1 /* Machine-dependent ELF dynamic relocation inline functions. x86-64 version.
2 Copyright (C) 2001-2019 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>
29 #include <cpu-features.c>
31 /* Return nonzero iff ELF header is compatible with the running host. */
32 static inline int __attribute__ ((unused
))
33 elf_machine_matches_host (const ElfW(Ehdr
) *ehdr
)
35 return ehdr
->e_machine
== EM_X86_64
;
39 /* Return the link-time address of _DYNAMIC. Conveniently, this is the
40 first element of the GOT. This must be inlined in a function which
42 static inline ElfW(Addr
) __attribute__ ((unused
))
43 elf_machine_dynamic (void)
45 /* This produces an IP-relative reloc which is resolved at link time. */
46 extern const ElfW(Addr
) _GLOBAL_OFFSET_TABLE_
[] attribute_hidden
;
47 return _GLOBAL_OFFSET_TABLE_
[0];
51 /* Return the run-time load address of the shared object. */
52 static inline ElfW(Addr
) __attribute__ ((unused
))
53 elf_machine_load_address (void)
55 /* Compute the difference between the runtime address of _DYNAMIC as seen
56 by an IP-relative reference, and the link-time address found in the
57 special unrelocated first GOT entry. */
58 extern ElfW(Dyn
) _DYNAMIC
[] attribute_hidden
;
59 return (ElfW(Addr
)) &_DYNAMIC
- elf_machine_dynamic ();
62 /* Set up the loaded object described by L so its unrelocated PLT
63 entries will jump to the on-demand fixup code in dl-runtime.c. */
65 static inline int __attribute__ ((unused
, always_inline
))
66 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
69 extern void _dl_runtime_resolve_fxsave (ElfW(Word
)) attribute_hidden
;
70 extern void _dl_runtime_resolve_xsave (ElfW(Word
)) attribute_hidden
;
71 extern void _dl_runtime_resolve_xsavec (ElfW(Word
)) attribute_hidden
;
72 extern void _dl_runtime_profile_sse (ElfW(Word
)) attribute_hidden
;
73 extern void _dl_runtime_profile_avx (ElfW(Word
)) attribute_hidden
;
74 extern void _dl_runtime_profile_avx512 (ElfW(Word
)) attribute_hidden
;
76 if (l
->l_info
[DT_JMPREL
] && lazy
)
78 /* The GOT entries for functions in the PLT have not yet been filled
79 in. Their initial contents will arrange when called to push an
80 offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
81 and then jump to _GLOBAL_OFFSET_TABLE_[2]. */
82 got
= (Elf64_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
83 /* If a library is prelinked but we have to relocate anyway,
84 we have to be able to undo the prelinking of .got.plt.
85 The prelinker saved us here address of .plt + 0x16. */
88 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
89 l
->l_mach
.gotplt
= (ElfW(Addr
)) &got
[3];
91 /* Identify this shared object. */
92 *(ElfW(Addr
) *) (got
+ 1) = (ElfW(Addr
)) l
;
94 /* The got[2] entry contains the address of a function which gets
95 called to get the address of a so far unresolved function and
96 jump to it. The profiling extension of the dynamic linker allows
97 to intercept the calls to collect information. In this case we
98 don't store the address in the GOT so that all future calls also
99 end in this function. */
100 if (__glibc_unlikely (profile
))
102 if (HAS_ARCH_FEATURE (AVX512F_Usable
))
103 *(ElfW(Addr
) *) (got
+ 2) = (ElfW(Addr
)) &_dl_runtime_profile_avx512
;
104 else if (HAS_ARCH_FEATURE (AVX_Usable
))
105 *(ElfW(Addr
) *) (got
+ 2) = (ElfW(Addr
)) &_dl_runtime_profile_avx
;
107 *(ElfW(Addr
) *) (got
+ 2) = (ElfW(Addr
)) &_dl_runtime_profile_sse
;
109 if (GLRO(dl_profile
) != NULL
110 && _dl_name_match_p (GLRO(dl_profile
), l
))
111 /* This is the object we are looking for. Say that we really
112 want profiling and the timers are started. */
113 GL(dl_profile_map
) = l
;
117 /* This function will get called to fix up the GOT entry
118 indicated by the offset on the stack, and then jump to
119 the resolved address. */
120 if (GLRO(dl_x86_cpu_features
).xsave_state_size
!= 0)
121 *(ElfW(Addr
) *) (got
+ 2)
122 = (HAS_ARCH_FEATURE (XSAVEC_Usable
)
123 ? (ElfW(Addr
)) &_dl_runtime_resolve_xsavec
124 : (ElfW(Addr
)) &_dl_runtime_resolve_xsave
);
126 *(ElfW(Addr
) *) (got
+ 2)
127 = (ElfW(Addr
)) &_dl_runtime_resolve_fxsave
;
131 if (l
->l_info
[ADDRIDX (DT_TLSDESC_GOT
)] && lazy
)
132 *(ElfW(Addr
)*)(D_PTR (l
, l_info
[ADDRIDX (DT_TLSDESC_GOT
)]) + l
->l_addr
)
133 = (ElfW(Addr
)) &_dl_tlsdesc_resolve_rela
;
138 /* Initial entry point code for the dynamic linker.
139 The C function `_dl_start' is the real entry point;
140 its return value is the user program's entry point. */
141 #define RTLD_START asm ("\n\
145 .globl _dl_start_user\n\
150 # Save the user entry point address in %r12.\n\
152 # See if we were run as a command with the executable file\n\
153 # name as an extra leading argument.\n\
154 movl _dl_skip_args(%rip), %eax\n\
155 # Pop the original argument count.\n\
157 # Adjust the stack pointer to skip _dl_skip_args words.\n\
158 leaq (%rsp,%rax,8), %rsp\n\
159 # Subtract _dl_skip_args from argc.\n\
161 # Push argc back on the stack.\n\
163 # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\
166 # Save %rsp value in %r13.\n\
168 # And align stack for the _dl_init call. \n\
170 # _dl_loaded -> rdi\n\
171 movq _rtld_local(%rip), %rdi\n\
173 leaq 16(%r13,%rdx,8), %rcx\n\
175 leaq 8(%r13), %rdx\n\
176 # Clear %rbp to mark outermost frame obviously even for constructors.\n\
178 # Call the function to run the initializers.\n\
180 # Pass our finalizer function to the user in %rdx, as per ELF ABI.\n\
181 leaq _dl_fini(%rip), %rdx\n\
182 # And make sure %rsp points to argc stored on the stack.\n\
184 # Jump to the user's entry point.\n\
189 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
190 TLS variable, so undefined references should not be allowed to
192 ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one
193 of the main executable's symbols, as for a COPY reloc.
194 ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation may
195 against protected data whose address be external due to copy relocation.
197 #define elf_machine_type_class(type) \
198 ((((type) == R_X86_64_JUMP_SLOT \
199 || (type) == R_X86_64_DTPMOD64 \
200 || (type) == R_X86_64_DTPOFF64 \
201 || (type) == R_X86_64_TPOFF64 \
202 || (type) == R_X86_64_TLSDESC) \
203 * ELF_RTYPE_CLASS_PLT) \
204 | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY) \
205 | (((type) == R_X86_64_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
207 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
208 #define ELF_MACHINE_JMP_SLOT R_X86_64_JUMP_SLOT
210 /* The relative ifunc relocation. */
211 // XXX This is a work-around for a broken linker. Remove!
212 #define ELF_MACHINE_IRELATIVE R_X86_64_IRELATIVE
214 /* The x86-64 never uses Elf64_Rel/Elf32_Rel relocations. */
215 #define ELF_MACHINE_NO_REL 1
216 #define ELF_MACHINE_NO_RELA 0
218 /* We define an initialization function. This is called very early in
220 #define DL_PLATFORM_INIT dl_platform_init ()
222 static inline void __attribute__ ((unused
))
223 dl_platform_init (void)
226 /* init_cpu_features has been called early from __libc_start_main in
227 static executable. */
228 init_cpu_features (&GLRO(dl_x86_cpu_features
));
230 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
231 /* Avoid an empty string which would disturb us. */
232 GLRO(dl_platform
) = NULL
;
236 static inline ElfW(Addr
)
237 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
238 const ElfW(Sym
) *refsym
, const ElfW(Sym
) *sym
,
239 const ElfW(Rela
) *reloc
,
240 ElfW(Addr
) *reloc_addr
, ElfW(Addr
) value
)
242 return *reloc_addr
= value
;
245 /* Return the final value of a PLT relocation. On x86-64 the
246 JUMP_SLOT relocation ignores the addend. */
247 static inline ElfW(Addr
)
248 elf_machine_plt_value (struct link_map
*map
, const ElfW(Rela
) *reloc
,
255 /* Names of the architecture-specific auditing callback functions. */
256 #define ARCH_LA_PLTENTER x86_64_gnu_pltenter
257 #define ARCH_LA_PLTEXIT x86_64_gnu_pltexit
259 #endif /* !dl_machine_h */
263 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
264 MAP is the object containing the reloc. */
267 __attribute__ ((always_inline
))
268 elf_machine_rela (struct link_map
*map
, const ElfW(Rela
) *reloc
,
269 const ElfW(Sym
) *sym
, const struct r_found_version
*version
,
270 void *const reloc_addr_arg
, int skip_ifunc
)
272 ElfW(Addr
) *const reloc_addr
= reloc_addr_arg
;
273 const unsigned long int r_type
= ELFW(R_TYPE
) (reloc
->r_info
);
275 # if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
276 if (__glibc_unlikely (r_type
== R_X86_64_RELATIVE
))
278 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
279 /* This is defined in rtld.c, but nowhere in the static libc.a;
280 make the reference weak so static programs can still link.
281 This declaration cannot be done when compiling rtld.c
282 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
283 common defn for _dl_rtld_map, which is incompatible with a
284 weak decl in the same file. */
286 weak_extern (GL(dl_rtld_map
));
288 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
290 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
294 # if !defined RTLD_BOOTSTRAP
295 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
296 relocation updates the whole 64-bit entry. */
297 if (__glibc_unlikely (r_type
== R_X86_64_RELATIVE64
))
298 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) map
->l_addr
+ reloc
->r_addend
;
301 if (__glibc_unlikely (r_type
== R_X86_64_NONE
))
305 # ifndef RTLD_BOOTSTRAP
306 const ElfW(Sym
) *const refsym
= sym
;
308 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
309 ElfW(Addr
) value
= SYMBOL_ADDRESS (sym_map
, sym
, true);
312 && __glibc_unlikely (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
)
313 && __glibc_likely (sym
->st_shndx
!= SHN_UNDEF
)
314 && __glibc_likely (!skip_ifunc
))
316 # ifndef RTLD_BOOTSTRAP
318 && sym_map
->l_type
!= lt_executable
319 && !sym_map
->l_relocated
)
322 = (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
324 %s: Relink `%s' with `%s' for IFUNC symbol `%s'\n",
325 RTLD_PROGNAME
, map
->l_name
,
327 strtab
+ refsym
->st_name
);
330 value
= ((ElfW(Addr
) (*) (void)) value
) ();
335 # ifndef RTLD_BOOTSTRAP
337 case R_X86_64_SIZE64
:
338 /* Set to symbol size plus addend. */
339 *(Elf64_Addr
*) (uintptr_t) reloc_addr
340 = (Elf64_Addr
) sym
->st_size
+ reloc
->r_addend
;
343 case R_X86_64_SIZE32
:
345 case R_X86_64_SIZE64
:
347 /* Set to symbol size plus addend. */
348 value
= sym
->st_size
;
351 case R_X86_64_GLOB_DAT
:
352 case R_X86_64_JUMP_SLOT
:
353 *reloc_addr
= value
+ reloc
->r_addend
;
356 # ifndef RESOLVE_CONFLICT_FIND_MAP
357 case R_X86_64_DTPMOD64
:
358 # ifdef RTLD_BOOTSTRAP
359 /* During startup the dynamic linker is always the module
361 XXX If this relocation is necessary move before RESOLVE
365 /* Get the information from the link map returned by the
368 *reloc_addr
= sym_map
->l_tls_modid
;
371 case R_X86_64_DTPOFF64
:
372 # ifndef RTLD_BOOTSTRAP
373 /* During relocation all TLS symbols are defined and used.
374 Therefore the offset is already correct. */
377 value
= sym
->st_value
+ reloc
->r_addend
;
379 /* This relocation type computes a signed offset that is
380 usually negative. The symbol and addend values are 32
381 bits but the GOT entry is 64 bits wide and the whole
382 64-bit entry is used as a signed quantity, so we need
383 to sign-extend the computed value to 64 bits. */
384 *(Elf64_Sxword
*) reloc_addr
= (Elf64_Sxword
) (Elf32_Sword
) value
;
391 case R_X86_64_TLSDESC
:
393 struct tlsdesc
volatile *td
=
394 (struct tlsdesc
volatile *)reloc_addr
;
396 # ifndef RTLD_BOOTSTRAP
399 td
->arg
= (void*)reloc
->r_addend
;
400 td
->entry
= _dl_tlsdesc_undefweak
;
405 # ifndef RTLD_BOOTSTRAP
407 CHECK_STATIC_TLS (map
, sym_map
);
409 if (!TRY_STATIC_TLS (map
, sym_map
))
411 td
->arg
= _dl_make_tlsdesc_dynamic
412 (sym_map
, sym
->st_value
+ reloc
->r_addend
);
413 td
->entry
= _dl_tlsdesc_dynamic
;
419 td
->arg
= (void*)(sym
->st_value
- sym_map
->l_tls_offset
421 td
->entry
= _dl_tlsdesc_return
;
426 case R_X86_64_TPOFF64
:
427 /* The offset is negative, forward from the thread pointer. */
428 # ifndef RTLD_BOOTSTRAP
432 # ifndef RTLD_BOOTSTRAP
433 CHECK_STATIC_TLS (map
, sym_map
);
435 /* We know the offset of the object the symbol is contained in.
436 It is a negative value which will be added to the
438 value
= (sym
->st_value
+ reloc
->r_addend
439 - sym_map
->l_tls_offset
);
441 /* The symbol and addend values are 32 bits but the GOT
442 entry is 64 bits wide and the whole 64-bit entry is used
443 as a signed quantity, so we need to sign-extend the
444 computed value to 64 bits. */
445 *(Elf64_Sxword
*) reloc_addr
= (Elf64_Sxword
) (Elf32_Sword
) value
;
453 # ifndef RTLD_BOOTSTRAP
455 /* value + r_addend may be > 0xffffffff and R_X86_64_64
456 relocation updates the whole 64-bit entry. */
457 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) value
+ reloc
->r_addend
;
460 case R_X86_64_SIZE32
:
461 /* Set to symbol size plus addend. */
462 value
= sym
->st_size
;
466 value
+= reloc
->r_addend
;
467 *(unsigned int *) reloc_addr
= value
;
470 if (__glibc_unlikely (value
> UINT_MAX
))
475 %s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
476 # ifndef RESOLVE_CONFLICT_FIND_MAP
479 strtab
= (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
481 _dl_error_printf (fmt
, RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
484 # ifndef RESOLVE_CONFLICT_FIND_MAP
485 /* Not needed for dl-conflict.c. */
487 value
+= reloc
->r_addend
- (ElfW(Addr
)) reloc_addr
;
488 *(unsigned int *) reloc_addr
= value
;
489 if (__glibc_unlikely (value
!= (int) value
))
492 %s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
498 /* This can happen in trace mode if an object could not be
501 memcpy (reloc_addr_arg
, (void *) value
,
502 MIN (sym
->st_size
, refsym
->st_size
));
503 if (__glibc_unlikely (sym
->st_size
> refsym
->st_size
)
504 || (__glibc_unlikely (sym
->st_size
< refsym
->st_size
)
505 && GLRO(dl_verbose
)))
508 %s: Symbol `%s' has different size in shared object, consider re-linking\n";
513 case R_X86_64_IRELATIVE
:
514 value
= map
->l_addr
+ reloc
->r_addend
;
515 value
= ((ElfW(Addr
) (*) (void)) value
) ();
519 _dl_reloc_bad_type (map
, r_type
, 0);
527 __attribute ((always_inline
))
528 elf_machine_rela_relative (ElfW(Addr
) l_addr
, const ElfW(Rela
) *reloc
,
529 void *const reloc_addr_arg
)
531 ElfW(Addr
) *const reloc_addr
= reloc_addr_arg
;
532 #if !defined RTLD_BOOTSTRAP
533 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
534 relocation updates the whole 64-bit entry. */
535 if (__glibc_unlikely (ELFW(R_TYPE
) (reloc
->r_info
) == R_X86_64_RELATIVE64
))
536 *(Elf64_Addr
*) reloc_addr
= (Elf64_Addr
) l_addr
+ reloc
->r_addend
;
540 assert (ELFW(R_TYPE
) (reloc
->r_info
) == R_X86_64_RELATIVE
);
541 *reloc_addr
= l_addr
+ reloc
->r_addend
;
546 __attribute ((always_inline
))
547 elf_machine_lazy_rel (struct link_map
*map
,
548 ElfW(Addr
) l_addr
, const ElfW(Rela
) *reloc
,
551 ElfW(Addr
) *const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
552 const unsigned long int r_type
= ELFW(R_TYPE
) (reloc
->r_info
);
554 /* Check for unexpected PLT reloc type. */
555 if (__glibc_likely (r_type
== R_X86_64_JUMP_SLOT
))
557 /* Prelink has been deprecated. */
558 if (__glibc_likely (map
->l_mach
.plt
== 0))
559 *reloc_addr
+= l_addr
;
563 + (((ElfW(Addr
)) reloc_addr
) - map
->l_mach
.gotplt
) * 2;
565 else if (__glibc_likely (r_type
== R_X86_64_TLSDESC
))
567 struct tlsdesc
volatile * __attribute__((__unused__
)) td
=
568 (struct tlsdesc
volatile *)reloc_addr
;
570 td
->arg
= (void*)reloc
;
571 td
->entry
= (void*)(D_PTR (map
, l_info
[ADDRIDX (DT_TLSDESC_PLT
)])
574 else if (__glibc_unlikely (r_type
== R_X86_64_IRELATIVE
))
576 ElfW(Addr
) value
= map
->l_addr
+ reloc
->r_addend
;
577 if (__glibc_likely (!skip_ifunc
))
578 value
= ((ElfW(Addr
) (*) (void)) value
) ();
582 _dl_reloc_bad_type (map
, r_type
, 1);
585 #endif /* RESOLVE_MAP */