sysdeps/powerpc/powerpc32/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   2    Copyright (C) 1995-2003, 2005, 2006, 2011 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef dl_machine_h
  20 #define dl_machine_h
  21
  22 #define ELF_MACHINE_NAME "powerpc"
  23
  24 #include <assert.h>
  25 #include <dl-tls.h>
  26
  27 /* Translate a processor specific dynamic tag to the index
  28    in l_info array.  */
  29 #define DT_PPC(x) (DT_PPC_##x - DT_LOPROC + DT_NUM)
  30
  31 /* Return nonzero iff ELF header is compatible with the running host.  */
  32 static inline int
  33 elf_machine_matches_host (const Elf32_Ehdr *ehdr)
  34 {
  35   return ehdr->e_machine == EM_PPC;
  36 }
  37
  38 /* Return the value of the GOT pointer.  */
  39 static inline Elf32_Addr * __attribute__ ((const))
  40 ppc_got (void)
  41 {
  42   Elf32_Addr *got;
  43
  44   asm ("bcl 20,31,1f\n"
  45        "1:      mflr %0\n"
  46        "        addis %0,%0,_GLOBAL_OFFSET_TABLE_-1b@ha\n"
  47        "        addi %0,%0,_GLOBAL_OFFSET_TABLE_-1b@l\n"
  48        : "=b" (got) : : "lr");
  49
  50   return got;
  51 }
  52
  53 /* Return the link-time address of _DYNAMIC, stored as
  54    the first value in the GOT. */
  55 static inline Elf32_Addr __attribute__ ((const))
  56 elf_machine_dynamic (void)
  57 {
  58   return *ppc_got ();
  59 }
  60
  61 /* Return the run-time load address of the shared object.  */
  62 static inline Elf32_Addr __attribute__ ((const))
  63 elf_machine_load_address (void)
  64 {
  65   Elf32_Addr *branchaddr;
  66   Elf32_Addr runtime_dynamic;
  67
  68   /* This is much harder than you'd expect.  Possibly I'm missing something.
  69      The 'obvious' way:
  70
  71        Apparently, "bcl 20,31,$+4" is what should be used to load LR
  72        with the address of the next instruction.
  73        I think this is so that machines that do bl/blr pairing don't
  74        get confused.
  75
  76      asm ("bcl 20,31,0f ;"
  77           "0: mflr 0 ;"
  78           "lis %0,0b@ha;"
  79           "addi %0,%0,0b@l;"
  80           "subf %0,%0,0"
  81           : "=b" (addr) : : "r0", "lr");
  82
  83      doesn't work, because the linker doesn't have to (and in fact doesn't)
  84      update the @ha and @l references; the loader (which runs after this
  85      code) will do that.
  86
  87      Instead, we use the following trick:
  88
  89      The linker puts the _link-time_ address of _DYNAMIC at the first
  90      word in the GOT. We could branch to that address, if we wanted,
  91      by using an @local reloc; the linker works this out, so it's safe
  92      to use now. We can't, of course, actually branch there, because
  93      we'd cause an illegal instruction exception; so we need to compute
  94      the address ourselves. That gives us the following code: */
  95
  96   /* Get address of the 'b _DYNAMIC@local'...  */
  97   asm ("bcl 20,31,0f;"
  98        "b _DYNAMIC@local;"
  99        "0:"
 100        : "=l" (branchaddr));
 101
 102   /* So now work out the difference between where the branch actually points,
 103      and the offset of that location in memory from the start of the file.  */
 104   runtime_dynamic = ((Elf32_Addr) branchaddr
 105                      + ((Elf32_Sword) (*branchaddr << 6 & 0xffffff00) >> 6));
 106
 107   return runtime_dynamic - elf_machine_dynamic ();
 108 }
 109
 110 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */
 111
 112 /* The PLT uses Elf32_Rela relocs.  */
 113 #define elf_machine_relplt elf_machine_rela
 114
 115 /* Mask identifying addresses reserved for the user program,
 116    where the dynamic linker should not map anything.  */
 117 #define ELF_MACHINE_USER_ADDRESS_MASK   0xf0000000UL
 118
 119 /* The actual _start code is in dl-start.S.  Use a really
 120    ugly bit of assembler to let dl-start.o see _dl_start.  */
 121 #define RTLD_START asm (".globl _dl_start");
 122
 123 /* Decide where a relocatable object should be loaded.  */
 124 extern ElfW(Addr)
 125 __elf_preferred_address(struct link_map *loader, size_t maplength,
 126                         ElfW(Addr) mapstartpref);
 127 #define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
 128   __elf_preferred_address (loader, maplength, mapstartpref)
 129
 130 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry, so
 131    PLT entries should not be allowed to define the value.
 132    ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
 133    of the main executable's symbols, as for a COPY reloc.  */
 134 /* We never want to use a PLT entry as the destination of a
 135    reloc, when what is being relocated is a branch. This is
 136    partly for efficiency, but mostly so we avoid loops.  */
 137 #define elf_machine_type_class(type)                    \
 138   ((((type) == R_PPC_JMP_SLOT                           \
 139     || (type) == R_PPC_REL24                            \
 140     || ((type) >= R_PPC_DTPMOD32 /* contiguous TLS */   \
 141         && (type) <= R_PPC_DTPREL32)                    \
 142     || (type) == R_PPC_ADDR24) * ELF_RTYPE_CLASS_PLT)   \
 143    | (((type) == R_PPC_COPY) * ELF_RTYPE_CLASS_COPY))
 144
 145 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 146 #define ELF_MACHINE_JMP_SLOT    R_PPC_JMP_SLOT
 147
 148 /* The PowerPC never uses REL relocations.  */
 149 #define ELF_MACHINE_NO_REL 1
 150
 151 /* Set up the loaded object described by MAP so its unrelocated PLT
 152    entries will jump to the on-demand fixup code in dl-runtime.c.
 153    Also install a small trampoline to be used by entries that have
 154    been relocated to an address too far away for a single branch.  */
 155 extern int __elf_machine_runtime_setup (struct link_map *map,
 156                                         int lazy, int profile);
 157
 158 static inline int
 159 elf_machine_runtime_setup (struct link_map *map,
 160                            int lazy, int profile)
 161 {
 162   if (map->l_info[DT_JMPREL] == 0)
 163     return lazy;
 164
 165   if (map->l_info[DT_PPC(GOT)] == 0)
 166     /* Handle old style PLT.  */
 167     return __elf_machine_runtime_setup (map, lazy, profile);
 168
 169   /* New style non-exec PLT consisting of an array of addresses.  */
 170   map->l_info[DT_PPC(GOT)]->d_un.d_ptr += map->l_addr;
 171   if (lazy)
 172     {
 173       Elf32_Addr *plt, *got, glink;
 174       Elf32_Word num_plt_entries;
 175       void (*dlrr) (void);
 176       extern void _dl_runtime_resolve (void);
 177       extern void _dl_prof_resolve (void);
 178
 179       if (__builtin_expect (!profile, 1))
 180         dlrr = _dl_runtime_resolve;
 181       else
 182         {
 183           if (GLRO(dl_profile) != NULL
 184               &&_dl_name_match_p (GLRO(dl_profile), map))
 185             GL(dl_profile_map) = map;
 186           dlrr = _dl_prof_resolve;
 187         }
 188       got = (Elf32_Addr *) map->l_info[DT_PPC(GOT)]->d_un.d_ptr;
 189       glink = got[1];
 190       got[1] = (Elf32_Addr) dlrr;
 191       got[2] = (Elf32_Addr) map;
 192
 193       /* Relocate everything in .plt by the load address offset.  */
 194       plt = (Elf32_Addr *) D_PTR (map, l_info[DT_PLTGOT]);
 195       num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
 196                          / sizeof (Elf32_Rela));
 197
 198       /* If a library is prelinked but we have to relocate anyway,
 199          we have to be able to undo the prelinking of .plt section.
 200          The prelinker saved us at got[1] address of .glink
 201          section's start.  */
 202       if (glink)
 203         {
 204           glink += map->l_addr;
 205           while (num_plt_entries-- != 0)
 206             *plt++ = glink, glink += 4;
 207         }
 208       else
 209         while (num_plt_entries-- != 0)
 210           *plt++ += map->l_addr;
 211     }
 212   return lazy;
 213 }
 214
 215 /* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
 216 extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
 217                                            Elf32_Addr *reloc_addr,
 218                                            Elf32_Addr finaladdr);
 219
 220 static inline Elf32_Addr
 221 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 222                        const Elf32_Rela *reloc,
 223                        Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
 224 {
 225   if (map->l_info[DT_PPC(GOT)] == 0)
 226     /* Handle old style PLT.  */
 227     return __elf_machine_fixup_plt (map, reloc_addr, finaladdr);
 228
 229   *reloc_addr = finaladdr;
 230   return finaladdr;
 231 }
 232
 233 /* Return the final value of a plt relocation.  */
 234 static inline Elf32_Addr
 235 elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
 236                        Elf32_Addr value)
 237 {
 238   return value + reloc->r_addend;
 239 }
 240
 241
 242 /* Names of the architecture-specific auditing callback functions.  */
 243 #define ARCH_LA_PLTENTER ppc32_gnu_pltenter
 244 #define ARCH_LA_PLTEXIT ppc32_gnu_pltexit
 245
 246 #endif /* dl_machine_h */
 247
 248 #ifdef RESOLVE_MAP
 249
 250 /* Do the actual processing of a reloc, once its target address
 251    has been determined.  */
 252 extern void __process_machine_rela (struct link_map *map,
 253                                     const Elf32_Rela *reloc,
 254                                     struct link_map *sym_map,
 255                                     const Elf32_Sym *sym,
 256                                     const Elf32_Sym *refsym,
 257                                     Elf32_Addr *const reloc_addr,
 258                                     Elf32_Addr finaladdr,
 259                                     int rinfo) attribute_hidden;
 260
 261 /* Call _dl_signal_error when a resolved value overflows a relocated area.  */
 262 extern void _dl_reloc_overflow (struct link_map *map,
 263                                 const char *name,
 264                                 Elf32_Addr *const reloc_addr,
 265                                 const Elf32_Sym *refsym) attribute_hidden;
 266
 267 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 268    LOADADDR is the load address of the object; INFO is an array indexed
 269    by DT_* of the .dynamic section info.  */
 270
 271 auto inline void __attribute__ ((always_inline))
 272 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 273                   const Elf32_Sym *sym, const struct r_found_version *version,
 274                   void *const reloc_addr_arg, int skip_ifunc)
 275 {
 276   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 277   const Elf32_Sym *const refsym = sym;
 278   Elf32_Addr value;
 279   const int r_type = ELF32_R_TYPE (reloc->r_info);
 280   struct link_map *sym_map = NULL;
 281
 282 #ifndef RESOLVE_CONFLICT_FIND_MAP
 283   if (r_type == R_PPC_RELATIVE)
 284     {
 285       *reloc_addr = map->l_addr + reloc->r_addend;
 286       return;
 287     }
 288
 289   if (__builtin_expect (r_type == R_PPC_NONE, 0))
 290     return;
 291
 292   /* binutils on ppc32 includes st_value in r_addend for relocations
 293      against local symbols.  */
 294   if (__builtin_expect (ELF32_ST_BIND (sym->st_info) == STB_LOCAL, 0)
 295       && sym->st_shndx != SHN_UNDEF)
 296     value = map->l_addr;
 297   else
 298     {
 299       sym_map = RESOLVE_MAP (&sym, version, r_type);
 300       value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
 301     }
 302   value += reloc->r_addend;
 303 #else
 304   value = reloc->r_addend;
 305 #endif
 306
 307   if (sym != NULL
 308       && __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
 309       && __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
 310       && __builtin_expect (!skip_ifunc, 1))
 311     value = ((Elf32_Addr (*) (void)) value) ();
 312
 313   /* A small amount of code is duplicated here for speed.  In libc,
 314      more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
 315      libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
 316      R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
 317      wouldn't usually handle).  As an bonus, doing this here allows
 318      the switch statement in __process_machine_rela to work.  */
 319   switch (r_type)
 320     {
 321     case R_PPC_GLOB_DAT:
 322     case R_PPC_ADDR32:
 323       *reloc_addr = value;
 324       break;
 325
 326 #ifndef RESOLVE_CONFLICT_FIND_MAP
 327 # ifdef RTLD_BOOTSTRAP
 328 #  define NOT_BOOTSTRAP 0
 329 # else
 330 #  define NOT_BOOTSTRAP 1
 331 # endif
 332
 333     case R_PPC_DTPMOD32:
 334       if (!NOT_BOOTSTRAP)
 335         /* During startup the dynamic linker is always index 1.  */
 336         *reloc_addr = 1;
 337       else if (sym_map != NULL)
 338         /* Get the information from the link map returned by the
 339            RESOLVE_MAP function.  */
 340         *reloc_addr = sym_map->l_tls_modid;
 341       break;
 342     case R_PPC_DTPREL32:
 343       /* During relocation all TLS symbols are defined and used.
 344          Therefore the offset is already correct.  */
 345       if (NOT_BOOTSTRAP && sym_map != NULL)
 346         *reloc_addr = TLS_DTPREL_VALUE (sym, reloc);
 347       break;
 348     case R_PPC_TPREL32:
 349       if (!NOT_BOOTSTRAP || sym_map != NULL)
 350         {
 351           if (NOT_BOOTSTRAP)
 352             CHECK_STATIC_TLS (map, sym_map);
 353           *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 354         }
 355       break;
 356 #endif
 357
 358     case R_PPC_JMP_SLOT:
 359 #ifdef RESOLVE_CONFLICT_FIND_MAP
 360       RESOLVE_CONFLICT_FIND_MAP (map, reloc_addr);
 361 #endif
 362       if (map->l_info[DT_PPC(GOT)] != 0)
 363         {
 364           *reloc_addr = value;
 365           break;
 366         }
 367       /* FALLTHROUGH */
 368
 369     default:
 370       __process_machine_rela (map, reloc, sym_map, sym, refsym,
 371                               reloc_addr, value, r_type);
 372     }
 373 }
 374
 375 auto inline void __attribute__ ((always_inline))
 376 elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
 377                            void *const reloc_addr_arg)
 378 {
 379   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 380   *reloc_addr = l_addr + reloc->r_addend;
 381 }
 382
 383 auto inline void __attribute__ ((always_inline))
 384 elf_machine_lazy_rel (struct link_map *map,
 385                       Elf32_Addr l_addr, const Elf32_Rela *reloc,
 386                       int skip_ifunc)
 387 {
 388   /* elf_machine_runtime_setup handles this. */
 389 }
 390
 391 /* The SVR4 ABI specifies that the JMPREL relocs must be inside the
 392    DT_RELA table.  */
 393 #define ELF_MACHINE_PLTREL_OVERLAP 1
 394
 395 #endif /* RESOLVE_MAP */