ldso/ldso/i386/elfinterp.c

   1 /* vi: set sw=4 ts=4: */
   2 /* i386 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         Elf32_Sym *symtab;
  53         int symtab_index;
  54         char *rel_addr;
  55         char *new_addr;
  56         char **got_addr;
  57         unsigned long instr_addr;
  58         char *symname;
  59
  60         rel_addr = (char *)tpnt->dynamic_info[DT_JMPREL];
  61         this_reloc = (ELF_RELOC *)(intptr_t)(rel_addr + reloc_entry);
  62         symtab_index = ELF32_R_SYM(this_reloc->r_info);
  63
  64         symtab = (Elf32_Sym *)(intptr_t)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 = ((unsigned long)this_reloc->r_offset +
  70                       (unsigned long)tpnt->loadaddr);
  71         got_addr = (char **)instr_addr;
  72
  73         /* Get the address of the GOT entry. */
  74         new_addr = _dl_find_hash(symname, tpnt->symbol_scope, tpnt, ELF_RTYPE_CLASS_PLT, NULL);
  75         if (unlikely(!new_addr)) {
  76                 _dl_dprintf(2, "%s: can't resolve symbol '%s' in lib '%s'.\n", _dl_progname, symname, tpnt->libname);
  77                 _dl_exit(1);
  78         }
  79
  80 #if defined (__SUPPORT_LD_DEBUG__)
  81         if ((unsigned long)got_addr < 0x40000000) {
  82                 if (_dl_debug_bindings) {
  83                         _dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
  84                         if (_dl_debug_detail)
  85                                 _dl_dprintf(_dl_debug_file,
  86                                             "\n\tpatched: %x ==> %x @ %x",
  87                                             *got_addr, new_addr, got_addr);
  88                 }
  89         }
  90         if (!_dl_debug_nofixups) {
  91                 *got_addr = new_addr;
  92         }
  93 #else
  94         *got_addr = new_addr;
  95 #endif
  96
  97         return (unsigned long)new_addr;
  98 }
  99
 100 static int
 101 _dl_parse(struct elf_resolve *tpnt, struct dyn_elf *scope,
 102           unsigned long rel_addr, unsigned long rel_size,
 103           int (*reloc_fnc)(struct elf_resolve *tpnt, struct dyn_elf *scope,
 104                            ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab))
 105 {
 106         unsigned int i;
 107         char *strtab;
 108         Elf32_Sym *symtab;
 109         ELF_RELOC *rpnt;
 110         int symtab_index;
 111
 112         /* Parse the relocation information. */
 113         rpnt = (ELF_RELOC *)(intptr_t)rel_addr;
 114         rel_size /= sizeof(ELF_RELOC);
 115
 116         symtab = (Elf32_Sym *)(intptr_t)tpnt->dynamic_info[DT_SYMTAB];
 117         strtab = (char *)tpnt->dynamic_info[DT_STRTAB];
 118
 119         for (i = 0; i < rel_size; i++, rpnt++) {
 120                 int res;
 121
 122                 symtab_index = ELF32_R_SYM(rpnt->r_info);
 123
 124                 debug_sym(symtab, strtab, symtab_index);
 125                 debug_reloc(symtab, strtab, rpnt);
 126
 127                 res = reloc_fnc(tpnt, scope, rpnt, symtab, strtab);
 128
 129                 if (res == 0)
 130                         continue;
 131
 132                 _dl_dprintf(2, "\n%s: ", _dl_progname);
 133
 134                 if (symtab_index)
 135                         _dl_dprintf(2, "symbol '%s': ",
 136                                     strtab + symtab[symtab_index].st_name);
 137
 138                 if (unlikely(res < 0)) {
 139                         int reloc_type = ELF32_R_TYPE(rpnt->r_info);
 140
 141 #if defined (__SUPPORT_LD_DEBUG__)
 142                         _dl_dprintf(2, "can't handle reloc type '%s' in lib '%s'\n",
 143                                     _dl_reltypes(reloc_type), tpnt->libname);
 144 #else
 145                         _dl_dprintf(2, "can't handle reloc type %x in lib '%s'\n",
 146                                     reloc_type, tpnt->libname);
 147 #endif
 148                         return res;
 149                 } else if (unlikely(res > 0)) {
 150                         _dl_dprintf(2, "can't resolve symbol in lib '%s'.\n", tpnt->libname);
 151                         return res;
 152                 }
 153         }
 154
 155         return 0;
 156 }
 157
 158 static int
 159 _dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 160              ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab)
 161 {
 162         int reloc_type;
 163         int symtab_index;
 164         char *symname;
 165         struct elf_resolve *tls_tpnt = 0;
 166         unsigned long *reloc_addr;
 167         unsigned long symbol_addr;
 168 #if defined (__SUPPORT_LD_DEBUG__)
 169         unsigned long old_val;
 170 #endif
 171         struct symbol_ref sym_ref;
 172
 173         reloc_addr = (unsigned long *)(intptr_t)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
 174         reloc_type = ELF32_R_TYPE(rpnt->r_info);
 175         symtab_index = ELF32_R_SYM(rpnt->r_info);
 176         symbol_addr = 0;
 177         sym_ref.sym = &symtab[symtab_index];
 178         sym_ref.tpnt = NULL;
 179         symname = strtab + symtab[symtab_index].st_name;
 180
 181         if (symtab_index) {
 182                 symbol_addr = (unsigned long)_dl_find_hash(symname, scope, tpnt,
 183                                                            elf_machine_type_class(reloc_type), &sym_ref);
 184
 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_TYPE(symtab[symtab_index].st_info) != STT_TLS)
 191                                         && ELF32_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK))
 192                         return 1;
 193                 tls_tpnt = sym_ref.tpnt;
 194         } else {
 195                 symbol_addr = symtab[symtab_index].st_value;
 196                 tls_tpnt = tpnt;
 197         }
 198
 199
 200 #if defined (__SUPPORT_LD_DEBUG__)
 201         old_val = *reloc_addr;
 202 #endif
 203
 204         switch (reloc_type) {
 205                 case R_386_NONE:
 206                         break;
 207                 case R_386_32:
 208                         *reloc_addr += symbol_addr;
 209                         break;
 210                 case R_386_PC32:
 211                         *reloc_addr += symbol_addr - (unsigned long)reloc_addr;
 212                         break;
 213                 case R_386_GLOB_DAT:
 214                 case R_386_JMP_SLOT:
 215                         *reloc_addr = symbol_addr;
 216                         break;
 217                 case R_386_RELATIVE:
 218                         *reloc_addr += (unsigned long)tpnt->loadaddr;
 219                         break;
 220                 case R_386_COPY:
 221                         if (symbol_addr) {
 222 #if defined (__SUPPORT_LD_DEBUG__)
 223                                 if (_dl_debug_move)
 224                                         _dl_dprintf(_dl_debug_file,
 225                                                     "\n%s move %d bytes from %x to %x",
 226                                                     symname, symtab[symtab_index].st_size,
 227                                                     symbol_addr, reloc_addr);
 228 #endif
 229
 230                                 _dl_memcpy((char *)reloc_addr,
 231                                            (char *)symbol_addr,
 232                                            symtab[symtab_index].st_size);
 233                         }
 234                         break;
 235 #if defined USE_TLS && USE_TLS
 236                 case R_386_TLS_DTPMOD32:
 237                         *reloc_addr = tls_tpnt->l_tls_modid;
 238                         break;
 239                 case R_386_TLS_DTPOFF32:
 240                         /* During relocation all TLS symbols are defined and used.
 241                          * Therefore the offset is already correct. */
 242                         *reloc_addr = symbol_addr;
 243                         break;
 244                 case R_386_TLS_TPOFF32:
 245                         /* The offset is positive, backward from the thread pointer. */
 246                         CHECK_STATIC_TLS((struct link_map*) tls_tpnt);
 247                         *reloc_addr += tls_tpnt->l_tls_offset - symbol_addr;
 248                         break;
 249                 case R_386_TLS_TPOFF:
 250                         /* The offset is negative, forward from the thread pointer. */
 251                         CHECK_STATIC_TLS((struct link_map*) tls_tpnt);
 252                         *reloc_addr += symbol_addr - tls_tpnt->l_tls_offset;
 253                         break;
 254 #endif
 255                 default:
 256                         return -1;
 257         }
 258
 259 #if defined (__SUPPORT_LD_DEBUG__)
 260         if (_dl_debug_reloc && _dl_debug_detail)
 261                 _dl_dprintf(_dl_debug_file, "\n\tpatched: %x ==> %x @ %x\n",
 262                             old_val, *reloc_addr, reloc_addr);
 263 #endif
 264
 265         return 0;
 266 }
 267
 268 static int
 269 _dl_do_lazy_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 270                   ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab)
 271 {
 272         int reloc_type;
 273         unsigned long *reloc_addr;
 274 #if defined (__SUPPORT_LD_DEBUG__)
 275         unsigned long old_val;
 276 #endif
 277
 278         (void)scope;
 279         (void)symtab;
 280         (void)strtab;
 281
 282         reloc_addr = (unsigned long *)(intptr_t)(tpnt->loadaddr + (unsigned long)rpnt->r_offset);
 283         reloc_type = ELF32_R_TYPE(rpnt->r_info);
 284
 285 #if defined (__SUPPORT_LD_DEBUG__)
 286         old_val = *reloc_addr;
 287 #endif
 288
 289         switch (reloc_type) {
 290                 case R_386_NONE:
 291                         break;
 292                 case R_386_JMP_SLOT:
 293                         *reloc_addr += (unsigned long)tpnt->loadaddr;
 294                         break;
 295                 default:
 296                         return -1;
 297         }
 298
 299 #if defined (__SUPPORT_LD_DEBUG__)
 300         if (_dl_debug_reloc && _dl_debug_detail)
 301                 _dl_dprintf(_dl_debug_file, "\n\tpatched: %x ==> %x @ %x\n",
 302                             old_val, *reloc_addr, reloc_addr);
 303 #endif
 304
 305         return 0;
 306 }
 307
 308 void
 309 _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 310                                       unsigned long rel_addr,
 311                                       unsigned long rel_size)
 312 {
 313         (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
 314 }
 315
 316 int
 317 _dl_parse_relocation_information(struct dyn_elf *rpnt,
 318                                  unsigned long rel_addr,
 319                                  unsigned long rel_size)
 320 {
 321         return _dl_parse(rpnt->dyn, rpnt->dyn->symbol_scope, rel_addr, rel_size, _dl_do_reloc);
 322 }