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1 /* Machine-dependent ELF dynamic relocation inline functions. x86-64 version.
2 Copyright (C) 2001-2006, 2008-2010, 2011 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 Elf64_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 Elf64_Addr
__attribute__ ((unused
))
42 elf_machine_dynamic (void)
46 /* This works because we have our GOT address available in the small PIC
48 addr
= (Elf64_Addr
) &_DYNAMIC
;
54 /* Return the run-time load address of the shared object. */
55 static inline Elf64_Addr
__attribute__ ((unused
))
56 elf_machine_load_address (void)
60 /* The easy way is just the same as on x86:
62 leaq _dl_start(%%rip), %1
64 but this does not work with binutils since we then have
65 a R_X86_64_32S relocation in a shared lib.
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. Note that this is the address
70 of _dl_start before any relocation performed at runtime. In case
71 the binary is prelinked the resulting "address" is actually a
72 load offset which is zero if the binary was loaded at the address
73 it is prelinked for. */
75 asm ("leaq _dl_start(%%rip), %0\n\t"
76 "subq 1f(%%rip), %0\n\t"
77 ".section\t.data.rel.ro\n"
78 "1:\t.quad _dl_start\n\t"
80 : "=r" (addr
) : : "cc");
85 /* Set up the loaded object described by L so its unrelocated PLT
86 entries will jump to the on-demand fixup code in dl-runtime.c. */
88 static inline int __attribute__ ((unused
, always_inline
))
89 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
92 extern void _dl_runtime_resolve (Elf64_Word
) attribute_hidden
;
93 extern void _dl_runtime_profile (Elf64_Word
) attribute_hidden
;
95 if (l
->l_info
[DT_JMPREL
] && lazy
)
97 /* The GOT entries for functions in the PLT have not yet been filled
98 in. Their initial contents will arrange when called to push an
99 offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
100 and then jump to _GLOBAL_OFFSET_TABLE_[2]. */
101 got
= (Elf64_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
102 /* If a library is prelinked but we have to relocate anyway,
103 we have to be able to undo the prelinking of .got.plt.
104 The prelinker saved us here address of .plt + 0x16. */
107 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
108 l
->l_mach
.gotplt
= (Elf64_Addr
) &got
[3];
110 got
[1] = (Elf64_Addr
) l
; /* Identify this shared object. */
112 /* The got[2] entry contains the address of a function which gets
113 called to get the address of a so far unresolved function and
114 jump to it. The profiling extension of the dynamic linker allows
115 to intercept the calls to collect information. In this case we
116 don't store the address in the GOT so that all future calls also
117 end in this function. */
118 if (__builtin_expect (profile
, 0))
120 got
[2] = (Elf64_Addr
) &_dl_runtime_profile
;
122 if (GLRO(dl_profile
) != NULL
123 && _dl_name_match_p (GLRO(dl_profile
), l
))
124 /* This is the object we are looking for. Say that we really
125 want profiling and the timers are started. */
126 GL(dl_profile_map
) = l
;
129 /* This function will get called to fix up the GOT entry indicated by
130 the offset on the stack, and then jump to the resolved address. */
131 got
[2] = (Elf64_Addr
) &_dl_runtime_resolve
;
134 if (l
->l_info
[ADDRIDX (DT_TLSDESC_GOT
)] && lazy
)
135 *(Elf64_Addr
*)(D_PTR (l
, l_info
[ADDRIDX (DT_TLSDESC_GOT
)]) + l
->l_addr
)
136 = (Elf64_Addr
) &_dl_tlsdesc_resolve_rela
;
141 /* Initial entry point code for the dynamic linker.
142 The C function `_dl_start' is the real entry point;
143 its return value is the user program's entry point. */
144 #define RTLD_START asm ("\n\
148 .globl _dl_start_user\n\
153 # Save the user entry point address in %r12.\n\
155 # See if we were run as a command with the executable file\n\
156 # name as an extra leading argument.\n\
157 movl _dl_skip_args(%rip), %eax\n\
158 # Pop the original argument count.\n\
160 # Adjust the stack pointer to skip _dl_skip_args words.\n\
161 leaq (%rsp,%rax,8), %rsp\n\
162 # Subtract _dl_skip_args from argc.\n\
164 # Push argc back on the stack.\n\
166 # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\
169 # Save %rsp value in %r13.\n\
171 # And align stack for the _dl_init_internal call. \n\
173 # _dl_loaded -> rdi\n\
174 movq _rtld_local(%rip), %rdi\n\
176 leaq 16(%r13,%rdx,8), %rcx\n\
178 leaq 8(%r13), %rdx\n\
179 # Clear %rbp to mark outermost frame obviously even for constructors.\n\
181 # Call the function to run the initializers.\n\
182 call _dl_init_internal@PLT\n\
183 # Pass our finalizer function to the user in %rdx, as per ELF ABI.\n\
184 leaq _dl_fini(%rip), %rdx\n\
185 # And make sure %rsp points to argc stored on the stack.\n\
187 # Jump to the user's entry point.\n\
192 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
193 TLS variable, so undefined references should not be allowed to
195 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
196 of the main executable's symbols, as for a COPY reloc. */
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))
206 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
207 #define ELF_MACHINE_JMP_SLOT R_X86_64_JUMP_SLOT
209 /* The relative ifunc relocation. */
210 // XXX This is a work-around for a broken linker. Remove!
211 #define ELF_MACHINE_IRELATIVE R_X86_64_IRELATIVE
213 /* The x86-64 never uses Elf64_Rel relocations. */
214 #define ELF_MACHINE_NO_REL 1
216 /* We define an initialization function. This is called very early in
218 #define DL_PLATFORM_INIT dl_platform_init ()
220 static inline void __attribute__ ((unused
))
221 dl_platform_init (void)
223 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
224 /* Avoid an empty string which would disturb us. */
225 GLRO(dl_platform
) = NULL
;
228 static inline Elf64_Addr
229 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
230 const Elf64_Rela
*reloc
,
231 Elf64_Addr
*reloc_addr
, Elf64_Addr value
)
233 return *reloc_addr
= value
;
236 /* Return the final value of a PLT relocation. On x86-64 the
237 JUMP_SLOT relocation ignores the addend. */
238 static inline Elf64_Addr
239 elf_machine_plt_value (struct link_map
*map
, const Elf64_Rela
*reloc
,
246 /* Names of the architecture-specific auditing callback functions. */
247 #define ARCH_LA_PLTENTER x86_64_gnu_pltenter
248 #define ARCH_LA_PLTEXIT x86_64_gnu_pltexit
250 #endif /* !dl_machine_h */
254 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
255 MAP is the object containing the reloc. */
258 __attribute__ ((always_inline
))
259 elf_machine_rela (struct link_map
*map
, const Elf64_Rela
*reloc
,
260 const Elf64_Sym
*sym
, const struct r_found_version
*version
,
261 void *const reloc_addr_arg
, int skip_ifunc
)
263 Elf64_Addr
*const reloc_addr
= reloc_addr_arg
;
264 const unsigned long int r_type
= ELF64_R_TYPE (reloc
->r_info
);
266 # if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
267 if (__builtin_expect (r_type
== R_X86_64_RELATIVE
, 0))
269 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
270 /* This is defined in rtld.c, but nowhere in the static libc.a;
271 make the reference weak so static programs can still link.
272 This declaration cannot be done when compiling rtld.c
273 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
274 common defn for _dl_rtld_map, which is incompatible with a
275 weak decl in the same file. */
277 weak_extern (GL(dl_rtld_map
));
279 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
281 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
285 if (__builtin_expect (r_type
== R_X86_64_NONE
, 0))
289 # ifndef RTLD_BOOTSTRAP
290 const Elf64_Sym
*const refsym
= sym
;
292 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
293 Elf64_Addr value
= (sym
== NULL
? 0
294 : (Elf64_Addr
) sym_map
->l_addr
+ sym
->st_value
);
297 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
,
299 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
300 && __builtin_expect (!skip_ifunc
, 1))
301 value
= ((Elf64_Addr (*) (void)) value
) ();
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. */
330 *reloc_addr
= sym
->st_value
+ reloc
->r_addend
;
333 case R_X86_64_TLSDESC
:
335 struct tlsdesc
volatile *td
=
336 (struct tlsdesc
volatile *)reloc_addr
;
338 # ifndef RTLD_BOOTSTRAP
341 td
->arg
= (void*)reloc
->r_addend
;
342 td
->entry
= _dl_tlsdesc_undefweak
;
347 # ifndef RTLD_BOOTSTRAP
349 CHECK_STATIC_TLS (map
, sym_map
);
351 if (!TRY_STATIC_TLS (map
, sym_map
))
353 td
->arg
= _dl_make_tlsdesc_dynamic
354 (sym_map
, sym
->st_value
+ reloc
->r_addend
);
355 td
->entry
= _dl_tlsdesc_dynamic
;
361 td
->arg
= (void*)(sym
->st_value
- sym_map
->l_tls_offset
363 td
->entry
= _dl_tlsdesc_return
;
368 case R_X86_64_TPOFF64
:
369 /* The offset is negative, forward from the thread pointer. */
370 # ifndef RTLD_BOOTSTRAP
374 # ifndef RTLD_BOOTSTRAP
375 CHECK_STATIC_TLS (map
, sym_map
);
377 /* We know the offset of the object the symbol is contained in.
378 It is a negative value which will be added to the
380 *reloc_addr
= (sym
->st_value
+ reloc
->r_addend
381 - sym_map
->l_tls_offset
);
386 # ifndef RTLD_BOOTSTRAP
388 *reloc_addr
= value
+ reloc
->r_addend
;
391 value
+= reloc
->r_addend
;
392 *(unsigned int *) reloc_addr
= value
;
395 if (__builtin_expect (value
> UINT_MAX
, 0))
400 %s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
401 # ifndef RESOLVE_CONFLICT_FIND_MAP
404 strtab
= (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
406 _dl_error_printf (fmt
,
407 rtld_progname
?: "<program name unknown>",
408 strtab
+ refsym
->st_name
);
411 # ifndef RESOLVE_CONFLICT_FIND_MAP
412 /* Not needed for dl-conflict.c. */
414 value
+= reloc
->r_addend
- (Elf64_Addr
) reloc_addr
;
415 *(unsigned int *) reloc_addr
= value
;
416 if (__builtin_expect (value
!= (int) value
, 0))
419 %s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
425 /* This can happen in trace mode if an object could not be
428 memcpy (reloc_addr_arg
, (void *) value
,
429 MIN (sym
->st_size
, refsym
->st_size
));
430 if (__builtin_expect (sym
->st_size
> refsym
->st_size
, 0)
431 || (__builtin_expect (sym
->st_size
< refsym
->st_size
, 0)
432 && GLRO(dl_verbose
)))
435 %s: Symbol `%s' has different size in shared object, consider re-linking\n";
440 case R_X86_64_IRELATIVE
:
441 value
= map
->l_addr
+ reloc
->r_addend
;
442 value
= ((Elf64_Addr (*) (void)) value
) ();
446 _dl_reloc_bad_type (map
, r_type
, 0);
454 __attribute ((always_inline
))
455 elf_machine_rela_relative (Elf64_Addr l_addr
, const Elf64_Rela
*reloc
,
456 void *const reloc_addr_arg
)
458 Elf64_Addr
*const reloc_addr
= reloc_addr_arg
;
459 assert (ELF64_R_TYPE (reloc
->r_info
) == R_X86_64_RELATIVE
);
460 *reloc_addr
= l_addr
+ reloc
->r_addend
;
464 __attribute ((always_inline
))
465 elf_machine_lazy_rel (struct link_map
*map
,
466 Elf64_Addr l_addr
, const Elf64_Rela
*reloc
,
469 Elf64_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
470 const unsigned long int r_type
= ELF64_R_TYPE (reloc
->r_info
);
472 /* Check for unexpected PLT reloc type. */
473 if (__builtin_expect (r_type
== R_X86_64_JUMP_SLOT
, 1))
475 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
476 *reloc_addr
+= l_addr
;
480 + (((Elf64_Addr
) reloc_addr
) - map
->l_mach
.gotplt
) * 2;
482 else if (__builtin_expect (r_type
== R_X86_64_TLSDESC
, 1))
484 struct tlsdesc
volatile * __attribute__((__unused__
)) td
=
485 (struct tlsdesc
volatile *)reloc_addr
;
487 td
->arg
= (void*)reloc
;
488 td
->entry
= (void*)(D_PTR (map
, l_info
[ADDRIDX (DT_TLSDESC_PLT
)])
491 else if (__builtin_expect (r_type
== R_X86_64_IRELATIVE
, 0))
493 Elf64_Addr value
= map
->l_addr
+ reloc
->r_addend
;
494 if (__builtin_expect (!skip_ifunc
, 1))
495 value
= ((Elf64_Addr (*) (void)) value
) ();
499 _dl_reloc_bad_type (map
, r_type
, 1);
502 #endif /* RESOLVE_MAP */