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 Free Software Foundation, Inc.
5 This file is part of BFD, the Binary File Descriptor library.
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.
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.
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. */
22 #define TARGET_PAGE_SIZE 4096
23 #define ZMAGIC_DISK_BLOCK_SIZE 1024
24 #define SEGMENT_SIZE TARGET_PAGE_SIZE
25 #define TEXT_START_ADDR 0x0
27 #define MACHTYPE_OK(mtype) ((mtype) == M_386 || (mtype) == M_UNKNOWN)
32 #include "aout/aout64.h"
33 #include "aout/stab_gnu.h"
35 #include "libaout.h" /* BFD a.out internal data structures */
37 #define DEFAULT_ARCH bfd_arch_i386
39 /* Do not "beautify" the CONCAT* macro args. Traditional C will not
40 remove whitespace added here, and thus will fail to concatenate
42 #define MY(OP) CONCAT2 (i386linux_,OP)
43 #define TARGETNAME "a.out-i386-linux"
45 extern const bfd_target
MY(vec
);
47 /* We always generate QMAGIC files in preference to ZMAGIC files. It
48 would be possible to make this a linker option, if that ever
51 static void MY_final_link_callback
52 PARAMS ((bfd
*, file_ptr
*, file_ptr
*, file_ptr
*));
53 static bfd_boolean i386linux_bfd_final_link
54 PARAMS ((bfd
*, struct bfd_link_info
*));
55 static bfd_boolean i386linux_write_object_contents
PARAMS ((bfd
*));
58 i386linux_bfd_final_link (abfd
, info
)
60 struct bfd_link_info
*info
;
62 obj_aout_subformat (abfd
) = q_magic_format
;
63 return NAME(aout
,final_link
) (abfd
, info
, MY_final_link_callback
);
66 #define MY_bfd_final_link i386linux_bfd_final_link
68 /* Set the machine type correctly. */
71 i386linux_write_object_contents (abfd
)
74 struct external_exec exec_bytes
;
75 struct internal_exec
*execp
= exec_hdr (abfd
);
77 N_SET_MACHTYPE (*execp
, M_386
);
79 obj_reloc_entry_size (abfd
) = RELOC_STD_SIZE
;
81 WRITE_HEADERS(abfd
, execp
);
86 #define MY_write_object_contents i386linux_write_object_contents
88 /* Code to link against Linux a.out shared libraries. */
90 /* See if a symbol name is a reference to the global offset table. */
92 #ifndef GOT_REF_PREFIX
93 #define GOT_REF_PREFIX "__GOT_"
96 #define IS_GOT_SYM(name) (CONST_STRNEQ (name, GOT_REF_PREFIX))
98 /* See if a symbol name is a reference to the procedure linkage table. */
100 #ifndef PLT_REF_PREFIX
101 #define PLT_REF_PREFIX "__PLT_"
104 #define IS_PLT_SYM(name) (CONST_STRNEQ (name, PLT_REF_PREFIX))
106 /* This string is used to generate specialized error messages. */
109 #define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
112 /* This special symbol is a set vector that contains a list of
113 pointers to fixup tables. It will be present in any dynamically
114 linked file. The linker generated fixup table should also be added
115 to the list, and it should always appear in the second slot (the
116 first one is a dummy with a magic number that is defined in
119 #ifndef SHARABLE_CONFLICTS
120 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
123 /* We keep a list of fixups. The terminology is a bit strange, but
124 each fixup contains two 32 bit numbers. A regular fixup contains
125 an address and a pointer, and at runtime we should store the
126 address at the location pointed to by the pointer. A builtin fixup
127 contains two pointers, and we should read the address using one
128 pointer and store it at the location pointed to by the other
129 pointer. Builtin fixups come into play when we have duplicate
130 __GOT__ symbols for the same variable. The builtin fixup will copy
131 the GOT pointer from one over into the other. */
136 struct linux_link_hash_entry
*h
;
139 /* Nonzero if this is a jump instruction that needs to be fixed,
140 zero if this is just a pointer */
146 /* We don't need a special hash table entry structure, but we do need
147 to keep some information between linker passes, so we use a special
150 struct linux_link_hash_entry
152 struct aout_link_hash_entry root
;
155 struct linux_link_hash_table
157 struct aout_link_hash_table root
;
159 /* First dynamic object found in link. */
162 /* Number of fixups. */
165 /* Number of builtin fixups. */
166 size_t local_builtins
;
168 /* List of fixups. */
169 struct fixup
*fixup_list
;
172 static struct bfd_hash_entry
*linux_link_hash_newfunc
173 PARAMS ((struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *));
174 static struct bfd_link_hash_table
*linux_link_hash_table_create
176 static struct fixup
*new_fixup
177 PARAMS ((struct bfd_link_info
*, struct linux_link_hash_entry
*,
179 static bfd_boolean linux_link_create_dynamic_sections
180 PARAMS ((bfd
*, struct bfd_link_info
*));
181 static bfd_boolean linux_add_one_symbol
182 PARAMS ((struct bfd_link_info
*, bfd
*, const char *, flagword
, asection
*,
183 bfd_vma
, const char *, bfd_boolean
, bfd_boolean
,
184 struct bfd_link_hash_entry
**));
185 static bfd_boolean linux_tally_symbols
186 PARAMS ((struct linux_link_hash_entry
*, PTR
));
187 static bfd_boolean linux_finish_dynamic_link
188 PARAMS ((bfd
*, struct bfd_link_info
*));
190 /* Routine to create an entry in an Linux link hash table. */
192 static struct bfd_hash_entry
*
193 linux_link_hash_newfunc (entry
, table
, string
)
194 struct bfd_hash_entry
*entry
;
195 struct bfd_hash_table
*table
;
198 struct linux_link_hash_entry
*ret
= (struct linux_link_hash_entry
*) entry
;
200 /* Allocate the structure if it has not already been allocated by a
202 if (ret
== (struct linux_link_hash_entry
*) NULL
)
203 ret
= ((struct linux_link_hash_entry
*)
204 bfd_hash_allocate (table
, sizeof (struct linux_link_hash_entry
)));
206 return (struct bfd_hash_entry
*) ret
;
208 /* Call the allocation method of the superclass. */
209 ret
= ((struct linux_link_hash_entry
*)
210 NAME(aout
,link_hash_newfunc
) ((struct bfd_hash_entry
*) ret
,
214 /* Set local fields; there aren't any. */
217 return (struct bfd_hash_entry
*) ret
;
220 /* Create a Linux link hash table. */
222 static struct bfd_link_hash_table
*
223 linux_link_hash_table_create (abfd
)
226 struct linux_link_hash_table
*ret
;
227 bfd_size_type amt
= sizeof (struct linux_link_hash_table
);
229 ret
= (struct linux_link_hash_table
*) bfd_alloc (abfd
, amt
);
230 if (ret
== (struct linux_link_hash_table
*) NULL
)
231 return (struct bfd_link_hash_table
*) NULL
;
232 if (!NAME(aout
,link_hash_table_init
) (&ret
->root
, abfd
,
233 linux_link_hash_newfunc
,
234 sizeof (struct linux_link_hash_entry
)))
237 return (struct bfd_link_hash_table
*) NULL
;
241 ret
->fixup_count
= 0;
242 ret
->local_builtins
= 0;
243 ret
->fixup_list
= NULL
;
245 return &ret
->root
.root
;
248 /* Look up an entry in a Linux link hash table. */
250 #define linux_link_hash_lookup(table, string, create, copy, follow) \
251 ((struct linux_link_hash_entry *) \
252 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
255 /* Traverse a Linux link hash table. */
257 #define linux_link_hash_traverse(table, func, info) \
258 (aout_link_hash_traverse \
260 (bfd_boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func), \
263 /* Get the Linux link hash table from the info structure. This is
266 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
268 /* Store the information for a new fixup. */
270 static struct fixup
*
271 new_fixup (info
, h
, value
, builtin
)
272 struct bfd_link_info
*info
;
273 struct linux_link_hash_entry
*h
;
279 f
= (struct fixup
*) bfd_hash_allocate (&info
->hash
->table
,
280 sizeof (struct fixup
));
283 f
->next
= linux_hash_table (info
)->fixup_list
;
284 linux_hash_table (info
)->fixup_list
= f
;
287 f
->builtin
= builtin
;
289 ++linux_hash_table (info
)->fixup_count
;
293 /* We come here once we realize that we are going to link to a shared
294 library. We need to create a special section that contains the
295 fixup table, and we ultimately need to add a pointer to this into
296 the set vector for SHARABLE_CONFLICTS. At this point we do not
297 know the size of the section, but that's OK - we just need to
298 create it for now. */
301 linux_link_create_dynamic_sections (abfd
, info
)
303 struct bfd_link_info
*info ATTRIBUTE_UNUSED
;
306 register asection
*s
;
308 /* Note that we set the SEC_IN_MEMORY flag. */
309 flags
= SEC_ALLOC
| SEC_LOAD
| SEC_HAS_CONTENTS
| SEC_IN_MEMORY
;
311 /* We choose to use the name ".linux-dynamic" for the fixup table.
313 s
= bfd_make_section_with_flags (abfd
, ".linux-dynamic", flags
);
315 || ! bfd_set_section_alignment (abfd
, s
, 2))
323 /* Function to add a single symbol to the linker hash table. This is
324 a wrapper around _bfd_generic_link_add_one_symbol which handles the
325 tweaking needed for dynamic linking support. */
328 linux_add_one_symbol (info
, abfd
, name
, flags
, section
, value
, string
,
329 copy
, collect
, hashp
)
330 struct bfd_link_info
*info
;
339 struct bfd_link_hash_entry
**hashp
;
341 struct linux_link_hash_entry
*h
;
344 /* Look up and see if we already have this symbol in the hash table.
345 If we do, and the defining entry is from a shared library, we
346 need to create the dynamic sections.
348 FIXME: What if abfd->xvec != info->output_bfd->xvec? We may
349 want to be able to link Linux a.out and ELF objects together,
350 but serious confusion is possible. */
354 if (! info
->relocatable
355 && linux_hash_table (info
)->dynobj
== NULL
356 && strcmp (name
, SHARABLE_CONFLICTS
) == 0
357 && (flags
& BSF_CONSTRUCTOR
) != 0
358 && abfd
->xvec
== info
->output_bfd
->xvec
)
360 if (! linux_link_create_dynamic_sections (abfd
, info
))
362 linux_hash_table (info
)->dynobj
= abfd
;
366 if (bfd_is_abs_section (section
)
367 && abfd
->xvec
== info
->output_bfd
->xvec
)
369 h
= linux_link_hash_lookup (linux_hash_table (info
), name
, FALSE
,
372 && (h
->root
.root
.type
== bfd_link_hash_defined
373 || h
->root
.root
.type
== bfd_link_hash_defweak
))
378 *hashp
= (struct bfd_link_hash_entry
*) h
;
380 f
= new_fixup (info
, h
, value
, ! IS_PLT_SYM (name
));
383 f
->jump
= IS_PLT_SYM (name
);
389 /* Do the usual procedure for adding a symbol. */
390 if (! _bfd_generic_link_add_one_symbol (info
, abfd
, name
, flags
, section
,
391 value
, string
, copy
, collect
,
395 /* Insert a pointer to our table in the set vector. The dynamic
396 linker requires this information */
401 /* Here we do our special thing to add the pointer to the
402 dynamic section in the SHARABLE_CONFLICTS set vector. */
403 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
405 BFD_ASSERT (s
!= NULL
);
407 if (! (_bfd_generic_link_add_one_symbol
408 (info
, linux_hash_table (info
)->dynobj
, SHARABLE_CONFLICTS
,
409 BSF_GLOBAL
| BSF_CONSTRUCTOR
, s
, (bfd_vma
) 0, NULL
,
410 FALSE
, FALSE
, NULL
)))
417 /* We will crawl the hash table and come here for every global symbol.
418 We will examine each entry and see if there are indications that we
419 need to add a fixup. There are two possible cases - one is where
420 you have duplicate definitions of PLT or GOT symbols - these will
421 have already been caught and added as "builtin" fixups. If we find
422 that the corresponding non PLT/GOT symbol is also present, we
423 convert it to a regular fixup instead.
425 This function is called via linux_link_hash_traverse. */
428 linux_tally_symbols (h
, data
)
429 struct linux_link_hash_entry
*h
;
432 struct bfd_link_info
*info
= (struct bfd_link_info
*) data
;
433 struct fixup
*f
, *f1
;
435 struct linux_link_hash_entry
*h1
, *h2
;
438 if (h
->root
.root
.type
== bfd_link_hash_undefined
439 && CONST_STRNEQ (h
->root
.root
.root
.string
, NEEDS_SHRLIB
))
445 name
= h
->root
.root
.root
.string
+ sizeof NEEDS_SHRLIB
- 1;
446 p
= strrchr (name
, '_');
448 alloc
= (char *) bfd_malloc ((bfd_size_type
) strlen (name
) + 1);
450 if (p
== NULL
|| alloc
== NULL
)
451 (*_bfd_error_handler
) (_("Output file requires shared library `%s'\n"),
455 strcpy (alloc
, name
);
456 p
= strrchr (alloc
, '_');
458 (*_bfd_error_handler
)
459 (_("Output file requires shared library `%s.so.%s'\n"),
467 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
468 is_plt
= IS_PLT_SYM (h
->root
.root
.root
.string
);
470 if (is_plt
|| IS_GOT_SYM (h
->root
.root
.root
.string
))
472 /* Look up this symbol twice. Once just as a regular lookup,
473 and then again following all of the indirect links until we
474 reach a real symbol. */
475 h1
= linux_link_hash_lookup (linux_hash_table (info
),
476 (h
->root
.root
.root
.string
477 + sizeof PLT_REF_PREFIX
- 1),
479 /* h2 does not follow indirect symbols. */
480 h2
= linux_link_hash_lookup (linux_hash_table (info
),
481 (h
->root
.root
.root
.string
482 + sizeof PLT_REF_PREFIX
- 1),
483 FALSE
, FALSE
, FALSE
);
485 /* The real symbol must exist but if it is also an ABS symbol,
486 there is no need to have a fixup. This is because they both
487 came from the same library. If on the other hand, we had to
488 use an indirect symbol to get to the real symbol, we add the
489 fixup anyway, since there are cases where these symbols come
490 from different shared libraries */
492 && (((h1
->root
.root
.type
== bfd_link_hash_defined
493 || h1
->root
.root
.type
== bfd_link_hash_defweak
)
494 && ! bfd_is_abs_section (h1
->root
.root
.u
.def
.section
))
495 || h2
->root
.root
.type
== bfd_link_hash_indirect
))
497 /* See if there is a "builtin" fixup already present
498 involving this symbol. If so, convert it to a regular
499 fixup. In the end, this relaxes some of the requirements
500 about the order of performing fixups. */
502 for (f1
= linux_hash_table (info
)->fixup_list
;
506 if ((f1
->h
!= h
&& f1
->h
!= h1
)
507 || (! f1
->builtin
&& ! f1
->jump
))
512 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
514 f
= new_fixup (info
, h1
, f1
->h
->root
.root
.u
.def
.value
, 0);
523 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
525 f
= new_fixup (info
, h1
, h
->root
.root
.u
.def
.value
, 0);
528 /* FIXME: No way to return error. */
535 /* Quick and dirty way of stripping these symbols from the
537 if (bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
538 h
->root
.written
= TRUE
;
544 /* This is called to set the size of the .linux-dynamic section is.
545 It is called by the Linux linker emulation before_allocation
546 routine. We have finished reading all of the input files, and now
547 we just scan the hash tables to find out how many additional fixups
551 bfd_i386linux_size_dynamic_sections (output_bfd
, info
)
553 struct bfd_link_info
*info
;
558 if (output_bfd
->xvec
!= &MY(vec
))
561 /* First find the fixups... */
562 linux_link_hash_traverse (linux_hash_table (info
),
566 /* If there are builtin fixups, leave room for a marker. This is
567 used by the dynamic linker so that it knows that all that follow
568 are builtin fixups instead of regular fixups. */
569 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
573 ++linux_hash_table (info
)->fixup_count
;
574 ++linux_hash_table (info
)->local_builtins
;
579 if (linux_hash_table (info
)->dynobj
== NULL
)
581 if (linux_hash_table (info
)->fixup_count
> 0)
586 /* Allocate memory for our fixup table. We will fill it in later. */
587 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
591 s
->size
= linux_hash_table (info
)->fixup_count
+ 1;
593 s
->contents
= (bfd_byte
*) bfd_zalloc (output_bfd
, s
->size
);
594 if (s
->contents
== NULL
)
601 /* We come here once we are ready to actually write the fixup table to
602 the output file. Scan the fixup tables and so forth and generate
603 the stuff we need. */
606 linux_finish_dynamic_link (output_bfd
, info
)
608 struct bfd_link_info
*info
;
610 asection
*s
, *os
, *is
;
611 bfd_byte
*fixup_table
;
612 struct linux_link_hash_entry
*h
;
614 unsigned int new_addr
;
616 unsigned int fixups_written
;
618 if (linux_hash_table (info
)->dynobj
== NULL
)
621 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
623 BFD_ASSERT (s
!= NULL
);
624 os
= s
->output_section
;
627 #ifdef LINUX_LINK_DEBUG
628 printf ("Fixup table file offset: %x VMA: %x\n",
629 os
->filepos
+ s
->output_offset
,
630 os
->vma
+ s
->output_offset
);
633 fixup_table
= s
->contents
;
634 bfd_put_32 (output_bfd
,
635 (bfd_vma
) linux_hash_table (info
)->fixup_count
, fixup_table
);
638 /* Fill in fixup table. */
639 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
644 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
645 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
647 (*_bfd_error_handler
)
648 (_("Symbol %s not defined for fixups\n"),
649 f
->h
->root
.root
.root
.string
);
653 is
= f
->h
->root
.root
.u
.def
.section
;
654 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
655 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
657 #ifdef LINUX_LINK_DEBUG
658 printf ("Fixup(%d) %s: %x %x\n",f
->jump
, f
->h
->root
.root
.string
,
664 /* Relative address */
665 new_addr
= new_addr
- (f
->value
+ 5);
666 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
668 bfd_put_32 (output_bfd
, f
->value
+ 1, fixup_table
);
673 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
675 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
681 if (linux_hash_table (info
)->local_builtins
!= 0)
683 /* Special marker so we know to switch to the other type of fixup */
684 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
686 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
689 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
694 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
695 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
697 (*_bfd_error_handler
)
698 (_("Symbol %s not defined for fixups\n"),
699 f
->h
->root
.root
.root
.string
);
703 is
= f
->h
->root
.root
.u
.def
.section
;
704 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
705 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
707 #ifdef LINUX_LINK_DEBUG
708 printf ("Fixup(B) %s: %x %x\n", f
->h
->root
.root
.string
,
712 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
714 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
720 if (linux_hash_table (info
)->fixup_count
!= fixups_written
)
722 (*_bfd_error_handler
) (_("Warning: fixup count mismatch\n"));
723 while (linux_hash_table (info
)->fixup_count
> fixups_written
)
725 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
727 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
733 h
= linux_link_hash_lookup (linux_hash_table (info
),
734 "__BUILTIN_FIXUPS__",
735 FALSE
, FALSE
, FALSE
);
738 && (h
->root
.root
.type
== bfd_link_hash_defined
739 || h
->root
.root
.type
== bfd_link_hash_defweak
))
741 is
= h
->root
.root
.u
.def
.section
;
742 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
743 new_addr
= h
->root
.root
.u
.def
.value
+ section_offset
;
745 #ifdef LINUX_LINK_DEBUG
746 printf ("Builtin fixup table at %x\n", new_addr
);
749 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
752 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
754 if (bfd_seek (output_bfd
, (file_ptr
) (os
->filepos
+ s
->output_offset
),
758 if (bfd_bwrite ((PTR
) s
->contents
, s
->size
, output_bfd
) != s
->size
)
764 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
765 #define MY_add_one_symbol linux_add_one_symbol
766 #define MY_finish_dynamic_link linux_finish_dynamic_link
768 #define MY_zmagic_contiguous 1
770 #include "aout-target.h"