1 /* BFD back-end for linux flavored i386 a.out binaries.
2 Copyright (C) 1992, 1993, 1994, 1995 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
20 #define TARGET_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 extern const bfd_target MY(vec);
41 /* We always generate QMAGIC files in preference to ZMAGIC files. It
42 would be possible to make this a linker option, if that ever
45 static void MY_final_link_callback
46 PARAMS ((bfd *, file_ptr *, file_ptr *, file_ptr *));
49 i386linux_bfd_final_link (abfd, info)
51 struct bfd_link_info *info;
53 obj_aout_subformat (abfd) = q_magic_format;
54 return NAME(aout,final_link) (abfd, info, MY_final_link_callback);
57 #define MY_bfd_final_link i386linux_bfd_final_link
59 /* Set the machine type correctly. */
62 i386linux_write_object_contents (abfd)
65 struct external_exec exec_bytes;
66 struct internal_exec *execp = exec_hdr (abfd);
68 N_SET_MACHTYPE (*execp, M_386);
70 obj_reloc_entry_size (abfd) = RELOC_STD_SIZE;
72 WRITE_HEADERS(abfd, execp);
77 #define MY_write_object_contents i386linux_write_object_contents
79 /* Code to link against Linux a.out shared libraries. */
81 /* See if a symbol name is a reference to the global offset table. */
83 #ifndef GOT_REF_PREFIX
84 #define GOT_REF_PREFIX "__GOT_"
87 #define IS_GOT_SYM(name) \
88 (strncmp (name, GOT_REF_PREFIX, sizeof GOT_REF_PREFIX - 1) == 0)
90 /* See if a symbol name is a reference to the procedure linkage table. */
92 #ifndef PLT_REF_PREFIX
93 #define PLT_REF_PREFIX "__PLT_"
96 #define IS_PLT_SYM(name) \
97 (strncmp (name, PLT_REF_PREFIX, sizeof PLT_REF_PREFIX - 1) == 0)
99 /* This string is used to generate specialized error messages. */
102 #define NEEDS_SHRLIB "__NEEDS_SHRLIB_"
105 /* This special symbol is a set vector that contains a list of
106 pointers to fixup tables. It will be present in any dynamicly
107 linked file. The linker generated fixup table should also be added
108 to the list, and it should always appear in the second slot (the
109 first one is a dummy with a magic number that is defined in
112 #ifndef SHARABLE_CONFLICTS
113 #define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
116 /* We keep a list of fixups. The terminology is a bit strange, but
117 each fixup contains two 32 bit numbers. A regular fixup contains
118 an address and a pointer, and at runtime we should store the
119 address at the location pointed to by the pointer. A builtin fixup
120 contains two pointers, and we should read the address using one
121 pointer and store it at the location pointed to by the other
122 pointer. Builtin fixups come into play when we have duplicate
123 __GOT__ symbols for the same variable. The builtin fixup will copy
124 the GOT pointer from one over into the other. */
129 struct linux_link_hash_entry *h;
132 /* Nonzero if this is a jump instruction that needs to be fixed,
133 zero if this is just a pointer */
139 /* We don't need a special hash table entry structure, but we do need
140 to keep some information between linker passes, so we use a special
143 struct linux_link_hash_entry
145 struct aout_link_hash_entry root;
148 struct linux_link_hash_table
150 struct aout_link_hash_table root;
152 /* First dynamic object found in link. */
155 /* Number of fixups. */
158 /* Number of builtin fixups. */
159 size_t local_builtins;
161 /* List of fixups. */
162 struct fixup *fixup_list;
165 static struct bfd_hash_entry *linux_link_hash_newfunc
166 PARAMS ((struct bfd_hash_entry *, struct bfd_hash_table *, const char *));
167 static struct bfd_link_hash_table *linux_link_hash_table_create
169 static struct fixup *new_fixup
170 PARAMS ((struct bfd_link_info *, struct linux_link_hash_entry *,
172 static boolean linux_link_create_dynamic_sections
173 PARAMS ((bfd *, struct bfd_link_info *));
174 static boolean linux_add_one_symbol
175 PARAMS ((struct bfd_link_info *, bfd *, const char *, flagword, asection *,
176 bfd_vma, const char *, boolean, boolean,
177 struct bfd_link_hash_entry **));
178 static boolean linux_tally_symbols
179 PARAMS ((struct linux_link_hash_entry *, PTR));
180 static boolean linux_finish_dynamic_link
181 PARAMS ((bfd *, struct bfd_link_info *));
183 /* Routine to create an entry in an Linux link hash table. */
185 static struct bfd_hash_entry *
186 linux_link_hash_newfunc (entry, table, string)
187 struct bfd_hash_entry *entry;
188 struct bfd_hash_table *table;
191 struct linux_link_hash_entry *ret = (struct linux_link_hash_entry *) entry;
193 /* Allocate the structure if it has not already been allocated by a
195 if (ret == (struct linux_link_hash_entry *) NULL)
196 ret = ((struct linux_link_hash_entry *)
197 bfd_hash_allocate (table, sizeof (struct linux_link_hash_entry)));
199 return (struct bfd_hash_entry *) ret;
201 /* Call the allocation method of the superclass. */
202 ret = ((struct linux_link_hash_entry *)
203 NAME(aout,link_hash_newfunc) ((struct bfd_hash_entry *) ret,
207 /* Set local fields; there aren't any. */
210 return (struct bfd_hash_entry *) ret;
213 /* Create a Linux link hash table. */
215 static struct bfd_link_hash_table *
216 linux_link_hash_table_create (abfd)
219 struct linux_link_hash_table *ret;
221 ret = ((struct linux_link_hash_table *)
222 bfd_alloc (abfd, sizeof (struct linux_link_hash_table)));
223 if (ret == (struct linux_link_hash_table *) NULL)
224 return (struct bfd_link_hash_table *) NULL;
225 if (! NAME(aout,link_hash_table_init) (&ret->root, abfd,
226 linux_link_hash_newfunc))
229 return (struct bfd_link_hash_table *) NULL;
233 ret->fixup_count = 0;
234 ret->local_builtins = 0;
235 ret->fixup_list = NULL;
237 return &ret->root.root;
240 /* Look up an entry in a Linux link hash table. */
242 #define linux_link_hash_lookup(table, string, create, copy, follow) \
243 ((struct linux_link_hash_entry *) \
244 aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
247 /* Traverse a Linux link hash table. */
249 #define linux_link_hash_traverse(table, func, info) \
250 (aout_link_hash_traverse \
252 (boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func), \
255 /* Get the Linux link hash table from the info structure. This is
258 #define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
260 /* Store the information for a new fixup. */
262 static struct fixup *
263 new_fixup (info, h, value, builtin)
264 struct bfd_link_info *info;
265 struct linux_link_hash_entry *h;
271 f = (struct fixup *) bfd_hash_allocate (&info->hash->table,
272 sizeof (struct fixup));
275 f->next = linux_hash_table (info)->fixup_list;
276 linux_hash_table (info)->fixup_list = f;
279 f->builtin = builtin;
281 ++linux_hash_table (info)->fixup_count;
285 /* We come here once we realize that we are going to link to a shared
286 library. We need to create a special section that contains the
287 fixup table, and we ultimately need to add a pointer to this into
288 the set vector for SHARABLE_CONFLICTS. At this point we do not
289 know the size of the section, but that's OK - we just need to
290 create it for now. */
293 linux_link_create_dynamic_sections (abfd, info)
295 struct bfd_link_info *info;
298 register asection *s;
300 /* Note that we set the SEC_IN_MEMORY flag. */
301 flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY;
303 /* We choose to use the name ".linux-dynamic" for the fixup table.
305 s = bfd_make_section (abfd, ".linux-dynamic");
307 || ! bfd_set_section_flags (abfd, s, flags)
308 || ! bfd_set_section_alignment (abfd, s, 2))
316 /* Function to add a single symbol to the linker hash table. This is
317 a wrapper around _bfd_generic_link_add_one_symbol which handles the
318 tweaking needed for dynamic linking support. */
321 linux_add_one_symbol (info, abfd, name, flags, section, value, string,
322 copy, collect, hashp)
323 struct bfd_link_info *info;
332 struct bfd_link_hash_entry **hashp;
334 struct linux_link_hash_entry *h;
337 /* Look up and see if we already have this symbol in the hash table.
338 If we do, and the defining entry is from a shared library, we
339 need to create the dynamic sections.
341 FIXME: What if abfd->xvec != info->hash->creator? We may want to
342 be able to link Linux a.out and ELF objects together, but serious
343 confusion is possible. */
347 if (! info->relocateable
348 && linux_hash_table (info)->dynobj == NULL
349 && strcmp (name, SHARABLE_CONFLICTS) == 0
350 && (flags & BSF_CONSTRUCTOR) != 0
351 && abfd->xvec == info->hash->creator)
353 if (! linux_link_create_dynamic_sections (abfd, info))
355 linux_hash_table (info)->dynobj = abfd;
359 if (bfd_is_abs_section (section)
360 && abfd->xvec == info->hash->creator)
362 h = linux_link_hash_lookup (linux_hash_table (info), name, false,
365 && (h->root.root.type == bfd_link_hash_defined
366 || h->root.root.type == bfd_link_hash_defweak))
371 *hashp = (struct bfd_link_hash_entry *) h;
373 f = new_fixup (info, h, value, ! IS_PLT_SYM (name));
376 f->jump = IS_PLT_SYM (name);
382 /* Do the usual procedure for adding a symbol. */
383 if (! _bfd_generic_link_add_one_symbol (info, abfd, name, flags, section,
384 value, string, copy, collect,
388 /* Insert a pointer to our table in the set vector. The dynamic
389 linker requires this information */
394 /* Here we do our special thing to add the pointer to the
395 dynamic section in the SHARABLE_CONFLICTS set vector. */
396 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
398 BFD_ASSERT (s != NULL);
400 if (! (_bfd_generic_link_add_one_symbol
401 (info, linux_hash_table (info)->dynobj, SHARABLE_CONFLICTS,
402 BSF_GLOBAL | BSF_CONSTRUCTOR, s, 0, NULL, false, false, NULL)))
409 /* We will crawl the hash table and come here for every global symbol.
410 We will examine each entry and see if there are indications that we
411 need to add a fixup. There are two possible cases - one is where
412 you have duplicate definitions of PLT or GOT symbols - these will
413 have already been caught and added as "builtin" fixups. If we find
414 that the corresponding non PLT/GOT symbol is also present, we
415 convert it to a regular fixup instead.
417 This function is called via linux_link_hash_traverse. */
420 linux_tally_symbols (h, data)
421 struct linux_link_hash_entry *h;
424 struct bfd_link_info *info = (struct bfd_link_info *) data;
425 struct fixup *f, *f1;
427 struct linux_link_hash_entry *h1, *h2;
430 if (h->root.root.type == bfd_link_hash_undefined
431 && strncmp (h->root.root.root.string, NEEDS_SHRLIB,
432 sizeof NEEDS_SHRLIB - 1) == 0)
438 name = h->root.root.root.string + sizeof NEEDS_SHRLIB - 1;
439 p = strrchr (name, '_');
441 alloc = (char *) malloc (strlen (name) + 1);
443 if (p == NULL || alloc == NULL)
444 (*_bfd_error_handler) ("Output file requires shared library `%s'\n",
448 strcpy (alloc, name);
449 p = strrchr (alloc, '_');
451 (*_bfd_error_handler)
452 ("Output file requires shared library `%s.so.%s'\n",
460 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
461 is_plt = IS_PLT_SYM (h->root.root.root.string);
463 if (is_plt || IS_GOT_SYM (h->root.root.root.string))
465 /* Look up this symbol twice. Once just as a regular lookup,
466 and then again following all of the indirect links until we
467 reach a real symbol. */
468 h1 = linux_link_hash_lookup (linux_hash_table (info),
469 (h->root.root.root.string
470 + sizeof PLT_REF_PREFIX - 1),
472 /* h2 does not follow indirect symbols. */
473 h2 = linux_link_hash_lookup (linux_hash_table (info),
474 (h->root.root.root.string
475 + sizeof PLT_REF_PREFIX - 1),
476 false, false, false);
478 /* The real symbol must exist but if it is also an ABS symbol,
479 there is no need to have a fixup. This is because they both
480 came from the same library. If on the other hand, we had to
481 use an indirect symbol to get to the real symbol, we add the
482 fixup anyway, since there are cases where these symbols come
483 from different shared libraries */
485 && (((h1->root.root.type == bfd_link_hash_defined
486 || h1->root.root.type == bfd_link_hash_defweak)
487 && ! bfd_is_abs_section (h1->root.root.u.def.section))
488 || h2->root.root.type == bfd_link_hash_indirect))
490 /* See if there is a "builtin" fixup already present
491 involving this symbol. If so, convert it to a regular
492 fixup. In the end, this relaxes some of the requirements
493 about the order of performing fixups. */
495 for (f1 = linux_hash_table (info)->fixup_list;
499 if ((f1->h != h && f1->h != h1)
500 || (! f1->builtin && ! f1->jump))
505 && bfd_is_abs_section (h->root.root.u.def.section))
507 f = new_fixup (info, h1, f1->h->root.root.u.def.value, 0);
516 && bfd_is_abs_section (h->root.root.u.def.section))
518 f = new_fixup (info, h1, h->root.root.u.def.value, 0);
521 /* FIXME: No way to return error. */
528 /* Quick and dirty way of stripping these symbols from the
530 if (bfd_is_abs_section (h->root.root.u.def.section))
531 h->root.written = true;
537 /* This is called to set the size of the .linux-dynamic section is.
538 It is called by the Linux linker emulation before_allocation
539 routine. We have finished reading all of the input files, and now
540 we just scan the hash tables to find out how many additional fixups
544 bfd_linux_size_dynamic_sections (output_bfd, info)
546 struct bfd_link_info *info;
551 if (output_bfd->xvec != &MY(vec))
554 /* First find the fixups... */
555 linux_link_hash_traverse (linux_hash_table (info),
559 /* If there are builtin fixups, leave room for a marker. This is
560 used by the dynamic linker so that it knows that all that follow
561 are builtin fixups instead of regular fixups. */
562 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
566 ++linux_hash_table (info)->fixup_count;
567 ++linux_hash_table (info)->local_builtins;
572 if (linux_hash_table (info)->dynobj == NULL)
574 if (linux_hash_table (info)->fixup_count > 0)
579 /* Allocate memory for our fixup table. We will fill it in later. */
580 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
584 s->_raw_size = 8 + linux_hash_table (info)->fixup_count * 8;
585 s->contents = (bfd_byte *) bfd_alloc (output_bfd, s->_raw_size);
586 if (s->contents == NULL)
588 memset (s->contents, 0, (size_t) s->_raw_size);
594 /* We come here once we are ready to actually write the fixup table to
595 the output file. Scan the fixup tables and so forth and generate
596 the stuff we need. */
599 linux_finish_dynamic_link (output_bfd, info)
601 struct bfd_link_info *info;
603 asection *s, *os, *is;
604 bfd_byte *fixup_table;
605 struct linux_link_hash_entry *h;
607 unsigned int new_addr;
609 unsigned int fixups_written;
611 if (linux_hash_table (info)->dynobj == NULL)
614 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
616 BFD_ASSERT (s != NULL);
617 os = s->output_section;
620 #ifdef LINUX_LINK_DEBUG
621 printf ("Fixup table file offset: %x VMA: %x\n",
622 os->filepos + s->output_offset,
623 os->vma + s->output_offset);
626 fixup_table = s->contents;
627 bfd_put_32 (output_bfd, linux_hash_table (info)->fixup_count, fixup_table);
630 /* Fill in fixup table. */
631 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
636 if (f->h->root.root.type != bfd_link_hash_defined
637 && f->h->root.root.type != bfd_link_hash_defweak)
639 (*_bfd_error_handler)
640 ("Symbol %s not defined for fixups\n",
641 f->h->root.root.root.string);
645 is = f->h->root.root.u.def.section;
646 section_offset = is->output_section->vma + is->output_offset;
647 new_addr = f->h->root.root.u.def.value + section_offset;
649 #ifdef LINUX_LINK_DEBUG
650 printf ("Fixup(%d) %s: %x %x\n",f->jump, f->h->root.root.string,
656 /* Relative address */
657 new_addr = new_addr - (f->value + 5);
658 bfd_put_32 (output_bfd, new_addr, fixup_table);
660 bfd_put_32 (output_bfd, f->value + 1, fixup_table);
665 bfd_put_32 (output_bfd, new_addr, fixup_table);
667 bfd_put_32 (output_bfd, f->value, fixup_table);
673 if (linux_hash_table (info)->local_builtins != 0)
675 /* Special marker so we know to switch to the other type of fixup */
676 bfd_put_32 (output_bfd, 0, fixup_table);
678 bfd_put_32 (output_bfd, 0, fixup_table);
681 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
686 if (f->h->root.root.type != bfd_link_hash_defined
687 && f->h->root.root.type != bfd_link_hash_defweak)
689 (*_bfd_error_handler)
690 ("Symbol %s not defined for fixups\n",
691 f->h->root.root.root.string);
695 is = f->h->root.root.u.def.section;
696 section_offset = is->output_section->vma + is->output_offset;
697 new_addr = f->h->root.root.u.def.value + section_offset;
699 #ifdef LINUX_LINK_DEBUG
700 printf ("Fixup(B) %s: %x %x\n", f->h->root.root.string,
704 bfd_put_32 (output_bfd, new_addr, fixup_table);
706 bfd_put_32 (output_bfd, f->value, fixup_table);
712 if (linux_hash_table (info)->fixup_count != fixups_written)
714 (*_bfd_error_handler) ("Warning: fixup count mismatch\n");
715 while (linux_hash_table (info)->fixup_count > fixups_written)
717 bfd_put_32 (output_bfd, 0, fixup_table);
719 bfd_put_32 (output_bfd, 0, fixup_table);
725 h = linux_link_hash_lookup (linux_hash_table (info),
726 "__BUILTIN_FIXUPS__",
727 false, false, false);
730 && (h->root.root.type == bfd_link_hash_defined
731 || h->root.root.type == bfd_link_hash_defweak))
733 is = h->root.root.u.def.section;
734 section_offset = is->output_section->vma + is->output_offset;
735 new_addr = h->root.root.u.def.value + section_offset;
737 #ifdef LINUX_LINK_DEBUG
738 printf ("Builtin fixup table at %x\n", new_addr);
741 bfd_put_32 (output_bfd, new_addr, fixup_table);
744 bfd_put_32 (output_bfd, 0, fixup_table);
746 if (bfd_seek (output_bfd, os->filepos + s->output_offset, SEEK_SET) != 0)
749 if (bfd_write ((PTR) s->contents, 1, s->_raw_size, output_bfd)
756 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
757 #define MY_add_one_symbol linux_add_one_symbol
758 #define MY_finish_dynamic_link linux_finish_dynamic_link
760 #define MY_zmagic_contiguous 1
762 #include "aout-target.h"