1 /* VxWorks support for ELF
2 Copyright (C) 2005-2023 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
31 static bool
32 elf_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. */
48 bool
49 elf_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
79 bool
80 elf_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. */
129 int
130 elf_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
149 bool
150 elf_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
215 bool
216 elf_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
238 bool
239 elf_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
260 bool
261 elf_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 /* Add dynamic tags. */
299
300 bool
301 _bfd_elf_maybe_vxworks_add_dynamic_tags (bfd *output_bfd,
302 struct bfd_link_info *info,
303 bool need_dynamic_reloc)
304 {
305 struct elf_link_hash_table *htab = elf_hash_table (info);
306 return (_bfd_elf_add_dynamic_tags (output_bfd, info,
307 need_dynamic_reloc)
308 && (!htab->dynamic_sections_created
309 || htab->target_os != is_vxworks
310 || elf_vxworks_add_dynamic_entries (output_bfd, info)));
311 }