1 /* VxWorks support for ELF 2 Copyright (C) 2005-2020 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 3 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, see <http://www.gnu.org/licenses/>. */ 18 19 /* This file provides routines used by all VxWorks targets. */ 20 21 #include "sysdep.h" 22 #include "bfd.h" 23 #include "libbfd.h" 24 #include "elf-bfd.h" 25 #include "elf-vxworks.h" 26 #include "elf/vxworks.h" 27 28 /* Return true if symbol NAME, as defined by ABFD, is one of the special 29 __GOTT_BASE__ or __GOTT_INDEX__ symbols. */ 30 31 static bfd_boolean 32 elf_vxworks_gott_symbol_p (bfd *abfd, const char *name) 33 { 34 char leading; 35 36 leading = bfd_get_symbol_leading_char (abfd); 37 if (leading) 38 { 39 if (*name != leading) 40 return FALSE; 41 name++; 42 } 43 return (strcmp (name, "__GOTT_BASE__") == 0 44 || strcmp (name, "__GOTT_INDEX__") == 0); 45 } 46 47 /* Tweak magic VxWorks symbols as they are loaded. */ 48 bfd_boolean 49 elf_vxworks_add_symbol_hook (bfd *abfd, 50 struct bfd_link_info *info, 51 Elf_Internal_Sym *sym, 52 const char **namep, 53 flagword *flagsp, 54 asection **secp ATTRIBUTE_UNUSED, 55 bfd_vma *valp ATTRIBUTE_UNUSED) 56 { 57 /* Ideally these "magic" symbols would be exported by libc.so.1 58 which would be found via a DT_NEEDED tag, and then handled 59 specially by the linker at runtime. Except shared libraries 60 don't even link to libc.so.1 by default... 61 If the symbol is imported from, or will be put in a shared library, 62 give the symbol weak binding to get the desired samantics. 63 This transformation will be undone in 64 elf_i386_vxworks_link_output_symbol_hook. */ 65 if ((bfd_link_pic (info) || abfd->flags & DYNAMIC) 66 && elf_vxworks_gott_symbol_p (abfd, *namep)) 67 { 68 sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info)); 69 *flagsp |= BSF_WEAK; 70 } 71 72 return TRUE; 73 } 74 75 /* Perform VxWorks-specific handling of the create_dynamic_sections hook. 76 When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded 77 section. */ 78 79 bfd_boolean 80 elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info, 81 asection **srelplt2_out) 82 { 83 struct elf_link_hash_table *htab; 84 const struct elf_backend_data *bed; 85 asection *s; 86 87 htab = elf_hash_table (info); 88 bed = get_elf_backend_data (dynobj); 89 90 if (!bfd_link_pic (info)) 91 { 92 s = bfd_make_section_anyway_with_flags (dynobj, 93 bed->default_use_rela_p 94 ? ".rela.plt.unloaded" 95 : ".rel.plt.unloaded", 96 SEC_HAS_CONTENTS | SEC_IN_MEMORY 97 | SEC_READONLY 98 | SEC_LINKER_CREATED); 99 if (s == NULL 100 || !bfd_set_section_alignment (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 int 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 1; 144 } 145 146 /* Copy relocations into the output file. Fixes up relocations against PLT 147 entries, then calls the generic routine. */ 148 149 bfd_boolean 150 elf_vxworks_emit_relocs (bfd *output_bfd, 151 asection *input_section, 152 Elf_Internal_Shdr *input_rel_hdr, 153 Elf_Internal_Rela *internal_relocs, 154 struct elf_link_hash_entry **rel_hash) 155 { 156 const struct elf_backend_data *bed; 157 int j; 158 159 bed = get_elf_backend_data (output_bfd); 160 161 if (output_bfd->flags & (DYNAMIC|EXEC_P)) 162 { 163 Elf_Internal_Rela *irela; 164 Elf_Internal_Rela *irelaend; 165 struct elf_link_hash_entry **hash_ptr; 166 167 for (irela = internal_relocs, 168 irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr) 169 * bed->s->int_rels_per_ext_rel), 170 hash_ptr = rel_hash; 171 irela < irelaend; 172 irela += bed->s->int_rels_per_ext_rel, 173 hash_ptr++) 174 { 175 if (*hash_ptr 176 && (*hash_ptr)->def_dynamic 177 && !(*hash_ptr)->def_regular 178 && ((*hash_ptr)->root.type == bfd_link_hash_defined 179 || (*hash_ptr)->root.type == bfd_link_hash_defweak) 180 && (*hash_ptr)->root.u.def.section->output_section != NULL) 181 { 182 /* This is a relocation from an executable or shared 183 library against a symbol in a different shared 184 library. We are creating a definition in the output 185 file but it does not come from any of our normal (.o) 186 files. ie. a PLT stub. Normally this would be a 187 relocation against against SHN_UNDEF with the VMA of 188 the PLT stub. This upsets the VxWorks loader. 189 Convert it to a section-relative relocation. This 190 gets some other symbols (for instance .dynbss), but 191 is conservatively correct. */ 192 for (j = 0; j < bed->s->int_rels_per_ext_rel; j++) 193 { 194 asection *sec = (*hash_ptr)->root.u.def.section; 195 int this_idx = sec->output_section->target_index; 196 197 irela[j].r_info 198 = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info)); 199 irela[j].r_addend += (*hash_ptr)->root.u.def.value; 200 irela[j].r_addend += sec->output_offset; 201 } 202 /* Stop the generic routine adjusting this entry. */ 203 *hash_ptr = NULL; 204 } 205 } 206 } 207 return _bfd_elf_link_output_relocs (output_bfd, input_section, 208 input_rel_hdr, internal_relocs, 209 rel_hash); 210 } 211 212 213 /* Set the sh_link and sh_info fields on the static plt relocation secton. */ 214 215 bfd_boolean 216 elf_vxworks_final_write_processing (bfd *abfd) 217 { 218 asection * sec; 219 struct bfd_elf_section_data *d; 220 221 sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded"); 222 if (!sec) 223 sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded"); 224 if (sec) 225 { 226 d = elf_section_data (sec); 227 d->this_hdr.sh_link = elf_onesymtab (abfd); 228 sec = bfd_get_section_by_name (abfd, ".plt"); 229 if (sec) 230 d->this_hdr.sh_info = elf_section_data (sec)->this_idx; 231 } 232 return _bfd_elf_final_write_processing (abfd); 233 } 234 235 /* Add the dynamic entries required by VxWorks. These point to the 236 tls sections. */ 237 238 bfd_boolean 239 elf_vxworks_add_dynamic_entries (bfd *output_bfd, struct bfd_link_info *info) 240 { 241 if (bfd_get_section_by_name (output_bfd, ".tls_data")) 242 { 243 if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_START, 0) 244 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_SIZE, 0) 245 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_ALIGN, 0)) 246 return FALSE; 247 } 248 if (bfd_get_section_by_name (output_bfd, ".tls_vars")) 249 { 250 if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_START, 0) 251 || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_SIZE, 0)) 252 return FALSE; 253 } 254 return TRUE; 255 } 256 257 /* If *DYN is one of the VxWorks-specific dynamic entries, then fill 258 in the value now and return TRUE. Otherwise return FALSE. */ 259 260 bfd_boolean 261 elf_vxworks_finish_dynamic_entry (bfd *output_bfd, Elf_Internal_Dyn *dyn) 262 { 263 asection *sec; 264 265 switch (dyn->d_tag) 266 { 267 default: 268 return FALSE; 269 270 case DT_VX_WRS_TLS_DATA_START: 271 sec = bfd_get_section_by_name (output_bfd, ".tls_data"); 272 dyn->d_un.d_ptr = sec->vma; 273 break; 274 275 case DT_VX_WRS_TLS_DATA_SIZE: 276 sec = bfd_get_section_by_name (output_bfd, ".tls_data"); 277 dyn->d_un.d_val = sec->size; 278 break; 279 280 case DT_VX_WRS_TLS_DATA_ALIGN: 281 sec = bfd_get_section_by_name (output_bfd, ".tls_data"); 282 dyn->d_un.d_val = (bfd_size_type) 1 << bfd_section_alignment (sec); 283 break; 284 285 case DT_VX_WRS_TLS_VARS_START: 286 sec = bfd_get_section_by_name (output_bfd, ".tls_vars"); 287 dyn->d_un.d_ptr = sec->vma; 288 break; 289 290 case DT_VX_WRS_TLS_VARS_SIZE: 291 sec = bfd_get_section_by_name (output_bfd, ".tls_vars"); 292 dyn->d_un.d_val = sec->size; 293 break; 294 } 295 return TRUE; 296 } 297 298 299