1 /* VxWorks support for ELF
2 Copyright 2005, 2007 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 2 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, MA 02111-1307, USA.
19 */
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
29 /* Return true if symbol NAME, as defined by ABFD, is one of the special
30 __GOTT_BASE__ or __GOTT_INDEX__ symbols. */
31
32 static bfd_boolean
elf_vxworks_gott_symbol_p(bfd * abfd,const char * name)33 elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
34 {
35 char leading;
36
37 leading = bfd_get_symbol_leading_char (abfd);
38 if (leading)
39 {
40 if (*name != leading)
41 return FALSE;
42 name++;
43 }
44 return (strcmp (name, "__GOTT_BASE__") == 0
45 || strcmp (name, "__GOTT_INDEX__") == 0);
46 }
47
48 /* Tweak magic VxWorks symbols as they are loaded. */
49 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)50 elf_vxworks_add_symbol_hook (bfd *abfd,
51 struct bfd_link_info *info,
52 Elf_Internal_Sym *sym,
53 const char **namep,
54 flagword *flagsp,
55 asection **secp ATTRIBUTE_UNUSED,
56 bfd_vma *valp ATTRIBUTE_UNUSED)
57 {
58 /* Ideally these "magic" symbols would be exported by libc.so.1
59 which would be found via a DT_NEEDED tag, and then handled
60 specially by the linker at runtime. Except shared libraries
61 don't even link to libc.so.1 by default...
62 If the symbol is imported from, or will be put in a shared library,
63 give the symbol weak binding to get the desired samantics.
64 This transformation will be undone in
65 elf_i386_vxworks_link_output_symbol_hook. */
66 if ((info->shared || abfd->flags & DYNAMIC)
67 && elf_vxworks_gott_symbol_p (abfd, *namep))
68 {
69 sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
70 *flagsp |= BSF_WEAK;
71 }
72
73 return TRUE;
74 }
75
76 /* Perform VxWorks-specific handling of the create_dynamic_sections hook.
77 When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
78 section. */
79
80 bfd_boolean
elf_vxworks_create_dynamic_sections(bfd * dynobj,struct bfd_link_info * info,asection ** srelplt2_out)81 elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
82 asection **srelplt2_out)
83 {
84 struct elf_link_hash_table *htab;
85 const struct elf_backend_data *bed;
86 asection *s;
87
88 htab = elf_hash_table (info);
89 bed = get_elf_backend_data (dynobj);
90
91 if (!info->shared)
92 {
93 s = bfd_make_section_with_flags (dynobj,
94 bed->default_use_rela_p
95 ? ".rela.plt.unloaded"
96 : ".rel.plt.unloaded",
97 SEC_HAS_CONTENTS | SEC_IN_MEMORY
98 | SEC_READONLY | 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 bfd_boolean
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 TRUE;
144 }
145
146
147 /* Copy relocations into the output file. Fixes up relocations againt PLT
148 entries, then calls the generic routine. */
149
150 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)151 elf_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 Elf_Internal_Rela *irela;
159 Elf_Internal_Rela *irelaend;
160 int j;
161
162 bed = get_elf_backend_data (output_bfd);
163
164 irela = internal_relocs;
165 irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
166 * bed->s->int_rels_per_ext_rel);
167 while (irela < irelaend)
168 {
169 if ((output_bfd->flags & (DYNAMIC|EXEC_P))
170 && *rel_hash
171 && (*rel_hash)->def_dynamic
172 && !(*rel_hash)->def_regular
173 && ((*rel_hash)->root.type == bfd_link_hash_defined
174 || (*rel_hash)->root.type == bfd_link_hash_defweak)
175 && (*rel_hash)->root.u.def.section->output_section != NULL)
176 {
177 /* This is a relocation from an executable or shared library
178 against a symbol in a different shared library. We are
179 creating a definition in the output file but it does not come
180 from any of our normal (.o) files. ie. a PLT stub.
181 Normally this would be a relocation against against SHN_UNDEF
182 with the VMA of the PLT stub. This upsets the VxWorks loader.
183 Convert it to a section-relative relocation.
184 This gets some other symbols (for instance .dynbss),
185 but is conservatively correct. */
186 for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
187 {
188 asection *sec = (*rel_hash)->root.u.def.section;
189 int this_idx = sec->output_section->target_index;
190
191 irela[j].r_info = ELF32_R_INFO (this_idx,
192 ELF32_R_TYPE (irela[j].r_info));
193 irela[j].r_addend += (*rel_hash)->root.u.def.value;
194 irela[j].r_addend += sec->output_offset;
195 }
196 /* Stop the generic routine adjusting this entry. */
197 *rel_hash = NULL;
198 }
199 irela += bed->s->int_rels_per_ext_rel;
200 rel_hash++;
201 }
202 return _bfd_elf_link_output_relocs (output_bfd, input_section,
203 input_rel_hdr, internal_relocs,
204 rel_hash);
205 }
206
207
208 /* Set the sh_link and sh_info fields on the static plt relocation secton. */
209
210 void
elf_vxworks_final_write_processing(bfd * abfd,bfd_boolean linker ATTRIBUTE_UNUSED)211 elf_vxworks_final_write_processing (bfd *abfd,
212 bfd_boolean linker ATTRIBUTE_UNUSED)
213 {
214 asection * sec;
215 struct bfd_elf_section_data *d;
216
217 sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
218 if (!sec)
219 sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
220 if (!sec)
221 return;
222 d = elf_section_data (sec);
223 d->this_hdr.sh_link = elf_tdata (abfd)->symtab_section;
224 sec = bfd_get_section_by_name (abfd, ".plt");
225 if (sec)
226 d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
227 }
228