1 /* IBM S/390-specific support for ELF 32 and 64 bit functions
2 Copyright (C) 2000-2014 Free Software Foundation, Inc.
3 Contributed by Andreas Krebbel.
4
5 This file is part of BFD, the Binary File Descriptor library.
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
20 02110-1301, USA. */
21
22
23 /* Return TRUE if H is an IFUNC symbol. Simply checking for the
24 symbol type might not be enough since it might get changed to
25 STT_FUNC for pointer equality reasons. */
26 static inline bfd_boolean
s390_is_ifunc_symbol_p(struct elf_link_hash_entry * h)27 s390_is_ifunc_symbol_p (struct elf_link_hash_entry *h)
28 {
29 struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
30 return h->type == STT_GNU_IFUNC || eh->ifunc_resolver_address != 0;
31 }
32
33 /* Create sections needed by STT_GNU_IFUNC symbol. */
34
35 static bfd_boolean
s390_elf_create_ifunc_sections(bfd * abfd,struct bfd_link_info * info)36 s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
37 {
38 flagword flags;
39 asection *s;
40 const struct elf_backend_data *bed = get_elf_backend_data (abfd);
41 struct elf_link_hash_table *htab = elf_hash_table (info);
42
43 if (htab->iplt != NULL)
44 return TRUE;
45
46 flags = bed->dynamic_sec_flags;
47
48 if (info->shared)
49 {
50 s = bfd_make_section_with_flags (abfd, ".rela.ifunc",
51 flags | SEC_READONLY);
52 if (s == NULL
53 || ! bfd_set_section_alignment (abfd, s,
54 bed->s->log_file_align))
55 return FALSE;
56 htab->irelifunc = s;
57 }
58
59 /* Create .iplt, .rel[a].iplt, and .igot.plt. */
60 s = bfd_make_section_with_flags (abfd, ".iplt",
61 flags | SEC_CODE | SEC_READONLY);
62 if (s == NULL
63 || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
64 return FALSE;
65 htab->iplt = s;
66
67 s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY);
68 if (s == NULL
69 || ! bfd_set_section_alignment (abfd, s,
70 bed->s->log_file_align))
71 return FALSE;
72 htab->irelplt = s;
73
74 s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
75 if (s == NULL
76 || !bfd_set_section_alignment (abfd, s,
77 bed->s->log_file_align))
78 return FALSE;
79 htab->igotplt = s;
80
81 return TRUE;
82 }
83
84
85 /* Allocate space in .plt, .got and associated reloc sections for
86 dynamic relocs against a STT_GNU_IFUNC symbol definition. */
87
88 static bfd_boolean
s390_elf_allocate_ifunc_dyn_relocs(struct bfd_link_info * info,struct elf_link_hash_entry * h,struct elf_dyn_relocs ** head)89 s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
90 struct elf_link_hash_entry *h,
91 struct elf_dyn_relocs **head)
92 {
93 struct elf_dyn_relocs *p;
94 struct elf_link_hash_table *htab;
95 struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
96
97 htab = elf_hash_table (info);
98 eh->ifunc_resolver_address = h->root.u.def.value;
99 eh->ifunc_resolver_section = h->root.u.def.section;
100
101 /* Support garbage collection against STT_GNU_IFUNC symbols. */
102 if (h->plt.refcount <= 0 && h->got.refcount <= 0)
103 {
104 /* When building shared library, we need to handle the case
105 where it is marked with regular reference, but not non-GOT
106 reference. It may happen if we didn't see STT_GNU_IFUNC
107 symbol at the time when checking relocations. */
108 if (info->shared
109 && !h->non_got_ref
110 && h->ref_regular)
111 for (p = *head; p != NULL; p = p->next)
112 if (p->count)
113 {
114 h->non_got_ref = 1;
115 goto keep;
116 }
117
118 h->got = htab->init_got_offset;
119 h->plt = htab->init_plt_offset;
120 *head = NULL;
121 return TRUE;
122 }
123
124 /* Return and discard space for dynamic relocations against it if
125 it is never referenced in a non-shared object. */
126 if (!h->ref_regular)
127 {
128 if (h->plt.refcount > 0
129 || h->got.refcount > 0)
130 abort ();
131 h->got = htab->init_got_offset;
132 h->plt = htab->init_plt_offset;
133 *head = NULL;
134 return TRUE;
135 }
136
137 keep:
138 /* Without checking h->plt.refcount here we allocate a PLT slot.
139 When setting plt.refcount in check_relocs it might not have been
140 known that this will be an IFUNC symol. */
141 h->plt.offset = htab->iplt->size;
142 h->needs_plt = 1;
143 htab->iplt->size += PLT_ENTRY_SIZE;
144 htab->igotplt->size += GOT_ENTRY_SIZE;
145 htab->irelplt->size += RELA_ENTRY_SIZE;
146 htab->irelplt->reloc_count++;
147
148 /* In order to make pointer equality work with IFUNC symbols defined
149 in a non-PIE executable and referenced in a shared lib, we turn
150 the symbol into a STT_FUNC symbol and make the symbol value to
151 point to the IPLT slot. That way the referencing shared lib will
152 always get the PLT slot address when resolving the respective
153 R_390_GLOB_DAT/R_390_64 relocs on that symbol. */
154 if (info->executable && !info->shared && h->def_regular && h->ref_dynamic)
155 {
156 h->root.u.def.section = htab->iplt;
157 h->root.u.def.value = h->plt.offset;
158 h->size = PLT_ENTRY_SIZE;
159 h->type = STT_FUNC;
160 }
161
162 /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
163 there is a non-GOT reference in a shared object. */
164 if (!info->shared || !h->non_got_ref)
165 *head = NULL;
166
167 /* Finally, allocate space. */
168 p = *head;
169 if (p != NULL)
170 {
171 bfd_size_type count = 0;
172 do
173 {
174 count += p->count;
175 p = p->next;
176 }
177 while (p != NULL);
178 htab->irelifunc->size += count * RELA_ENTRY_SIZE;
179 }
180
181 /* Decide whether the got.iplt slot can be used. This has to be
182 avoided if the values in the GOT slots could differ for pointer
183 equality reasons. */
184 if (h->got.refcount <= 0
185 || (info->shared
186 && (h->dynindx == -1 || h->forced_local))
187 || (info->executable && info->shared)
188 || htab->sgot == NULL)
189 {
190 /* Use .got.iplt. */
191 h->got.offset = (bfd_vma) -1;
192 }
193 else
194 {
195 h->got.offset = htab->sgot->size;
196 htab->sgot->size += GOT_ENTRY_SIZE;
197 if (info->shared)
198 htab->srelgot->size += RELA_ENTRY_SIZE;
199 }
200
201 return TRUE;
202 }
203
204 static bfd_boolean
elf_s390_allocate_local_syminfo(bfd * abfd,Elf_Internal_Shdr * symtab_hdr)205 elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
206 {
207 bfd_size_type size;
208
209 size = symtab_hdr->sh_info;
210 size *= (sizeof (bfd_signed_vma) /* local got */
211 + sizeof (struct plt_entry) /* local plt */
212 + sizeof(char)); /* local tls type */
213 elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
214 bfd_zalloc (abfd, size));
215 if (elf_local_got_refcounts (abfd) == NULL)
216 return FALSE;
217 elf_s390_local_plt (abfd)
218 = (struct plt_entry*)(elf_local_got_refcounts (abfd)
219 + symtab_hdr->sh_info);
220 elf_s390_local_got_tls_type (abfd)
221 = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);
222
223 return TRUE;
224 }
225
226 /* Pick ELFOSABI_GNU if IFUNC symbols are used. */
227
228 static bfd_boolean
elf_s390_add_symbol_hook(bfd * abfd,struct bfd_link_info * info,Elf_Internal_Sym * sym,const char ** namep ATTRIBUTE_UNUSED,flagword * flagsp ATTRIBUTE_UNUSED,asection ** secp ATTRIBUTE_UNUSED,bfd_vma * valp ATTRIBUTE_UNUSED)229 elf_s390_add_symbol_hook (bfd *abfd,
230 struct bfd_link_info *info,
231 Elf_Internal_Sym *sym,
232 const char **namep ATTRIBUTE_UNUSED,
233 flagword *flagsp ATTRIBUTE_UNUSED,
234 asection **secp ATTRIBUTE_UNUSED,
235 bfd_vma *valp ATTRIBUTE_UNUSED)
236 {
237 if ((ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC
238 || ELF_ST_BIND (sym->st_info) == STB_GNU_UNIQUE)
239 && (abfd->flags & DYNAMIC) == 0
240 && bfd_get_flavour (info->output_bfd) == bfd_target_elf_flavour)
241 elf_tdata (info->output_bfd)->has_gnu_symbols = TRUE;
242
243 return TRUE;
244 }
245