1 /* VxWorks support for ELF
2 Copyright (C) 2005-2016 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 bfd_boolean
elf_vxworks_gott_symbol_p(bfd * abfd,const char * name)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 bfd_boolean
elf_vxworks_add_symbol_hook(bfd * abfd,struct bfd_link_info * info,Elf_Internal_Sym * sym,const char ** namep,flagword * flagsp,asection ** secp ATTRIBUTE_UNUSED,bfd_vma * valp ATTRIBUTE_UNUSED)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 bfd_boolean
elf_vxworks_create_dynamic_sections(bfd * dynobj,struct bfd_link_info * info,asection ** srelplt2_out)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 (dynobj, 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
elf_vxworks_link_output_symbol_hook(struct bfd_link_info * info ATTRIBUTE_UNUSED,const char * name,Elf_Internal_Sym * sym,asection * input_sec ATTRIBUTE_UNUSED,struct elf_link_hash_entry * h)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 bfd_boolean
elf_vxworks_emit_relocs(bfd * output_bfd,asection * input_section,Elf_Internal_Shdr * input_rel_hdr,Elf_Internal_Rela * internal_relocs,struct elf_link_hash_entry ** rel_hash)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 void
elf_vxworks_final_write_processing(bfd * abfd,bfd_boolean linker ATTRIBUTE_UNUSED)216 elf_vxworks_final_write_processing (bfd *abfd,
217 bfd_boolean linker ATTRIBUTE_UNUSED)
218 {
219 asection * sec;
220 struct bfd_elf_section_data *d;
221
222 sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
223 if (!sec)
224 sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
225 if (!sec)
226 return;
227 d = elf_section_data (sec);
228 d->this_hdr.sh_link = elf_onesymtab (abfd);
229 sec = bfd_get_section_by_name (abfd, ".plt");
230 if (sec)
231 d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
232 }
233
234 /* Add the dynamic entries required by VxWorks. These point to the
235 tls sections. */
236
237 bfd_boolean
elf_vxworks_add_dynamic_entries(bfd * output_bfd,struct bfd_link_info * info)238 elf_vxworks_add_dynamic_entries (bfd *output_bfd, struct bfd_link_info *info)
239 {
240 if (bfd_get_section_by_name (output_bfd, ".tls_data"))
241 {
242 if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_START, 0)
243 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_SIZE, 0)
244 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_ALIGN, 0))
245 return FALSE;
246 }
247 if (bfd_get_section_by_name (output_bfd, ".tls_vars"))
248 {
249 if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_START, 0)
250 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_SIZE, 0))
251 return FALSE;
252 }
253 return TRUE;
254 }
255
256 /* If *DYN is one of the VxWorks-specific dynamic entries, then fill
257 in the value now and return TRUE. Otherwise return FALSE. */
258
259 bfd_boolean
elf_vxworks_finish_dynamic_entry(bfd * output_bfd,Elf_Internal_Dyn * dyn)260 elf_vxworks_finish_dynamic_entry (bfd *output_bfd, Elf_Internal_Dyn *dyn)
261 {
262 asection *sec;
263
264 switch (dyn->d_tag)
265 {
266 default:
267 return FALSE;
268
269 case DT_VX_WRS_TLS_DATA_START:
270 sec = bfd_get_section_by_name (output_bfd, ".tls_data");
271 dyn->d_un.d_ptr = sec->vma;
272 break;
273
274 case DT_VX_WRS_TLS_DATA_SIZE:
275 sec = bfd_get_section_by_name (output_bfd, ".tls_data");
276 dyn->d_un.d_val = sec->size;
277 break;
278
279 case DT_VX_WRS_TLS_DATA_ALIGN:
280 sec = bfd_get_section_by_name (output_bfd, ".tls_data");
281 dyn->d_un.d_val
282 = (bfd_size_type)1 << bfd_get_section_alignment (output_bfd,
283 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