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 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_warning
)
439 h
= (struct linux_link_hash_entry
*) h
->root
.root
.u
.i
.link
;
441 if (h
->root
.root
.type
== bfd_link_hash_undefined
442 && CONST_STRNEQ (h
->root
.root
.root
.string
, NEEDS_SHRLIB
))
448 name
= h
->root
.root
.root
.string
+ sizeof NEEDS_SHRLIB
- 1;
449 p
= strrchr (name
, '_');
451 alloc
= (char *) bfd_malloc ((bfd_size_type
) strlen (name
) + 1);
453 if (p
== NULL
|| alloc
== NULL
)
454 (*_bfd_error_handler
) (_("Output file requires shared library `%s'\n"),
458 strcpy (alloc
, name
);
459 p
= strrchr (alloc
, '_');
461 (*_bfd_error_handler
)
462 (_("Output file requires shared library `%s.so.%s'\n"),
470 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
471 is_plt
= IS_PLT_SYM (h
->root
.root
.root
.string
);
473 if (is_plt
|| IS_GOT_SYM (h
->root
.root
.root
.string
))
475 /* Look up this symbol twice. Once just as a regular lookup,
476 and then again following all of the indirect links until we
477 reach a real symbol. */
478 h1
= linux_link_hash_lookup (linux_hash_table (info
),
479 (h
->root
.root
.root
.string
480 + sizeof PLT_REF_PREFIX
- 1),
482 /* h2 does not follow indirect symbols. */
483 h2
= linux_link_hash_lookup (linux_hash_table (info
),
484 (h
->root
.root
.root
.string
485 + sizeof PLT_REF_PREFIX
- 1),
486 FALSE
, FALSE
, FALSE
);
488 /* The real symbol must exist but if it is also an ABS symbol,
489 there is no need to have a fixup. This is because they both
490 came from the same library. If on the other hand, we had to
491 use an indirect symbol to get to the real symbol, we add the
492 fixup anyway, since there are cases where these symbols come
493 from different shared libraries */
495 && (((h1
->root
.root
.type
== bfd_link_hash_defined
496 || h1
->root
.root
.type
== bfd_link_hash_defweak
)
497 && ! bfd_is_abs_section (h1
->root
.root
.u
.def
.section
))
498 || h2
->root
.root
.type
== bfd_link_hash_indirect
))
500 /* See if there is a "builtin" fixup already present
501 involving this symbol. If so, convert it to a regular
502 fixup. In the end, this relaxes some of the requirements
503 about the order of performing fixups. */
505 for (f1
= linux_hash_table (info
)->fixup_list
;
509 if ((f1
->h
!= h
&& f1
->h
!= h1
)
510 || (! f1
->builtin
&& ! f1
->jump
))
515 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
517 f
= new_fixup (info
, h1
, f1
->h
->root
.root
.u
.def
.value
, 0);
526 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
528 f
= new_fixup (info
, h1
, h
->root
.root
.u
.def
.value
, 0);
531 /* FIXME: No way to return error. */
538 /* Quick and dirty way of stripping these symbols from the
540 if (bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
541 h
->root
.written
= TRUE
;
547 /* This is called to set the size of the .linux-dynamic section is.
548 It is called by the Linux linker emulation before_allocation
549 routine. We have finished reading all of the input files, and now
550 we just scan the hash tables to find out how many additional fixups
554 bfd_i386linux_size_dynamic_sections (output_bfd
, info
)
556 struct bfd_link_info
*info
;
561 if (output_bfd
->xvec
!= &MY(vec
))
564 /* First find the fixups... */
565 linux_link_hash_traverse (linux_hash_table (info
),
569 /* If there are builtin fixups, leave room for a marker. This is
570 used by the dynamic linker so that it knows that all that follow
571 are builtin fixups instead of regular fixups. */
572 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
576 ++linux_hash_table (info
)->fixup_count
;
577 ++linux_hash_table (info
)->local_builtins
;
582 if (linux_hash_table (info
)->dynobj
== NULL
)
584 if (linux_hash_table (info
)->fixup_count
> 0)
589 /* Allocate memory for our fixup table. We will fill it in later. */
590 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
594 s
->size
= linux_hash_table (info
)->fixup_count
+ 1;
596 s
->contents
= (bfd_byte
*) bfd_zalloc (output_bfd
, s
->size
);
597 if (s
->contents
== NULL
)
604 /* We come here once we are ready to actually write the fixup table to
605 the output file. Scan the fixup tables and so forth and generate
606 the stuff we need. */
609 linux_finish_dynamic_link (output_bfd
, info
)
611 struct bfd_link_info
*info
;
613 asection
*s
, *os
, *is
;
614 bfd_byte
*fixup_table
;
615 struct linux_link_hash_entry
*h
;
617 unsigned int new_addr
;
619 unsigned int fixups_written
;
621 if (linux_hash_table (info
)->dynobj
== NULL
)
624 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
626 BFD_ASSERT (s
!= NULL
);
627 os
= s
->output_section
;
630 #ifdef LINUX_LINK_DEBUG
631 printf ("Fixup table file offset: %x VMA: %x\n",
632 os
->filepos
+ s
->output_offset
,
633 os
->vma
+ s
->output_offset
);
636 fixup_table
= s
->contents
;
637 bfd_put_32 (output_bfd
,
638 (bfd_vma
) linux_hash_table (info
)->fixup_count
, fixup_table
);
641 /* Fill in fixup table. */
642 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
647 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
648 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
650 (*_bfd_error_handler
)
651 (_("Symbol %s not defined for fixups\n"),
652 f
->h
->root
.root
.root
.string
);
656 is
= f
->h
->root
.root
.u
.def
.section
;
657 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
658 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
660 #ifdef LINUX_LINK_DEBUG
661 printf ("Fixup(%d) %s: %x %x\n",f
->jump
, f
->h
->root
.root
.string
,
667 /* Relative address */
668 new_addr
= new_addr
- (f
->value
+ 5);
669 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
671 bfd_put_32 (output_bfd
, f
->value
+ 1, fixup_table
);
676 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
678 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
684 if (linux_hash_table (info
)->local_builtins
!= 0)
686 /* Special marker so we know to switch to the other type of fixup */
687 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
689 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
692 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
697 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
698 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
700 (*_bfd_error_handler
)
701 (_("Symbol %s not defined for fixups\n"),
702 f
->h
->root
.root
.root
.string
);
706 is
= f
->h
->root
.root
.u
.def
.section
;
707 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
708 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
710 #ifdef LINUX_LINK_DEBUG
711 printf ("Fixup(B) %s: %x %x\n", f
->h
->root
.root
.string
,
715 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
717 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
723 if (linux_hash_table (info
)->fixup_count
!= fixups_written
)
725 (*_bfd_error_handler
) (_("Warning: fixup count mismatch\n"));
726 while (linux_hash_table (info
)->fixup_count
> fixups_written
)
728 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
730 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
736 h
= linux_link_hash_lookup (linux_hash_table (info
),
737 "__BUILTIN_FIXUPS__",
738 FALSE
, FALSE
, FALSE
);
741 && (h
->root
.root
.type
== bfd_link_hash_defined
742 || h
->root
.root
.type
== bfd_link_hash_defweak
))
744 is
= h
->root
.root
.u
.def
.section
;
745 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
746 new_addr
= h
->root
.root
.u
.def
.value
+ section_offset
;
748 #ifdef LINUX_LINK_DEBUG
749 printf ("Builtin fixup table at %x\n", new_addr
);
752 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
755 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
757 if (bfd_seek (output_bfd
, (file_ptr
) (os
->filepos
+ s
->output_offset
),
761 if (bfd_bwrite ((PTR
) s
->contents
, s
->size
, output_bfd
) != s
->size
)
767 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
768 #define MY_add_one_symbol linux_add_one_symbol
769 #define MY_finish_dynamic_link linux_finish_dynamic_link
771 #define MY_zmagic_contiguous 1
773 #include "aout-target.h"