libexec/ld.elf_so/arch/mips/mips_reloc.c

   1 /*      $NetBSD: mips_reloc.c,v 1.60 2010/09/24 15:20:52 matt Exp $     */
   2
   3 /*
   4  * Copyright 1997 Michael L. Hitch <mhitch@montana.edu>
   5  * Portions copyright 2002 Charles M. Hannum <root@ihack.net>
   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. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. The name of the author may not be used to endorse or promote products
  17  *    derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include <sys/cdefs.h>
  32 #ifndef lint
  33 __RCSID("$NetBSD: mips_reloc.c,v 1.60 2010/09/24 15:20:52 matt Exp $");
  34 #endif /* not lint */
  35
  36 #include <sys/types.h>
  37 #include <sys/endian.h>
  38
  39 #include <stdlib.h>
  40 #include <string.h>
  41
  42 #include "debug.h"
  43 #include "rtld.h"
  44
  45 #ifdef __mips_o32
  46 #define SUPPORT_OLD_BROKEN_LD
  47 #endif
  48
  49 void _rtld_bind_start(void);
  50 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
  51 caddr_t _rtld_bind(Elf_Word, Elf_Addr, Elf_Addr, Elf_Addr);
  52
  53 /*
  54  * It is possible for the compiler to emit relocations for unaligned data.
  55  * We handle this situation with these inlines.
  56  */
  57
  58 #if ELFSIZE == 64
  59 /*
  60  * ELF64 MIPS encodes the relocs uniquely.  The first 32-bits of info contain
  61  * the symbol index.  The top 32-bits contain three relocation types encoded
  62  * in big-endian integer with first relocation in LSB.  This means for little
  63  * endian we have to byte swap that interger (r_type).
  64  */
  65 #define Elf_Sxword                      Elf64_Sxword
  66 #define ELF_R_NXTTYPE_64_P(r_type)      ((((r_type) >> 8) & 0xff) == R_TYPE(64))
  67 #if BYTE_ORDER == LITTLE_ENDIAN
  68 #undef ELF_R_SYM
  69 #undef ELF_R_TYPE
  70 #define ELF_R_SYM(r_info)               ((r_info) & 0xffffffff)
  71 #define ELF_R_TYPE(r_info)              bswap32((r_info) >> 32)
  72 #endif
  73 #else
  74 #define ELF_R_NXTTYPE_64_P(r_type)      (0)
  75 #define Elf_Sxword                      Elf32_Sword
  76 #endif
  77 #define GOT1_MASK                       (~(Elf_Addr)0 >> 1)
  78
  79 static inline Elf_Sxword
  80 load_ptr(void *where, size_t len)
  81 {
  82         Elf_Sxword val;
  83
  84         if (__predict_true(((uintptr_t)where & (len - 1)) == 0)) {
  85 #if ELFSIZE == 64
  86                 if (len == sizeof(Elf_Sxword))
  87                         return *(Elf_Sxword *)where;
  88 #endif
  89                 return *(Elf_Sword *)where;
  90         }
  91
  92         val = 0;
  93 #if BYTE_ORDER == LITTLE_ENDIAN
  94         (void)memcpy(&val, where, len);
  95 #endif
  96 #if BYTE_ORDER == BIG_ENDIAN
  97         (void)memcpy((uint8_t *)((&val)+1) - len, where, len);
  98 #endif
  99         return (len == sizeof(Elf_Sxword)) ? val : (Elf_Sword)val;
 100 }
 101
 102 static inline void
 103 store_ptr(void *where, Elf_Sxword val, size_t len)
 104 {
 105         if (__predict_true(((uintptr_t)where & (len - 1)) == 0)) {
 106 #if ELFSIZE == 64
 107                 if (len == sizeof(Elf_Sxword)) {
 108                         *(Elf_Sxword *)where = val;
 109                         return;
 110                 }
 111 #endif
 112                 *(Elf_Sword *)where = val;
 113                 return;
 114         }
 115 #if BYTE_ORDER == LITTLE_ENDIAN
 116         (void)memcpy(where, &val, len);
 117 #endif
 118 #if BYTE_ORDER == BIG_ENDIAN
 119         (void)memcpy(where, (const uint8_t *)((&val)+1) - len, len);
 120 #endif
 121 }
 122
 123
 124 void
 125 _rtld_setup_pltgot(const Obj_Entry *obj)
 126 {
 127         obj->pltgot[0] = (Elf_Addr) &_rtld_bind_start;
 128         /* XXX only if obj->pltgot[1] & 0x80000000 ?? */
 129         obj->pltgot[1] |= (Elf_Addr) obj;
 130 }
 131
 132 void
 133 _rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
 134 {
 135         const Elf_Rel *rel = 0, *rellim;
 136         Elf_Addr relsz = 0;
 137         void *where;
 138         const Elf_Sym *symtab = NULL, *sym;
 139         Elf_Addr *got = NULL;
 140         Elf_Word local_gotno = 0, symtabno = 0, gotsym = 0;
 141         size_t i;
 142
 143         for (; dynp->d_tag != DT_NULL; dynp++) {
 144                 switch (dynp->d_tag) {
 145                 case DT_REL:
 146                         rel = (const Elf_Rel *)(relocbase + dynp->d_un.d_ptr);
 147                         break;
 148                 case DT_RELSZ:
 149                         relsz = dynp->d_un.d_val;
 150                         break;
 151                 case DT_SYMTAB:
 152                         symtab = (const Elf_Sym *)(relocbase + dynp->d_un.d_ptr);
 153                         break;
 154                 case DT_PLTGOT:
 155                         got = (Elf_Addr *)(relocbase + dynp->d_un.d_ptr);
 156                         break;
 157                 case DT_MIPS_LOCAL_GOTNO:
 158                         local_gotno = dynp->d_un.d_val;
 159                         break;
 160                 case DT_MIPS_SYMTABNO:
 161                         symtabno = dynp->d_un.d_val;
 162                         break;
 163                 case DT_MIPS_GOTSYM:
 164                         gotsym = dynp->d_un.d_val;
 165                         break;
 166                 }
 167         }
 168
 169         i = (got[1] & 0x80000000) ? 2 : 1;
 170         /* Relocate the local GOT entries */
 171         got += i;
 172         for (; i < local_gotno; i++)
 173                 *got++ += relocbase;
 174         sym = symtab + gotsym;
 175         /* Now do the global GOT entries */
 176         for (i = gotsym; i < symtabno; i++) {
 177                 *got = sym->st_value + relocbase;
 178                 ++sym;
 179                 ++got;
 180         }
 181
 182         rellim = (const Elf_Rel *)((uintptr_t)rel + relsz);
 183         for (; rel < rellim; rel++) {
 184                 Elf_Word r_symndx, r_type;
 185
 186                 where = (void *)(relocbase + rel->r_offset);
 187
 188                 r_symndx = ELF_R_SYM(rel->r_info);
 189                 r_type = ELF_R_TYPE(rel->r_info);
 190
 191                 switch (r_type & 0xff) {
 192                 case R_TYPE(REL32): {
 193                         const size_t rlen =
 194                             ELF_R_NXTTYPE_64_P(r_type)
 195                                 ? sizeof(Elf_Sxword)
 196                                 : sizeof(Elf_Sword);
 197                         Elf_Sxword old = load_ptr(where, rlen);
 198                         Elf_Sxword val = old;
 199 #if ELFSIZE == 64
 200                         assert(r_type == R_TYPE(REL32)
 201                             || r_type == (R_TYPE(REL32)|(R_TYPE(64) << 8)));
 202 #endif
 203                         assert(r_symndx < gotsym);
 204                         sym = symtab + r_symndx;
 205                         assert(ELF_ST_BIND(sym->st_info) == STB_LOCAL);
 206                         val += relocbase;
 207                         store_ptr(where, val, sizeof(Elf_Sword));
 208                         rdbg(("REL32/L(%p) %p -> %p in <self>",
 209                             where, (void *)old, (void *)val));
 210                         store_ptr(where, val, rlen);
 211                         break;
 212                 }
 213
 214                 case R_TYPE(GPREL32):
 215                 case R_TYPE(NONE):
 216                         break;
 217
 218
 219                 default:
 220                         abort();
 221                 }
 222         }
 223 }
 224
 225 int
 226 _rtld_relocate_nonplt_objects(Obj_Entry *obj)
 227 {
 228         const Elf_Rel *rel;
 229         Elf_Addr *got = obj->pltgot;
 230         const Elf_Sym *sym, *def;
 231         const Obj_Entry *defobj;
 232         Elf_Word i;
 233 #ifdef SUPPORT_OLD_BROKEN_LD
 234         int broken;
 235 #endif
 236
 237 #ifdef SUPPORT_OLD_BROKEN_LD
 238         broken = 0;
 239         sym = obj->symtab;
 240         for (i = 1; i < 12; i++)
 241                 if (sym[i].st_info == ELF_ST_INFO(STB_LOCAL, STT_NOTYPE))
 242                         broken = 1;
 243         dbg(("%s: broken=%d", obj->path, broken));
 244 #endif
 245
 246         i = (got[1] & 0x80000000) ? 2 : 1;
 247         /* Relocate the local GOT entries */
 248         got += i;
 249         for (; i < obj->local_gotno; i++)
 250                 *got++ += (Elf_Addr)obj->relocbase;
 251         sym = obj->symtab + obj->gotsym;
 252         /* Now do the global GOT entries */
 253         for (i = obj->gotsym; i < obj->symtabno; i++) {
 254                 rdbg((" doing got %d sym %p (%s, %lx)", i - obj->gotsym, sym,
 255                     sym->st_name + obj->strtab, (u_long) *got));
 256
 257 #ifdef SUPPORT_OLD_BROKEN_LD
 258                 if (ELF_ST_TYPE(sym->st_info) == STT_FUNC &&
 259                     broken && sym->st_shndx == SHN_UNDEF) {
 260                         /*
 261                          * XXX DANGER WILL ROBINSON!
 262                          * You might think this is stupid, as it intentionally
 263                          * defeats lazy binding -- and you'd be right.
 264                          * Unfortunately, for lazy binding to work right, we
 265                          * need to a way to force the GOT slots used for
 266                          * function pointers to be resolved immediately.  This
 267                          * is supposed to be done automatically by the linker,
 268                          * by not outputting a PLT slot and setting st_value
 269                          * to 0 if there are non-PLT references, but older
 270                          * versions of GNU ld do not do this.
 271                          */
 272                         def = _rtld_find_symdef(i, obj, &defobj, false);
 273                         if (def == NULL)
 274                                 return -1;
 275                         *got = def->st_value + (Elf_Addr)defobj->relocbase;
 276                 } else
 277 #endif
 278                 if (ELF_ST_TYPE(sym->st_info) == STT_FUNC &&
 279                     sym->st_value != 0 && sym->st_shndx == SHN_UNDEF) {
 280                         /*
 281                          * If there are non-PLT references to the function,
 282                          * st_value should be 0, forcing us to resolve the
 283                          * address immediately.
 284                          *
 285                          * XXX DANGER WILL ROBINSON!
 286                          * The linker is not outputting PLT slots for calls to
 287                          * functions that are defined in the same shared
 288                          * library.  This is a bug, because it can screw up
 289                          * link ordering rules if the symbol is defined in
 290                          * more than one module.  For now, if there is a
 291                          * definition, we fail the test above and force a full
 292                          * symbol lookup.  This means that all intra-module
 293                          * calls are bound immediately.  - mycroft, 2003/09/24
 294                          */
 295                         *got = sym->st_value + (Elf_Addr)obj->relocbase;
 296                 } else if (sym->st_info == ELF_ST_INFO(STB_GLOBAL, STT_SECTION)) {
 297                         /* Symbols with index SHN_ABS are not relocated. */
 298                         if (sym->st_shndx != SHN_ABS)
 299                                 *got = sym->st_value +
 300                                     (Elf_Addr)obj->relocbase;
 301                 } else {
 302                         def = _rtld_find_symdef(i, obj, &defobj, false);
 303                         if (def == NULL)
 304                                 return -1;
 305                         *got = def->st_value + (Elf_Addr)defobj->relocbase;
 306                 }
 307
 308                 rdbg(("  --> now %lx", (u_long) *got));
 309                 ++sym;
 310                 ++got;
 311         }
 312
 313         got = obj->pltgot;
 314         for (rel = obj->rel; rel < obj->rellim; rel++) {
 315                 Elf_Word        r_symndx, r_type;
 316                 void            *where;
 317
 318                 where = obj->relocbase + rel->r_offset;
 319                 r_symndx = ELF_R_SYM(rel->r_info);
 320                 r_type = ELF_R_TYPE(rel->r_info);
 321
 322                 switch (r_type & 0xff) {
 323                 case R_TYPE(NONE):
 324                         break;
 325
 326                 case R_TYPE(REL32): {
 327                         /* 32-bit PC-relative reference */
 328                         const size_t rlen =
 329                             ELF_R_NXTTYPE_64_P(r_type)
 330                                 ? sizeof(Elf_Sxword)
 331                                 : sizeof(Elf_Sword);
 332                         Elf_Sxword old = load_ptr(where, rlen);
 333                         Elf_Sxword val = old;
 334
 335                         def = obj->symtab + r_symndx;
 336
 337                         if (r_symndx >= obj->gotsym) {
 338                                 val += got[obj->local_gotno + r_symndx - obj->gotsym];
 339                                 rdbg(("REL32/G(%p) %p --> %p (%s) in %s",
 340                                     where, (void *)old, (void *)val,
 341                                     obj->strtab + def->st_name,
 342                                     obj->path));
 343                         } else {
 344                                 /*
 345                                  * XXX: ABI DIFFERENCE!
 346                                  *
 347                                  * Old NetBSD binutils would generate shared
 348                                  * libs with section-relative relocations being
 349                                  * already adjusted for the start address of
 350                                  * the section.
 351                                  *
 352                                  * New binutils, OTOH, generate shared libs
 353                                  * with the same relocations being based at
 354                                  * zero, so we need to add in the start address
 355                                  * of the section.
 356                                  *
 357                                  * --rkb, Oct 6, 2001
 358                                  */
 359
 360                                 if (def->st_info ==
 361                                     ELF_ST_INFO(STB_LOCAL, STT_SECTION)
 362 #ifdef SUPPORT_OLD_BROKEN_LD
 363                                     && !broken
 364 #endif
 365                                     )
 366                                         val += (Elf_Addr)def->st_value;
 367
 368                                 val += (Elf_Addr)obj->relocbase;
 369
 370                                 rdbg(("REL32/L(%p) %p -> %p (%s) in %s",
 371                                     where, (void *)old, (void *)val,
 372                                     obj->strtab + def->st_name, obj->path));
 373                         }
 374                         store_ptr(where, val, rlen);
 375                         break;
 376                 }
 377
 378                 default:
 379                         rdbg(("sym = %lu, type = %lu, offset = %p, "
 380                             "contents = %p, symbol = %s",
 381                             (u_long)r_symndx, (u_long)ELF_R_TYPE(rel->r_info),
 382                             (void *)rel->r_offset,
 383                             (void *)load_ptr(where, sizeof(Elf_Sword)),
 384                             obj->strtab + obj->symtab[r_symndx].st_name));
 385                         _rtld_error("%s: Unsupported relocation type %ld "
 386                             "in non-PLT relocations",
 387                             obj->path, (u_long) ELF_R_TYPE(rel->r_info));
 388                         return -1;
 389                 }
 390         }
 391
 392         return 0;
 393 }
 394
 395 int
 396 _rtld_relocate_plt_lazy(const Obj_Entry *obj)
 397 {
 398         /* PLT fixups were done above in the GOT relocation. */
 399         return 0;
 400 }
 401
 402 static inline int
 403 _rtld_relocate_plt_object(const Obj_Entry *obj, Elf_Word sym, Elf_Addr *tp)
 404 {
 405         Elf_Addr *got = obj->pltgot;
 406         const Elf_Sym *def;
 407         const Obj_Entry *defobj;
 408         Elf_Addr new_value;
 409
 410         def = _rtld_find_plt_symdef(sym, obj, &defobj, tp != NULL);
 411         if (__predict_false(def == NULL))
 412                 return -1;
 413         if (__predict_false(def == &_rtld_sym_zero))
 414                 return 0;
 415
 416         new_value = (Elf_Addr)(defobj->relocbase + def->st_value);
 417         rdbg(("bind now/fixup in %s --> new=%p",
 418             defobj->strtab + def->st_name, (void *)new_value));
 419         got[obj->local_gotno + sym - obj->gotsym] = new_value;
 420
 421         if (tp)
 422                 *tp = new_value;
 423         return 0;
 424 }
 425
 426 caddr_t
 427 _rtld_bind(Elf_Word a0, Elf_Addr a1, Elf_Addr a2, Elf_Addr a3)
 428 {
 429         Elf_Addr *got = (Elf_Addr *)(a2 - 0x7ff0);
 430         const Obj_Entry *obj = (Obj_Entry *)(got[1] & GOT1_MASK);
 431         Elf_Addr new_value = 0; /* XXX gcc */
 432         int err;
 433
 434         err = _rtld_relocate_plt_object(obj, a0, &new_value);
 435         if (err)
 436                 _rtld_die();
 437
 438         return (caddr_t)new_value;
 439 }
 440
 441 int
 442 _rtld_relocate_plt_objects(const Obj_Entry *obj)
 443 {
 444         const Elf_Sym *sym = obj->symtab + obj->gotsym;
 445         Elf_Word i;
 446
 447         for (i = obj->gotsym; i < obj->symtabno; i++, sym++) {
 448                 if (ELF_ST_TYPE(sym->st_info) == STT_FUNC)
 449                         if (_rtld_relocate_plt_object(obj, i, NULL) < 0)
 450                                 return -1;
 451         }
 452
 453         return 0;
 454 }