1/* VxWorks support for ELF
2   Copyright 2005, 2006, 2007, 2009 Free Software Foundation, Inc.
3
4   This file is part of BFD, the Binary File Descriptor library.
5
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 3 of the License, or
9   (at your option) any later version.
10
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.
15
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,
19   MA 02111-1307, USA.  */
20
21/* This file provides routines used by all VxWorks targets.  */
22
23#include "sysdep.h"
24#include "bfd.h"
25#include "libbfd.h"
26#include "elf-bfd.h"
27#include "elf-vxworks.h"
28#include "elf/vxworks.h"
29
30/* Return true if symbol NAME, as defined by ABFD, is one of the special
31   __GOTT_BASE__ or __GOTT_INDEX__ symbols.  */
32
33static bfd_boolean
34elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
35{
36  char leading;
37
38  leading = bfd_get_symbol_leading_char (abfd);
39  if (leading)
40    {
41      if (*name != leading)
42	return FALSE;
43      name++;
44    }
45  return (strcmp (name, "__GOTT_BASE__") == 0
46	  || strcmp (name, "__GOTT_INDEX__") == 0);
47}
48
49/* Tweak magic VxWorks symbols as they are loaded.  */
50bfd_boolean
51elf_vxworks_add_symbol_hook (bfd *abfd,
52			     struct bfd_link_info *info,
53			     Elf_Internal_Sym *sym,
54			     const char **namep,
55			     flagword *flagsp,
56			     asection **secp ATTRIBUTE_UNUSED,
57			     bfd_vma *valp ATTRIBUTE_UNUSED)
58{
59  /* Ideally these "magic" symbols would be exported by libc.so.1
60     which would be found via a DT_NEEDED tag, and then handled
61     specially by the linker at runtime.  Except shared libraries
62     don't even link to libc.so.1 by default...
63     If the symbol is imported from, or will be put in a shared library,
64     give the symbol weak binding to get the desired samantics.
65     This transformation will be undone in
66     elf_i386_vxworks_link_output_symbol_hook. */
67  if ((info->shared || abfd->flags & DYNAMIC)
68      && elf_vxworks_gott_symbol_p (abfd, *namep))
69    {
70      sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
71      *flagsp |= BSF_WEAK;
72    }
73
74  return TRUE;
75}
76
77/* Perform VxWorks-specific handling of the create_dynamic_sections hook.
78   When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
79   section.  */
80
81bfd_boolean
82elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
83				     asection **srelplt2_out)
84{
85  struct elf_link_hash_table *htab;
86  const struct elf_backend_data *bed;
87  asection *s;
88
89  htab = elf_hash_table (info);
90  bed = get_elf_backend_data (dynobj);
91
92  if (!info->shared)
93    {
94      s = bfd_make_section_with_flags (dynobj,
95				       bed->default_use_rela_p
96				       ? ".rela.plt.unloaded"
97				       : ".rel.plt.unloaded",
98				       SEC_HAS_CONTENTS | SEC_IN_MEMORY
99				       | SEC_READONLY | SEC_LINKER_CREATED);
100      if (s == NULL
101	  || !bfd_set_section_alignment (dynobj, s, bed->s->log_file_align))
102	return FALSE;
103
104      *srelplt2_out = s;
105    }
106
107  /* Mark the GOT and PLT symbols as having relocations; they might
108     not, but we won't know for sure until we build the GOT in
109     finish_dynamic_symbol.  Also make sure that the GOT symbol
110     is entered into the dynamic symbol table; the loader uses it
111     to initialize __GOTT_BASE__[__GOTT_INDEX__].  */
112  if (htab->hgot)
113    {
114      htab->hgot->indx = -2;
115      htab->hgot->other &= ~ELF_ST_VISIBILITY (-1);
116      htab->hgot->forced_local = 0;
117      if (!bfd_elf_link_record_dynamic_symbol (info, htab->hgot))
118	return FALSE;
119    }
120  if (htab->hplt)
121    {
122      htab->hplt->indx = -2;
123      htab->hplt->type = STT_FUNC;
124    }
125
126  return TRUE;
127}
128
129/* Tweak magic VxWorks symbols as they are written to the output file.  */
130int
131elf_vxworks_link_output_symbol_hook (struct bfd_link_info *info
132				       ATTRIBUTE_UNUSED,
133				     const char *name,
134				     Elf_Internal_Sym *sym,
135				     asection *input_sec ATTRIBUTE_UNUSED,
136				     struct elf_link_hash_entry *h)
137{
138  /* Reverse the effects of the hack in elf_vxworks_add_symbol_hook.  */
139  if (h
140      && h->root.type == bfd_link_hash_undefweak
141      && elf_vxworks_gott_symbol_p (h->root.u.undef.abfd, name))
142    sym->st_info = ELF_ST_INFO (STB_GLOBAL, ELF_ST_TYPE (sym->st_info));
143
144  return 1;
145}
146
147/* Copy relocations into the output file.  Fixes up relocations against PLT
148   entries, then calls the generic routine.  */
149
150bfd_boolean
151elf_vxworks_emit_relocs (bfd *output_bfd,
152			 asection *input_section,
153			 Elf_Internal_Shdr *input_rel_hdr,
154			 Elf_Internal_Rela *internal_relocs,
155			 struct elf_link_hash_entry **rel_hash)
156{
157  const struct elf_backend_data *bed;
158  int j;
159
160  bed = get_elf_backend_data (output_bfd);
161
162  if (output_bfd->flags & (DYNAMIC|EXEC_P))
163    {
164      Elf_Internal_Rela *irela;
165      Elf_Internal_Rela *irelaend;
166      struct elf_link_hash_entry **hash_ptr;
167
168      for (irela = internal_relocs,
169	     irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
170				 * bed->s->int_rels_per_ext_rel),
171	     hash_ptr = rel_hash;
172	   irela < irelaend;
173	   irela += bed->s->int_rels_per_ext_rel,
174	     hash_ptr++)
175	{
176	  if (*hash_ptr
177	      && (*hash_ptr)->def_dynamic
178	      && !(*hash_ptr)->def_regular
179	      && ((*hash_ptr)->root.type == bfd_link_hash_defined
180		  || (*hash_ptr)->root.type == bfd_link_hash_defweak)
181	      && (*hash_ptr)->root.u.def.section->output_section != NULL)
182	    {
183	      /* This is a relocation from an executable or shared
184	         library against a symbol in a different shared
185	         library.  We are creating a definition in the output
186	         file but it does not come from any of our normal (.o)
187	         files. ie. a PLT stub.  Normally this would be a
188	         relocation against against SHN_UNDEF with the VMA of
189	         the PLT stub.  This upsets the VxWorks loader.
190	         Convert it to a section-relative relocation.  This
191	         gets some other symbols (for instance .dynbss), but
192	         is conservatively correct.  */
193	      for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
194		{
195		  asection *sec = (*hash_ptr)->root.u.def.section;
196		  int this_idx = sec->output_section->target_index;
197
198		  irela[j].r_info
199		    = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info));
200		  irela[j].r_addend += (*hash_ptr)->root.u.def.value;
201		  irela[j].r_addend += sec->output_offset;
202		}
203	      /* Stop the generic routine adjusting this entry.  */
204	      *hash_ptr = NULL;
205	    }
206	}
207    }
208  return _bfd_elf_link_output_relocs (output_bfd, input_section,
209				      input_rel_hdr, internal_relocs,
210				      rel_hash);
211}
212
213
214/* Set the sh_link and sh_info fields on the static plt relocation secton.  */
215
216void
217elf_vxworks_final_write_processing (bfd *abfd,
218				    bfd_boolean linker ATTRIBUTE_UNUSED)
219{
220  asection * sec;
221  struct bfd_elf_section_data *d;
222
223  sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
224  if (!sec)
225    sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
226  if (!sec)
227    return;
228  d = elf_section_data (sec);
229  d->this_hdr.sh_link = elf_tdata (abfd)->symtab_section;
230  sec = bfd_get_section_by_name (abfd, ".plt");
231  if (sec)
232    d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
233}
234
235/* Add the dynamic entries required by VxWorks.  These point to the
236   tls sections.  */
237
238bfd_boolean
239elf_vxworks_add_dynamic_entries (bfd *output_bfd, struct bfd_link_info *info)
240{
241  if (bfd_get_section_by_name (output_bfd, ".tls_data"))
242    {
243      if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_START, 0)
244	  || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_SIZE, 0)
245	  || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_ALIGN, 0))
246	return FALSE;
247    }
248  if (bfd_get_section_by_name (output_bfd, ".tls_vars"))
249    {
250      if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_START, 0)
251	  || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_SIZE, 0))
252	return FALSE;
253    }
254  return TRUE;
255}
256
257/* If *DYN is one of the VxWorks-specific dynamic entries, then fill
258   in the value now  and return TRUE.  Otherwise return FALSE.  */
259
260bfd_boolean
261elf_vxworks_finish_dynamic_entry (bfd *output_bfd, Elf_Internal_Dyn *dyn)
262{
263  asection *sec;
264
265  switch (dyn->d_tag)
266    {
267    default:
268      return FALSE;
269
270    case DT_VX_WRS_TLS_DATA_START:
271      sec = bfd_get_section_by_name (output_bfd, ".tls_data");
272      dyn->d_un.d_ptr = sec->vma;
273      break;
274
275    case DT_VX_WRS_TLS_DATA_SIZE:
276      sec = bfd_get_section_by_name (output_bfd, ".tls_data");
277      dyn->d_un.d_val = sec->size;
278      break;
279
280    case DT_VX_WRS_TLS_DATA_ALIGN:
281      sec = bfd_get_section_by_name (output_bfd, ".tls_data");
282      dyn->d_un.d_val
283	= (bfd_size_type)1 << bfd_get_section_alignment (abfd, sec);
284      break;
285
286    case DT_VX_WRS_TLS_VARS_START:
287      sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
288      dyn->d_un.d_ptr = sec->vma;
289      break;
290
291    case DT_VX_WRS_TLS_VARS_SIZE:
292      sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
293      dyn->d_un.d_val = sec->size;
294      break;
295    }
296  return TRUE;
297}
298
299
300