1 /* Machine-dependent ELF dynamic relocation inline functions. x86-64 version.
2 Copyright (C) 2001-2014 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Andreas Jaeger <aj@suse.de>.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
23 #define ELF_MACHINE_NAME "x86_64"
25 #include <sys/param.h>
28 #include <dl-tlsdesc.h>
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
)
34 return ehdr
->e_machine
== EM_X86_64
;
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
41 static inline ElfW(Addr
) __attribute__ ((unused
))
42 elf_machine_dynamic (void)
44 /* This produces an IP-relative reloc which is resolved at link time. */
45 extern const ElfW(Addr
) _GLOBAL_OFFSET_TABLE_
[] attribute_hidden
;
46 return _GLOBAL_OFFSET_TABLE_
[0];
50 /* Return the run-time load address of the shared object. */
51 static inline ElfW(Addr
) __attribute__ ((unused
))
52 elf_machine_load_address (void)
54 /* Compute the difference between the runtime address of _DYNAMIC as seen
55 by an IP-relative reference, and the link-time address found in the
56 special unrelocated first GOT entry. */
57 extern ElfW(Dyn
) _DYNAMIC
[] attribute_hidden
;
58 return (ElfW(Addr
)) &_DYNAMIC
- elf_machine_dynamic ();
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. */
64 static inline int __attribute__ ((unused
, always_inline
))
65 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
68 extern void _dl_runtime_resolve (ElfW(Word
)) attribute_hidden
;
69 extern void _dl_runtime_profile (ElfW(Word
)) attribute_hidden
;
71 if (l
->l_info
[DT_JMPREL
] && lazy
)
73 /* The GOT entries for functions in the PLT have not yet been filled
74 in. Their initial contents will arrange when called to push an
75 offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
76 and then jump to _GLOBAL_OFFSET_TABLE_[2]. */
77 got
= (Elf64_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
78 /* If a library is prelinked but we have to relocate anyway,
79 we have to be able to undo the prelinking of .got.plt.
80 The prelinker saved us here address of .plt + 0x16. */
83 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
84 l
->l_mach
.gotplt
= (ElfW(Addr
)) &got
[3];
86 /* Identify this shared object. */
87 *(ElfW(Addr
) *) (got
+ 1) = (ElfW(Addr
)) l
;
89 /* The got[2] entry contains the address of a function which gets
90 called to get the address of a so far unresolved function and
91 jump to it. The profiling extension of the dynamic linker allows
92 to intercept the calls to collect information. In this case we
93 don't store the address in the GOT so that all future calls also
94 end in this function. */
95 if (__glibc_unlikely (profile
))
97 *(ElfW(Addr
) *) (got
+ 2) = (ElfW(Addr
)) &_dl_runtime_profile
;
99 if (GLRO(dl_profile
) != NULL
100 && _dl_name_match_p (GLRO(dl_profile
), l
))
101 /* This is the object we are looking for. Say that we really
102 want profiling and the timers are started. */
103 GL(dl_profile_map
) = l
;
106 /* This function will get called to fix up the GOT entry indicated by
107 the offset on the stack, and then jump to the resolved address. */
108 *(ElfW(Addr
) *) (got
+ 2) = (ElfW(Addr
)) &_dl_runtime_resolve
;
111 if (l
->l_info
[ADDRIDX (DT_TLSDESC_GOT
)] && lazy
)
112 *(ElfW(Addr
)*)(D_PTR (l
, l_info
[ADDRIDX (DT_TLSDESC_GOT
)]) + l
->l_addr
)
113 = (ElfW(Addr
)) &_dl_tlsdesc_resolve_rela
;
118 /* Initial entry point code for the dynamic linker.
119 The C function `_dl_start' is the real entry point;
120 its return value is the user program's entry point. */
121 #define RTLD_START asm ("\n\
125 .globl _dl_start_user\n\
130 # Save the user entry point address in %r12.\n\
132 # See if we were run as a command with the executable file\n\
133 # name as an extra leading argument.\n\
134 movl _dl_skip_args(%rip), %eax\n\
135 # Pop the original argument count.\n\
137 # Adjust the stack pointer to skip _dl_skip_args words.\n\
138 leaq (%rsp,%rax,8), %rsp\n\
139 # Subtract _dl_skip_args from argc.\n\
141 # Push argc back on the stack.\n\
143 # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\
146 # Save %rsp value in %r13.\n\
148 # And align stack for the _dl_init call. \n\
150 # _dl_loaded -> rdi\n\
151 movq _rtld_local(%rip), %rdi\n\
153 leaq 16(%r13,%rdx,8), %rcx\n\
155 leaq 8(%r13), %rdx\n\
156 # Clear %rbp to mark outermost frame obviously even for constructors.\n\
158 # Call the function to run the initializers.\n\
160 # Pass our finalizer function to the user in %rdx, as per ELF ABI.\n\
161 leaq _dl_fini(%rip), %rdx\n\
162 # And make sure %rsp points to argc stored on the stack.\n\
164 # Jump to the user's entry point.\n\
169 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
170 TLS variable, so undefined references should not be allowed to
172 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
173 of the main executable's symbols, as for a COPY reloc. */
174 #define elf_machine_type_class(type) \
175 ((((type) == R_X86_64_JUMP_SLOT \
176 || (type) == R_X86_64_DTPMOD64 \
177 || (type) == R_X86_64_DTPOFF64 \
178 || (type) == R_X86_64_TPOFF64 \
179 || (type) == R_X86_64_TLSDESC) \
180 * ELF_RTYPE_CLASS_PLT) \
181 | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY))
183 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
184 #define ELF_MACHINE_JMP_SLOT R_X86_64_JUMP_SLOT
186 /* The relative ifunc relocation. */
187 // XXX This is a work-around for a broken linker. Remove!
188 #define ELF_MACHINE_IRELATIVE R_X86_64_IRELATIVE
190 /* The x86-64 never uses Elf64_Rel/Elf32_Rel relocations. */
191 #define ELF_MACHINE_NO_REL 1
192 #define ELF_MACHINE_NO_RELA 0
194 /* We define an initialization function. This is called very early in
196 #define DL_PLATFORM_INIT dl_platform_init ()
198 static inline void __attribute__ ((unused
))
199 dl_platform_init (void)
201 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
202 /* Avoid an empty string which would disturb us. */
203 GLRO(dl_platform
) = NULL
;
206 static inline ElfW(Addr
)
207 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
208 const ElfW(Rela
) *reloc
,
209 ElfW(Addr
) *reloc_addr
, ElfW(Addr
) value
)
211 return *reloc_addr
= value
;
214 /* Return the final value of a PLT relocation. On x86-64 the
215 JUMP_SLOT relocation ignores the addend. */
216 static inline ElfW(Addr
)
217 elf_machine_plt_value (struct link_map
*map
, const ElfW(Rela
) *reloc
,
224 /* Names of the architecture-specific auditing callback functions. */
225 #define ARCH_LA_PLTENTER x86_64_gnu_pltenter
226 #define ARCH_LA_PLTEXIT x86_64_gnu_pltexit
228 #endif /* !dl_machine_h */
232 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
233 MAP is the object containing the reloc. */
236 __attribute__ ((always_inline
))
237 elf_machine_rela (struct link_map
*map
, const ElfW(Rela
) *reloc
,
238 const ElfW(Sym
) *sym
, const struct r_found_version
*version
,
239 void *const reloc_addr_arg
, int skip_ifunc
)
241 ElfW(Addr
) *const reloc_addr
= reloc_addr_arg
;
242 const unsigned long int r_type
= ELFW(R_TYPE
) (reloc
->r_info
);
244 # if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
245 if (__glibc_unlikely (r_type
== R_X86_64_RELATIVE
))
247 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
248 /* This is defined in rtld.c, but nowhere in the static libc.a;
249 make the reference weak so static programs can still link.
250 This declaration cannot be done when compiling rtld.c
251 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
252 common defn for _dl_rtld_map, which is incompatible with a
253 weak decl in the same file. */
255 weak_extern (GL(dl_rtld_map
));
257 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
259 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
263 # if !defined RTLD_BOOTSTRAP
264 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
265 relocation updates the whole 64-bit entry. */
266 if (__glibc_unlikely (r_type
== R_X86_64_RELATIVE64
))
267 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) map
->l_addr
+ reloc
->r_addend
;
270 if (__glibc_unlikely (r_type
== R_X86_64_NONE
))
274 # ifndef RTLD_BOOTSTRAP
275 const ElfW(Sym
) *const refsym
= sym
;
277 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
278 ElfW(Addr
) value
= (sym
== NULL
? 0
279 : (ElfW(Addr
)) sym_map
->l_addr
+ sym
->st_value
);
282 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
,
284 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
285 && __builtin_expect (!skip_ifunc
, 1))
286 value
= ((ElfW(Addr
) (*) (void)) value
) ();
290 # ifndef RTLD_BOOTSTRAP
292 case R_X86_64_SIZE64
:
293 /* Set to symbol size plus addend. */
294 *(Elf64_Addr
*) (uintptr_t) reloc_addr
295 = (Elf64_Addr
) sym
->st_size
+ reloc
->r_addend
;
298 case R_X86_64_SIZE32
:
300 case R_X86_64_SIZE64
:
302 /* Set to symbol size plus addend. */
303 value
= sym
->st_size
;
305 case R_X86_64_GLOB_DAT
:
306 case R_X86_64_JUMP_SLOT
:
307 *reloc_addr
= value
+ reloc
->r_addend
;
310 # ifndef RESOLVE_CONFLICT_FIND_MAP
311 case R_X86_64_DTPMOD64
:
312 # ifdef RTLD_BOOTSTRAP
313 /* During startup the dynamic linker is always the module
315 XXX If this relocation is necessary move before RESOLVE
319 /* Get the information from the link map returned by the
322 *reloc_addr
= sym_map
->l_tls_modid
;
325 case R_X86_64_DTPOFF64
:
326 # ifndef RTLD_BOOTSTRAP
327 /* During relocation all TLS symbols are defined and used.
328 Therefore the offset is already correct. */
331 value
= sym
->st_value
+ reloc
->r_addend
;
333 /* This relocation type computes a signed offset that is
334 usually negative. The symbol and addend values are 32
335 bits but the GOT entry is 64 bits wide and the whole
336 64-bit entry is used as a signed quantity, so we need
337 to sign-extend the computed value to 64 bits. */
338 *(Elf64_Sxword
*) reloc_addr
= (Elf64_Sxword
) (Elf32_Sword
) value
;
345 case R_X86_64_TLSDESC
:
347 struct tlsdesc
volatile *td
=
348 (struct tlsdesc
volatile *)reloc_addr
;
350 # ifndef RTLD_BOOTSTRAP
353 td
->arg
= (void*)reloc
->r_addend
;
354 td
->entry
= _dl_tlsdesc_undefweak
;
359 # ifndef RTLD_BOOTSTRAP
361 CHECK_STATIC_TLS (map
, sym_map
);
363 if (!TRY_STATIC_TLS (map
, sym_map
))
365 td
->arg
= _dl_make_tlsdesc_dynamic
366 (sym_map
, sym
->st_value
+ reloc
->r_addend
);
367 td
->entry
= _dl_tlsdesc_dynamic
;
373 td
->arg
= (void*)(sym
->st_value
- sym_map
->l_tls_offset
375 td
->entry
= _dl_tlsdesc_return
;
380 case R_X86_64_TPOFF64
:
381 /* The offset is negative, forward from the thread pointer. */
382 # ifndef RTLD_BOOTSTRAP
386 # ifndef RTLD_BOOTSTRAP
387 CHECK_STATIC_TLS (map
, sym_map
);
389 /* We know the offset of the object the symbol is contained in.
390 It is a negative value which will be added to the
392 value
= (sym
->st_value
+ reloc
->r_addend
393 - sym_map
->l_tls_offset
);
395 /* The symbol and addend values are 32 bits but the GOT
396 entry is 64 bits wide and the whole 64-bit entry is used
397 as a signed quantity, so we need to sign-extend the
398 computed value to 64 bits. */
399 *(Elf64_Sxword
*) reloc_addr
= (Elf64_Sxword
) (Elf32_Sword
) value
;
407 # ifndef RTLD_BOOTSTRAP
409 /* value + r_addend may be > 0xffffffff and R_X86_64_64
410 relocation updates the whole 64-bit entry. */
411 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) value
+ reloc
->r_addend
;
414 case R_X86_64_SIZE32
:
415 /* Set to symbol size plus addend. */
416 value
= sym
->st_size
;
419 value
+= reloc
->r_addend
;
420 *(unsigned int *) reloc_addr
= value
;
423 if (__glibc_unlikely (value
> UINT_MAX
))
428 %s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
429 # ifndef RESOLVE_CONFLICT_FIND_MAP
432 strtab
= (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
434 _dl_error_printf (fmt
, RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
437 # ifndef RESOLVE_CONFLICT_FIND_MAP
438 /* Not needed for dl-conflict.c. */
440 value
+= reloc
->r_addend
- (ElfW(Addr
)) reloc_addr
;
441 *(unsigned int *) reloc_addr
= value
;
442 if (__glibc_unlikely (value
!= (int) value
))
445 %s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
451 /* This can happen in trace mode if an object could not be
454 memcpy (reloc_addr_arg
, (void *) value
,
455 MIN (sym
->st_size
, refsym
->st_size
));
456 if (__builtin_expect (sym
->st_size
> refsym
->st_size
, 0)
457 || (__builtin_expect (sym
->st_size
< refsym
->st_size
, 0)
458 && GLRO(dl_verbose
)))
461 %s: Symbol `%s' has different size in shared object, consider re-linking\n";
466 case R_X86_64_IRELATIVE
:
467 value
= map
->l_addr
+ reloc
->r_addend
;
468 value
= ((ElfW(Addr
) (*) (void)) value
) ();
472 _dl_reloc_bad_type (map
, r_type
, 0);
480 __attribute ((always_inline
))
481 elf_machine_rela_relative (ElfW(Addr
) l_addr
, const ElfW(Rela
) *reloc
,
482 void *const reloc_addr_arg
)
484 ElfW(Addr
) *const reloc_addr
= reloc_addr_arg
;
485 #if !defined RTLD_BOOTSTRAP
486 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
487 relocation updates the whole 64-bit entry. */
488 if (__glibc_unlikely (ELFW(R_TYPE
) (reloc
->r_info
) == R_X86_64_RELATIVE64
))
489 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) l_addr
+ reloc
->r_addend
;
493 assert (ELFW(R_TYPE
) (reloc
->r_info
) == R_X86_64_RELATIVE
);
494 *reloc_addr
= l_addr
+ reloc
->r_addend
;
499 __attribute ((always_inline
))
500 elf_machine_lazy_rel (struct link_map
*map
,
501 ElfW(Addr
) l_addr
, const ElfW(Rela
) *reloc
,
504 ElfW(Addr
) *const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
505 const unsigned long int r_type
= ELFW(R_TYPE
) (reloc
->r_info
);
507 /* Check for unexpected PLT reloc type. */
508 if (__glibc_likely (r_type
== R_X86_64_JUMP_SLOT
))
510 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
511 *reloc_addr
+= l_addr
;
515 + (((ElfW(Addr
)) reloc_addr
) - map
->l_mach
.gotplt
) * 2;
517 else if (__glibc_likely (r_type
== R_X86_64_TLSDESC
))
519 struct tlsdesc
volatile * __attribute__((__unused__
)) td
=
520 (struct tlsdesc
volatile *)reloc_addr
;
522 td
->arg
= (void*)reloc
;
523 td
->entry
= (void*)(D_PTR (map
, l_info
[ADDRIDX (DT_TLSDESC_PLT
)])
526 else if (__glibc_unlikely (r_type
== R_X86_64_IRELATIVE
))
528 ElfW(Addr
) value
= map
->l_addr
+ reloc
->r_addend
;
529 if (__glibc_likely (!skip_ifunc
))
530 value
= ((ElfW(Addr
) (*) (void)) value
) ();
534 _dl_reloc_bad_type (map
, r_type
, 1);
537 #endif /* RESOLVE_MAP */