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 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 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 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 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 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
