sysdeps/x86_64/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  x86-64 version.
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Andreas Jaeger <aj@suse.de>.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #ifndef dl_machine_h
  22 #define dl_machine_h
  23
  24 #define ELF_MACHINE_NAME "x86_64"
  25
  26 #include <sys/param.h>
  27 #include <sysdep.h>
  28 #include <tls.h>
  29
  30 /* Return nonzero iff ELF header is compatible with the running host.  */
  31 static inline int __attribute__ ((unused))
  32 elf_machine_matches_host (const Elf64_Ehdr *ehdr)
  33 {
  34   return ehdr->e_machine == EM_X86_64;
  35 }
  36
  37
  38 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  39    first element of the GOT.  This must be inlined in a function which
  40    uses global data.  */
  41 static inline Elf64_Addr __attribute__ ((unused))
  42 elf_machine_dynamic (void)
  43 {
  44   Elf64_Addr addr;
  45
  46   /* This works because we have our GOT address available in the small PIC
  47      model.  */
  48   addr = (Elf64_Addr) &_DYNAMIC;
  49
  50   return addr;
  51 }
  52
  53
  54 /* Return the run-time load address of the shared object.  */
  55 static inline Elf64_Addr __attribute__ ((unused))
  56 elf_machine_load_address (void)
  57 {
  58   register Elf64_Addr addr, tmp;
  59
  60   /* The easy way is just the same as on x86:
  61        leaq _dl_start, %0
  62        leaq _dl_start(%%rip), %1
  63        subq %0, %1
  64      but this does not work with binutils since we then have
  65      a R_X86_64_32S relocation in a shared lib.
  66
  67      Instead we store the address of _dl_start in the data section
  68      and compare it with the current value that we can get via
  69      an RIP relative addressing mode.  */
  70
  71   asm ("movq 1f(%%rip), %1\n"
  72        "0:\tleaq _dl_start(%%rip), %0\n\t"
  73        "subq %1, %0\n\t"
  74        ".section\t.data\n"
  75        "1:\t.quad _dl_start\n\t"
  76        ".previous\n\t"
  77        : "=r" (addr), "=r" (tmp) : : "cc");
  78
  79   return addr;
  80 }
  81
  82 /* Set up the loaded object described by L so its unrelocated PLT
  83    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  84
  85 static inline int __attribute__ ((unused, always_inline))
  86 elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
  87 {
  88   Elf64_Addr *got;
  89   extern void _dl_runtime_resolve (Elf64_Word) attribute_hidden;
  90   extern void _dl_runtime_profile (Elf64_Word) attribute_hidden;
  91
  92   if (l->l_info[DT_JMPREL] && lazy)
  93     {
  94       /* The GOT entries for functions in the PLT have not yet been filled
  95          in.  Their initial contents will arrange when called to push an
  96          offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
  97          and then jump to _GLOBAL_OFFSET_TABLE[2].  */
  98       got = (Elf64_Addr *) D_PTR (l, l_info[DT_PLTGOT]);
  99       /* If a library is prelinked but we have to relocate anyway,
 100          we have to be able to undo the prelinking of .got.plt.
 101          The prelinker saved us here address of .plt + 0x16.  */
 102       if (got[1])
 103         {
 104           l->l_mach.plt = got[1] + l->l_addr;
 105           l->l_mach.gotplt = (Elf64_Addr) &got[3];
 106         }
 107       got[1] = (Elf64_Addr) l;  /* Identify this shared object.  */
 108
 109       /* The got[2] entry contains the address of a function which gets
 110          called to get the address of a so far unresolved function and
 111          jump to it.  The profiling extension of the dynamic linker allows
 112          to intercept the calls to collect information.  In this case we
 113          don't store the address in the GOT so that all future calls also
 114          end in this function.  */
 115       if (__builtin_expect (profile, 0))
 116         {
 117           got[2] = (Elf64_Addr) &_dl_runtime_profile;
 118
 119           if (GLRO(dl_profile) != NULL
 120               && _dl_name_match_p (GLRO(dl_profile), l))
 121             /* This is the object we are looking for.  Say that we really
 122                want profiling and the timers are started.  */
 123             GL(dl_profile_map) = l;
 124         }
 125       else
 126         /* This function will get called to fix up the GOT entry indicated by
 127            the offset on the stack, and then jump to the resolved address.  */
 128         got[2] = (Elf64_Addr) &_dl_runtime_resolve;
 129     }
 130
 131   return lazy;
 132 }
 133
 134 /* Initial entry point code for the dynamic linker.
 135    The C function `_dl_start' is the real entry point;
 136    its return value is the user program's entry point.  */
 137 #define RTLD_START asm ("\n\
 138 .text\n\
 139         .align 16\n\
 140 .globl _start\n\
 141 .globl _dl_start_user\n\
 142 _start:\n\
 143         movq %rsp, %rdi\n\
 144         call _dl_start\n\
 145 _dl_start_user:\n\
 146         # Save the user entry point address in %r12.\n\
 147         movq %rax, %r12\n\
 148         # See if we were run as a command with the executable file\n\
 149         # name as an extra leading argument.\n\
 150         movl _dl_skip_args(%rip), %eax\n\
 151         # Pop the original argument count.\n\
 152         popq %rdx\n\
 153         # Adjust the stack pointer to skip _dl_skip_args words.\n\
 154         leaq (%rsp,%rax,8), %rsp\n\
 155         # Subtract _dl_skip_args from argc.\n\
 156         subl %eax, %edx\n\
 157         # Push argc back on the stack.\n\
 158         pushq %rdx\n\
 159         # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\
 160         # argc -> rsi\n\
 161         movq %rdx, %rsi\n\
 162         # Save %rsp value in %r13.\n\
 163         movq %rsp, %r13\n\
 164         # And align stack for the _dl_init_internal call. \n\
 165         andq $-16, %rsp\n\
 166         # _dl_loaded -> rdi\n\
 167         movq _rtld_local(%rip), %rdi\n\
 168         # env -> rcx\n\
 169         leaq 16(%r13,%rdx,8), %rcx\n\
 170         # argv -> rdx\n\
 171         leaq 8(%r13), %rdx\n\
 172         # Clear %rbp to mark outermost frame obviously even for constructors.\n\
 173         xorq %rbp, %rbp\n\
 174         # Call the function to run the initializers.\n\
 175         call _dl_init_internal@PLT\n\
 176         # Pass our finalizer function to the user in %rdx, as per ELF ABI.\n\
 177         leaq _dl_fini(%rip), %rdx\n\
 178         # And make sure %rsp points to argc stored on the stack.\n\
 179         movq %r13, %rsp\n\
 180         # Jump to the user's entry point.\n\
 181         jmp *%r12\n\
 182 .previous\n\
 183 ");
 184
 185 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
 186    TLS variable, so undefined references should not be allowed to
 187    define the value.
 188    ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
 189    of the main executable's symbols, as for a COPY reloc.  */
 190 #if defined USE_TLS && (!defined RTLD_BOOTSTRAP || USE___THREAD)
 191 # define elf_machine_type_class(type)                                         \
 192   ((((type) == R_X86_64_JUMP_SLOT                                             \
 193      || (type) == R_X86_64_DTPMOD64                                           \
 194      || (type) == R_X86_64_DTPOFF64 || (type) == R_X86_64_TPOFF64)            \
 195     * ELF_RTYPE_CLASS_PLT)                                                    \
 196    | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY))
 197 #else
 198 # define elf_machine_type_class(type) \
 199   ((((type) == R_X86_64_JUMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
 200    | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY))
 201 #endif
 202
 203 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 204 #define ELF_MACHINE_JMP_SLOT    R_X86_64_JUMP_SLOT
 205
 206 /* The x86-64 never uses Elf64_Rel relocations.  */
 207 #define ELF_MACHINE_NO_REL 1
 208
 209 /* We define an initialization functions.  This is called very early in
 210    _dl_sysdep_start.  */
 211 #define DL_PLATFORM_INIT dl_platform_init ()
 212
 213 static inline void __attribute__ ((unused))
 214 dl_platform_init (void)
 215 {
 216   if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
 217     /* Avoid an empty string which would disturb us.  */
 218     GLRO(dl_platform) = NULL;
 219 }
 220
 221 static inline Elf64_Addr
 222 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 223                        const Elf64_Rela *reloc,
 224                        Elf64_Addr *reloc_addr, Elf64_Addr value)
 225 {
 226   return *reloc_addr = value;
 227 }
 228
 229 /* Return the final value of a plt relocation.  On x86-64 the
 230    JUMP_SLOT relocation ignores the addend. */
 231 static inline Elf64_Addr
 232 elf_machine_plt_value (struct link_map *map, const Elf64_Rela *reloc,
 233                        Elf64_Addr value)
 234 {
 235   return value;
 236 }
 237
 238
 239 /* Names of the architecture-specific auditing callback functions.  */
 240 #define ARCH_LA_PLTENTER x86_64_gnu_pltenter
 241 #define ARCH_LA_PLTEXIT x86_64_gnu_pltexit
 242
 243 #endif /* !dl_machine_h */
 244
 245 #ifdef RESOLVE_MAP
 246
 247 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 248    MAP is the object containing the reloc.  */
 249
 250 auto inline void
 251 __attribute__ ((always_inline))
 252 elf_machine_rela (struct link_map *map, const Elf64_Rela *reloc,
 253                   const Elf64_Sym *sym, const struct r_found_version *version,
 254                   void *const reloc_addr_arg)
 255 {
 256   Elf64_Addr *const reloc_addr = reloc_addr_arg;
 257   const unsigned long int r_type = ELF64_R_TYPE (reloc->r_info);
 258
 259 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
 260   if (__builtin_expect (r_type == R_X86_64_RELATIVE, 0))
 261     {
 262 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
 263       /* This is defined in rtld.c, but nowhere in the static libc.a;
 264          make the reference weak so static programs can still link.
 265          This declaration cannot be done when compiling rtld.c
 266          (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
 267          common defn for _dl_rtld_map, which is incompatible with a
 268          weak decl in the same file.  */
 269 #  ifndef SHARED
 270       weak_extern (GL(dl_rtld_map));
 271 #  endif
 272       if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.  */
 273 # endif
 274         *reloc_addr = map->l_addr + reloc->r_addend;
 275     }
 276   else
 277 #endif
 278   if (__builtin_expect (r_type == R_X86_64_NONE, 0))
 279     return;
 280   else
 281     {
 282 #ifndef RTLD_BOOTSTRAP
 283       const Elf64_Sym *const refsym = sym;
 284 #endif
 285 #ifndef RTLD_BOOTSTRAP
 286       struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
 287       Elf64_Addr value = (sym == NULL ? 0
 288                           : (Elf64_Addr) sym_map->l_addr + sym->st_value);
 289 #else
 290       Elf64_Addr value = RESOLVE (&sym, version, r_type);
 291
 292 # ifndef RTLD_BOOTSTRAP
 293       if (sym != NULL)
 294 # endif
 295         value += sym->st_value;
 296 #endif
 297
 298 #if defined RTLD_BOOTSTRAP && !USE___THREAD
 299       assert (r_type == R_X86_64_GLOB_DAT || r_type == R_X86_64_JUMP_SLOT);
 300       *reloc_addr = value + reloc->r_addend;
 301 #else
 302       switch (r_type)
 303         {
 304         case R_X86_64_GLOB_DAT:
 305         case R_X86_64_JUMP_SLOT:
 306           *reloc_addr = value + reloc->r_addend;
 307           break;
 308
 309 #if defined USE_TLS && !defined RESOLVE_CONFLICT_FIND_MAP
 310         case R_X86_64_DTPMOD64:
 311 # ifdef RTLD_BOOTSTRAP
 312           /* During startup the dynamic linker is always the module
 313              with index 1.
 314              XXX If this relocation is necessary move before RESOLVE
 315              call.  */
 316           *reloc_addr = 1;
 317 # else
 318           /* Get the information from the link map returned by the
 319              resolve function.  */
 320           if (sym_map != NULL)
 321             *reloc_addr = sym_map->l_tls_modid;
 322 # endif
 323           break;
 324         case R_X86_64_DTPOFF64:
 325 # ifndef RTLD_BOOTSTRAP
 326           /* During relocation all TLS symbols are defined and used.
 327              Therefore the offset is already correct.  */
 328           if (sym != NULL)
 329             *reloc_addr = sym->st_value + reloc->r_addend;
 330 # endif
 331           break;
 332         case R_X86_64_TPOFF64:
 333           /* The offset is negative, forward from the thread pointer.  */
 334 # ifndef RTLD_BOOTSTRAP
 335           if (sym != NULL)
 336 # endif
 337             {
 338 # ifndef RTLD_BOOTSTRAP
 339               CHECK_STATIC_TLS (map, sym_map);
 340 # endif
 341               /* We know the offset of the object the symbol is contained in.
 342                  It is a negative value which will be added to the
 343                  thread pointer.  */
 344               *reloc_addr = (sym->st_value + reloc->r_addend
 345                              - sym_map->l_tls_offset);
 346             }
 347           break;
 348 #endif  /* use TLS */
 349
 350 #ifndef RTLD_BOOTSTRAP
 351         case R_X86_64_64:
 352           *reloc_addr = value + reloc->r_addend;
 353           break;
 354         case R_X86_64_32:
 355           *(unsigned int *) reloc_addr = value + reloc->r_addend;
 356           if (value + reloc->r_addend > UINT_MAX)
 357             {
 358               const char *strtab;
 359
 360               strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
 361
 362               _dl_error_printf ("\
 363 %s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n",
 364                                 rtld_progname ?: "<program name unknown>",
 365                                 strtab + refsym->st_name);
 366             }
 367           break;
 368 # ifndef RESOLVE_CONFLICT_FIND_MAP
 369           /* Not needed for dl-conflict.c.  */
 370         case R_X86_64_PC32:
 371           *(unsigned int *) reloc_addr = value + reloc->r_addend
 372             - (Elf64_Addr) reloc_addr;
 373           if (value + reloc->r_addend - (Elf64_Addr) reloc_addr
 374               != (int)(value + reloc->r_addend - (Elf64_Addr) reloc_addr))
 375             {
 376               const char *strtab;
 377
 378               strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
 379
 380               _dl_error_printf ("\
 381 %s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n",
 382                                 rtld_progname ?: "<program name unknown>",
 383                                 strtab + refsym->st_name);
 384             }
 385           break;
 386         case R_X86_64_COPY:
 387           if (sym == NULL)
 388             /* This can happen in trace mode if an object could not be
 389                found.  */
 390             break;
 391           if (__builtin_expect (sym->st_size > refsym->st_size, 0)
 392               || (__builtin_expect (sym->st_size < refsym->st_size, 0)
 393                   && GLRO(dl_verbose)))
 394             {
 395               const char *strtab;
 396
 397               strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
 398               _dl_error_printf ("\
 399 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
 400                                 rtld_progname ?: "<program name unknown>",
 401                                 strtab + refsym->st_name);
 402             }
 403           memcpy (reloc_addr_arg, (void *) value,
 404                   MIN (sym->st_size, refsym->st_size));
 405           break;
 406 # endif
 407         default:
 408           _dl_reloc_bad_type (map, r_type, 0);
 409           break;
 410 #endif
 411         }
 412 #endif
 413     }
 414 }
 415
 416 auto inline void
 417 __attribute ((always_inline))
 418 elf_machine_rela_relative (Elf64_Addr l_addr, const Elf64_Rela *reloc,
 419                            void *const reloc_addr_arg)
 420 {
 421   Elf64_Addr *const reloc_addr = reloc_addr_arg;
 422   assert (ELF64_R_TYPE (reloc->r_info) == R_X86_64_RELATIVE);
 423   *reloc_addr = l_addr + reloc->r_addend;
 424 }
 425
 426 auto inline void
 427 __attribute ((always_inline))
 428 elf_machine_lazy_rel (struct link_map *map,
 429                       Elf64_Addr l_addr, const Elf64_Rela *reloc)
 430 {
 431   Elf64_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
 432   const unsigned long int r_type = ELF64_R_TYPE (reloc->r_info);
 433
 434   /* Check for unexpected PLT reloc type.  */
 435   if (__builtin_expect (r_type == R_X86_64_JUMP_SLOT, 1))
 436     {
 437       if (__builtin_expect (map->l_mach.plt, 0) == 0)
 438         *reloc_addr += l_addr;
 439       else
 440         *reloc_addr =
 441           map->l_mach.plt
 442           + (((Elf64_Addr) reloc_addr) - map->l_mach.gotplt) * 2;
 443     }
 444   else
 445     _dl_reloc_bad_type (map, r_type, 1);
 446 }
 447
 448 #endif /* RESOLVE_MAP */