sysdeps/powerpc/powerpc32/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   2    Copyright (C) 1995-2023 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    <https://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 #include <dl-static-tls.h>
  29 #include <dl-machine-rel.h>
  30
  31 /* Translate a processor specific dynamic tag to the index
  32    in l_info array.  */
  33 #define DT_PPC(x) (DT_PPC_##x - DT_LOPROC + DT_NUM)
  34
  35 /* Return nonzero iff ELF header is compatible with the running host.  */
  36 static inline int
  37 elf_machine_matches_host (const Elf32_Ehdr *ehdr)
  38 {
  39   return ehdr->e_machine == EM_PPC;
  40 }
  41
  42 /* Return the value of the GOT pointer.  */
  43 static inline Elf32_Addr * __attribute__ ((const))
  44 ppc_got (void)
  45 {
  46   Elf32_Addr *got;
  47
  48   asm ("bcl 20,31,1f\n"
  49        "1:      mflr %0\n"
  50        "        addis %0,%0,_GLOBAL_OFFSET_TABLE_-1b@ha\n"
  51        "        addi %0,%0,_GLOBAL_OFFSET_TABLE_-1b@l\n"
  52        : "=b" (got) : : "lr");
  53
  54   return got;
  55 }
  56
  57 /* Return the link-time address of _DYNAMIC, stored as
  58    the first value in the GOT. */
  59 static inline Elf32_Addr __attribute__ ((const))
  60 elf_machine_dynamic (void)
  61 {
  62   return *ppc_got ();
  63 }
  64
  65 /* Return the run-time load address of the shared object.  */
  66 static inline Elf32_Addr __attribute__ ((const))
  67 elf_machine_load_address (void)
  68 {
  69   Elf32_Addr *branchaddr;
  70   Elf32_Addr runtime_dynamic;
  71
  72   /* This is much harder than you'd expect.  Possibly I'm missing something.
  73      The 'obvious' way:
  74
  75        Apparently, "bcl 20,31,$+4" is what should be used to load LR
  76        with the address of the next instruction.
  77        I think this is so that machines that do bl/blr pairing don't
  78        get confused.
  79
  80      asm ("bcl 20,31,0f ;"
  81           "0: mflr 0 ;"
  82           "lis %0,0b@ha;"
  83           "addi %0,%0,0b@l;"
  84           "subf %0,%0,0"
  85           : "=b" (addr) : : "r0", "lr");
  86
  87      doesn't work, because the linker doesn't have to (and in fact doesn't)
  88      update the @ha and @l references; the loader (which runs after this
  89      code) will do that.
  90
  91      Instead, we use the following trick:
  92
  93      The linker puts the _link-time_ address of _DYNAMIC at the first
  94      word in the GOT. We could branch to that address, if we wanted,
  95      by using an @local reloc; the linker works this out, so it's safe
  96      to use now. We can't, of course, actually branch there, because
  97      we'd cause an illegal instruction exception; so we need to compute
  98      the address ourselves. That gives us the following code: */
  99
 100   /* Get address of the 'b _DYNAMIC@local'...  */
 101   asm ("bcl 20,31,0f;"
 102        "b _DYNAMIC@local;"
 103        "0:"
 104        : "=l" (branchaddr));
 105
 106   /* So now work out the difference between where the branch actually points,
 107      and the offset of that location in memory from the start of the file.  */
 108   runtime_dynamic = ((Elf32_Addr) branchaddr
 109                      + ((Elf32_Sword) (*branchaddr << 6 & 0xffffff00) >> 6));
 110
 111   return runtime_dynamic - elf_machine_dynamic ();
 112 }
 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 /* We define an initialization function to initialize HWCAP/HWCAP2 and
 151    platform data so it can be copied into the TCB later.  This is called
 152    very early in _dl_sysdep_start for dynamically linked binaries.  */
 153 #ifdef SHARED
 154 # define DL_PLATFORM_INIT dl_platform_init ()
 155
 156 static inline void __attribute__ ((unused))
 157 dl_platform_init (void)
 158 {
 159   __tcb_parse_hwcap_and_convert_at_platform ();
 160 }
 161 #endif
 162
 163 /* Set up the loaded object described by MAP so its unrelocated PLT
 164    entries will jump to the on-demand fixup code in dl-runtime.c.
 165    Also install a small trampoline to be used by entries that have
 166    been relocated to an address too far away for a single branch.  */
 167 extern int __elf_machine_runtime_setup (struct link_map *map,
 168                                         int lazy, int profile);
 169
 170 static inline int
 171 elf_machine_runtime_setup (struct link_map *map, struct r_scope_elem *scope[],
 172                            int lazy, int profile)
 173 {
 174   if (map->l_info[DT_JMPREL] == 0)
 175     return lazy;
 176
 177   if (map->l_info[DT_PPC(GOT)] == 0)
 178     /* Handle old style PLT.  */
 179     return __elf_machine_runtime_setup (map, lazy, profile);
 180
 181   /* New style non-exec PLT consisting of an array of addresses.  */
 182   map->l_info[DT_PPC(GOT)]->d_un.d_ptr += map->l_addr;
 183   if (lazy)
 184     {
 185       Elf32_Addr *plt, *got, glink;
 186       Elf32_Word num_plt_entries;
 187       void (*dlrr) (void);
 188       extern void _dl_runtime_resolve (void);
 189       extern void _dl_prof_resolve (void);
 190
 191       if (__glibc_likely (!profile))
 192         dlrr = _dl_runtime_resolve;
 193       else
 194         {
 195           if (GLRO(dl_profile) != NULL
 196               &&_dl_name_match_p (GLRO(dl_profile), map))
 197             GL(dl_profile_map) = map;
 198           dlrr = _dl_prof_resolve;
 199         }
 200       got = (Elf32_Addr *) map->l_info[DT_PPC(GOT)]->d_un.d_ptr;
 201       glink = got[1];
 202       got[1] = (Elf32_Addr) dlrr;
 203       got[2] = (Elf32_Addr) map;
 204
 205       /* Relocate everything in .plt by the load address offset.  */
 206       plt = (Elf32_Addr *) D_PTR (map, l_info[DT_PLTGOT]);
 207       num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
 208                          / sizeof (Elf32_Rela));
 209
 210       /* If a library is prelinked but we have to relocate anyway,
 211          we have to be able to undo the prelinking of .plt section.
 212          The prelinker saved us at got[1] address of .glink
 213          section's start.  */
 214       if (glink)
 215         {
 216           glink += map->l_addr;
 217           while (num_plt_entries-- != 0)
 218             *plt++ = glink, glink += 4;
 219         }
 220       else
 221         while (num_plt_entries-- != 0)
 222           *plt++ += map->l_addr;
 223     }
 224   return lazy;
 225 }
 226
 227 /* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
 228 extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
 229                                            Elf32_Addr *reloc_addr,
 230                                            Elf32_Addr finaladdr);
 231
 232 static inline Elf32_Addr
 233 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 234                        const ElfW(Sym) *refsym, const ElfW(Sym) *sym,
 235                        const Elf32_Rela *reloc,
 236                        Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
 237 {
 238   if (map->l_info[DT_PPC(GOT)] == 0)
 239     /* Handle old style PLT.  */
 240     return __elf_machine_fixup_plt (map, reloc_addr, finaladdr);
 241
 242   *reloc_addr = finaladdr;
 243   return finaladdr;
 244 }
 245
 246 /* Return the final value of a plt relocation.  */
 247 static inline Elf32_Addr
 248 elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
 249                        Elf32_Addr value)
 250 {
 251   return value + reloc->r_addend;
 252 }
 253
 254
 255 /* Names of the architecture-specific auditing callback functions.  */
 256 #define ARCH_LA_PLTENTER ppc32_gnu_pltenter
 257 #define ARCH_LA_PLTEXIT ppc32_gnu_pltexit
 258
 259 #endif /* dl_machine_h */
 260
 261 #ifdef RESOLVE_MAP
 262
 263 /* Do the actual processing of a reloc, once its target address
 264    has been determined.  */
 265 extern void __process_machine_rela (struct link_map *map,
 266                                     const Elf32_Rela *reloc,
 267                                     struct link_map *sym_map,
 268                                     const Elf32_Sym *sym,
 269                                     const Elf32_Sym *refsym,
 270                                     Elf32_Addr *const reloc_addr,
 271                                     Elf32_Addr finaladdr,
 272                                     int rinfo, bool skip_ifunc)
 273   attribute_hidden;
 274
 275 /* Call _dl_signal_error when a resolved value overflows a relocated area.  */
 276 extern void _dl_reloc_overflow (struct link_map *map,
 277                                 const char *name,
 278                                 Elf32_Addr *const reloc_addr,
 279                                 const Elf32_Sym *refsym) attribute_hidden;
 280
 281 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 282    LOADADDR is the load address of the object; INFO is an array indexed
 283    by DT_* of the .dynamic section info.  */
 284
 285 static inline void __attribute__ ((always_inline))
 286 elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
 287                   const Elf32_Rela *reloc, const Elf32_Sym *sym,
 288                   const struct r_found_version *version,
 289                   void *const reloc_addr_arg, int skip_ifunc)
 290 {
 291   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 292   const Elf32_Sym *const refsym = sym;
 293   Elf32_Addr value;
 294   const int r_type = ELF32_R_TYPE (reloc->r_info);
 295   struct link_map *sym_map = NULL;
 296
 297   if (r_type == R_PPC_RELATIVE)
 298     {
 299       *reloc_addr = map->l_addr + reloc->r_addend;
 300       return;
 301     }
 302
 303   if (__glibc_unlikely (r_type == R_PPC_NONE))
 304     return;
 305
 306   /* binutils on ppc32 includes st_value in r_addend for relocations
 307      against local symbols.  */
 308   if (__builtin_expect (ELF32_ST_BIND (sym->st_info) == STB_LOCAL, 0)
 309       && sym->st_shndx != SHN_UNDEF)
 310     {
 311       sym_map = map;
 312       value = map->l_addr;
 313     }
 314   else
 315     {
 316       sym_map = RESOLVE_MAP (map, scope, &sym, version, r_type);
 317       value = SYMBOL_ADDRESS (sym_map, sym, true);
 318     }
 319   value += reloc->r_addend;
 320
 321   if (sym != NULL
 322       && __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
 323       && __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
 324       && __builtin_expect (!skip_ifunc, 1))
 325     value = elf_ifunc_invoke (value);
 326
 327   /* A small amount of code is duplicated here for speed.  In libc,
 328      more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
 329      libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
 330      R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
 331      wouldn't usually handle).  As an bonus, doing this here allows
 332      the switch statement in __process_machine_rela to work.  */
 333   switch (r_type)
 334     {
 335     case R_PPC_GLOB_DAT:
 336     case R_PPC_ADDR32:
 337       *reloc_addr = value;
 338       break;
 339
 340 #ifdef RTLD_BOOTSTRAP
 341 # define NOT_BOOTSTRAP 0
 342 #else
 343 # define NOT_BOOTSTRAP 1
 344 #endif
 345
 346     case R_PPC_DTPMOD32:
 347       if (map->l_info[DT_PPC(OPT)]
 348           && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
 349         {
 350           if (!NOT_BOOTSTRAP)
 351             {
 352               reloc_addr[0] = 0;
 353               reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
 354                                + TLS_DTV_OFFSET);
 355               break;
 356             }
 357           else if (sym_map != NULL)
 358             {
 359 #ifndef SHARED
 360               CHECK_STATIC_TLS (map, sym_map);
 361 #else
 362               if (TRY_STATIC_TLS (map, sym_map))
 363 #endif
 364                 {
 365                   reloc_addr[0] = 0;
 366                   /* Set up for local dynamic.  */
 367                   reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
 368                                    + TLS_DTV_OFFSET);
 369                   break;
 370                 }
 371             }
 372         }
 373       if (!NOT_BOOTSTRAP)
 374         /* During startup the dynamic linker is always index 1.  */
 375         *reloc_addr = 1;
 376       else if (sym_map != NULL)
 377         /* Get the information from the link map returned by the
 378            RESOLVE_MAP function.  */
 379         *reloc_addr = sym_map->l_tls_modid;
 380       break;
 381     case R_PPC_DTPREL32:
 382       if (map->l_info[DT_PPC(OPT)]
 383           && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
 384         {
 385           if (!NOT_BOOTSTRAP)
 386             {
 387               *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 388               break;
 389             }
 390           else if (sym_map != NULL)
 391             {
 392               /* This reloc is always preceded by R_PPC_DTPMOD32.  */
 393 #ifndef SHARED
 394               assert (HAVE_STATIC_TLS (map, sym_map));
 395 #else
 396               if (HAVE_STATIC_TLS (map, sym_map))
 397 #endif
 398                 {
 399                   *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 400                   break;
 401                 }
 402             }
 403         }
 404       /* During relocation all TLS symbols are defined and used.
 405          Therefore the offset is already correct.  */
 406       if (NOT_BOOTSTRAP && sym_map != NULL)
 407         *reloc_addr = TLS_DTPREL_VALUE (sym, reloc);
 408       break;
 409     case R_PPC_TPREL32:
 410       if (!NOT_BOOTSTRAP || sym_map != NULL)
 411         {
 412           if (NOT_BOOTSTRAP)
 413             CHECK_STATIC_TLS (map, sym_map);
 414           *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
 415         }
 416       break;
 417
 418     case R_PPC_JMP_SLOT:
 419       if (map->l_info[DT_PPC(GOT)] != 0)
 420         {
 421           *reloc_addr = value;
 422           break;
 423         }
 424       /* FALLTHROUGH */
 425
 426     default:
 427       __process_machine_rela (map, reloc, sym_map, sym, refsym,
 428                               reloc_addr, value, r_type, skip_ifunc);
 429     }
 430 }
 431
 432 static inline void __attribute__ ((always_inline))
 433 elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
 434                            void *const reloc_addr_arg)
 435 {
 436   Elf32_Addr *const reloc_addr = reloc_addr_arg;
 437   *reloc_addr = l_addr + reloc->r_addend;
 438 }
 439
 440 static inline void __attribute__ ((always_inline))
 441 elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
 442                       Elf32_Addr l_addr, const Elf32_Rela *reloc,
 443                       int skip_ifunc)
 444 {
 445   /* elf_machine_runtime_setup handles this. */
 446 }
 447
 448 #endif /* RESOLVE_MAP */