sysdeps/powerpc/powerpc32/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   2    Copyright (C) 1995-2015 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 #include <dl-irel.h>
  27
  28 /* Translate a processor specific dynamic tag to the index
  29    in l_info array.  */
  30 #define DT_PPC(x) (DT_PPC_##x - DT_LOPROC + DT_NUM)
  31
  32 /* Return nonzero iff ELF header is compatible with the running host.  */
  33 static inline int
  34 elf_machine_matches_host (const Elf32_Ehdr *ehdr)
  35 {
  36   return ehdr->e_machine == EM_PPC;
  37 }
  38
  39 /* Return the value of the GOT pointer.  */
  40 static inline Elf32_Addr * __attribute__ ((const))
  41 ppc_got (void)
  42 {
  43   Elf32_Addr *got;
  44
  45   asm ("bcl 20,31,1f\n"
  46        "1:      mflr %0\n"
  47        "        addis %0,%0,_GLOBAL_OFFSET_TABLE_-1b@ha\n"
  48        "        addi %0,%0,_GLOBAL_OFFSET_TABLE_-1b@l\n"
  49        : "=b" (got) : : "lr");
  50
  51   return got;
  52 }
  53
  54 /* Return the link-time address of _DYNAMIC, stored as
  55    the first value in the GOT. */
  56 static inline Elf32_Addr __attribute__ ((const))
  57 elf_machine_dynamic (void)
  58 {
  59   return *ppc_got ();
  60 }
  61
  62 /* Return the run-time load address of the shared object.  */
  63 static inline Elf32_Addr __attribute__ ((const))
  64 elf_machine_load_address (void)
  65 {
  66   Elf32_Addr *branchaddr;
  67   Elf32_Addr runtime_dynamic;
  68
  69   /* This is much harder than you'd expect.  Possibly I'm missing something.
  70      The 'obvious' way:
  71
  72        Apparently, "bcl 20,31,$+4" is what should be used to load LR
  73        with the address of the next instruction.
  74        I think this is so that machines that do bl/blr pairing don't
  75        get confused.
  76
  77      asm ("bcl 20,31,0f ;"
  78           "0: mflr 0 ;"
  79           "lis %0,0b@ha;"
  80           "addi %0,%0,0b@l;"
  81           "subf %0,%0,0"
  82           : "=b" (addr) : : "r0", "lr");
  83
  84      doesn't work, because the linker doesn't have to (and in fact doesn't)
  85      update the @ha and @l references; the loader (which runs after this
  86      code) will do that.
  87
  88      Instead, we use the following trick:
  89
  90      The linker puts the _link-time_ address of _DYNAMIC at the first
  91      word in the GOT. We could branch to that address, if we wanted,
  92      by using an @local reloc; the linker works this out, so it's safe
  93      to use now. We can't, of course, actually branch there, because
  94      we'd cause an illegal instruction exception; so we need to compute
  95      the address ourselves. That gives us the following code: */
  96
  97   /* Get address of the 'b _DYNAMIC@local'...  */
  98   asm ("bcl 20,31,0f;"
  99        "b _DYNAMIC@local;"
 100        "0:"
 101        : "=l" (branchaddr));
 102
 103   /* So now work out the difference between where the branch actually points,
 104      and the offset of that location in memory from the start of the file.  */
 105   runtime_dynamic = ((Elf32_Addr) branchaddr
 106                      + ((Elf32_Sword) (*branchaddr << 6 & 0xffffff00) >> 6));
 107
 108   return runtime_dynamic - elf_machine_dynamic ();
 109 }
 110
 111 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */
 112
 113 /* The PLT uses Elf32_Rela relocs.  */
 114 #define elf_machine_relplt elf_machine_rela
 115
 116 /* Mask identifying addresses reserved for the user program,
 117    where the dynamic linker should not map anything.  */
 118 #define ELF_MACHINE_USER_ADDRESS_MASK   0xf0000000UL
 119
 120 /* The actual _start code is in dl-start.S.  Use a really
 121    ugly bit of assembler to let dl-start.o see _dl_start.  */
 122 #define RTLD_START asm (".globl _dl_start");
 123
 124 /* Decide where a relocatable object should be loaded.  */
 125 extern ElfW(Addr)
 126 __elf_preferred_address(struct link_map *loader, size_t maplength,
 127                         ElfW(Addr) mapstartpref);
 128 #define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
 129   __elf_preferred_address (loader, maplength, mapstartpref)
 130
 131 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry, so
 132    PLT entries should not be allowed to define the value.
 133    ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
 134    of the main executable's symbols, as for a COPY reloc.  */
 135 /* We never want to use a PLT entry as the destination of a
 136    reloc, when what is being relocated is a branch. This is
 137    partly for efficiency, but mostly so we avoid loops.  */
 138 #define elf_machine_type_class(type)                    \
 139   ((((type) == R_PPC_JMP_SLOT                           \
 140     || (type) == R_PPC_REL24                            \
 141     || ((type) >= R_PPC_DTPMOD32 /* contiguous TLS */   \
 142         && (type) <= R_PPC_DTPREL32)                    \
 143     || (type) == R_PPC_ADDR24) * ELF_RTYPE_CLASS_PLT)   \
 144    | (((type) == R_PPC_COPY) * ELF_RTYPE_CLASS_COPY))
 145
 146 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 147 #define ELF_MACHINE_JMP_SLOT    R_PPC_JMP_SLOT
 148
 149 /* The PowerPC never uses REL relocations.  */
 150 #define ELF_MACHINE_NO_REL 1
 151 #define ELF_MACHINE_NO_RELA 0
 152
 153 /* Set up the loaded object described by MAP so its unrelocated PLT
 154    entries will jump to the on-demand fixup code in dl-runtime.c.
 155    Also install a small trampoline to be used by entries that have
 156    been relocated to an address too far away for a single branch.  */
 157 extern int __elf_machine_runtime_setup (struct link_map *map,
 158                                         int lazy, int profile);
 159
 160 static inline int
 161 elf_machine_runtime_setup (struct link_map *map,
 162                            int lazy, int profile)
 163 {
 164   if (map->l_info[DT_JMPREL] == 0)
 165     return lazy;
 166
 167   if (map->l_info[DT_PPC(GOT)] == 0)
 168     /* Handle old style PLT.  */
 169     return __elf_machine_runtime_setup (map, lazy, profile);
 170
 171   /* New style non-exec PLT consisting of an array of addresses.  */
 172   map->l_info[DT_PPC(GOT)]->d_un.d_ptr += map->l_addr;
 173   if (lazy)
 174     {
 175       Elf32_Addr *plt, *got, glink;
 176       Elf32_Word num_plt_entries;
 177       void (*dlrr) (void);
 178       extern void _dl_runtime_resolve (void);
 179       extern void _dl_prof_resolve (void);
 180
 181       if (__glibc_likely (!profile))
 182         dlrr = _dl_runtime_resolve;
 183       else
 184         {
 185           if (GLRO(dl_profile) != NULL
 186               &&_dl_name_match_p (GLRO(dl_profile), map))
 187             GL(dl_profile_map) = map;
 188           dlrr = _dl_prof_resolve;
 189         }
 190       got = (Elf32_Addr *) map->l_info[DT_PPC(GOT)]->d_un.d_ptr;
 191       glink = got[1];
 192       got[1] = (Elf32_Addr) dlrr;
 193       got[2] = (Elf32_Addr) map;
 194
 195       /* Relocate everything in .plt by the load address offset.  */
 196       plt = (Elf32_Addr *) D_PTR (map, l_info[DT_PLTGOT]);
 197       num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
 198                          / sizeof (Elf32_Rela));
 199
 200       /* If a library is prelinked but we have to relocate anyway,
 201          we have to be able to undo the prelinking of .plt section.
 202          The prelinker saved us at got[1] address of .glink
 203          section's start.  */
 204       if (glink)
 205         {
 206           glink += map->l_addr;
 207           while (num_plt_entries-- != 0)
 208             *plt++ = glink, glink += 4;
 209         }
 210       else
 211         while (num_plt_entries-- != 0)
 212           *plt++ += map->l_addr;
 213     }
 214   return lazy;
 215 }
 216
 217 /* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
 218 extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
 219                                            Elf32_Addr *reloc_addr,
 220                                            Elf32_Addr finaladdr);
 221
 222 static inline Elf32_Addr
 223 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 224                        const Elf32_Rela *reloc,
 225                        Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
 226 {
 227   if (map->l_info[DT_PPC(GOT)] == 0)
 228     /* Handle old style PLT.  */
 229     return __elf_machine_fixup_plt (map, reloc_addr, finaladdr);
 230
 231   *reloc_addr = finaladdr;
 232   return finaladdr;
 233 }
 234
 235 /* Return the final value of a plt relocation.  */
 236 static inline Elf32_Addr
 237 elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
 238                        Elf32_Addr value)
 239 {
 240   return value + reloc->r_addend;
 241 }
 242
 243
 244 /* Names of the architecture-specific auditing callback functions.  */
 245 #define ARCH_LA_PLTENTER ppc32_gnu_pltenter
 246 #define ARCH_LA_PLTEXIT ppc32_gnu_pltexit
 247
 248 #endif /* dl_machine_h */
 249
 250 #ifdef RESOLVE_MAP
 251
 252 /* Do the actual processing of a reloc, once its target address
 253    has been determined.  */
 254 extern void __process_machine_rela (struct link_map *map,
 255                                     const Elf32_Rela *reloc,
 256                                     struct link_map *sym_map,
 257                                     const Elf32_Sym *sym,
 258                                     const Elf32_Sym *refsym,
 259                                     Elf32_Addr *const reloc_addr,
 260                                     Elf32_Addr finaladdr,
 261                                     int rinfo) attribute_hidden;
 262
 263 /* Call _dl_signal_error when a resolved value overflows a relocated area.  */
 264 extern void _dl_reloc_overflow (struct link_map *map,
 265                                 const char *name,
 266                                 Elf32_Addr *const reloc_addr,
 267                                 const Elf32_Sym *refsym) attribute_hidden;
 268
 269 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 270    LOADADDR is the load address of the object; INFO is an array indexed
 271    by DT_* of the .dynamic section info.  */
 272
 273 auto inline void __attribute__ ((always_inline))
 274 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 275                   const Elf32_Sym *sym, const struct r_found_version *version,
 276                   void *const reloc_addr_arg, int skip_ifunc)
 277 {
 278   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 279   const Elf32_Sym *const refsym = sym;
 280   Elf32_Addr value;
 281   const int r_type = ELF32_R_TYPE (reloc->r_info);
 282   struct link_map *sym_map = NULL;
 283
 284 #ifndef RESOLVE_CONFLICT_FIND_MAP
 285   if (r_type == R_PPC_RELATIVE)
 286     {
 287       *reloc_addr = map->l_addr + reloc->r_addend;
 288       return;
 289     }
 290
 291   if (__glibc_unlikely (r_type == R_PPC_NONE))
 292     return;
 293
 294   /* binutils on ppc32 includes st_value in r_addend for relocations
 295      against local symbols.  */
 296   if (__builtin_expect (ELF32_ST_BIND (sym->st_info) == STB_LOCAL, 0)
 297       && sym->st_shndx != SHN_UNDEF)
 298     value = map->l_addr;
 299   else
 300     {
 301       sym_map = RESOLVE_MAP (&sym, version, r_type);
 302       value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
 303     }
 304   value += reloc->r_addend;
 305 #else
 306   value = reloc->r_addend;
 307 #endif
 308
 309   if (sym != NULL
 310       && __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
 311       && __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
 312       && __builtin_expect (!skip_ifunc, 1))
 313     value = elf_ifunc_invoke (value);
 314
 315   /* A small amount of code is duplicated here for speed.  In libc,
 316      more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
 317      libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
 318      R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
 319      wouldn't usually handle).  As an bonus, doing this here allows
 320      the switch statement in __process_machine_rela to work.  */
 321   switch (r_type)
 322     {
 323     case R_PPC_GLOB_DAT:
 324     case R_PPC_ADDR32:
 325       *reloc_addr = value;
 326       break;
 327
 328 #ifndef RESOLVE_CONFLICT_FIND_MAP
 329 # ifdef RTLD_BOOTSTRAP
 330 #  define NOT_BOOTSTRAP 0
 331 # else
 332 #  define NOT_BOOTSTRAP 1
 333 # endif
 334
 335     case R_PPC_DTPMOD32:
 336       if (!NOT_BOOTSTRAP)
 337         /* During startup the dynamic linker is always index 1.  */
 338         *reloc_addr = 1;
 339       else if (sym_map != NULL)
 340         /* Get the information from the link map returned by the
 341            RESOLVE_MAP function.  */
 342         *reloc_addr = sym_map->l_tls_modid;
 343       break;
 344     case R_PPC_DTPREL32:
 345       /* During relocation all TLS symbols are defined and used.
 346          Therefore the offset is already correct.  */
 347       if (NOT_BOOTSTRAP && sym_map != NULL)
 348         *reloc_addr = TLS_DTPREL_VALUE (sym, reloc);
 349       break;
 350     case R_PPC_TPREL32:
 351       if (!NOT_BOOTSTRAP || sym_map != NULL)
 352         {
 353           if (NOT_BOOTSTRAP)
 354             CHECK_STATIC_TLS (map, sym_map);
 355           *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 356         }
 357       break;
 358 #endif
 359
 360     case R_PPC_JMP_SLOT:
 361 #ifdef RESOLVE_CONFLICT_FIND_MAP
 362       RESOLVE_CONFLICT_FIND_MAP (map, reloc_addr);
 363 #endif
 364       if (map->l_info[DT_PPC(GOT)] != 0)
 365         {
 366           *reloc_addr = value;
 367           break;
 368         }
 369       /* FALLTHROUGH */
 370
 371     default:
 372       __process_machine_rela (map, reloc, sym_map, sym, refsym,
 373                               reloc_addr, value, r_type);
 374     }
 375 }
 376
 377 auto inline void __attribute__ ((always_inline))
 378 elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
 379                            void *const reloc_addr_arg)
 380 {
 381   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 382   *reloc_addr = l_addr + reloc->r_addend;
 383 }
 384
 385 auto inline void __attribute__ ((always_inline))
 386 elf_machine_lazy_rel (struct link_map *map,
 387                       Elf32_Addr l_addr, const Elf32_Rela *reloc,
 388                       int skip_ifunc)
 389 {
 390   /* elf_machine_runtime_setup handles this. */
 391 }
 392
 393 #endif /* RESOLVE_MAP */