret == (struct linux_link_hash_entry *) NULL)
180 ret = ((struct linux_link_hash_entry *)
181 bfd_hash_allocate (table, sizeof (struct linux_link_hash_entry)));
183 return (struct bfd_hash_entry *) ret;
185 /* Call the allocation method of the superclass. */
186 ret = ((struct linux_link_hash_entry *)
187 NAME(aout,link_hash_newfunc) ((struct bfd_hash_entry *) ret,
191 /* Set local fields; there aren't any. */
194 return (struct bfd_hash_entry *) ret;
197 /* Create a Linux link hash table. */
199 static struct bfd_link_hash_table *
200 linux_link_hash_table_create (bfd *abfd)
202 struct linux_link_hash_table *ret;
203 bfd_size_type amt = sizeof (struct linux_link_hash_table);
205 ret = (struct linux_link_hash_table *) bfd_zmalloc (amt);
206 if (ret == (struct linux_link_hash_table *) NULL)
207 return (struct bfd_link_hash_table *) NULL;
208 if (!NAME(aout,link_hash_table_init) (&ret->root, abfd,
209 linux_link_hash_newfunc,
210 sizeof (struct linux_link_hash_entry)))
213 return (struct bfd_link_hash_table *) NULL;
216 return &ret->root.root;
219 /* Look up an entry in a Linux link hash table. */
221 #define linux_link_hash_lookup(table, string, create, copy, follow) \
222 ((struct linux_link_hash_entry *) \
223 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
226 /* Traverse a Linux link hash table. */
228 #define linux_link_hash_traverse(table, func, info) \
229 (aout_link_hash_traverse \
231 (bfd_boolean (*) (struct aout_link_hash_entry *, void *)) (func), \
234 /* Get the Linux link hash table from the info structure. This is
237 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
239 /* Store the information for a new fixup. */
241 static struct fixup *
242 new_fixup (struct bfd_link_info *info,
243 struct linux_link_hash_entry *h,
249 f = (struct fixup *) bfd_hash_allocate (&info->hash->table,
250 sizeof (struct fixup));
253 f->next = linux_hash_table (info)->fixup_list;
254 linux_hash_table (info)->fixup_list = f;
257 f->builtin = builtin;
259 ++linux_hash_table (info)->fixup_count;
263 /* We come here once we realize that we are going to link to a shared
264 library. We need to create a special section that contains the
265 fixup table, and we ultimately need to add a pointer to this into
266 the set vector for SHARABLE_CONFLICTS. At this point we do not
267 know the size of the section, but that's OK - we just need to
268 create it for now. */
271 linux_link_create_dynamic_sections (bfd *abfd,
272 struct bfd_link_info *info ATTRIBUTE_UNUSED)
277 /* Note that we set the SEC_IN_MEMORY flag. */
278 flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY;
280 /* We choose to use the name ".linux-dynamic" for the fixup table.
282 s = bfd_make_section_with_flags (abfd, ".linux-dynamic", flags);
284 || ! bfd_set_section_alignment (abfd, s, 2))
292 /* Function to add a single symbol to the linker hash table. This is
293 a wrapper around _bfd_generic_link_add_one_symbol which handles the
294 tweaking needed for dynamic linking support. */
297 linux_add_one_symbol (struct bfd_link_info *info,
306 struct bfd_link_hash_entry **hashp)
308 struct linux_link_hash_entry *h;
311 /* Look up and see if we already have this symbol in the hash table.
312 If we do, and the defining entry is from a shared library, we
313 need to create the dynamic sections.
315 FIXME: What if abfd->xvec != info->output_bfd->xvec? We may
316 want to be able to link Linux a.out and ELF objects together,
317 but serious confusion is possible. */
321 if (! bfd_link_relocatable (info)
322 && linux_hash_table (info)->dynobj == NULL
323 && strcmp (name, SHARABLE_CONFLICTS) == 0
324 && (flags & BSF_CONSTRUCTOR) != 0
325 && abfd->xvec == info->output_bfd->xvec)
327 if (! linux_link_create_dynamic_sections (abfd, info))
329 linux_hash_table (info)->dynobj = abfd;
333 if (bfd_is_abs_section (section)
334 && abfd->xvec == info->output_bfd->xvec)
336 h = linux_link_hash_lookup (linux_hash_table (info), name, FALSE,
339 && (h->root.root.type == bfd_link_hash_defined
340 || h->root.root.type == bfd_link_hash_defweak))
345 *hashp = (struct bfd_link_hash_entry *) h;
347 f = new_fixup (info, h, value, ! IS_PLT_SYM (name));
350 f->jump = IS_PLT_SYM (name);
356 /* Do the usual procedure for adding a symbol. */
357 if (! _bfd_generic_link_add_one_symbol (info, abfd, name, flags, section,
358 value, string, copy, collect,
362 /* Insert a pointer to our table in the set vector. The dynamic
363 linker requires this information */
368 /* Here we do our special thing to add the pointer to the
369 dynamic section in the SHARABLE_CONFLICTS set vector. */
370 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
372 BFD_ASSERT (s != NULL);
374 if (! (_bfd_generic_link_add_one_symbol
375 (info, linux_hash_table (info)->dynobj, SHARABLE_CONFLICTS,
376 BSF_GLOBAL | BSF_CONSTRUCTOR, s, (bfd_vma) 0, NULL,
377 FALSE, FALSE, NULL)))
384 /* We will crawl the hash table and come here for every global symbol.
385 We will examine each entry and see if there are indications that we
386 need to add a fixup. There are two possible cases - one is where
387 you have duplicate definitions of PLT or GOT symbols - these will
388 have already been caught and added as "builtin" fixups. If we find
389 that the corresponding non PLT/GOT symbol is also present, we
390 convert it to a regular fixup instead.
392 This function is called via linux_link_hash_traverse. */
395 linux_tally_symbols (struct linux_link_hash_entry *h, void * data)
397 struct bfd_link_info *info = (struct bfd_link_info *) data;
398 struct fixup *f, *f1;
400 struct linux_link_hash_entry *h1, *h2;
403 if (h->root.root.type == bfd_link_hash_undefined
404 && CONST_STRNEQ (h->root.root.root.string, NEEDS_SHRLIB))
410 name = h->root.root.root.string + sizeof NEEDS_SHRLIB - 1;
411 p = strrchr (name, '_');
413 alloc = (char *) bfd_malloc ((bfd_size_type) strlen (name) + 1);
415 if (p == NULL || alloc == NULL)
416 (*_bfd_error_handler) (_("Output file requires shared library `%s'\n"),
420 strcpy (alloc, name);
421 p = strrchr (alloc, '_');
423 (*_bfd_error_handler)
424 (_("Output file requires shared library `%s.so.%s'\n"),
432 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
433 is_plt = IS_PLT_SYM (h->root.root.root.string);
435 if (is_plt || IS_GOT_SYM (h->root.root.root.string))
437 /* Look up this symbol twice. Once just as a regular lookup,
438 and then again following all of the indirect links until we
439 reach a real symbol. */
440 h1 = linux_link_hash_lookup (linux_hash_table (info),
441 (h->root.root.root.string
442 + sizeof PLT_REF_PREFIX - 1),
444 /* h2 does not follow indirect symbols. */
445 h2 = linux_link_hash_lookup (linux_hash_table (info),
446 (h->root.root.root.string
447 + sizeof PLT_REF_PREFIX - 1),
448 FALSE, FALSE, FALSE);
450 /* The real symbol must exist but if it is also an ABS symbol,
451 there is no need to have a fixup. This is because they both
452 came from the same library. If on the other hand, we had to
453 use an indirect symbol to get to the real symbol, we add the
454 fixup anyway, since there are cases where these symbols come
455 from different shared libraries */
457 && (((h1->root.root.type == bfd_link_hash_defined
458 || h1->root.root.type == bfd_link_hash_defweak)
459 && ! bfd_is_abs_section (h1->root.root.u.def.section))
460 || h2->root.root.type == bfd_link_hash_indirect))
462 /* See if there is a "builtin" fixup already present
463 involving this symbol. If so, convert it to a regular
464 fixup. In the end, this relaxes some of the requirements
465 about the order of performing fixups. */
467 for (f1 = linux_hash_table (info)->fixup_list;
471 if ((f1->h != h && f1->h != h1)
472 || (! f1->builtin && ! f1->jump))
477 && bfd_is_abs_section (h->root.root.u.def.section))
479 f = new_fixup (info, h1, f1->h->root.root.u.def.value, 0);
488 && bfd_is_abs_section (h->root.root.u.def.section))
490 f = new_fixup (info, h1, h->root.root.u.def.value, 0);
493 /* FIXME: No way to return error. */
500 /* Quick and dirty way of stripping these symbols from the
502 if (bfd_is_abs_section (h->root.root.u.def.section))
503 h->root.written = TRUE;
509 /* This is called to set the size of the .linux-dynamic section is.
510 It is called by the Linux linker emulation before_allocation
511 routine. We have finished reading all of the input files, and now
512 we just scan the hash tables to find out how many additional fixups
516 bfd_i386linux_size_dynamic_sections (bfd *output_bfd,
517 struct bfd_link_info *info)
522 if (output_bfd->xvec != &MY(vec))
525 /* First find the fixups... */
526 linux_link_hash_traverse (linux_hash_table (info),
530 /* If there are builtin fixups, leave room for a marker. This is
531 used by the dynamic linker so that it knows that all that follow
532 are builtin fixups instead of regular fixups. */
533 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
537 ++linux_hash_table (info)->fixup_count;
538 ++linux_hash_table (info)->local_builtins;
543 if (linux_hash_table (info)->dynobj == NULL)
545 if (linux_hash_table (info)->fixup_count > 0)
550 /* Allocate memory for our fixup table. We will fill it in later. */
551 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
555 s->size = linux_hash_table (info)->fixup_count + 1;
557 s->contents = (bfd_byte *) bfd_zalloc (output_bfd, s->size);
558 if (s->contents == NULL)
565 /* We come here once we are ready to actually write the fixup table to
566 the output file. Scan the fixup tables and so forth and generate
567 the stuff we need. */
570 linux_finish_dynamic_link (bfd *output_bfd,
571 struct bfd_link_info *info)
573 asection *s, *os, *is;
574 bfd_byte *fixup_table;
575 struct linux_link_hash_entry *h;
577 unsigned int new_addr;
579 unsigned int fixups_written;
581 if (linux_hash_table (info)->dynobj == NULL)
584 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
586 BFD_ASSERT (s != NULL);
587 os = s->output_section;
590 #ifdef LINUX_LINK_DEBUG
591 printf ("Fixup table file offset: %x VMA: %x\n",
592 os->filepos + s->output_offset,
593 os->vma + s->output_offset);
596 fixup_table = s->contents;
597 bfd_put_32 (output_bfd,
598 (bfd_vma) linux_hash_table (info)->fixup_count, fixup_table);
601 /* Fill in fixup table. */
602 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
607 if (f->h->root.root.type != bfd_link_hash_defined
608 && f->h->root.root.type != bfd_link_hash_defweak)
610 (*_bfd_error_handler)
611 (_("Symbol %s not defined for fixups\n"),
612 f->h->root.root.root.string);
616 is = f->h->root.root.u.def.section;
617 section_offset = is->output_section->vma + is->output_offset;
618 new_addr = f->h->root.root.u.def.value + section_offset;
620 #ifdef LINUX_LINK_DEBUG
621 printf ("Fixup(%d) %s: %x %x\n",f->jump, f->h->root.root.string,
627 /* Relative address */
628 new_addr = new_addr - (f->value + 5);
629 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
631 bfd_put_32 (output_bfd, f->value + 1, fixup_table);
636 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
638 bfd_put_32 (output_bfd, f->value, fixup_table);
644 if (linux_hash_table (info)->local_builtins != 0)
646 /* Special marker so we know to switch to the other type of fixup */
647 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
649 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
652 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
657 if (f->h->root.root.type != bfd_link_hash_defined
658 && f->h->root.root.type != bfd_link_hash_defweak)
660 (*_bfd_error_handler)
661 (_("Symbol %s not defined for fixups\n"),
662 f->h->root.root.root.string);
666 is = f->h->root.root.u.def.section;
667 section_offset = is->output_section->vma + is->output_offset;
668 new_addr = f->h->root.root.u.def.value + section_offset;
670 #ifdef LINUX_LINK_DEBUG
671 printf ("Fixup(B) %s: %x %x\n", f->h->root.root.string,
675 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
677 bfd_put_32 (output_bfd, f->value, fixup_table);
683 if (linux_hash_table (info)->fixup_count != fixups_written)
685 (*_bfd_error_handler) (_("Warning: fixup count mismatch\n"));
686 while (linux_hash_table (info)->fixup_count > fixups_written)
688 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
690 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
696 h = linux_link_hash_lookup (linux_hash_table (info),
697 "__BUILTIN_FIXUPS__",
698 FALSE, FALSE, FALSE);
701 && (h->root.root.type == bfd_link_hash_defined
702 || h->root.root.type == bfd_link_hash_defweak))
704 is = h->root.root.u.def.section;
705 section_offset = is->output_section->vma + is->output_offset;
706 new_addr = h->root.root.u.def.value + section_offset;
708 #ifdef LINUX_LINK_DEBUG
709 printf ("Builtin fixup table at %x\n", new_addr);
712 bfd_put_32 (output_bfd, (bfd_vma) new_addr, fixup_table);
715 bfd_put_32 (output_bfd, (bfd_vma) 0, fixup_table);
717 if (bfd_seek (output_bfd, (file_ptr) (os->filepos + s->output_offset),
721 if (bfd_bwrite (s->contents, s->size, output_bfd) != s->size)
727 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
728 #define MY_add_one_symbol linux_add_one_symbol
729 #define MY_finish_dynamic_link linux_finish_dynamic_link
731 #define MY_zmagic_contiguous 1
733 #include "aout-target.h"