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, tpnt->symbol_scope, tpnt, ELF_RTYPE_CLASS_PLT);
  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 dyn_elf *scope,
  98           unsigned long rel_addr, unsigned long rel_size,
  99           int (*reloc_fnc)(struct elf_resolve *tpnt, struct dyn_elf *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 dyn_elf *scope,
 155              ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 156 {
 157         int reloc_type;
 158         int symtab_index;
 159         char *symname;
 160         ElfW(Sym) *sym;
 161         ElfW(Addr) *reloc_addr;
 162         ElfW(Addr) symbol_addr;
 163 #if defined (__SUPPORT_LD_DEBUG__)
 164         ElfW(Addr) old_val;
 165 #endif
 166
 167         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
 168         reloc_type = ELF_R_TYPE(rpnt->r_info);
 169         symtab_index = ELF_R_SYM(rpnt->r_info);
 170         sym = &symtab[symtab_index];
 171         symbol_addr = 0;
 172         symname = strtab + sym->st_name;
 173
 174         if (symtab_index) {
 175                 symbol_addr = (ElfW(Addr))_dl_find_hash(symname, scope, tpnt,
 176                                                             elf_machine_type_class(reloc_type));
 177                 /*
 178                  * We want to allow undefined references to weak symbols - this
 179                  * might have been intentional.  We should not be linking local
 180                  * symbols here, so all bases should be covered.
 181                  */
 182                 if (unlikely(!symbol_addr && ELF_ST_BIND(sym->st_info) != STB_WEAK)) {
 183                         _dl_dprintf(2, "%s: can't resolve symbol '%s'\n", _dl_progname, symname);
 184                         _dl_exit(1);
 185                 }
 186         }
 187
 188 #if defined (__SUPPORT_LD_DEBUG__)
 189         old_val = *reloc_addr;
 190 #endif
 191
 192         switch (reloc_type) {
 193                 case R_X86_64_NONE:
 194                         break;
 195
 196                 case R_X86_64_64:
 197                         *reloc_addr = symbol_addr + rpnt->r_addend;
 198                         break;
 199
 200                 case R_X86_64_PC32:
 201                         *reloc_addr = symbol_addr + rpnt->r_addend - rpnt->r_offset;
 202                         break;
 203
 204                 case R_X86_64_GLOB_DAT:
 205                 case R_X86_64_JUMP_SLOT:
 206                         *reloc_addr = symbol_addr + rpnt->r_addend;
 207                         break;
 208
 209                 /* handled by elf_machine_relative()
 210                 case R_X86_64_RELATIVE:
 211                         *reloc_addr = map->l_addr + rpnt->r_addend;
 212                         break;
 213                 */
 214                 case R_X86_64_DTPMOD64:
 215                         *reloc_addr = 1;
 216                         break;
 217                 case R_X86_64_DTPOFF64:
 218                         *reloc_addr = sym->st_value + rpnt->r_addend;
 219                         break;
 220                 case R_X86_64_TPOFF64:
 221                         *reloc_addr = sym->st_value + rpnt->r_addend - symbol_addr;
 222                         break;
 223                 case R_X86_64_32:
 224                         *(unsigned int *) reloc_addr = symbol_addr + rpnt->r_addend;
 225                         /* XXX: should check for overflow eh ? */
 226                         break;
 227
 228                 case R_X86_64_COPY:
 229                         if (symbol_addr) {
 230 #if defined (__SUPPORT_LD_DEBUG__)
 231                                 if (_dl_debug_move)
 232                                         _dl_dprintf(_dl_debug_file,
 233                                                     "\t%s move %d bytes from %x to %x\n",
 234                                                     symname, sym->st_size,
 235                                                     symbol_addr, reloc_addr);
 236 #endif
 237
 238                                 _dl_memcpy((char *)reloc_addr,
 239                                            (char *)symbol_addr,
 240                                            sym->st_size);
 241                         } else
 242                                 _dl_dprintf(_dl_debug_file, "no symbol_addr to copy !?\n");
 243                         break;
 244
 245                 default:
 246                         return -1;      /* Calls _dl_exit(1). */
 247         }
 248
 249 #if defined (__SUPPORT_LD_DEBUG__)
 250         if (_dl_debug_reloc && _dl_debug_detail)
 251                 _dl_dprintf(_dl_debug_file, "\tpatched: %x ==> %x @ %x\n",
 252                             old_val, *reloc_addr, reloc_addr);
 253 #endif
 254
 255         return 0;
 256 }
 257
 258 static int
 259 _dl_do_lazy_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 260                   ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 261 {
 262         int reloc_type;
 263         int symtab_index;
 264         ElfW(Addr) *reloc_addr;
 265 #if defined (__SUPPORT_LD_DEBUG__)
 266         ElfW(Addr) old_val;
 267 #endif
 268
 269         (void)scope;
 270         symtab_index = ELF_R_SYM(rpnt->r_info);
 271         (void)strtab;
 272
 273         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + rpnt->r_offset);
 274         reloc_type = ELF_R_TYPE(rpnt->r_info);
 275
 276 #if defined (__SUPPORT_LD_DEBUG__)
 277         old_val = *reloc_addr;
 278 #endif
 279
 280         switch (reloc_type) {
 281                 case R_X86_64_NONE:
 282                         break;
 283                 case R_X86_64_JUMP_SLOT:
 284                         *reloc_addr += (unsigned long)tpnt->loadaddr;
 285                         break;
 286                 default:
 287                         _dl_exit(1);
 288         }
 289
 290 #if defined (__SUPPORT_LD_DEBUG__)
 291         if (_dl_debug_reloc && _dl_debug_detail)
 292                 _dl_dprintf(_dl_debug_file, "\tpatched_lazy: %x ==> %x @ %x\n",
 293                             old_val, *reloc_addr, reloc_addr);
 294 #endif
 295
 296         return 0;
 297 }
 298
 299 void
 300 _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 301                                       unsigned long rel_addr,
 302                                       unsigned long rel_size)
 303 {
 304         (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
 305 }
 306
 307 int
 308 _dl_parse_relocation_information(struct dyn_elf *rpnt,
 309                                  unsigned long rel_addr,
 310                                  unsigned long rel_size)
 311 {
 312         return _dl_parse(rpnt->dyn, rpnt->dyn->symbol_scope, rel_addr, rel_size, _dl_do_reloc);
 313 }