1 /* BFD back-end for linux flavored i386 a.out binaries.
2 Copyright (C) 1992, 1993, 1994 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 2 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
20 #define PAGE_SIZE 4096
21 #define ZMAGIC_DISK_BLOCK_SIZE 1024
22 #define SEGMENT_SIZE 4096
23 #define TEXT_START_ADDR 0x0
24 #define N_SHARED_LIB(x) 0
25 #define BYTES_IN_WORD 4
30 #include "aout/aout64.h"
31 #include "aout/stab_gnu.h"
33 #include "libaout.h" /* BFD a.out internal data structures */
35 #define DEFAULT_ARCH bfd_arch_i386
36 #define MY(OP) CAT(i386linux_,OP)
37 #define TARGETNAME "a.out-i386-linux"
39 /* We always generate QMAGIC files in preference to ZMAGIC files. It
40 would be possible to make this a linker option, if that ever
43 static void MY_final_link_callback
44 PARAMS ((bfd
*, file_ptr
*, file_ptr
*, file_ptr
*));
47 i386linux_bfd_final_link (abfd
, info
)
49 struct bfd_link_info
*info
;
51 obj_aout_subformat (abfd
) = q_magic_format
;
52 return NAME(aout
,final_link
) (abfd
, info
, MY_final_link_callback
);
55 #define MY_bfd_final_link i386linux_bfd_final_link
57 /* Set the machine type correctly. */
60 i386linux_write_object_contents (abfd
)
63 struct external_exec exec_bytes
;
64 struct internal_exec
*execp
= exec_hdr (abfd
);
66 N_SET_MACHTYPE (*execp
, M_386
);
68 obj_reloc_entry_size (abfd
) = RELOC_STD_SIZE
;
70 WRITE_HEADERS(abfd
, execp
);
75 #define MY_write_object_contents i386linux_write_object_contents
77 /* Code to link against Linux a.out shared libraries. */
79 /* See if a symbol name is a reference to the global offset table. */
81 #ifndef GOT_REF_PREFIX
82 #define GOT_REF_PREFIX "__GOT_"
85 #define IS_GOT_SYM(name) \
86 (strncmp (name, GOT_REF_PREFIX, sizeof GOT_REF_PREFIX - 1) == 0)
88 /* See if a symbol name is a reference to the procedure linkage table. */
90 #ifndef PLT_REF_PREFIX
91 #define PLT_REF_PREFIX "__PLT_"
94 #define IS_PLT_SYM(name) \
95 (strncmp (name, PLT_REF_PREFIX, sizeof PLT_REF_PREFIX - 1) == 0)
97 /* This special symbol is a set vector that contains a list of
98 pointers to fixup tables. It will be present in any dynamicly
99 linked file. The linker generated fixup table should also be added
100 to the list, and it should always appear in the second slot (the
101 first one is a dummy with a magic number that is defined in
104 #ifndef SHARABLE_CONFLICTS
105 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
108 /* We keep a list of fixups. The terminology is a bit strange, but
109 each fixup contains two 32 bit numbers. A regular fixup contains
110 an address and a pointer, and at runtime we should store the
111 address at the location pointed to by the pointer. A builtin fixup
112 contains two pointers, and we should read the address using one
113 pointer and store it at the location pointed to by the other
114 pointer. Builtin fixups come into play when we have duplicate
115 __GOT__ symbols for the same variable. The builtin fixup will copy
116 the GOT pointer from one over into the other. */
121 struct linux_link_hash_entry
*h
;
124 /* Nonzero if this is a jump instruction that needs to be fixed,
125 zero if this is just a pointer */
131 /* We don't need a special hash table entry structure, but we do need
132 to keep some information between linker passes, so we use a special
135 struct linux_link_hash_entry
137 struct aout_link_hash_entry root
;
140 struct linux_link_hash_table
142 struct aout_link_hash_table root
;
144 /* First dynamic object found in link. */
147 /* Number of fixups. */
150 /* Number of builtin fixups. */
151 size_t local_builtins
;
153 /* List of fixups. */
154 struct fixup
*fixup_list
;
157 static struct bfd_hash_entry
*linux_link_hash_newfunc
158 PARAMS ((struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *));
159 static struct bfd_link_hash_table
*linux_link_hash_table_create
161 static struct fixup
*new_fixup
162 PARAMS ((struct bfd_link_info
*, struct linux_link_hash_entry
*,
164 static boolean linux_link_create_dynamic_sections
165 PARAMS ((bfd
*, struct bfd_link_info
*));
166 static boolean linux_add_one_symbol
167 PARAMS ((struct bfd_link_info
*, bfd
*, const char *, flagword
, asection
*,
168 bfd_vma
, const char *, boolean
, boolean
,
169 struct bfd_link_hash_entry
**));
170 static boolean linux_tally_symbols
171 PARAMS ((struct linux_link_hash_entry
*, PTR
));
172 static boolean linux_finish_dynamic_link
173 PARAMS ((bfd
*, struct bfd_link_info
*));
175 /* Routine to create an entry in an Linux link hash table. */
177 static struct bfd_hash_entry
*
178 linux_link_hash_newfunc (entry
, table
, string
)
179 struct bfd_hash_entry
*entry
;
180 struct bfd_hash_table
*table
;
183 struct linux_link_hash_entry
*ret
= (struct linux_link_hash_entry
*) entry
;
185 /* Allocate the structure if it has not already been allocated by a
187 if (ret
== (struct linux_link_hash_entry
*) NULL
)
188 ret
= ((struct linux_link_hash_entry
*)
189 bfd_hash_allocate (table
, sizeof (struct linux_link_hash_entry
)));
191 return (struct bfd_hash_entry
*) ret
;
193 /* Call the allocation method of the superclass. */
194 ret
= ((struct linux_link_hash_entry
*)
195 NAME(aout
,link_hash_newfunc
) ((struct bfd_hash_entry
*) ret
,
199 /* Set local fields; there aren't any. */
202 return (struct bfd_hash_entry
*) ret
;
205 /* Create a Linux link hash table. */
207 static struct bfd_link_hash_table
*
208 linux_link_hash_table_create (abfd
)
211 struct linux_link_hash_table
*ret
;
213 ret
= ((struct linux_link_hash_table
*)
214 malloc (sizeof (struct linux_link_hash_table
)));
215 if (ret
== (struct linux_link_hash_table
*) NULL
)
217 bfd_set_error (bfd_error_no_memory
);
218 return (struct bfd_link_hash_table
*) NULL
;
220 if (! NAME(aout
,link_hash_table_init
) (&ret
->root
, abfd
,
221 linux_link_hash_newfunc
))
224 return (struct bfd_link_hash_table
*) NULL
;
228 ret
->fixup_count
= 0;
229 ret
->local_builtins
= 0;
230 ret
->fixup_list
= NULL
;
232 return &ret
->root
.root
;
235 /* Look up an entry in a Linux link hash table. */
237 #define linux_link_hash_lookup(table, string, create, copy, follow) \
238 ((struct linux_link_hash_entry *) \
239 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
242 /* Traverse a Linux link hash table. */
244 #define linux_link_hash_traverse(table, func, info) \
245 (aout_link_hash_traverse \
247 (boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func), \
250 /* Get the Linux link hash table from the info structure. This is
253 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
255 /* Store the information for a new fixup. */
257 static struct fixup
*
258 new_fixup (info
, h
, value
, builtin
)
259 struct bfd_link_info
*info
;
260 struct linux_link_hash_entry
*h
;
266 f
= (struct fixup
*) bfd_hash_allocate (&info
->hash
->table
,
267 sizeof (struct fixup
));
270 f
->next
= linux_hash_table (info
)->fixup_list
;
271 linux_hash_table (info
)->fixup_list
= f
;
274 f
->builtin
= builtin
;
276 ++linux_hash_table (info
)->fixup_count
;
280 /* We come here once we realize that we are going to link to a shared
281 library. We need to create a special section that contains the
282 fixup table, and we ultimately need to add a pointer to this into
283 the set vector for SHARABLE_CONFLICTS. At this point we do not
284 know the size of the section, but that's OK - we just need to
285 create it for now. */
288 linux_link_create_dynamic_sections (abfd
, info
)
290 struct bfd_link_info
*info
;
293 register asection
*s
;
295 /* Note that we set the SEC_IN_MEMORY flag. */
296 flags
= SEC_ALLOC
| SEC_LOAD
| SEC_HAS_CONTENTS
| SEC_IN_MEMORY
;
298 /* We choose to use the name ".linux-dynamic" for the fixup table.
300 s
= bfd_make_section (abfd
, ".linux-dynamic");
302 || ! bfd_set_section_flags (abfd
, s
, flags
)
303 || ! bfd_set_section_alignment (abfd
, s
, 2))
311 /* Function to add a single symbol to the linker hash table. This is
312 a wrapper around _bfd_generic_link_add_one_symbol which handles the
313 tweaking needed for dynamic linking support. */
316 linux_add_one_symbol (info
, abfd
, name
, flags
, section
, value
, string
,
317 copy
, collect
, hashp
)
318 struct bfd_link_info
*info
;
327 struct bfd_link_hash_entry
**hashp
;
329 struct linux_link_hash_entry
*h
;
332 /* Look up and see if we already have this symbol in the hash table.
333 If we do, and the defining entry is from a shared library, we
334 need to create the dynamic sections.
336 FIXME: What if abfd->xvec != info->hash->creator? We may want to
337 be able to link Linux a.out and ELF objects together, but serious
338 confusion is possible. */
342 if (! info
->relocateable
343 && linux_hash_table (info
)->dynobj
== NULL
344 && strcmp (name
, SHARABLE_CONFLICTS
) == 0
345 && (flags
& BSF_CONSTRUCTOR
) != 0
346 && abfd
->xvec
== info
->hash
->creator
)
348 if (! linux_link_create_dynamic_sections (abfd
, info
))
350 linux_hash_table (info
)->dynobj
= abfd
;
354 if (bfd_is_abs_section (section
)
355 && abfd
->xvec
== info
->hash
->creator
)
357 h
= linux_link_hash_lookup (linux_hash_table (info
), name
, false,
360 && (h
->root
.root
.type
== bfd_link_hash_defined
361 || h
->root
.root
.type
== bfd_link_hash_defweak
))
366 *hashp
= (struct bfd_link_hash_entry
*) h
;
368 f
= new_fixup (info
, h
, value
, ! IS_PLT_SYM (name
));
371 f
->jump
= IS_PLT_SYM (name
);
377 /* Do the usual procedure for adding a symbol. */
378 if (! _bfd_generic_link_add_one_symbol (info
, abfd
, name
, flags
, section
,
379 value
, string
, copy
, collect
,
383 /* Insert a pointer to our table in the set vector. The dynamic
384 linker requires this information */
389 /* Here we do our special thing to add the pointer to the
390 dynamic section in the SHARABLE_CONFLICTS set vector. */
391 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
393 BFD_ASSERT (s
!= NULL
);
395 if (! (_bfd_generic_link_add_one_symbol
396 (info
, linux_hash_table (info
)->dynobj
, SHARABLE_CONFLICTS
,
397 BSF_GLOBAL
| BSF_CONSTRUCTOR
, s
, 0, NULL
, false, false, NULL
)))
404 /* We will crawl the hash table and come here for every global symbol.
405 We will examine each entry and see if there are indications that we
406 need to add a fixup. There are two possible cases - one is where
407 you have duplicate definitions of PLT or GOT symbols - these will
408 have already been caught and added as "builtin" fixups. If we find
409 that the corresponding non PLT/GOT symbol is also present, we
410 convert it to a regular fixup instead.
412 This function is called via linux_link_hash_traverse. */
415 linux_tally_symbols (h
, data
)
416 struct linux_link_hash_entry
*h
;
419 struct bfd_link_info
*info
= (struct bfd_link_info
*) data
;
420 struct fixup
*f
, *f1
;
422 struct linux_link_hash_entry
*h1
, *h2
;
425 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
426 is_plt
= IS_PLT_SYM (h
->root
.root
.root
.string
);
428 if (is_plt
|| IS_GOT_SYM (h
->root
.root
.root
.string
))
430 /* Look up this symbol twice. Once just as a regular lookup,
431 and then again following all of the indirect links until we
432 reach a real symbol. */
433 h1
= linux_link_hash_lookup (linux_hash_table (info
),
434 (h
->root
.root
.root
.string
435 + sizeof PLT_REF_PREFIX
- 1),
437 /* h2 does not follow indirect symbols. */
438 h2
= linux_link_hash_lookup (linux_hash_table (info
),
439 (h
->root
.root
.root
.string
440 + sizeof PLT_REF_PREFIX
- 1),
441 false, false, false);
443 /* The real symbol must exist but if it is also an ABS symbol,
444 there is no need to have a fixup. This is because they both
445 came from the same library. If on the other hand, we had to
446 use an indirect symbol to get to the real symbol, we add the
447 fixup anyway, since there are cases where these symbols come
448 from different shared libraries */
450 && (((h1
->root
.root
.type
== bfd_link_hash_defined
451 || h1
->root
.root
.type
== bfd_link_hash_defweak
)
452 && ! bfd_is_abs_section (h1
->root
.root
.u
.def
.section
))
453 || h2
->root
.root
.type
== bfd_link_hash_indirect
))
455 /* See if there is a "builtin" fixup already present
456 involving this symbol. If so, convert it to a regular
457 fixup. In the end, this relaxes some of the requirements
458 about the order of performing fixups. */
460 for (f1
= linux_hash_table (info
)->fixup_list
;
464 if ((f1
->h
!= h
&& f1
->h
!= h1
)
465 || (! f1
->builtin
&& ! f1
->jump
))
470 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
472 f
= new_fixup (info
, h1
, f1
->h
->root
.root
.u
.def
.value
, 0);
481 && bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
483 f
= new_fixup (info
, h1
, h
->root
.root
.u
.def
.value
, 0);
486 /* FIXME: No way to return error. */
493 /* Quick and dirty way of stripping these symbols from the
495 if (bfd_is_abs_section (h
->root
.root
.u
.def
.section
))
496 h
->root
.written
= true;
502 /* This is called to set the size of the .linux-dynamic section is.
503 It is called by the Linux linker emulation before_allocation
504 routine. We have finished reading all of the input files, and now
505 we just scan the hash tables to find out how many additional fixups
509 bfd_linux_size_dynamic_sections (output_bfd
, info
)
511 struct bfd_link_info
*info
;
516 /* First find the fixups... */
517 linux_link_hash_traverse (linux_hash_table (info
),
521 /* If there are builtin fixups, leave room for a marker. This is
522 used by the dynamic linker so that it knows that all that follow
523 are builtin fixups instead of regular fixups. */
524 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
528 ++linux_hash_table (info
)->fixup_count
;
529 ++linux_hash_table (info
)->local_builtins
;
534 if (linux_hash_table (info
)->dynobj
== NULL
)
536 if (linux_hash_table (info
)->fixup_count
> 0)
541 /* Allocate memory for our fixup table. We will fill it in later. */
542 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
546 s
->_raw_size
= 8 + linux_hash_table (info
)->fixup_count
* 8;
547 s
->contents
= (bfd_byte
*) bfd_alloc (output_bfd
, s
->_raw_size
);
548 if (s
->contents
== NULL
)
550 bfd_set_error (bfd_error_no_memory
);
553 memset (s
->contents
, 0, s
->_raw_size
);
559 /* We come here once we are ready to actually write the fixup table to
560 the output file. Scan the fixup tables and so forth and generate
561 the stuff we need. */
564 linux_finish_dynamic_link (output_bfd
, info
)
566 struct bfd_link_info
*info
;
568 asection
*s
, *os
, *is
;
569 bfd_byte
*fixup_table
;
570 struct linux_link_hash_entry
*h
;
572 unsigned int new_addr
;
576 if (linux_hash_table (info
)->dynobj
== NULL
)
579 s
= bfd_get_section_by_name (linux_hash_table (info
)->dynobj
,
581 BFD_ASSERT (s
!= NULL
);
582 os
= s
->output_section
;
585 #ifdef LINUX_LINK_DEBUG
586 printf ("Fixup table file offset: %x VMA: %x\n",
587 os
->filepos
+ s
->output_offset
,
588 os
->vma
+ s
->output_offset
);
591 fixup_table
= s
->contents
;
592 bfd_put_32 (output_bfd
, linux_hash_table (info
)->fixup_count
, fixup_table
);
595 /* Fill in fixup table. */
596 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
601 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
602 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
606 "Symbol %s not defined for fixups\n",
607 f
->h
->root
.root
.root
.string
);
611 is
= f
->h
->root
.root
.u
.def
.section
;
612 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
613 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
615 #ifdef LINUX_LINK_DEBUG
616 printf ("Fixup(%d) %s: %x %x\n",f
->jump
, f
->h
->root
.root
.string
,
622 /* Relative address */
623 new_addr
= new_addr
- (f
->value
+ 5);
624 bfd_put_32 (output_bfd
, new_addr
, fixup_table
);
626 bfd_put_32 (output_bfd
, f
->value
+ 1, fixup_table
);
631 bfd_put_32 (output_bfd
, new_addr
, fixup_table
);
633 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
639 if (linux_hash_table (info
)->local_builtins
!= 0)
641 /* Special marker so we know to switch to the other type of fixup */
642 bfd_put_32 (output_bfd
, 0, fixup_table
);
644 bfd_put_32 (output_bfd
, 0, fixup_table
);
647 for (f
= linux_hash_table (info
)->fixup_list
; f
!= NULL
; f
= f
->next
)
652 if (f
->h
->root
.root
.type
!= bfd_link_hash_defined
653 && f
->h
->root
.root
.type
!= bfd_link_hash_defweak
)
657 "Symbol %s not defined for fixups\n",
658 f
->h
->root
.root
.root
.string
);
662 is
= f
->h
->root
.root
.u
.def
.section
;
663 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
664 new_addr
= f
->h
->root
.root
.u
.def
.value
+ section_offset
;
666 #ifdef LINUX_LINK_DEBUG
667 printf ("Fixup(B) %s: %x %x\n", f
->h
->root
.root
.string
,
671 bfd_put_32 (output_bfd
, new_addr
, fixup_table
);
673 bfd_put_32 (output_bfd
, f
->value
, fixup_table
);
679 if (linux_hash_table (info
)->fixup_count
!= fixups_written
)
682 fprintf (stderr
, "Warning: fixup count mismatch\n");
683 while (linux_hash_table (info
)->fixup_count
> fixups_written
)
685 bfd_put_32 (output_bfd
, 0, fixup_table
);
687 bfd_put_32 (output_bfd
, 0, fixup_table
);
693 h
= linux_link_hash_lookup (linux_hash_table (info
),
694 "__BUILTIN_FIXUPS__",
695 false, false, false);
698 && (h
->root
.root
.type
== bfd_link_hash_defined
699 || h
->root
.root
.type
== bfd_link_hash_defweak
))
701 is
= h
->root
.root
.u
.def
.section
;
702 section_offset
= is
->output_section
->vma
+ is
->output_offset
;
703 new_addr
= h
->root
.root
.u
.def
.value
+ section_offset
;
705 #ifdef LINUX_LINK_DEBUG
706 printf ("Builtin fixup table at %x\n", new_addr
);
709 bfd_put_32 (output_bfd
, new_addr
, fixup_table
);
712 bfd_put_32 (output_bfd
, 0, fixup_table
);
714 if (bfd_seek (output_bfd
, os
->filepos
+ s
->output_offset
, SEEK_SET
) != 0)
717 if (bfd_write ((PTR
) s
->contents
, 1, s
->_raw_size
, output_bfd
)
724 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
725 #define MY_add_one_symbol linux_add_one_symbol
726 #define MY_finish_dynamic_link linux_finish_dynamic_link
728 #define MY_zmagic_contiguous 1
730 #include "aout-target.h"