ldso/ldso/arm/elfinterp.c

   1 /* vi: set sw=4 ts=4: */
   2 /* ARM ELF shared library loader suppport
   3  *
   4  * Copyright (C) 2001-2004 Erik Andersen
   5  *
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. The name of the above contributors may not be
  14  *    used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 /* Program to load an ELF binary on a linux system, and run it.
  31    References to symbols in sharable libraries can be resolved by either
  32    an ELF sharable library or a linux style of shared library. */
  33
  34 /* Disclaimer:  I have never seen any AT&T source code for SVr4, nor have
  35    I ever taken any courses on internals.  This program was developed using
  36    information available through the book "UNIX SYSTEM V RELEASE 4,
  37    Programmers guide: Ansi C and Programming Support Tools", which did
  38    a more than adequate job of explaining everything required to get this
  39    working. */
  40
  41 #include "ldso.h"
  42
  43 extern int _dl_linux_resolve(void);
  44
  45 unsigned long _dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
  46 {
  47         ELF_RELOC *this_reloc;
  48         char *strtab;
  49         char *symname;
  50         Elf32_Sym *symtab;
  51         ELF_RELOC *rel_addr;
  52         int symtab_index;
  53         unsigned long new_addr;
  54         char **got_addr;
  55         unsigned long instr_addr;
  56
  57         rel_addr = (ELF_RELOC *) tpnt->dynamic_info[DT_JMPREL];
  58
  59         this_reloc = rel_addr + reloc_entry;
  60         symtab_index = ELF32_R_SYM(this_reloc->r_info);
  61
  62         symtab = (Elf32_Sym *) tpnt->dynamic_info[DT_SYMTAB];
  63         strtab = (char *) tpnt->dynamic_info[DT_STRTAB];
  64         symname = strtab + symtab[symtab_index].st_name;
  65
  66         /* Address of jump instruction to fix up */
  67         instr_addr = ((unsigned long) this_reloc->r_offset +
  68                 (unsigned long) tpnt->loadaddr);
  69         got_addr = (char **) instr_addr;
  70
  71         /* Get the address of the GOT entry */
  72         new_addr = _dl_find_hash(symname, &_dl_loaded_modules->symbol_scope,
  73                                  tpnt, ELF_RTYPE_CLASS_PLT, NULL);
  74         if (unlikely(!new_addr)) {
  75                 _dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
  76                         _dl_progname, symname);
  77                 _dl_exit(1);
  78         }
  79 #if defined (__SUPPORT_LD_DEBUG__)
  80 #if !defined __SUPPORT_LD_DEBUG_EARLY__
  81         if ((unsigned long) got_addr < 0x40000000)
  82 #endif
  83         {
  84                 if (_dl_debug_bindings)
  85                 {
  86                         _dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
  87                         if (_dl_debug_detail) _dl_dprintf(_dl_debug_file,
  88                                         "\tpatch %x ==> %x @ %x", *got_addr, new_addr, got_addr);
  89                 }
  90         }
  91         if (!_dl_debug_nofixups) {
  92                 *got_addr = (char *)new_addr;
  93         }
  94 #else
  95         *got_addr = (char *)new_addr;
  96 #endif
  97
  98         return new_addr;
  99 }
 100
 101 static int
 102 _dl_parse(struct elf_resolve *tpnt, struct r_scope_elem *scope,
 103           unsigned long rel_addr, unsigned long rel_size,
 104           int (*reloc_fnc) (struct elf_resolve *tpnt, struct r_scope_elem *scope,
 105                             ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab))
 106 {
 107         int i;
 108         char *strtab;
 109         int goof = 0;
 110         Elf32_Sym *symtab;
 111         ELF_RELOC *rpnt;
 112         int symtab_index;
 113
 114         /* Now parse the relocation information */
 115         rpnt = (ELF_RELOC *) rel_addr;
 116         rel_size = rel_size / sizeof(ELF_RELOC);
 117
 118         symtab = (Elf32_Sym *) tpnt->dynamic_info[DT_SYMTAB];
 119         strtab = (char *) tpnt->dynamic_info[DT_STRTAB];
 120
 121           for (i = 0; i < rel_size; i++, rpnt++) {
 122                 int res;
 123
 124                 symtab_index = ELF32_R_SYM(rpnt->r_info);
 125
 126                 debug_sym(symtab,strtab,symtab_index);
 127                 debug_reloc(symtab,strtab,rpnt);
 128
 129                 res = reloc_fnc (tpnt, scope, rpnt, symtab, strtab);
 130
 131                 if (res==0) continue;
 132
 133                 _dl_dprintf(2, "\n%s: ",_dl_progname);
 134
 135                 if (symtab_index)
 136                   _dl_dprintf(2, "symbol '%s': ", strtab + symtab[symtab_index].st_name);
 137
 138                 if (unlikely(res <0))
 139                 {
 140                         int reloc_type = ELF32_R_TYPE(rpnt->r_info);
 141 #if defined (__SUPPORT_LD_DEBUG__)
 142                         _dl_dprintf(2, "can't handle reloc type %s\n ", _dl_reltypes(reloc_type));
 143 #else
 144                         _dl_dprintf(2, "can't handle reloc type %x\n", reloc_type);
 145 #endif
 146                         _dl_exit(-res);
 147                 }
 148                 if (unlikely(res >0))
 149                 {
 150                         _dl_dprintf(2, "can't resolve symbol\n");
 151                         goof += res;
 152                 }
 153           }
 154           return goof;
 155 }
 156
 157 #if 0
 158 static unsigned long
 159 fix_bad_pc24 (unsigned long *const reloc_addr, unsigned long value)
 160 {
 161   static void *fix_page;
 162   static unsigned int fix_offset;
 163   unsigned int *fix_address;
 164   if (! fix_page)
 165     {
 166       fix_page = _dl_mmap (NULL,  PAGE_SIZE   , PROT_READ | PROT_WRITE | PROT_EXEC,
 167                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 168       fix_offset = 0;
 169     }
 170
 171   fix_address = (unsigned int *)(fix_page + fix_offset);
 172   fix_address[0] = 0xe51ff004;  /* ldr pc, [pc, #-4] */
 173   fix_address[1] = value;
 174
 175   fix_offset += 8;
 176   if (fix_offset >= PAGE_SIZE)
 177     fix_page = NULL;
 178
 179   return (unsigned long)fix_address;
 180 }
 181 #endif
 182
 183 static int
 184 _dl_do_reloc (struct elf_resolve *tpnt,struct r_scope_elem *scope,
 185               ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab)
 186 {
 187         int reloc_type;
 188         int symtab_index;
 189         unsigned long *reloc_addr;
 190         unsigned long symbol_addr;
 191         const Elf32_Sym *def = 0;
 192         struct symbol_ref sym_ref;
 193         struct elf_resolve *def_mod = 0;
 194         int goof = 0;
 195
 196         reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
 197
 198         reloc_type = ELF32_R_TYPE(rpnt->r_info);
 199         symtab_index = ELF32_R_SYM(rpnt->r_info);
 200         symbol_addr = 0;
 201         sym_ref.sym = &symtab[symtab_index];
 202         sym_ref.tpnt = NULL;
 203
 204         if (symtab_index) {
 205                 symbol_addr = _dl_find_hash(strtab + symtab[symtab_index].st_name,
 206                         scope, tpnt, elf_machine_type_class(reloc_type), &sym_ref);
 207
 208                 /*
 209                  * We want to allow undefined references to weak symbols - this might
 210                  * have been intentional.  We should not be linking local symbols
 211                  * here, so all bases should be covered.
 212                  */
 213                 if (!symbol_addr && (ELF_ST_TYPE(symtab[symtab_index].st_info) != STT_TLS)
 214                         && (ELF32_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK)) {
 215                         /* This may be non-fatal if called from dlopen.  */
 216                         return 1;
 217
 218                 }
 219                 if (_dl_trace_prelink)
 220                         _dl_debug_lookup (symname, tpnt, &symtab[symtab_index],
 221                                         &sym_ref, elf_machine_type_class(reloc_type));
 222                 def_mod = sym_ref.tpnt;
 223         } else {
 224                 /*
 225                  * Relocs against STN_UNDEF are usually treated as using a
 226                  * symbol value of zero, and using the module containing the
 227                  * reloc itself.
 228                  */
 229                 symbol_addr = symtab[symtab_index].st_value;
 230                 def_mod = tpnt;
 231         }
 232
 233 #if defined (__SUPPORT_LD_DEBUG__)
 234         {
 235                 unsigned long old_val = *reloc_addr;
 236 #endif
 237                 switch (reloc_type) {
 238                         case R_ARM_NONE:
 239                                 break;
 240                         case R_ARM_ABS32:
 241                                 *reloc_addr += symbol_addr;
 242                                 break;
 243                         case R_ARM_PC24:
 244 #if 0
 245                                 {
 246                                         unsigned long addend;
 247                                         long newvalue, topbits;
 248
 249                                         addend = *reloc_addr & 0x00ffffff;
 250                                         if (addend & 0x00800000) addend |= 0xff000000;
 251
 252                                         newvalue = symbol_addr - (unsigned long)reloc_addr + (addend << 2);
 253                                         topbits = newvalue & 0xfe000000;
 254                                         if (topbits != 0xfe000000 && topbits != 0x00000000)
 255                                         {
 256                                                 newvalue = fix_bad_pc24(reloc_addr, symbol_addr)
 257                                                         - (unsigned long)reloc_addr + (addend << 2);
 258                                                 topbits = newvalue & 0xfe000000;
 259                                                 if (unlikely(topbits != 0xfe000000 && topbits != 0x00000000))
 260                                                 {
 261                                                         _dl_dprintf(2,"symbol '%s': R_ARM_PC24 relocation out of range.",
 262                                                                 symtab[symtab_index].st_name);
 263                                                         _dl_exit(1);
 264                                                 }
 265                                         }
 266                                         newvalue >>= 2;
 267                                         symbol_addr = (*reloc_addr & 0xff000000) | (newvalue & 0x00ffffff);
 268                                         *reloc_addr = symbol_addr;
 269                                         break;
 270                                 }
 271 #else
 272                                 _dl_dprintf(2,"R_ARM_PC24: Compile shared libraries with -fPIC!\n");
 273                                 _dl_exit(1);
 274 #endif
 275                         case R_ARM_GLOB_DAT:
 276                         case R_ARM_JUMP_SLOT:
 277                                 *reloc_addr = symbol_addr;
 278                                 break;
 279                         case R_ARM_RELATIVE:
 280                                 *reloc_addr += (unsigned long) tpnt->loadaddr;
 281                                 break;
 282                         case R_ARM_COPY:
 283                                 _dl_memcpy((void *) reloc_addr,
 284                                            (void *) symbol_addr, symtab[symtab_index].st_size);
 285                                 break;
 286 #if defined USE_TLS && USE_TLS
 287                         case R_ARM_TLS_DTPMOD32:
 288                                 *reloc_addr = def_mod->l_tls_modid;
 289                                 break;
 290
 291                         case R_ARM_TLS_DTPOFF32:
 292                                 *reloc_addr += symbol_addr;
 293                                 break;
 294
 295                         case R_ARM_TLS_TPOFF32:
 296                                 CHECK_STATIC_TLS ((struct link_map *) def_mod);
 297                                 *reloc_addr += (symbol_addr + def_mod->l_tls_offset);
 298                                 break;
 299 #endif
 300                         default:
 301                                 return -1; /*call _dl_exit(1) */
 302                 }
 303 #if defined (__SUPPORT_LD_DEBUG__)
 304                 if (_dl_debug_reloc && _dl_debug_detail)
 305                         _dl_dprintf(_dl_debug_file, "\tpatch: %x ==> %x @ %x", old_val, *reloc_addr, reloc_addr);
 306         }
 307
 308 #endif
 309
 310         return goof;
 311 }
 312
 313 static int
 314 _dl_do_lazy_reloc (struct elf_resolve *tpnt, struct r_scope_elem *scope,
 315                    ELF_RELOC *rpnt, Elf32_Sym *symtab, char *strtab)
 316 {
 317         int reloc_type;
 318         unsigned long *reloc_addr;
 319
 320         reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
 321         reloc_type = ELF32_R_TYPE(rpnt->r_info);
 322
 323 #if defined (__SUPPORT_LD_DEBUG__)
 324         {
 325                 unsigned long old_val = *reloc_addr;
 326 #endif
 327                 switch (reloc_type) {
 328                         case R_ARM_NONE:
 329                                 break;
 330                         case R_ARM_JUMP_SLOT:
 331                                 *reloc_addr += (unsigned long) tpnt->loadaddr;
 332                                 break;
 333                         default:
 334                                 return -1; /*call _dl_exit(1) */
 335                 }
 336 #if defined (__SUPPORT_LD_DEBUG__)
 337                 if (_dl_debug_reloc && _dl_debug_detail)
 338                         _dl_dprintf(_dl_debug_file, "\tpatch: %x ==> %x @ %x", old_val, *reloc_addr, reloc_addr);
 339         }
 340
 341 #endif
 342         return 0;
 343
 344 }
 345
 346 void _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 347         unsigned long rel_addr, unsigned long rel_size)
 348 {
 349         (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
 350 }
 351
 352 int _dl_parse_relocation_information(struct dyn_elf *rpnt,
 353         struct r_scope_elem *scope, unsigned long rel_addr, unsigned long rel_size)
 354 {
 355         return _dl_parse(rpnt->dyn, scope, rel_addr, rel_size, _dl_do_reloc);
 356 }
 357