1/* VxWorks support for ELF
2   Copyright (C) 2005-2020 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, see <http://www.gnu.org/licenses/>.  */
18
19/* This file provides routines used by all VxWorks targets.  */
20
21#include "sysdep.h"
22#include "bfd.h"
23#include "libbfd.h"
24#include "elf-bfd.h"
25#include "elf-vxworks.h"
26#include "elf/vxworks.h"
27
28/* Return true if symbol NAME, as defined by ABFD, is one of the special
29   __GOTT_BASE__ or __GOTT_INDEX__ symbols.  */
30
31static bfd_boolean
32elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
33{
34  char leading;
35
36  leading = bfd_get_symbol_leading_char (abfd);
37  if (leading)
38    {
39      if (*name != leading)
40	return FALSE;
41      name++;
42    }
43  return (strcmp (name, "__GOTT_BASE__") == 0
44	  || strcmp (name, "__GOTT_INDEX__") == 0);
45}
46
47/* Tweak magic VxWorks symbols as they are loaded.  */
48bfd_boolean
49elf_vxworks_add_symbol_hook (bfd *abfd,
50			     struct bfd_link_info *info,
51			     Elf_Internal_Sym *sym,
52			     const char **namep,
53			     flagword *flagsp,
54			     asection **secp ATTRIBUTE_UNUSED,
55			     bfd_vma *valp ATTRIBUTE_UNUSED)
56{
57  /* Ideally these "magic" symbols would be exported by libc.so.1
58     which would be found via a DT_NEEDED tag, and then handled
59     specially by the linker at runtime.  Except shared libraries
60     don't even link to libc.so.1 by default...
61     If the symbol is imported from, or will be put in a shared library,
62     give the symbol weak binding to get the desired samantics.
63     This transformation will be undone in
64     elf_i386_vxworks_link_output_symbol_hook. */
65  if ((bfd_link_pic (info) || abfd->flags & DYNAMIC)
66      && elf_vxworks_gott_symbol_p (abfd, *namep))
67    {
68      sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
69      *flagsp |= BSF_WEAK;
70    }
71
72  return TRUE;
73}
74
75/* Perform VxWorks-specific handling of the create_dynamic_sections hook.
76   When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
77   section.  */
78
79bfd_boolean
80elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
81				     asection **srelplt2_out)
82{
83  struct elf_link_hash_table *htab;
84  const struct elf_backend_data *bed;
85  asection *s;
86
87  htab = elf_hash_table (info);
88  bed = get_elf_backend_data (dynobj);
89
90  if (!bfd_link_pic (info))
91    {
92      s = bfd_make_section_anyway_with_flags (dynobj,
93					      bed->default_use_rela_p
94					      ? ".rela.plt.unloaded"
95					      : ".rel.plt.unloaded",
96					      SEC_HAS_CONTENTS | SEC_IN_MEMORY
97					      | SEC_READONLY
98					      | SEC_LINKER_CREATED);
99      if (s == NULL
100	  || !bfd_set_section_alignment (s, bed->s->log_file_align))
101	return FALSE;
102
103      *srelplt2_out = s;
104    }
105
106  /* Mark the GOT and PLT symbols as having relocations; they might
107     not, but we won't know for sure until we build the GOT in
108     finish_dynamic_symbol.  Also make sure that the GOT symbol
109     is entered into the dynamic symbol table; the loader uses it
110     to initialize __GOTT_BASE__[__GOTT_INDEX__].  */
111  if (htab->hgot)
112    {
113      htab->hgot->indx = -2;
114      htab->hgot->other &= ~ELF_ST_VISIBILITY (-1);
115      htab->hgot->forced_local = 0;
116      if (!bfd_elf_link_record_dynamic_symbol (info, htab->hgot))
117	return FALSE;
118    }
119  if (htab->hplt)
120    {
121      htab->hplt->indx = -2;
122      htab->hplt->type = STT_FUNC;
123    }
124
125  return TRUE;
126}
127
128/* Tweak magic VxWorks symbols as they are written to the output file.  */
129int
130elf_vxworks_link_output_symbol_hook (struct bfd_link_info *info
131				       ATTRIBUTE_UNUSED,
132				     const char *name,
133				     Elf_Internal_Sym *sym,
134				     asection *input_sec ATTRIBUTE_UNUSED,
135				     struct elf_link_hash_entry *h)
136{
137  /* Reverse the effects of the hack in elf_vxworks_add_symbol_hook.  */
138  if (h
139      && h->root.type == bfd_link_hash_undefweak
140      && elf_vxworks_gott_symbol_p (h->root.u.undef.abfd, name))
141    sym->st_info = ELF_ST_INFO (STB_GLOBAL, ELF_ST_TYPE (sym->st_info));
142
143  return 1;
144}
145
146/* Copy relocations into the output file.  Fixes up relocations against PLT
147   entries, then calls the generic routine.  */
148
149bfd_boolean
150elf_vxworks_emit_relocs (bfd *output_bfd,
151			 asection *input_section,
152			 Elf_Internal_Shdr *input_rel_hdr,
153			 Elf_Internal_Rela *internal_relocs,
154			 struct elf_link_hash_entry **rel_hash)
155{
156  const struct elf_backend_data *bed;
157  int j;
158
159  bed = get_elf_backend_data (output_bfd);
160
161  if (output_bfd->flags & (DYNAMIC|EXEC_P))
162    {
163      Elf_Internal_Rela *irela;
164      Elf_Internal_Rela *irelaend;
165      struct elf_link_hash_entry **hash_ptr;
166
167      for (irela = internal_relocs,
168	     irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
169				 * bed->s->int_rels_per_ext_rel),
170	     hash_ptr = rel_hash;
171	   irela < irelaend;
172	   irela += bed->s->int_rels_per_ext_rel,
173	     hash_ptr++)
174	{
175	  if (*hash_ptr
176	      && (*hash_ptr)->def_dynamic
177	      && !(*hash_ptr)->def_regular
178	      && ((*hash_ptr)->root.type == bfd_link_hash_defined
179		  || (*hash_ptr)->root.type == bfd_link_hash_defweak)
180	      && (*hash_ptr)->root.u.def.section->output_section != NULL)
181	    {
182	      /* This is a relocation from an executable or shared
183		 library against a symbol in a different shared
184		 library.  We are creating a definition in the output
185		 file but it does not come from any of our normal (.o)
186		 files. ie. a PLT stub.  Normally this would be a
187		 relocation against against SHN_UNDEF with the VMA of
188		 the PLT stub.  This upsets the VxWorks loader.
189		 Convert it to a section-relative relocation.  This
190		 gets some other symbols (for instance .dynbss), but
191		 is conservatively correct.  */
192	      for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
193		{
194		  asection *sec = (*hash_ptr)->root.u.def.section;
195		  int this_idx = sec->output_section->target_index;
196
197		  irela[j].r_info
198		    = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info));
199		  irela[j].r_addend += (*hash_ptr)->root.u.def.value;
200		  irela[j].r_addend += sec->output_offset;
201		}
202	      /* Stop the generic routine adjusting this entry.  */
203	      *hash_ptr = NULL;
204	    }
205	}
206    }
207  return _bfd_elf_link_output_relocs (output_bfd, input_section,
208				      input_rel_hdr, internal_relocs,
209				      rel_hash);
210}
211
212
213/* Set the sh_link and sh_info fields on the static plt relocation secton.  */
214
215bfd_boolean
216elf_vxworks_final_write_processing (bfd *abfd)
217{
218  asection * sec;
219  struct bfd_elf_section_data *d;
220
221  sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
222  if (!sec)
223    sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
224  if (sec)
225    {
226      d = elf_section_data (sec);
227      d->this_hdr.sh_link = elf_onesymtab (abfd);
228      sec = bfd_get_section_by_name (abfd, ".plt");
229      if (sec)
230	d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
231    }
232  return _bfd_elf_final_write_processing (abfd);
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 = (bfd_size_type) 1 << bfd_section_alignment (sec);
283      break;
284
285    case DT_VX_WRS_TLS_VARS_START:
286      sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
287      dyn->d_un.d_ptr = sec->vma;
288      break;
289
290    case DT_VX_WRS_TLS_VARS_SIZE:
291      sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
292      dyn->d_un.d_val = sec->size;
293      break;
294    }
295  return TRUE;
296}
297
298
299