sysdeps/aarch64/dl-machine.h

   1 /* Copyright (C) 1995-2018 Free Software Foundation, Inc.
   2
   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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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 "aarch64"
  23
  24 #include <sysdep.h>
  25 #include <tls.h>
  26 #include <dl-tlsdesc.h>
  27 #include <dl-irel.h>
  28 #include <cpu-features.c>
  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 ElfW(Ehdr) *ehdr)
  33 {
  34   return ehdr->e_machine == EM_AARCH64;
  35 }
  36
  37 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  38    first element of the GOT. */
  39 static inline ElfW(Addr) __attribute__ ((unused))
  40 elf_machine_dynamic (void)
  41 {
  42   extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
  43   return _GLOBAL_OFFSET_TABLE_[0];
  44 }
  45
  46 /* Return the run-time load address of the shared object.  */
  47
  48 static inline ElfW(Addr) __attribute__ ((unused))
  49 elf_machine_load_address (void)
  50 {
  51   /* To figure out the load address we use the definition that for any symbol:
  52      dynamic_addr(symbol) = static_addr(symbol) + load_addr
  53
  54     _DYNAMIC sysmbol is used here as its link-time address stored in
  55     the special unrelocated first GOT entry.  */
  56
  57     extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
  58     return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic ();
  59 }
  60
  61 /* Set up the loaded object described by L so its unrelocated PLT
  62    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  63
  64 static inline int __attribute__ ((unused))
  65 elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
  66 {
  67   if (l->l_info[DT_JMPREL] && lazy)
  68     {
  69       ElfW(Addr) *got;
  70       extern void _dl_runtime_resolve (ElfW(Word));
  71       extern void _dl_runtime_profile (ElfW(Word));
  72
  73       got = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
  74       if (got[1])
  75         {
  76           l->l_mach.plt = got[1] + l->l_addr;
  77         }
  78       got[1] = (ElfW(Addr)) l;
  79
  80       /* The got[2] entry contains the address of a function which gets
  81          called to get the address of a so far unresolved function and
  82          jump to it.  The profiling extension of the dynamic linker allows
  83          to intercept the calls to collect information.  In this case we
  84          don't store the address in the GOT so that all future calls also
  85          end in this function.  */
  86       if ( profile)
  87         {
  88            got[2] = (ElfW(Addr)) &_dl_runtime_profile;
  89
  90           if (GLRO(dl_profile) != NULL
  91               && _dl_name_match_p (GLRO(dl_profile), l))
  92             /* Say that we really want profiling and the timers are
  93                started.  */
  94             GL(dl_profile_map) = l;
  95         }
  96       else
  97         {
  98           /* This function will get called to fix up the GOT entry
  99              indicated by the offset on the stack, and then jump to
 100              the resolved address.  */
 101           got[2] = (ElfW(Addr)) &_dl_runtime_resolve;
 102         }
 103     }
 104
 105   return lazy;
 106 }
 107
 108 /* Initial entry point for the dynamic linker. The C function
 109    _dl_start is the real entry point, its return value is the user
 110    program's entry point */
 111 #ifdef __LP64__
 112 # define RTLD_START RTLD_START_1 ("x", "3", "sp")
 113 #else
 114 # define RTLD_START RTLD_START_1 ("w", "2", "wsp")
 115 #endif
 116
 117
 118 #define RTLD_START_1(PTR, PTR_SIZE_LOG, PTR_SP) asm ("\
 119 .text                                                                   \n\
 120 .globl _start                                                           \n\
 121 .type _start, %function                                                 \n\
 122 .globl _dl_start_user                                                   \n\
 123 .type _dl_start_user, %function                                         \n\
 124 _start:                                                                 \n\
 125         mov     " PTR "0, " PTR_SP "                                    \n\
 126         bl      _dl_start                                               \n\
 127         // returns user entry point in x0                               \n\
 128         mov     x21, x0                                                 \n\
 129 _dl_start_user:                                                         \n\
 130         // get the original arg count                                   \n\
 131         ldr     " PTR "1, [sp]                                          \n\
 132         // get the argv address                                         \n\
 133         add     " PTR "2, " PTR_SP ", #(1<<"  PTR_SIZE_LOG ")           \n\
 134         // get _dl_skip_args to see if we were                          \n\
 135         // invoked as an executable                                     \n\
 136         adrp    x4, _dl_skip_args                                       \n\
 137         ldr     w4, [x4, #:lo12:_dl_skip_args]                          \n\
 138         // do we need to adjust argc/argv                               \n\
 139         cmp     w4, 0                                                   \n\
 140         beq     .L_done_stack_adjust                                    \n\
 141         // subtract _dl_skip_args from original arg count               \n\
 142         sub     " PTR "1, " PTR "1, " PTR "4                            \n\
 143         // store adjusted argc back to stack                            \n\
 144         str     " PTR "1, [sp]                                          \n\
 145         // find the first unskipped argument                            \n\
 146         mov     " PTR "3, " PTR "2                                      \n\
 147         add     " PTR "4, " PTR "2, " PTR "4, lsl #" PTR_SIZE_LOG "     \n\
 148         // shuffle argv down                                            \n\
 149 1:      ldr     " PTR "5, [x4], #(1<<"  PTR_SIZE_LOG ")                 \n\
 150         str     " PTR "5, [x3], #(1<<"  PTR_SIZE_LOG ")                 \n\
 151         cmp     " PTR "5, #0                                            \n\
 152         bne     1b                                                      \n\
 153         // shuffle envp down                                            \n\
 154 1:      ldr     " PTR "5, [x4], #(1<<"  PTR_SIZE_LOG ")                 \n\
 155         str     " PTR "5, [x3], #(1<<"  PTR_SIZE_LOG ")                 \n\
 156         cmp     " PTR "5, #0                                            \n\
 157         bne     1b                                                      \n\
 158         // shuffle auxv down                                            \n\
 159 1:      ldp     " PTR "0, " PTR "5, [x4, #(2<<"  PTR_SIZE_LOG ")]!      \n\
 160         stp     " PTR "0, " PTR "5, [x3], #(2<<"  PTR_SIZE_LOG ")       \n\
 161         cmp     " PTR "0, #0                                            \n\
 162         bne     1b                                                      \n\
 163         // Update _dl_argv                                              \n\
 164         adrp    x3, __GI__dl_argv                                       \n\
 165         str     " PTR "2, [x3, #:lo12:__GI__dl_argv]                    \n\
 166 .L_done_stack_adjust:                                                   \n\
 167         // compute envp                                                 \n\
 168         add     " PTR "3, " PTR "2, " PTR "1, lsl #" PTR_SIZE_LOG "     \n\
 169         add     " PTR "3, " PTR "3, #(1<<"  PTR_SIZE_LOG ")             \n\
 170         adrp    x16, _rtld_local                                        \n\
 171         add     " PTR "16, " PTR "16, #:lo12:_rtld_local                \n\
 172         ldr     " PTR "0, [x16]                                         \n\
 173         bl      _dl_init                                                \n\
 174         // load the finalizer function                                  \n\
 175         adrp    x0, _dl_fini                                            \n\
 176         add     " PTR "0, " PTR "0, #:lo12:_dl_fini                     \n\
 177         // jump to the user_s entry point                               \n\
 178         br      x21                                                     \n\
 179 ");
 180
 181 #define elf_machine_type_class(type)                                    \
 182   ((((type) == AARCH64_R(JUMP_SLOT)                                     \
 183      || (type) == AARCH64_R(TLS_DTPMOD)                                 \
 184      || (type) == AARCH64_R(TLS_DTPREL)                                 \
 185      || (type) == AARCH64_R(TLS_TPREL)                                  \
 186      || (type) == AARCH64_R(TLSDESC)) * ELF_RTYPE_CLASS_PLT)            \
 187    | (((type) == AARCH64_R(COPY)) * ELF_RTYPE_CLASS_COPY)               \
 188    | (((type) == AARCH64_R(GLOB_DAT)) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
 189
 190 #define ELF_MACHINE_JMP_SLOT    AARCH64_R(JUMP_SLOT)
 191
 192 /* AArch64 uses RELA not REL */
 193 #define ELF_MACHINE_NO_REL 1
 194 #define ELF_MACHINE_NO_RELA 0
 195
 196 #define DL_PLATFORM_INIT dl_platform_init ()
 197
 198 static inline void __attribute__ ((unused))
 199 dl_platform_init (void)
 200 {
 201   if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
 202     /* Avoid an empty string which would disturb us.  */
 203     GLRO(dl_platform) = NULL;
 204
 205 #ifdef SHARED
 206   /* init_cpu_features has been called early from __libc_start_main in
 207      static executable.  */
 208   init_cpu_features (&GLRO(dl_aarch64_cpu_features));
 209 #endif
 210 }
 211
 212
 213 static inline ElfW(Addr)
 214 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
 215                        const ElfW(Sym) *refsym, const ElfW(Sym) *sym,
 216                        const ElfW(Rela) *reloc,
 217                        ElfW(Addr) *reloc_addr,
 218                        ElfW(Addr) value)
 219 {
 220   return *reloc_addr = value;
 221 }
 222
 223 /* Return the final value of a plt relocation.  */
 224 static inline ElfW(Addr)
 225 elf_machine_plt_value (struct link_map *map,
 226                        const ElfW(Rela) *reloc,
 227                        ElfW(Addr) value)
 228 {
 229   return value;
 230 }
 231
 232 #endif
 233
 234 /* Names of the architecture-specific auditing callback functions.  */
 235 #define ARCH_LA_PLTENTER aarch64_gnu_pltenter
 236 #define ARCH_LA_PLTEXIT  aarch64_gnu_pltexit
 237
 238 #ifdef RESOLVE_MAP
 239
 240 auto inline void
 241 __attribute__ ((always_inline))
 242 elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
 243                   const ElfW(Sym) *sym, const struct r_found_version *version,
 244                   void *const reloc_addr_arg, int skip_ifunc)
 245 {
 246   ElfW(Addr) *const reloc_addr = reloc_addr_arg;
 247   const unsigned int r_type = ELFW (R_TYPE) (reloc->r_info);
 248
 249   if (__builtin_expect (r_type == AARCH64_R(RELATIVE), 0))
 250       *reloc_addr = map->l_addr + reloc->r_addend;
 251   else if (__builtin_expect (r_type == R_AARCH64_NONE, 0))
 252       return;
 253   else
 254     {
 255       const ElfW(Sym) *const refsym = sym;
 256       struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
 257       ElfW(Addr) value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
 258
 259       if (sym != NULL
 260           && __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
 261           && __glibc_likely (sym->st_shndx != SHN_UNDEF)
 262           && __glibc_likely (!skip_ifunc))
 263         value = elf_ifunc_invoke (value);
 264
 265       switch (r_type)
 266         {
 267         case AARCH64_R(COPY):
 268           if (sym == NULL)
 269               break;
 270
 271           if (sym->st_size > refsym->st_size
 272               || (GLRO(dl_verbose) && sym->st_size < refsym->st_size))
 273             {
 274               const char *strtab;
 275
 276               strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 277               _dl_error_printf ("\
 278 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
 279                                 RTLD_PROGNAME, strtab + refsym->st_name);
 280             }
 281           memcpy (reloc_addr_arg, (void *) value,
 282                   sym->st_size < refsym->st_size
 283                   ? sym->st_size : refsym->st_size);
 284           break;
 285
 286         case AARCH64_R(RELATIVE):
 287         case AARCH64_R(GLOB_DAT):
 288         case AARCH64_R(JUMP_SLOT):
 289         case AARCH64_R(ABS32):
 290 #ifdef __LP64__
 291         case AARCH64_R(ABS64):
 292 #endif
 293           *reloc_addr = value + reloc->r_addend;
 294           break;
 295
 296         case AARCH64_R(TLSDESC):
 297           {
 298             struct tlsdesc volatile *td =
 299               (struct tlsdesc volatile *)reloc_addr;
 300 #ifndef RTLD_BOOTSTRAP
 301             if (! sym)
 302               {
 303                 td->arg = (void*)reloc->r_addend;
 304                 td->entry = _dl_tlsdesc_undefweak;
 305               }
 306             else
 307 #endif
 308               {
 309 #ifndef RTLD_BOOTSTRAP
 310 # ifndef SHARED
 311                 CHECK_STATIC_TLS (map, sym_map);
 312 # else
 313                 if (!TRY_STATIC_TLS (map, sym_map))
 314                   {
 315                     td->arg = _dl_make_tlsdesc_dynamic
 316                       (sym_map, sym->st_value + reloc->r_addend);
 317                     td->entry = _dl_tlsdesc_dynamic;
 318                   }
 319                 else
 320 # endif
 321 #endif
 322                   {
 323                     td->arg = (void*)(sym->st_value + sym_map->l_tls_offset
 324                                       + reloc->r_addend);
 325                     td->entry = _dl_tlsdesc_return;
 326                   }
 327               }
 328             break;
 329           }
 330
 331         case AARCH64_R(TLS_DTPMOD):
 332 #ifdef RTLD_BOOTSTRAP
 333           *reloc_addr = 1;
 334 #else
 335           if (sym_map != NULL)
 336             {
 337               *reloc_addr = sym_map->l_tls_modid;
 338             }
 339 #endif
 340           break;
 341
 342         case AARCH64_R(TLS_DTPREL):
 343           if (sym)
 344             *reloc_addr = sym->st_value + reloc->r_addend;
 345           break;
 346
 347         case AARCH64_R(TLS_TPREL):
 348           if (sym)
 349             {
 350               CHECK_STATIC_TLS (map, sym_map);
 351               *reloc_addr =
 352                 sym->st_value + reloc->r_addend + sym_map->l_tls_offset;
 353             }
 354           break;
 355
 356         case AARCH64_R(IRELATIVE):
 357           value = map->l_addr + reloc->r_addend;
 358           value = elf_ifunc_invoke (value);
 359           *reloc_addr = value;
 360           break;
 361
 362         default:
 363           _dl_reloc_bad_type (map, r_type, 0);
 364           break;
 365         }
 366     }
 367 }
 368
 369 inline void
 370 __attribute__ ((always_inline))
 371 elf_machine_rela_relative (ElfW(Addr) l_addr,
 372                            const ElfW(Rela) *reloc,
 373                            void *const reloc_addr_arg)
 374 {
 375   ElfW(Addr) *const reloc_addr = reloc_addr_arg;
 376   *reloc_addr = l_addr + reloc->r_addend;
 377 }
 378
 379 inline void
 380 __attribute__ ((always_inline))
 381 elf_machine_lazy_rel (struct link_map *map,
 382                       ElfW(Addr) l_addr,
 383                       const ElfW(Rela) *reloc,
 384                       int skip_ifunc)
 385 {
 386   ElfW(Addr) *const reloc_addr = (void *) (l_addr + reloc->r_offset);
 387   const unsigned int r_type = ELFW (R_TYPE) (reloc->r_info);
 388   /* Check for unexpected PLT reloc type.  */
 389   if (__builtin_expect (r_type == AARCH64_R(JUMP_SLOT), 1))
 390     {
 391       if (__builtin_expect (map->l_mach.plt, 0) == 0)
 392         *reloc_addr += l_addr;
 393       else
 394         *reloc_addr = map->l_mach.plt;
 395     }
 396   else if (__builtin_expect (r_type == AARCH64_R(TLSDESC), 1))
 397     {
 398       const Elf_Symndx symndx = ELFW (R_SYM) (reloc->r_info);
 399       const ElfW (Sym) *symtab = (const void *)D_PTR (map, l_info[DT_SYMTAB]);
 400       const ElfW (Sym) *sym = &symtab[symndx];
 401       const struct r_found_version *version = NULL;
 402
 403       if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
 404         {
 405           const ElfW (Half) *vernum =
 406             (const void *)D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
 407           version = &map->l_versions[vernum[symndx] & 0x7fff];
 408         }
 409
 410       /* Always initialize TLS descriptors completely, because lazy
 411          initialization requires synchronization at every TLS access.  */
 412       elf_machine_rela (map, reloc, sym, version, reloc_addr, skip_ifunc);
 413     }
 414   else if (__glibc_unlikely (r_type == AARCH64_R(IRELATIVE)))
 415     {
 416       ElfW(Addr) value = map->l_addr + reloc->r_addend;
 417       if (__glibc_likely (!skip_ifunc))
 418         value = elf_ifunc_invoke (value);
 419       *reloc_addr = value;
 420     }
 421   else
 422     _dl_reloc_bad_type (map, r_type, 1);
 423 }
 424
 425 #endif