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 } 244