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         int reloc_type;
  51         ELF_RELOC *this_reloc;
  52         char *strtab;
  53         ElfW(Sym) *symtab;
  54         int symtab_index;
  55         char *rel_addr;
  56         char *new_addr;
  57         char **got_addr;
  58         ElfW(Addr) instr_addr;
  59         char *symname;
  60
  61         rel_addr = (char *)tpnt->dynamic_info[DT_JMPREL];
  62         this_reloc = (ELF_RELOC *)(rel_addr + reloc_entry);
  63         reloc_type = ELF_R_TYPE(this_reloc->r_info);
  64         symtab_index = ELF_R_SYM(this_reloc->r_info);
  65
  66         symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
  67         strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
  68         symname = strtab + symtab[symtab_index].st_name;
  69
  70         if (unlikely(reloc_type != R_X86_64_JUMP_SLOT)) {
  71                 _dl_dprintf(2, "%s: Incorrect relocation type in jump relocations\n",
  72                             _dl_progname);
  73                 _dl_exit(1);
  74         }
  75
  76         /* Address of the jump instruction to fix up. */
  77         instr_addr = (this_reloc->r_offset + tpnt->loadaddr);
  78         got_addr = (char **)instr_addr;
  79
  80         /* Get the address of the GOT entry. */
  81         new_addr = _dl_find_hash(symname, tpnt->symbol_scope, tpnt, ELF_RTYPE_CLASS_PLT);
  82         if (unlikely(!new_addr)) {
  83                 _dl_dprintf(2, "%s: Can't resolve symbol '%s'\n", _dl_progname, symname);
  84                 _dl_exit(1);
  85         }
  86
  87 #if defined (__SUPPORT_LD_DEBUG__)
  88         if ((unsigned long)got_addr < 0x40000000) {
  89                 if (_dl_debug_bindings) {
  90                         _dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
  91                         if (_dl_debug_detail)
  92                                 _dl_dprintf(_dl_debug_file,
  93                                             "\tpatched: %x ==> %x @ %x\n",
  94                                             *got_addr, new_addr, got_addr);
  95                 }
  96         }
  97         if (!_dl_debug_nofixups)
  98 #endif
  99                 *got_addr = new_addr;
 100
 101         return (unsigned long)new_addr;
 102 }
 103
 104 static int
 105 _dl_parse(struct elf_resolve *tpnt, struct dyn_elf *scope,
 106           unsigned long rel_addr, unsigned long rel_size,
 107           int (*reloc_fnc)(struct elf_resolve *tpnt, struct dyn_elf *scope,
 108                            ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab))
 109 {
 110         unsigned int i;
 111         char *strtab;
 112         ElfW(Sym) *symtab;
 113         ELF_RELOC *rpnt;
 114         int symtab_index;
 115
 116         /* Parse the relocation information. */
 117         rpnt = (ELF_RELOC *)rel_addr;
 118         rel_size /= sizeof(ELF_RELOC);
 119
 120         symtab = (ElfW(Sym) *)tpnt->dynamic_info[DT_SYMTAB];
 121         strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
 122
 123         for (i = 0; i < rel_size; i++, rpnt++) {
 124                 int res;
 125
 126                 symtab_index = ELF_R_SYM(rpnt->r_info);
 127
 128                 debug_sym(symtab, strtab, symtab_index);
 129                 debug_reloc(symtab, strtab, rpnt);
 130
 131                 res = reloc_fnc(tpnt, scope, rpnt, symtab, strtab);
 132
 133                 if (res == 0)
 134                         continue;
 135
 136                 _dl_dprintf(2, "\n%s: ", _dl_progname);
 137
 138                 if (symtab_index)
 139                         _dl_dprintf(2, "symbol '%s': ",
 140                                     strtab + symtab[symtab_index].st_name);
 141
 142                 if (unlikely(res < 0)) {
 143                         int reloc_type = ELF_R_TYPE(rpnt->r_info);
 144
 145                         _dl_dprintf(2, "can't handle reloc type "
 146 #if defined (__SUPPORT_LD_DEBUG__)
 147                                     "%s\n", _dl_reltypes(reloc_type));
 148 #else
 149                                     "%x\n", reloc_type);
 150 #endif
 151                         _dl_exit(-res);
 152                 } else if (unlikely(res > 0)) {
 153                         _dl_dprintf(2, "can't resolve symbol\n");
 154                         return res;
 155                 }
 156         }
 157
 158         return 0;
 159 }
 160
 161 static int
 162 _dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 163              ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 164 {
 165         int reloc_type;
 166         int symtab_index;
 167         char *symname;
 168         ElfW(Sym) *sym;
 169         ElfW(Addr) *reloc_addr;
 170         ElfW(Addr) symbol_addr;
 171 #if defined (__SUPPORT_LD_DEBUG__)
 172         ElfW(Addr) old_val;
 173 #endif
 174
 175         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
 176         reloc_type = ELF_R_TYPE(rpnt->r_info);
 177         symtab_index = ELF_R_SYM(rpnt->r_info);
 178         sym = &symtab[symtab_index];
 179         symbol_addr = 0;
 180         symname = strtab + sym->st_name;
 181
 182         if (symtab_index) {
 183                 symbol_addr = (ElfW(Addr))_dl_find_hash(symname, scope, tpnt,
 184                                                             elf_machine_type_class(reloc_type));
 185                 /*
 186                  * We want to allow undefined references to weak symbols - this
 187                  * might have been intentional.  We should not be linking local
 188                  * symbols here, so all bases should be covered.
 189                  */
 190                 if (unlikely(!symbol_addr && ELF_ST_BIND(sym->st_info) != STB_WEAK)) {
 191                         _dl_dprintf(2, "%s: can't resolve symbol '%s'\n", _dl_progname, symname);
 192                         _dl_exit(1);
 193                 };
 194         }
 195
 196 #if defined (__SUPPORT_LD_DEBUG__)
 197         old_val = *reloc_addr;
 198 #endif
 199
 200         switch (reloc_type) {
 201                 case R_X86_64_NONE:
 202                         break;
 203
 204                 case R_X86_64_64:
 205                         *reloc_addr = symbol_addr + rpnt->r_addend;
 206                         break;
 207
 208                 case R_X86_64_PC32:
 209                         *reloc_addr = symbol_addr + rpnt->r_addend - rpnt->r_offset;
 210                         break;
 211
 212                 case R_X86_64_GLOB_DAT:
 213                 case R_X86_64_JUMP_SLOT:
 214                         *reloc_addr = symbol_addr + rpnt->r_addend;
 215                         break;
 216
 217                 /* handled by elf_machine_relative()
 218                 case R_X86_64_RELATIVE:
 219                         *reloc_addr = map->l_addr + rpnt->r_addend;
 220                         break;
 221                 */
 222                 case R_X86_64_DTPMOD64:
 223                         *reloc_addr = 1;
 224                         break;
 225                 case R_X86_64_DTPOFF64:
 226                         *reloc_addr = sym->st_value + rpnt->r_addend;
 227                         break;
 228                 case R_X86_64_TPOFF64:
 229                         *reloc_addr = sym->st_value + rpnt->r_addend - symbol_addr;
 230                         break;
 231                 case R_X86_64_32:
 232                         *(unsigned int *) reloc_addr = symbol_addr + rpnt->r_addend;
 233                         /* XXX: should check for overflow eh ? */
 234                         break;
 235
 236                 case R_X86_64_COPY:
 237                         if (symbol_addr) {
 238 #if defined (__SUPPORT_LD_DEBUG__)
 239                                 if (_dl_debug_move)
 240                                         _dl_dprintf(_dl_debug_file,
 241                                                     "\t%s move %d bytes from %x to %x\n",
 242                                                     symname, sym->st_size,
 243                                                     symbol_addr, reloc_addr);
 244 #endif
 245
 246                                 _dl_memcpy((char *)reloc_addr,
 247                                            (char *)symbol_addr,
 248                                            sym->st_size);
 249                         } else
 250                                 _dl_dprintf(_dl_debug_file, "no symbol_addr to copy !?\n");
 251                         break;
 252
 253                 default:
 254                         return -1;      /* Calls _dl_exit(1). */
 255         }
 256
 257 #if defined (__SUPPORT_LD_DEBUG__)
 258         if (_dl_debug_reloc && _dl_debug_detail)
 259                 _dl_dprintf(_dl_debug_file, "\tpatched: %x ==> %x @ %x\n",
 260                             old_val, *reloc_addr, reloc_addr);
 261 #endif
 262
 263         return 0;
 264 }
 265
 266 static int
 267 _dl_do_lazy_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 268                   ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
 269 {
 270         int reloc_type;
 271         int symtab_index;
 272         ElfW(Addr) *reloc_addr;
 273 #if defined (__SUPPORT_LD_DEBUG__)
 274         ElfW(Addr) old_val;
 275 #endif
 276
 277         (void)scope;
 278         symtab_index = ELF_R_SYM(rpnt->r_info);
 279         (void)strtab;
 280
 281         reloc_addr = (ElfW(Addr)*)(tpnt->loadaddr + rpnt->r_offset);
 282         reloc_type = ELF_R_TYPE(rpnt->r_info);
 283
 284 #if defined (__SUPPORT_LD_DEBUG__)
 285         old_val = *reloc_addr;
 286 #endif
 287
 288         switch (reloc_type) {
 289                 case R_X86_64_NONE:
 290                         break;
 291                 case R_X86_64_JUMP_SLOT:
 292                         *reloc_addr += (unsigned long)tpnt->loadaddr;
 293                         break;
 294                 default:
 295                         _dl_exit(1);
 296         }
 297
 298 #if defined (__SUPPORT_LD_DEBUG__)
 299         if (_dl_debug_reloc && _dl_debug_detail)
 300                 _dl_dprintf(_dl_debug_file, "\tpatched_lazy: %x ==> %x @ %x\n",
 301                             old_val, *reloc_addr, reloc_addr);
 302 #endif
 303
 304         return 0;
 305 }
 306
 307 void
 308 _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 309                                       unsigned long rel_addr,
 310                                       unsigned long rel_size)
 311 {
 312         (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
 313 }
 314
 315 int
 316 _dl_parse_relocation_information(struct dyn_elf *rpnt,
 317                                  unsigned long rel_addr,
 318                                  unsigned long rel_size)
 319 {
 320         return _dl_parse(rpnt->dyn, rpnt->dyn->symbol_scope, rel_addr, rel_size, _dl_do_reloc);
 321 }