1 /* BFD back-end for linux flavored i386 a.out binaries.
2 Copyright 1992, 1993, 1994, 1995, 1996, 1997, 2001
3 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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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
25 #define N_SHARED_LIB(x) 0
26 #define BYTES_IN_WORD 4
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
39 #define MY(OP) CAT(i386linux_,OP)
40 #define TARGETNAME "a.out-i386-linux"
42 extern const bfd_target
MY(vec
);
44 /* We always generate QMAGIC files in preference to ZMAGIC files. It
45 would be possible to make this a linker option, if that ever
48 static void MY_final_link_callback
49 PARAMS ((bfd
*, file_ptr
*, file_ptr
*, file_ptr
*));
50 static boolean i386linux_bfd_final_link
51 PARAMS ((bfd
*, struct bfd_link_info
*));
52 static boolean i386linux_write_object_contents
PARAMS ((bfd
*));
55 i386linux_bfd_final_link (abfd
, info
)
57 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 (abfd
)
71 struct external_exec exec_bytes
;
72 struct internal_exec
*execp
= exec_hdr (abfd
);
74 N_SET_MACHTYPE (*execp
, M_386
);
76 obj_reloc_entry_size (abfd
) = RELOC_STD_SIZE
;
78 WRITE_HEADERS(abfd
, execp
);
83 #define MY_write_object_contents i386linux_write_object_contents
85 /* Code to link against Linux a.out shared libraries. */
87 /* See if a symbol name is a reference to the global offset table. */
89 #ifndef GOT_REF_PREFIX
90 #define GOT_REF_PREFIX "__GOT_"
93 #define IS_GOT_SYM(name) \
94 (strncmp (name, GOT_REF_PREFIX, sizeof GOT_REF_PREFIX - 1) == 0)
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) \
103 (strncmp (name, PLT_REF_PREFIX, sizeof PLT_REF_PREFIX - 1) == 0)
105 /* This string is used to generate specialized error messages. */
108 #define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
111 /* This special symbol is a set vector that contains a list of
112 pointers to fixup tables. It will be present in any dynamicly
113 linked file. The linker generated fixup table should also be added
114 to the list, and it should always appear in the second slot (the
115 first one is a dummy with a magic number that is defined in
118 #ifndef SHARABLE_CONFLICTS
119 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
122 /* We keep a list of fixups. The terminology is a bit strange, but
123 each fixup contains two 32 bit numbers. A regular fixup contains
124 an address and a pointer, and at runtime we should store the
125 address at the location pointed to by the pointer. A builtin fixup
126 contains two pointers, and we should read the address using one
127 pointer and store it at the location pointed to by the other
128 pointer. Builtin fixups come into play when we have duplicate
129 __GOT__ symbols for the same variable. The builtin fixup will copy
130 the GOT pointer from one over into the other. */
135 struct linux_link_hash_entry
*h
;
138 /* Nonzero if this is a jump instruction that needs to be fixed,
139 zero if this is just a pointer */
145 /* We don't need a special hash table entry structure, but we do need
146 to keep some information between linker passes, so we use a special
149 struct linux_link_hash_entry
151 struct aout_link_hash_entry root
;
154 struct linux_link_hash_table
156 struct aout_link_hash_table root
;
158 /* First dynamic object found in link. */
161 /* Number of fixups. */
164 /* Number of builtin fixups. */
165 size_t local_builtins
;
167 /* List of fixups. */
168 struct fixup
*fixup_list
;
171 static struct bfd_hash_entry
*linux_link_hash_newfunc
172 PARAMS ((struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *));
173 static struct bfd_link_hash_table
*linux_link_hash_table_create
175 static struct fixup
*new_fixup
176 PARAMS ((struct bfd_link_info
*, struct linux_link_hash_entry
*,
178 static boolean linux_link_create_dynamic_sections
179 PARAMS ((bfd
*, struct bfd_link_info
*));
180 static boolean linux_add_one_symbol
181 PARAMS ((struct bfd_link_info
*, bfd
*, const char *, flagword
, asection
*,
182 bfd_vma
, const char *, boolean
, boolean
,
183 struct bfd_link_hash_entry
**));
184 static boolean linux_tally_symbols
185 PARAMS ((struct linux_link_hash_entry
*, PTR
));
186 static boolean linux_finish_dynamic_link
187 PARAMS ((bfd
*, struct bfd_link_info
*));
189 /* Routine to create an entry in an Linux link hash table. */
191 static struct bfd_hash_entry
*
192 linux_link_hash_newfunc (entry
, table
, string
)
193 struct bfd_hash_entry
*entry
;
194 struct bfd_hash_table
*table
;
197 struct linux_link_hash_entry
*ret
= (struct linux_link_hash_entry
*) entry
;
199 /* Allocate the structure if it has not already been allocated by a
201 if (ret
== (struct linux_link_hash_entry
*) NULL
)
202 ret
= ((struct linux_link_hash_entry
*)
203 bfd_hash_allocate (table
, sizeof (struct linux_link_hash_entry
)));
205 return (struct bfd_hash_entry
*) ret
;
207 /* Call the allocation method of the superclass. */
208 ret
= ((struct linux_link_hash_entry
*)
209 NAME(aout
,link_hash_newfunc
) ((struct bfd_hash_entry
*) ret
,
213 /* Set local fields; there aren't any. */
216 return (struct bfd_hash_entry
*) ret
;
219 /* Create a Linux link hash table. */
221 static struct bfd_link_hash_table
*
222 linux_link_hash_table_create (abfd
)
225 struct linux_link_hash_table
*ret
;
226 bfd_size_type amt
= sizeof (struct linux_link_hash_table
);
228 ret
= (struct linux_link_hash_table
*) bfd_alloc (abfd
, amt
);
229 if (ret
== (struct linux_link_hash_table
*) NULL
)
230 return (struct bfd_link_hash_table
*) NULL
;
231 if (! NAME(aout
,link_hash_table_init
) (&ret
->root
, abfd
,
232 linux_link_hash_newfunc
))
235 return (struct bfd_link_hash_table
*) NULL
;
239 ret
->fixup_count
= 0;
240 ret
->local_builtins
= 0;
241 ret
->fixup_list
= NULL
;
243 return &ret
->root
.root
;
246 /* Look up an entry in a Linux link hash table. */
248 #define linux_link_hash_lookup(table, string, create, copy, follow) \
249 ((struct linux_link_hash_entry *) \
250 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
253 /* Traverse a Linux link hash table. */
255 #define linux_link_hash_traverse(table, func, info) \
256 (aout_link_hash_traverse \
258 (boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func), \
261 /* Get the Linux link hash table from the info structure. This is
264 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
266 /* Store the information for a new fixup. */
268 static struct fixup
*
269 new_fixup (info
, h
, value
, builtin
)
270 struct bfd_link_info
*info
;
271 struct linux_link_hash_entry
*h
;
277 f
= (struct fixup
*) bfd_hash_allocate (&info
->hash
->table
,
278 sizeof (struct fixup
));
281 f
->next
= linux_hash_table (info
)->fixup_list
;
282 linux_hash_table (info
)->fixup_list
= f
;
285 f
->builtin
= builtin
;
287 ++linux_hash_table (info
)->fixup_count
;
291 /* We come here once we realize that we are going to link to a shared
292 library. We need to create a special section that contains the
293 fixup table, and we ultimately need to add a pointer to this into
294 the set vector for SHARABLE_CONFLICTS. At this point we do not
295 know the size of the section, but that's OK - we just need to
296 create it for now. */
299 linux_link_create_dynamic_sections (abfd
, info
)
301 struct bfd_link_info
*info ATTRIBUTE_UNUSED
;
304 register asection
*s
;
306 /* Note that we set the SEC_IN_MEMORY flag. */
307 flags
= SEC_ALLOC
| SEC_LOAD
| SEC_HAS_CONTENTS
| SEC_IN_MEMORY
;
309 /* We choose to use the name ".linux-dynamic" for the fixup table.
311 s
= bfd_make_section (abfd
, ".linux-dynamic");
313 || ! bfd_set_section_flags (abfd
, s
, flags
)
314 || ! bfd_set_section_alignment (abfd
, s
, 2))
322 /* Function to add a single symbol to the linker hash table. This is
323 a wrapper around _bfd_generic_link_add_one_symbol which handles the
324 tweaking needed for dynamic linking support. */
327 linux_add_one_symbol (info
, abfd
, name
, flags
, section
, value
, string
,
328 copy
, collect
, hashp
)
329 struct bfd_link_info
*info
;
338 struct bfd_link_hash_entry
**hashp
;
340 struct linux_link_hash_entry
*h
;
343 /* Look up and see if we already have this symbol in the hash table.
344 If we do, and the defining entry is from a shared library, we
345 need to create the dynamic sections.
347 FIXME: What if abfd->xvec != info->hash->creator? We may want to
348 be able to link Linux a.out and ELF objects together, but serious
349 confusion is possible. */
353 if (! info
->relocateable
354 && linux_hash_table (info
)->dynobj
== NULL
355 && strcmp (name
, SHARABLE_CONFLICTS
) == 0
356 && (flags
& BSF_CONSTRUCTOR
) != 0
357 && abfd
->xvec
== info
->hash
->creator
)
359 if (! linux_link_create_dynamic_sections (abfd
, info
))
361 linux_hash_table (info
)->dynobj
= abfd
;
365 if (bfd_is_abs_section (section
)
366 && abfd
->xvec
== info
->hash
->creator
)
368 h
= linux_link_hash_lookup (linux_hash_table (info
), name
, false,
371 && (h
->root
.root
.type
== bfd_link_hash_defined
372 || h
->root
.root
.type
== bfd_link_hash_defweak
))
377 *hashp
= (struct bfd_link_hash_entry
*) h
;
379 f
= new_fixup (info
, h
, value
, ! IS_PLT_SYM (name
));
382 f
->jump
= IS_PLT_SYM (name
);
388 /* Do the usual procedure for adding a symbol. */
389 if (! _bfd_generic_link_add_one_symbol (info
, abfd
, name
, flags
, section
,
390 value
, string
, copy
, collect
,
394 /* Insert a pointer to our table in the set vector. The dynamic
395 linker requires this information */
400 /* Here we do our special thing to add the pointer to the
401 dynamic section in the SHARABLE_CONFLICTS set vector. */
402 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
404 BFD_ASSERT (s
!= NULL
);
406 if (! (_bfd_generic_link_add_one_symbol
407 (info
, linux_hash_table (info
)->dynobj
, SHARABLE_CONFLICTS
,
408 BSF_GLOBAL
| BSF_CONSTRUCTOR
, s
, (bfd_vma
) 0, NULL
,
409 false, false, NULL
)))
416 /* We will crawl the hash table and come here for every global symbol.
417 We will examine each entry and see if there are indications that we
418 need to add a fixup. There are two possible cases - one is where
419 you have duplicate definitions of PLT or GOT symbols - these will
420 have already been caught and added as "builtin" fixups. If we find
421 that the corresponding non PLT/GOT symbol is also present, we
422 convert it to a regular fixup instead.
424 This function is called via linux_link_hash_traverse. */
427 linux_tally_symbols (h
, data
)
428 struct linux_link_hash_entry
*h
;
431 struct bfd_link_info
*info
= (struct bfd_link_info
*) data
;
432 struct fixup
*f
, *f1
;
434 struct linux_link_hash_entry
*h1
, *h2
;
437 if (h
->root
.root
.type
== bfd_link_hash_undefined
438 && strncmp (h
->root
.root
.root
.string
, NEEDS_SHRLIB
,
439 sizeof NEEDS_SHRLIB
- 1) == 0)
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
->_raw_size
= linux_hash_table (info
)->fixup_count
+ 1;
593 s
->contents
= (bfd_byte
*) bfd_alloc (output_bfd
, s
->_raw_size
);
594 if (s
->contents
== NULL
)
596 memset (s
->contents
, 0, (size_t) s
->_raw_size
);
602 /* We come here once we are ready to actually write the fixup table to
603 the output file. Scan the fixup tables and so forth and generate
604 the stuff we need. */
607 linux_finish_dynamic_link (output_bfd
, info
)
609 struct bfd_link_info
*info
;
611 asection
*s
, *os
, *is
;
612 bfd_byte
*fixup_table
;
613 struct linux_link_hash_entry
*h
;
615 unsigned int new_addr
;
617 unsigned int fixups_written
;
619 if (linux_hash_table (info
)->dynobj
== NULL
)
622 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
624 BFD_ASSERT (s
!= NULL
);
625 os
= s
->output_section
;
628 #ifdef LINUX_LINK_DEBUG
629 printf ("Fixup table file offset: %x VMA: %x\n",
630 os
->filepos
+ s
->output_offset
,
631 os
->vma
+ s
->output_offset
);
634 fixup_table
= s
->contents
;
635 bfd_put_32 (output_bfd
,
636 (bfd_vma
) linux_hash_table (info
)->fixup_count
, fixup_table
);
639 /* Fill in fixup table. */
640 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
645 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
646 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
648 (*_bfd_error_handler
)
649 (_("Symbol %s not defined for fixups\n"),
650 f
->h
->root
.root
.root
.string
);
654 is
= f
->h
->root
.root
.u
.def
.section
;
655 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
656 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
658 #ifdef LINUX_LINK_DEBUG
659 printf ("Fixup(%d) %s: %x %x\n",f
->jump
, f
->h
->root
.root
.string
,
665 /* Relative address */
666 new_addr
= new_addr
- (f
->value
+ 5);
667 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
669 bfd_put_32 (output_bfd
, f
->value
+ 1, fixup_table
);
674 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
676 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
682 if (linux_hash_table (info
)->local_builtins
!= 0)
684 /* Special marker so we know to switch to the other type of fixup */
685 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
687 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
690 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
695 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
696 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
698 (*_bfd_error_handler
)
699 (_("Symbol %s not defined for fixups\n"),
700 f
->h
->root
.root
.root
.string
);
704 is
= f
->h
->root
.root
.u
.def
.section
;
705 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
706 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
708 #ifdef LINUX_LINK_DEBUG
709 printf ("Fixup(B) %s: %x %x\n", f
->h
->root
.root
.string
,
713 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
715 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
721 if (linux_hash_table (info
)->fixup_count
!= fixups_written
)
723 (*_bfd_error_handler
) (_("Warning: fixup count mismatch\n"));
724 while (linux_hash_table (info
)->fixup_count
> fixups_written
)
726 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
728 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
734 h
= linux_link_hash_lookup (linux_hash_table (info
),
735 "__BUILTIN_FIXUPS__",
736 false, false, false);
739 && (h
->root
.root
.type
== bfd_link_hash_defined
740 || h
->root
.root
.type
== bfd_link_hash_defweak
))
742 is
= h
->root
.root
.u
.def
.section
;
743 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
744 new_addr
= h
->root
.root
.u
.def
.value
+ section_offset
;
746 #ifdef LINUX_LINK_DEBUG
747 printf ("Builtin fixup table at %x\n", new_addr
);
750 bfd_put_32 (output_bfd
, (bfd_vma
) new_addr
, fixup_table
);
753 bfd_put_32 (output_bfd
, (bfd_vma
) 0, fixup_table
);
755 if (bfd_seek (output_bfd
, (file_ptr
) (os
->filepos
+ s
->output_offset
),
759 if (bfd_bwrite ((PTR
) s
->contents
, s
->_raw_size
, output_bfd
) != s
->_raw_size
)
765 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
766 #define MY_add_one_symbol linux_add_one_symbol
767 #define MY_finish_dynamic_link linux_finish_dynamic_link
769 #define MY_zmagic_contiguous 1
771 #include "aout-target.h"