sysdeps/powerpc/powerpc32/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   2    Copyright (C) 1995-2018 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 #include <hwcapinfo.h>
  28
  29 /* Translate a processor specific dynamic tag to the index
  30    in l_info array.  */
  31 #define DT_PPC(x) (DT_PPC_##x - DT_LOPROC + DT_NUM)
  32
  33 /* Return nonzero iff ELF header is compatible with the running host.  */
  34 static inline int
  35 elf_machine_matches_host (const Elf32_Ehdr *ehdr)
  36 {
  37   return ehdr->e_machine == EM_PPC;
  38 }
  39
  40 /* Return the value of the GOT pointer.  */
  41 static inline Elf32_Addr * __attribute__ ((const))
  42 ppc_got (void)
  43 {
  44   Elf32_Addr *got;
  45
  46   asm ("bcl 20,31,1f\n"
  47        "1:      mflr %0\n"
  48        "        addis %0,%0,_GLOBAL_OFFSET_TABLE_-1b@ha\n"
  49        "        addi %0,%0,_GLOBAL_OFFSET_TABLE_-1b@l\n"
  50        : "=b" (got) : : "lr");
  51
  52   return got;
  53 }
  54
  55 /* Return the link-time address of _DYNAMIC, stored as
  56    the first value in the GOT. */
  57 static inline Elf32_Addr __attribute__ ((const))
  58 elf_machine_dynamic (void)
  59 {
  60   return *ppc_got ();
  61 }
  62
  63 /* Return the run-time load address of the shared object.  */
  64 static inline Elf32_Addr __attribute__ ((const))
  65 elf_machine_load_address (void)
  66 {
  67   Elf32_Addr *branchaddr;
  68   Elf32_Addr runtime_dynamic;
  69
  70   /* This is much harder than you'd expect.  Possibly I'm missing something.
  71      The 'obvious' way:
  72
  73        Apparently, "bcl 20,31,$+4" is what should be used to load LR
  74        with the address of the next instruction.
  75        I think this is so that machines that do bl/blr pairing don't
  76        get confused.
  77
  78      asm ("bcl 20,31,0f ;"
  79           "0: mflr 0 ;"
  80           "lis %0,0b@ha;"
  81           "addi %0,%0,0b@l;"
  82           "subf %0,%0,0"
  83           : "=b" (addr) : : "r0", "lr");
  84
  85      doesn't work, because the linker doesn't have to (and in fact doesn't)
  86      update the @ha and @l references; the loader (which runs after this
  87      code) will do that.
  88
  89      Instead, we use the following trick:
  90
  91      The linker puts the _link-time_ address of _DYNAMIC at the first
  92      word in the GOT. We could branch to that address, if we wanted,
  93      by using an @local reloc; the linker works this out, so it's safe
  94      to use now. We can't, of course, actually branch there, because
  95      we'd cause an illegal instruction exception; so we need to compute
  96      the address ourselves. That gives us the following code: */
  97
  98   /* Get address of the 'b _DYNAMIC@local'...  */
  99   asm ("bcl 20,31,0f;"
 100        "b _DYNAMIC@local;"
 101        "0:"
 102        : "=l" (branchaddr));
 103
 104   /* So now work out the difference between where the branch actually points,
 105      and the offset of that location in memory from the start of the file.  */
 106   runtime_dynamic = ((Elf32_Addr) branchaddr
 107                      + ((Elf32_Sword) (*branchaddr << 6 & 0xffffff00) >> 6));
 108
 109   return runtime_dynamic - elf_machine_dynamic ();
 110 }
 111
 112 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */
 113
 114 /* The PLT uses Elf32_Rela relocs.  */
 115 #define elf_machine_relplt elf_machine_rela
 116
 117 /* Mask identifying addresses reserved for the user program,
 118    where the dynamic linker should not map anything.  */
 119 #define ELF_MACHINE_USER_ADDRESS_MASK   0xf0000000UL
 120
 121 /* The actual _start code is in dl-start.S.  Use a really
 122    ugly bit of assembler to let dl-start.o see _dl_start.  */
 123 #define RTLD_START asm (".globl _dl_start");
 124
 125 /* Decide where a relocatable object should be loaded.  */
 126 extern ElfW(Addr)
 127 __elf_preferred_address(struct link_map *loader, size_t maplength,
 128                         ElfW(Addr) mapstartpref);
 129 #define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
 130   __elf_preferred_address (loader, maplength, mapstartpref)
 131
 132 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry, so
 133    PLT entries should not be allowed to define the value.
 134    ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one
 135    of the main executable's symbols, as for a COPY reloc.  */
 136 /* We never want to use a PLT entry as the destination of a
 137    reloc, when what is being relocated is a branch. This is
 138    partly for efficiency, but mostly so we avoid loops.  */
 139 #define elf_machine_type_class(type)                    \
 140   ((((type) == R_PPC_JMP_SLOT                           \
 141     || (type) == R_PPC_REL24                            \
 142     || ((type) >= R_PPC_DTPMOD32 /* contiguous TLS */   \
 143         && (type) <= R_PPC_DTPREL32)                    \
 144     || (type) == R_PPC_ADDR24) * ELF_RTYPE_CLASS_PLT)   \
 145    | (((type) == R_PPC_COPY) * ELF_RTYPE_CLASS_COPY))
 146
 147 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 148 #define ELF_MACHINE_JMP_SLOT    R_PPC_JMP_SLOT
 149
 150 /* The PowerPC never uses REL relocations.  */
 151 #define ELF_MACHINE_NO_REL 1
 152 #define ELF_MACHINE_NO_RELA 0
 153
 154 /* We define an initialization function to initialize HWCAP/HWCAP2 and
 155    platform data so it can be copied into the TCB later.  This is called
 156    very early in _dl_sysdep_start for dynamically linked binaries.  */
 157 #ifdef SHARED
 158 # define DL_PLATFORM_INIT dl_platform_init ()
 159
 160 static inline void __attribute__ ((unused))
 161 dl_platform_init (void)
 162 {
 163   __tcb_parse_hwcap_and_convert_at_platform ();
 164 }
 165 #endif
 166
 167 /* Set up the loaded object described by MAP so its unrelocated PLT
 168    entries will jump to the on-demand fixup code in dl-runtime.c.
 169    Also install a small trampoline to be used by entries that have
 170    been relocated to an address too far away for a single branch.  */
 171 extern int __elf_machine_runtime_setup (struct link_map *map,
 172                                         int lazy, int profile);
 173
 174 static inline int
 175 elf_machine_runtime_setup (struct link_map *map,
 176                            int lazy, int profile)
 177 {
 178   if (map->l_info[DT_JMPREL] == 0)
 179     return lazy;
 180
 181   if (map->l_info[DT_PPC(GOT)] == 0)
 182     /* Handle old style PLT.  */
 183     return __elf_machine_runtime_setup (map, lazy, profile);
 184
 185   /* New style non-exec PLT consisting of an array of addresses.  */
 186   map->l_info[DT_PPC(GOT)]->d_un.d_ptr += map->l_addr;
 187   if (lazy)
 188     {
 189       Elf32_Addr *plt, *got, glink;
 190       Elf32_Word num_plt_entries;
 191       void (*dlrr) (void);
 192       extern void _dl_runtime_resolve (void);
 193       extern void _dl_prof_resolve (void);
 194
 195       if (__glibc_likely (!profile))
 196         dlrr = _dl_runtime_resolve;
 197       else
 198         {
 199           if (GLRO(dl_profile) != NULL
 200               &&_dl_name_match_p (GLRO(dl_profile), map))
 201             GL(dl_profile_map) = map;
 202           dlrr = _dl_prof_resolve;
 203         }
 204       got = (Elf32_Addr *) map->l_info[DT_PPC(GOT)]->d_un.d_ptr;
 205       glink = got[1];
 206       got[1] = (Elf32_Addr) dlrr;
 207       got[2] = (Elf32_Addr) map;
 208
 209       /* Relocate everything in .plt by the load address offset.  */
 210       plt = (Elf32_Addr *) D_PTR (map, l_info[DT_PLTGOT]);
 211       num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
 212                          / sizeof (Elf32_Rela));
 213
 214       /* If a library is prelinked but we have to relocate anyway,
 215          we have to be able to undo the prelinking of .plt section.
 216          The prelinker saved us at got[1] address of .glink
 217          section's start.  */
 218       if (glink)
 219         {
 220           glink += map->l_addr;
 221           while (num_plt_entries-- != 0)
 222             *plt++ = glink, glink += 4;
 223         }
 224       else
 225         while (num_plt_entries-- != 0)
 226           *plt++ += map->l_addr;
 227     }
 228   return lazy;
 229 }
 230
 231 /* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
 232 extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
 233                                            Elf32_Addr *reloc_addr,
 234                                            Elf32_Addr finaladdr);
 235
 236 static inline Elf32_Addr
 237 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 238                        const ElfW(Sym) *refsym, const ElfW(Sym) *sym,
 239                        const Elf32_Rela *reloc,
 240                        Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
 241 {
 242   if (map->l_info[DT_PPC(GOT)] == 0)
 243     /* Handle old style PLT.  */
 244     return __elf_machine_fixup_plt (map, reloc_addr, finaladdr);
 245
 246   *reloc_addr = finaladdr;
 247   return finaladdr;
 248 }
 249
 250 /* Return the final value of a plt relocation.  */
 251 static inline Elf32_Addr
 252 elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
 253                        Elf32_Addr value)
 254 {
 255   return value + reloc->r_addend;
 256 }
 257
 258
 259 /* Names of the architecture-specific auditing callback functions.  */
 260 #define ARCH_LA_PLTENTER ppc32_gnu_pltenter
 261 #define ARCH_LA_PLTEXIT ppc32_gnu_pltexit
 262
 263 #endif /* dl_machine_h */
 264
 265 #ifdef RESOLVE_MAP
 266
 267 /* Do the actual processing of a reloc, once its target address
 268    has been determined.  */
 269 extern void __process_machine_rela (struct link_map *map,
 270                                     const Elf32_Rela *reloc,
 271                                     struct link_map *sym_map,
 272                                     const Elf32_Sym *sym,
 273                                     const Elf32_Sym *refsym,
 274                                     Elf32_Addr *const reloc_addr,
 275                                     Elf32_Addr finaladdr,
 276                                     int rinfo) attribute_hidden;
 277
 278 /* Call _dl_signal_error when a resolved value overflows a relocated area.  */
 279 extern void _dl_reloc_overflow (struct link_map *map,
 280                                 const char *name,
 281                                 Elf32_Addr *const reloc_addr,
 282                                 const Elf32_Sym *refsym) attribute_hidden;
 283
 284 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 285    LOADADDR is the load address of the object; INFO is an array indexed
 286    by DT_* of the .dynamic section info.  */
 287
 288 auto inline void __attribute__ ((always_inline))
 289 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 290                   const Elf32_Sym *sym, const struct r_found_version *version,
 291                   void *const reloc_addr_arg, int skip_ifunc)
 292 {
 293   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 294   const Elf32_Sym *const refsym = sym;
 295   Elf32_Addr value;
 296   const int r_type = ELF32_R_TYPE (reloc->r_info);
 297   struct link_map *sym_map = NULL;
 298
 299 #ifndef RESOLVE_CONFLICT_FIND_MAP
 300   if (r_type == R_PPC_RELATIVE)
 301     {
 302       *reloc_addr = map->l_addr + reloc->r_addend;
 303       return;
 304     }
 305
 306   if (__glibc_unlikely (r_type == R_PPC_NONE))
 307     return;
 308
 309   /* binutils on ppc32 includes st_value in r_addend for relocations
 310      against local symbols.  */
 311   if (__builtin_expect (ELF32_ST_BIND (sym->st_info) == STB_LOCAL, 0)
 312       && sym->st_shndx != SHN_UNDEF)
 313     {
 314       sym_map = map;
 315       value = map->l_addr;
 316     }
 317   else
 318     {
 319       sym_map = RESOLVE_MAP (&sym, version, r_type);
 320       value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
 321     }
 322   value += reloc->r_addend;
 323 #else
 324   value = reloc->r_addend;
 325 #endif
 326
 327   if (sym != NULL
 328       && __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
 329       && __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
 330       && __builtin_expect (!skip_ifunc, 1))
 331     value = elf_ifunc_invoke (value);
 332
 333   /* A small amount of code is duplicated here for speed.  In libc,
 334      more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
 335      libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
 336      R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
 337      wouldn't usually handle).  As an bonus, doing this here allows
 338      the switch statement in __process_machine_rela to work.  */
 339   switch (r_type)
 340     {
 341     case R_PPC_GLOB_DAT:
 342     case R_PPC_ADDR32:
 343       *reloc_addr = value;
 344       break;
 345
 346 #ifndef RESOLVE_CONFLICT_FIND_MAP
 347 # ifdef RTLD_BOOTSTRAP
 348 #  define NOT_BOOTSTRAP 0
 349 # else
 350 #  define NOT_BOOTSTRAP 1
 351 # endif
 352
 353     case R_PPC_DTPMOD32:
 354       if (map->l_info[DT_PPC(OPT)]
 355           && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
 356         {
 357           if (!NOT_BOOTSTRAP)
 358             {
 359               reloc_addr[0] = 0;
 360               reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
 361                                + TLS_DTV_OFFSET);
 362               break;
 363             }
 364           else if (sym_map != NULL)
 365             {
 366 # ifndef SHARED
 367               CHECK_STATIC_TLS (map, sym_map);
 368 # else
 369               if (TRY_STATIC_TLS (map, sym_map))
 370 # endif
 371                 {
 372                   reloc_addr[0] = 0;
 373                   /* Set up for local dynamic.  */
 374                   reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
 375                                    + TLS_DTV_OFFSET);
 376                   break;
 377                 }
 378             }
 379         }
 380       if (!NOT_BOOTSTRAP)
 381         /* During startup the dynamic linker is always index 1.  */
 382         *reloc_addr = 1;
 383       else if (sym_map != NULL)
 384         /* Get the information from the link map returned by the
 385            RESOLVE_MAP function.  */
 386         *reloc_addr = sym_map->l_tls_modid;
 387       break;
 388     case R_PPC_DTPREL32:
 389       if (map->l_info[DT_PPC(OPT)]
 390           && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
 391         {
 392           if (!NOT_BOOTSTRAP)
 393             {
 394               *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 395               break;
 396             }
 397           else if (sym_map != NULL)
 398             {
 399               /* This reloc is always preceded by R_PPC_DTPMOD32.  */
 400 # ifndef SHARED
 401               assert (HAVE_STATIC_TLS (map, sym_map));
 402 # else
 403               if (HAVE_STATIC_TLS (map, sym_map))
 404 # endif
 405                 {
 406                   *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 407                   break;
 408                 }
 409             }
 410         }
 411       /* During relocation all TLS symbols are defined and used.
 412          Therefore the offset is already correct.  */
 413       if (NOT_BOOTSTRAP && sym_map != NULL)
 414         *reloc_addr = TLS_DTPREL_VALUE (sym, reloc);
 415       break;
 416     case R_PPC_TPREL32:
 417       if (!NOT_BOOTSTRAP || sym_map != NULL)
 418         {
 419           if (NOT_BOOTSTRAP)
 420             CHECK_STATIC_TLS (map, sym_map);
 421           *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 422         }
 423       break;
 424 #endif
 425
 426     case R_PPC_JMP_SLOT:
 427 #ifdef RESOLVE_CONFLICT_FIND_MAP
 428       RESOLVE_CONFLICT_FIND_MAP (map, reloc_addr);
 429 #endif
 430       if (map->l_info[DT_PPC(GOT)] != 0)
 431         {
 432           *reloc_addr = value;
 433           break;
 434         }
 435       /* FALLTHROUGH */
 436
 437     default:
 438       __process_machine_rela (map, reloc, sym_map, sym, refsym,
 439                               reloc_addr, value, r_type);
 440     }
 441 }
 442
 443 auto inline void __attribute__ ((always_inline))
 444 elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
 445                            void *const reloc_addr_arg)
 446 {
 447   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 448   *reloc_addr = l_addr + reloc->r_addend;
 449 }
 450
 451 auto inline void __attribute__ ((always_inline))
 452 elf_machine_lazy_rel (struct link_map *map,
 453                       Elf32_Addr l_addr, const Elf32_Rela *reloc,
 454                       int skip_ifunc)
 455 {
 456   /* elf_machine_runtime_setup handles this. */
 457 }
 458
 459 #endif /* RESOLVE_MAP */