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)
347 if (! linux_link_create_dynamic_sections (abfd, info))
349 linux_hash_table (info)->dynobj = abfd;
353 if (bfd_is_abs_section (section)
354 && (IS_GOT_SYM (name) || IS_PLT_SYM (name)))
356 h = linux_link_hash_lookup (linux_hash_table (info), name, false,
359 && h->root.root.type == bfd_link_hash_defined)
364 *hashp = (struct bfd_link_hash_entry *) h;
366 f = new_fixup (info, h, value, ! IS_PLT_SYM (name));
369 f->jump = IS_PLT_SYM (name);
375 /* Do the usual procedure for adding a symbol. */
376 if (! _bfd_generic_link_add_one_symbol (info, abfd, name, flags, section,
377 value, string, copy, collect,
381 /* Insert a pointer to our table in the set vector. The dynamic
382 linker requires this information */
387 /* Here we do our special thing to add the pointer to the
388 dynamic section in the SHARABLE_CONFLICTS set vector. */
389 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
391 BFD_ASSERT (s != NULL);
393 if (! (_bfd_generic_link_add_one_symbol
394 (info, linux_hash_table (info)->dynobj, SHARABLE_CONFLICTS,
395 BSF_GLOBAL | BSF_CONSTRUCTOR, s, 0, NULL, false, false, NULL)))
402 /* We will crawl the hash table and come here for every global symbol.
403 We will examine each entry and see if there are indications that we
404 need to add a fixup. There are two possible cases - one is where
405 you have duplicate definitions of PLT or GOT symbols - these will
406 have already been caught and added as "builtin" fixups. If we find
407 that the corresponding non PLT/GOT symbol is also present, we
408 convert it to a regular fixup instead.
410 This function is called via linux_link_hash_traverse. */
413 linux_tally_symbols (h, data)
414 struct linux_link_hash_entry *h;
417 struct bfd_link_info *info = (struct bfd_link_info *) data;
418 struct fixup *f, *f1;
420 struct linux_link_hash_entry *h1, *h2;
423 /* If this symbol is not a PLT/GOT, we do not even need to look at it */
424 is_plt = IS_PLT_SYM (h->root.root.root.string);
426 if (is_plt || IS_GOT_SYM (h->root.root.root.string))
428 /* Look up this symbol twice. Once just as a regular lookup,
429 and then again following all of the indirect links until we
430 reach a real symbol. */
431 h1 = linux_link_hash_lookup (linux_hash_table (info),
432 (h->root.root.root.string
433 + sizeof PLT_REF_PREFIX - 1),
435 /* h2 does not follow indirect symbols. */
436 h2 = linux_link_hash_lookup (linux_hash_table (info),
437 (h->root.root.root.string
438 + sizeof PLT_REF_PREFIX - 1),
439 false, false, false);
441 /* The real symbol must exist but if it is also an ABS symbol,
442 there is no need to have a fixup. This is because they both
443 came from the same library. If on the other hand, we had to
444 use an indirect symbol to get to the real symbol, we add the
445 fixup anyway, since there are cases where these symbols come
446 from different shared libraries */
448 && ((h1->root.root.type == bfd_link_hash_defined
449 && ! bfd_is_abs_section (h1->root.root.u.def.section))
450 || h2->root.root.type == bfd_link_hash_indirect))
452 /* See if there is a "builtin" fixup already present
453 involving this symbol. If so, convert it to a regular
454 fixup. In the end, this relaxes some of the requirements
455 about the order of performing fixups. */
457 for (f1 = linux_hash_table (info)->fixup_list;
462 || (! f1->builtin && ! f1->jump))
465 && bfd_is_abs_section (h->root.root.u.def.section))
467 f = new_fixup (info, h1, f1->h->root.root.u.def.value, 0);
476 && bfd_is_abs_section (h->root.root.u.def.section))
478 f = new_fixup (info, h1, h->root.root.u.def.value, 0);
481 /* FIXME: No way to return error. */
488 /* Quick and dirty way of stripping these symbols from the
490 if (bfd_is_abs_section (h->root.root.u.def.section))
491 h->root.written = true;
497 /* This is called to set the size of the .linux-dynamic section is.
498 It is called by the Linux linker emulation before_allocation
499 routine. We have finished reading all of the input files, and now
500 we just scan the hash tables to find out how many additional fixups
504 bfd_linux_size_dynamic_sections (output_bfd, info)
506 struct bfd_link_info *info;
511 /* First find the fixups... */
512 linux_link_hash_traverse (linux_hash_table (info),
516 /* If there are builtin fixups, leave room for a marker. This is
517 used by the dynamic linker so that it knows that all that follow
518 are builtin fixups instead of regular fixups. */
519 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
523 ++linux_hash_table (info)->fixup_count;
524 ++linux_hash_table (info)->local_builtins;
529 if (linux_hash_table (info)->dynobj == NULL)
531 if (linux_hash_table (info)->fixup_count > 0)
536 /* Allocate memory for our fixup table. We will fill it in later. */
537 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
541 s->_raw_size = 8 + linux_hash_table (info)->fixup_count * 8;
542 s->contents = (bfd_byte *) bfd_alloc (output_bfd, s->_raw_size);
543 if (s->contents == NULL)
545 bfd_set_error (bfd_error_no_memory);
548 memset (s->contents, 0, s->_raw_size);
554 /* We come here once we are ready to actually write the fixup table to
555 the output file. Scan the fixup tables and so forth and generate
556 the stuff we need. */
559 linux_finish_dynamic_link (output_bfd, info)
561 struct bfd_link_info *info;
563 asection *s, *os, *is;
564 bfd_byte *fixup_table;
565 struct linux_link_hash_entry *h;
567 unsigned int new_addr;
571 if (linux_hash_table (info)->dynobj == NULL)
574 s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
576 BFD_ASSERT (s != NULL);
577 os = s->output_section;
580 #ifdef LINUX_LINK_DEBUG
581 printf ("Fixup table file offset: %x VMA: %x\n",
582 os->filepos + s->output_offset,
583 os->vma + s->output_offset);
586 fixup_table = s->contents;
587 bfd_put_32 (output_bfd, linux_hash_table (info)->fixup_count, fixup_table);
590 /* Fill in fixup table. */
591 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
596 if (f->h->root.root.type != bfd_link_hash_defined)
600 "Symbol %s not defined for fixups\n",
601 f->h->root.root.root.string);
605 is = f->h->root.root.u.def.section;
606 section_offset = is->output_section->vma + is->output_offset;
607 new_addr = f->h->root.root.u.def.value + section_offset;
609 #ifdef LINUX_LINK_DEBUG
610 printf ("Fixup(%d) %s: %x %x\n",f->jump, f->h->root.root.string,
616 /* Relative address */
617 new_addr = new_addr - (f->value + 5);
618 bfd_put_32 (output_bfd, new_addr, fixup_table);
620 bfd_put_32 (output_bfd, f->value + 1, fixup_table);
625 bfd_put_32 (output_bfd, new_addr, fixup_table);
627 bfd_put_32 (output_bfd, f->value, fixup_table);
633 if (linux_hash_table (info)->local_builtins != 0)
635 /* Special marker so we know to switch to the other type of fixup */
636 bfd_put_32 (output_bfd, 0, fixup_table);
638 bfd_put_32 (output_bfd, 0, fixup_table);
641 for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
646 if (f->h->root.root.type != bfd_link_hash_defined)
650 "Symbol %s not defined for fixups\n",
651 f->h->root.root.root.string);
655 is = f->h->root.root.u.def.section;
656 section_offset = is->output_section->vma + is->output_offset;
657 new_addr = f->h->root.root.u.def.value + section_offset;
659 #ifdef LINUX_LINK_DEBUG
660 printf ("Fixup(B) %s: %x %x\n", f->h->root.root.string,
664 bfd_put_32 (output_bfd, new_addr, fixup_table);
666 bfd_put_32 (output_bfd, f->value, fixup_table);
672 if (linux_hash_table (info)->fixup_count != fixups_written)
675 fprintf (stderr, "Warning: fixup count mismatch\n");
676 while (linux_hash_table (info)->fixup_count > fixups_written)
678 bfd_put_32 (output_bfd, 0, fixup_table);
680 bfd_put_32 (output_bfd, 0, fixup_table);
686 h = linux_link_hash_lookup (linux_hash_table (info),
687 "__BUILTIN_FIXUPS__",
688 false, false, false);
690 if (h != NULL && h->root.root.type == bfd_link_hash_defined)
692 is = h->root.root.u.def.section;
693 section_offset = is->output_section->vma + is->output_offset;
694 new_addr = h->root.root.u.def.value + section_offset;
696 #ifdef LINUX_LINK_DEBUG
697 printf ("Builtin fixup table at %x\n", new_addr);
700 bfd_put_32 (output_bfd, new_addr, fixup_table);
703 bfd_put_32 (output_bfd, 0, fixup_table);
705 if (bfd_seek (output_bfd, os->filepos + s->output_offset, SEEK_SET) != 0)
708 if (bfd_write ((PTR) s->contents, 1, s->_raw_size, output_bfd)
715 #define MY_bfd_link_hash_table_create linux_link_hash_table_create
716 #define MY_add_one_symbol linux_add_one_symbol
717 #define MY_finish_dynamic_link linux_finish_dynamic_link
719 #define MY_zmagic_contiguous 1
721 #include "aout-target.h"