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| 1 /* IBM S/390-specific support for ELF 32 and 64 bit functions |
| 2 Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, |
| 3 2011, 2012 Free Software Foundation, Inc. |
| 4 Contributed by Andreas Krebbel. |
| 5 |
| 6 This file is part of BFD, the Binary File Descriptor library. |
| 7 |
| 8 This program is free software; you can redistribute it and/or modify |
| 9 it under the terms of the GNU General Public License as published by |
| 10 the Free Software Foundation; either version 3 of the License, or |
| 11 (at your option) any later version. |
| 12 |
| 13 This program is distributed in the hope that it will be useful, |
| 14 but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 GNU General Public License for more details. |
| 17 |
| 18 You should have received a copy of the GNU General Public License |
| 19 along with this program; if not, write to the Free Software |
| 20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA |
| 21 02110-1301, USA. */ |
| 22 |
| 23 |
| 24 /* Return TRUE if H is an IFUNC symbol. Simply checking for the |
| 25 symbol type might not be enough since it might get changed to |
| 26 STT_FUNC for pointer equality reasons. */ |
| 27 static inline bfd_boolean |
| 28 s390_is_ifunc_symbol_p (struct elf_link_hash_entry *h) |
| 29 { |
| 30 struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h; |
| 31 return h->type == STT_GNU_IFUNC || eh->ifunc_resolver_address != 0; |
| 32 } |
| 33 |
| 34 /* Create sections needed by STT_GNU_IFUNC symbol. */ |
| 35 |
| 36 static bfd_boolean |
| 37 s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info) |
| 38 { |
| 39 flagword flags; |
| 40 asection *s; |
| 41 const struct elf_backend_data *bed = get_elf_backend_data (abfd); |
| 42 struct elf_link_hash_table *htab = elf_hash_table (info); |
| 43 |
| 44 if (htab->iplt != NULL) |
| 45 return TRUE; |
| 46 |
| 47 flags = bed->dynamic_sec_flags; |
| 48 |
| 49 if (info->shared) |
| 50 { |
| 51 s = bfd_make_section_with_flags (abfd, ".rela.ifunc", |
| 52 flags | SEC_READONLY); |
| 53 if (s == NULL |
| 54 || ! bfd_set_section_alignment (abfd, s, |
| 55 bed->s->log_file_align)) |
| 56 return FALSE; |
| 57 htab->irelifunc = s; |
| 58 } |
| 59 |
| 60 /* Create .iplt, .rel[a].iplt, and .igot.plt. */ |
| 61 s = bfd_make_section_with_flags (abfd, ".iplt", |
| 62 flags | SEC_CODE | SEC_READONLY); |
| 63 if (s == NULL |
| 64 || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment)) |
| 65 return FALSE; |
| 66 htab->iplt = s; |
| 67 |
| 68 s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY); |
| 69 if (s == NULL |
| 70 || ! bfd_set_section_alignment (abfd, s, |
| 71 bed->s->log_file_align)) |
| 72 return FALSE; |
| 73 htab->irelplt = s; |
| 74 |
| 75 s = bfd_make_section_with_flags (abfd, ".igot.plt", flags); |
| 76 if (s == NULL |
| 77 || !bfd_set_section_alignment (abfd, s, |
| 78 bed->s->log_file_align)) |
| 79 return FALSE; |
| 80 htab->igotplt = s; |
| 81 |
| 82 return TRUE; |
| 83 } |
| 84 |
| 85 |
| 86 /* Allocate space in .plt, .got and associated reloc sections for |
| 87 dynamic relocs against a STT_GNU_IFUNC symbol definition. */ |
| 88 |
| 89 static bfd_boolean |
| 90 s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info, |
| 91 struct elf_link_hash_entry *h, |
| 92 struct elf_dyn_relocs **head) |
| 93 { |
| 94 struct elf_dyn_relocs *p; |
| 95 struct elf_link_hash_table *htab; |
| 96 struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h; |
| 97 |
| 98 htab = elf_hash_table (info); |
| 99 eh->ifunc_resolver_address = h->root.u.def.value; |
| 100 eh->ifunc_resolver_section = h->root.u.def.section; |
| 101 |
| 102 /* Support garbage collection against STT_GNU_IFUNC symbols. */ |
| 103 if (h->plt.refcount <= 0 && h->got.refcount <= 0) |
| 104 { |
| 105 /* When building shared library, we need to handle the case |
| 106 where it is marked with regular reference, but not non-GOT |
| 107 reference. It may happen if we didn't see STT_GNU_IFUNC |
| 108 symbol at the time when checking relocations. */ |
| 109 if (info->shared |
| 110 && !h->non_got_ref |
| 111 && h->ref_regular) |
| 112 for (p = *head; p != NULL; p = p->next) |
| 113 if (p->count) |
| 114 { |
| 115 h->non_got_ref = 1; |
| 116 goto keep; |
| 117 } |
| 118 |
| 119 h->got = htab->init_got_offset; |
| 120 h->plt = htab->init_plt_offset; |
| 121 *head = NULL; |
| 122 return TRUE; |
| 123 } |
| 124 |
| 125 /* Return and discard space for dynamic relocations against it if |
| 126 it is never referenced in a non-shared object. */ |
| 127 if (!h->ref_regular) |
| 128 { |
| 129 if (h->plt.refcount > 0 |
| 130 || h->got.refcount > 0) |
| 131 abort (); |
| 132 h->got = htab->init_got_offset; |
| 133 h->plt = htab->init_plt_offset; |
| 134 *head = NULL; |
| 135 return TRUE; |
| 136 } |
| 137 |
| 138 keep: |
| 139 /* Without checking h->plt.refcount here we allocate a PLT slot. |
| 140 When setting plt.refcount in check_relocs it might not have been |
| 141 known that this will be an IFUNC symol. */ |
| 142 h->plt.offset = htab->iplt->size; |
| 143 h->needs_plt = 1; |
| 144 htab->iplt->size += PLT_ENTRY_SIZE; |
| 145 htab->igotplt->size += GOT_ENTRY_SIZE; |
| 146 htab->irelplt->size += RELA_ENTRY_SIZE; |
| 147 htab->irelplt->reloc_count++; |
| 148 |
| 149 /* In order to make pointer equality work with IFUNC symbols defined |
| 150 in a non-PIE executable and referenced in a shared lib, we turn |
| 151 the symbol into a STT_FUNC symbol and make the symbol value to |
| 152 point to the IPLT slot. That way the referencing shared lib will |
| 153 always get the PLT slot address when resolving the respective |
| 154 R_390_GLOB_DAT/R_390_64 relocs on that symbol. */ |
| 155 if (info->executable && !info->shared && h->def_regular && h->ref_dynamic) |
| 156 { |
| 157 h->root.u.def.section = htab->iplt; |
| 158 h->root.u.def.value = h->plt.offset; |
| 159 h->size = PLT_ENTRY_SIZE; |
| 160 h->type = STT_FUNC; |
| 161 } |
| 162 |
| 163 /* We need dynamic relocation for STT_GNU_IFUNC symbol only when |
| 164 there is a non-GOT reference in a shared object. */ |
| 165 if (!info->shared || !h->non_got_ref) |
| 166 *head = NULL; |
| 167 |
| 168 /* Finally, allocate space. */ |
| 169 p = *head; |
| 170 if (p != NULL) |
| 171 { |
| 172 bfd_size_type count = 0; |
| 173 do |
| 174 { |
| 175 count += p->count; |
| 176 p = p->next; |
| 177 } |
| 178 while (p != NULL); |
| 179 htab->irelifunc->size += count * RELA_ENTRY_SIZE; |
| 180 } |
| 181 |
| 182 /* Decide whether the got.iplt slot can be used. This has to be |
| 183 avoided if the values in the GOT slots could differ for pointer |
| 184 equality reasons. */ |
| 185 if (h->got.refcount <= 0 |
| 186 || (info->shared |
| 187 && (h->dynindx == -1 || h->forced_local)) |
| 188 || (info->executable && info->shared) |
| 189 || htab->sgot == NULL) |
| 190 { |
| 191 /* Use .got.iplt. */ |
| 192 h->got.offset = (bfd_vma) -1; |
| 193 } |
| 194 else |
| 195 { |
| 196 h->got.offset = htab->sgot->size; |
| 197 htab->sgot->size += GOT_ENTRY_SIZE; |
| 198 if (info->shared) |
| 199 htab->srelgot->size += RELA_ENTRY_SIZE; |
| 200 } |
| 201 |
| 202 return TRUE; |
| 203 } |
| 204 |
| 205 static bfd_boolean |
| 206 elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr) |
| 207 { |
| 208 bfd_size_type size; |
| 209 |
| 210 size = symtab_hdr->sh_info; |
| 211 size *= (sizeof (bfd_signed_vma) /* local got */ |
| 212 + sizeof (struct plt_entry) /* local plt */ |
| 213 + sizeof(char)); /* local tls type */ |
| 214 elf_local_got_refcounts (abfd) = ((bfd_signed_vma *) |
| 215 bfd_zalloc (abfd, size)); |
| 216 if (elf_local_got_refcounts (abfd) == NULL) |
| 217 return FALSE; |
| 218 elf_s390_local_plt (abfd) |
| 219 = (struct plt_entry*)(elf_local_got_refcounts (abfd) |
| 220 + symtab_hdr->sh_info); |
| 221 elf_s390_local_got_tls_type (abfd) |
| 222 = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info); |
| 223 |
| 224 return TRUE; |
| 225 } |
| 226 |
| 227 /* Pick ELFOSABI_GNU if IFUNC symbols are used. */ |
| 228 |
| 229 static bfd_boolean |
| 230 elf_s390_add_symbol_hook (bfd *abfd, |
| 231 struct bfd_link_info *info, |
| 232 Elf_Internal_Sym *sym, |
| 233 const char **namep ATTRIBUTE_UNUSED, |
| 234 flagword *flagsp ATTRIBUTE_UNUSED, |
| 235 asection **secp ATTRIBUTE_UNUSED, |
| 236 bfd_vma *valp ATTRIBUTE_UNUSED) |
| 237 { |
| 238 if ((abfd->flags & DYNAMIC) == 0 |
| 239 && ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC) |
| 240 elf_tdata (info->output_bfd)->has_gnu_symbols = TRUE; |
| 241 |
| 242 return TRUE; |
| 243 } |
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