ldso/ldso/x86_64/elfinterp.c

   1 /* vi: set sw=4 ts=4: */
   2 /* x86_64 ELF shared library loader suppport
   3  *
   4  * Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
   5  *                              David Engel, Hongjiu Lu and Mitch D'Souza
   6  * Copyright (C) 2001-2004 Erik Andersen
   7  *
   8  * All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. The name of the above contributors may not be
  16  *    used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include "ldso.h"
  33
  34 /* Program to load an ELF binary on a linux system, and run it.
  35    References to symbols in sharable libraries can be resolved by either
  36    an ELF sharable library or a linux style of shared library. */
  37
  38 /* Disclaimer:  I have never seen any AT&T source code for SVr4, nor have
  39    I ever taken any courses on internals.  This program was developed using
  40    information available through the book "UNIX SYSTEM V RELEASE 4,
  41    Programmers guide: Ansi C and Programming Support Tools", which did
  42    a more than adequate job of explaining everything required to get this
  43    working. */
  44
  45 extern int _dl_linux_resolve(void);
  46
  47 unsigned long
  48 _dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
  49 {
  50         ELF_RELOC *this_reloc;
  51         char *strtab;
  52         ElfW(Sym) *symtab;
  53         int symtab_index;
  54         char *rel_addr;
  55         char *new_addr;
  56         char **got_addr;
  57         ElfW(Addr) instr_addr;
  58         char *symname;
  59
  60         rel_addr = (char *)tpnt->dynamic_info[DT_JMPREL];
  61         this_reloc = (ELF_RELOC *)(rel_addr + reloc_entry);
  62         symtab_index = ELF_R_SYM(this_reloc->r_info);
  63
  64         symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
  65         strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
  66         symname = strtab + symtab[symtab_index].st_name;
  67
  68         /* Address of the jump instruction to fix up. */
  69         instr_addr = (this_reloc->r_offset + tpnt->loadaddr);
  70         got_addr = (char **)instr_addr;
  71
  72         /* Get the address of the GOT entry. */
  73         new_addr = _dl_find_hash(symname, &_dl_loaded_modules->symbol_scope, tpnt, NULL, ELF_RTYPE_CLASS_PLT, NULL);
  74         if (unlikely(!new_addr)) {
  75                 _dl_dprintf(2, "%s: Can't resolve symbol '%s'\n", _dl_progname, symname);
  76                 _dl_exit(1);
  77         }
  78
  79 #if defined (__SUPPORT_LD_DEBUG__)
  80         if ((unsigned long)got_addr < 0x40000000) {
  81                 if (_dl_debug_bindings) {
  82                         _dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
  83                         if (_dl_debug_detail)
  84                                 _dl_dprintf(_dl_debug_file,
  85                                             "\tpatched: %x ==> %x @ %x\n",
  86                                             *got_addr, new_addr, got_addr);
  87                 }
  88         }
  89         if (!_dl_debug_nofixups)
  90 #endif
  91                 *got_addr = new_addr;
  92
  93         return (unsigned long)new_addr;
  94 }
  95
  96 static int
  97 _dl_parse(struct elf_resolve *tpnt, struct r_scope_elem *scope,
  98           unsigned long rel_addr, unsigned long rel_size,
  99           int (*reloc_fnc)(struct elf_resolve *tpnt, struct r_scope_elem *scope,
 100                            ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab))
 101 {
 102         unsigned int i;
 103         char *strtab;
 104         ElfW(Sym) *symtab;
 105         ELF_RELOC *rpnt;
 106         int symtab_index;
 107
 108         /* Parse the relocation information. */
 109         rpnt = (ELF_RELOC *)rel_addr;
 110         rel_size /= sizeof(ELF_RELOC);
 111
 112         symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
 113         strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
 114
 115         for (i = 0; i < rel_size; i++, rpnt++) {
 116                 int res;
 117
 118                 symtab_index = ELF_R_SYM(rpnt->r_info);
 119
 120                 debug_sym(symtab, strtab, symtab_index);
 121                 debug_reloc(symtab, strtab, rpnt);
 122
 123                 res = reloc_fnc(tpnt, scope, rpnt, symtab, strtab);
 124
 125                 if (res == 0)
 126                         continue;
 127
 128                 _dl_dprintf(2, "\n%s: ", _dl_progname);
 129
 130                 if (symtab_index)
 131                         _dl_dprintf(2, "symbol '%s': ",
 132                                     strtab + symtab[symtab_index].st_name);
 133
 134                 if (unlikely(res < 0)) {
 135                         int reloc_type = ELF_R_TYPE(rpnt->r_info);
 136
 137                         _dl_dprintf(2, "can't handle reloc type "
 138 #if defined (__SUPPORT_LD_DEBUG__)
 139                                     "%s\n", _dl_reltypes(reloc_type));
 140 #else
 141                                     "%x\n", reloc_type);
 142 #endif
 143                         _dl_exit(-res);
 144                 } else if (unlikely(res > 0)) {
 145                         _dl_dprintf(2, "can't resolve symbol\n");
 146                         return res;
 147                 }
 148         }
 149
 150         return 0;
 151 }
 152
 153 static int
 154 _dl_do_reloc(struct elf_resolve *tpnt, struct r_scope_elem *scope,
 155              ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 156 {
 157         int reloc_type;
 158         int symtab_index;
 159         char *symname;
 160         struct elf_resolve *tls_tpnt = 0;
 161         ElfW(Sym) *sym;
 162         ElfW(Addr) *reloc_addr;
 163         ElfW(Addr) symbol_addr;
 164 #if defined (__SUPPORT_LD_DEBUG__)
 165         ElfW(Addr) old_val;
 166 #endif
 167
 168         struct sym_val current_value = { NULL, NULL };
 169
 170         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
 171         reloc_type = ELF_R_TYPE(rpnt->r_info);
 172         symtab_index = ELF_R_SYM(rpnt->r_info);
 173         sym = &symtab[symtab_index];
 174         symbol_addr = 0;
 175         symname = strtab + sym->st_name;
 176
 177         if (symtab_index) {
 178                 symbol_addr = (ElfW(Addr))_dl_find_hash(symname, scope, tpnt, &current_value,
 179                                 elf_machine_type_class(reloc_type), &tls_tpnt);
 180                 /*
 181                  * We want to allow undefined references to weak symbols - this
 182                  * might have been intentional.  We should not be linking local
 183                  * symbols here, so all bases should be covered.
 184                  */
 185                 if (unlikely(!symbol_addr && (ELF_ST_TYPE(sym->st_info) != STT_TLS)
 186                                         && (ELF_ST_BIND(sym->st_info) != STB_WEAK))) {
 187                         /* This may be non-fatal if called from dlopen. */
 188                         return 1;
 189                 }
 190                 if (_dl_trace_prelink)
 191                         _dl_debug_lookup (symname, tpnt, &symtab[symtab_index],
 192                                                 &current_value, elf_machine_type_class(reloc_type));
 193         } else {
 194                 /* Relocs against STN_UNDEF are usually treated as using a
 195                  * symbol value of zero, and using the module containing the
 196                  * reloc itself. */
 197                 symbol_addr = sym->st_value;
 198                 tls_tpnt = tpnt;
 199         }
 200
 201 #if defined (__SUPPORT_LD_DEBUG__)
 202         old_val = *reloc_addr;
 203 #endif
 204
 205         switch (reloc_type) {
 206                 case R_X86_64_NONE:
 207                         break;
 208
 209                 case R_X86_64_64:
 210                         *reloc_addr = symbol_addr + rpnt->r_addend;
 211                         break;
 212
 213                 case R_X86_64_PC32:
 214                         *reloc_addr = symbol_addr + rpnt->r_addend - rpnt->r_offset;
 215                         break;
 216
 217                 case R_X86_64_GLOB_DAT:
 218                 case R_X86_64_JUMP_SLOT:
 219                         *reloc_addr = symbol_addr + rpnt->r_addend;
 220                         break;
 221
 222                 /* handled by elf_machine_relative()
 223                 case R_X86_64_RELATIVE:
 224                         *reloc_addr = map->l_addr + rpnt->r_addend;
 225                         break;
 226                 */
 227 #if defined USE_TLS && USE_TLS
 228                 case R_X86_64_DTPMOD64:
 229                         *reloc_addr = tls_tpnt->l_tls_modid;
 230                         break;
 231                 case R_X86_64_DTPOFF64:
 232                         /* During relocation all TLS symbols are defined and used.
 233                          * Therefore the offset is already correct.  */
 234                         *reloc_addr = symbol_addr + rpnt->r_addend;
 235                         break;
 236                 case R_X86_64_TPOFF64:
 237                         /* The offset is negative, forward from the thread pointer.
 238                          * We know the offset of the object the symbol is contained in.
 239                          * It is a negative value which will be added to the
 240                          * thread pointer.  */
 241                         CHECK_STATIC_TLS ((struct link_map *) tls_tpnt);
 242                         *reloc_addr = symbol_addr - tls_tpnt->l_tls_offset + rpnt->r_addend;
 243                         break;
 244 #endif
 245                 case R_X86_64_32:
 246                         *(unsigned int *) reloc_addr = symbol_addr + rpnt->r_addend;
 247                         /* XXX: should check for overflow eh ? */
 248                         break;
 249
 250                 case R_X86_64_COPY:
 251                         if (symbol_addr) {
 252 #if defined (__SUPPORT_LD_DEBUG__)
 253                                 if (_dl_debug_move)
 254                                         _dl_dprintf(_dl_debug_file,
 255                                                     "\t%s move %d bytes from %x to %x\n",
 256                                                     symname, sym->st_size,
 257                                                     symbol_addr, reloc_addr);
 258 #endif
 259
 260                                 _dl_memcpy((char *)reloc_addr,
 261                                            (char *)symbol_addr,
 262                                            sym->st_size);
 263                         } else
 264                                 _dl_dprintf(_dl_debug_file, "no symbol_addr to copy !?\n");
 265                         break;
 266
 267                 default:
 268                         return -1;      /* Calls _dl_exit(1). */
 269         }
 270
 271 #if defined (__SUPPORT_LD_DEBUG__)
 272         if (_dl_debug_reloc && _dl_debug_detail)
 273                 _dl_dprintf(_dl_debug_file, "\tpatched: %x ==> %x @ %x\n",
 274                             old_val, *reloc_addr, reloc_addr);
 275 #endif
 276
 277         return 0;
 278 }
 279
 280 static int
 281 _dl_do_lazy_reloc(struct elf_resolve *tpnt, struct r_scope_elem *scope,
 282                   ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 283 {
 284         int reloc_type;
 285         int symtab_index;
 286         ElfW(Addr) *reloc_addr;
 287 #if defined (__SUPPORT_LD_DEBUG__)
 288         ElfW(Addr) old_val;
 289 #endif
 290
 291         (void)scope;
 292         symtab_index = ELF_R_SYM(rpnt->r_info);
 293         (void)strtab;
 294
 295         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + rpnt->r_offset);
 296         reloc_type = ELF_R_TYPE(rpnt->r_info);
 297
 298 #if defined (__SUPPORT_LD_DEBUG__)
 299         old_val = *reloc_addr;
 300 #endif
 301
 302         switch (reloc_type) {
 303                 case R_X86_64_NONE:
 304                         break;
 305                 case R_X86_64_JUMP_SLOT:
 306                         *reloc_addr += (unsigned long)tpnt->loadaddr;
 307                         break;
 308                 default:
 309                         _dl_exit(1);
 310         }
 311
 312 #if defined (__SUPPORT_LD_DEBUG__)
 313         if (_dl_debug_reloc && _dl_debug_detail)
 314                 _dl_dprintf(_dl_debug_file, "\tpatched_lazy: %x ==> %x @ %x\n",
 315                             old_val, *reloc_addr, reloc_addr);
 316 #endif
 317
 318         return 0;
 319 }
 320
 321 void
 322 _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 323                                       unsigned long rel_addr,
 324                                       unsigned long rel_size)
 325 {
 326         (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
 327 }
 328
 329 int
 330 _dl_parse_relocation_information(struct dyn_elf *rpnt,
 331                                  struct r_scope_elem *scope,
 332                                  unsigned long rel_addr,
 333                                  unsigned long rel_size)
 334 {
 335         return _dl_parse(rpnt->dyn, scope, rel_addr, rel_size, _dl_do_reloc);
 336 }