1/* Machine-dependent ELF dynamic relocation inline functions. x86-64 version.
2 Copyright (C) 2001-2016 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, see
18 <http://www.gnu.org/licenses/>. */
19
20#ifndef dl_machine_h
21#define dl_machine_h
22
23#define ELF_MACHINE_NAME "x86_64"
24
25#include <sys/param.h>
26#include <sysdep.h>
27#include <tls.h>
28#include <dl-tlsdesc.h>
29#include <cpu-features.c>
30
31/* Return nonzero iff ELF header is compatible with the running host. */
32static inline int __attribute__ ((unused))
33elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
34{
35 return ehdr->e_machine == EM_X86_64;
36}
37
38
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
41 uses global data. */
42static inline ElfW(Addr) __attribute__ ((unused))
43elf_machine_dynamic (void)
44{
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];
48}
49
50
51/* Return the run-time load address of the shared object. */
52static inline ElfW(Addr) __attribute__ ((unused))
53elf_machine_load_address (void)
54{
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 ();
60}
61
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. */
64
65static inline int __attribute__ ((unused, always_inline))
66elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
67{
68 Elf64_Addr *got;
69 extern void _dl_runtime_resolve_sse (ElfW(Word)) attribute_hidden;
70 extern void _dl_runtime_resolve_avx (ElfW(Word)) attribute_hidden;
71 extern void _dl_runtime_resolve_avx512 (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;
75
76 if (l->l_info[DT_JMPREL] && lazy)
77 {
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. */
86 if (got[1])
87 {
88 l->l_mach.plt = got[1] + l->l_addr;
89 l->l_mach.gotplt = (ElfW(Addr)) &got[3];
90 }
91 /* Identify this shared object. */
92 *(ElfW(Addr) *) (got + 1) = (ElfW(Addr)) l;
93
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))
101 {
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;
106 else
107 *(ElfW(Addr) *) (got + 2) = (ElfW(Addr)) &_dl_runtime_profile_sse;
108
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;
114 }
115 else
116 {
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 (HAS_ARCH_FEATURE (AVX512F_Usable))
121 *(ElfW(Addr) *) (got + 2) = (ElfW(Addr)) &_dl_runtime_resolve_avx512;
122 else if (HAS_ARCH_FEATURE (AVX_Usable))
123 *(ElfW(Addr) *) (got + 2) = (ElfW(Addr)) &_dl_runtime_resolve_avx;
124 else
125 *(ElfW(Addr) *) (got + 2) = (ElfW(Addr)) &_dl_runtime_resolve_sse;
126 }
127 }
128
129 if (l->l_info[ADDRIDX (DT_TLSDESC_GOT)] && lazy)
130 *(ElfW(Addr)*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_GOT)]) + l->l_addr)
131 = (ElfW(Addr)) &_dl_tlsdesc_resolve_rela;
132
133 return lazy;
134}
135
136/* Initial entry point code for the dynamic linker.
137 The C function `_dl_start' is the real entry point;
138 its return value is the user program's entry point. */
139#define RTLD_START asm ("\n\
140.text\n\
141 .align 16\n\
142.globl _start\n\
143.globl _dl_start_user\n\
144_start:\n\
145 movq %rsp, %rdi\n\
146 call _dl_start\n\
147_dl_start_user:\n\
148 # Save the user entry point address in %r12.\n\
149 movq %rax, %r12\n\
150 # See if we were run as a command with the executable file\n\
151 # name as an extra leading argument.\n\
152 movl _dl_skip_args(%rip), %eax\n\
153 # Pop the original argument count.\n\
154 popq %rdx\n\
155 # Adjust the stack pointer to skip _dl_skip_args words.\n\
156 leaq (%rsp,%rax,8), %rsp\n\
157 # Subtract _dl_skip_args from argc.\n\
158 subl %eax, %edx\n\
159 # Push argc back on the stack.\n\
160 pushq %rdx\n\
161 # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\
162 # argc -> rsi\n\
163 movq %rdx, %rsi\n\
164 # Save %rsp value in %r13.\n\
165 movq %rsp, %r13\n\
166 # And align stack for the _dl_init call. \n\
167 andq $-16, %rsp\n\
168 # _dl_loaded -> rdi\n\
169 movq _rtld_local(%rip), %rdi\n\
170 # env -> rcx\n\
171 leaq 16(%r13,%rdx,8), %rcx\n\
172 # argv -> rdx\n\
173 leaq 8(%r13), %rdx\n\
174 # Clear %rbp to mark outermost frame obviously even for constructors.\n\
175 xorl %ebp, %ebp\n\
176 # Call the function to run the initializers.\n\
177 call _dl_init\n\
178 # Pass our finalizer function to the user in %rdx, as per ELF ABI.\n\
179 leaq _dl_fini(%rip), %rdx\n\
180 # And make sure %rsp points to argc stored on the stack.\n\
181 movq %r13, %rsp\n\
182 # Jump to the user's entry point.\n\
183 jmp *%r12\n\
184.previous\n\
185");
186
187/* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
188 TLS variable, so undefined references should not be allowed to
189 define the value.
190 ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one
191 of the main executable's symbols, as for a COPY reloc.
192 ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation may
193 against protected data whose address be external due to copy relocation.
194 */
195#define elf_machine_type_class(type) \
196 ((((type) == R_X86_64_JUMP_SLOT \
197 || (type) == R_X86_64_DTPMOD64 \
198 || (type) == R_X86_64_DTPOFF64 \
199 || (type) == R_X86_64_TPOFF64 \
200 || (type) == R_X86_64_TLSDESC) \
201 * ELF_RTYPE_CLASS_PLT) \
202 | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY) \
203 | (((type) == R_X86_64_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
204
205/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
206#define ELF_MACHINE_JMP_SLOT R_X86_64_JUMP_SLOT
207
208/* The relative ifunc relocation. */
209// XXX This is a work-around for a broken linker. Remove!
210#define ELF_MACHINE_IRELATIVE R_X86_64_IRELATIVE
211
212/* The x86-64 never uses Elf64_Rel/Elf32_Rel relocations. */
213#define ELF_MACHINE_NO_REL 1
214#define ELF_MACHINE_NO_RELA 0
215
216/* We define an initialization function. This is called very early in
217 _dl_sysdep_start. */
218#define DL_PLATFORM_INIT dl_platform_init ()
219
220static inline void __attribute__ ((unused))
221dl_platform_init (void)
222{
223 if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
224 /* Avoid an empty string which would disturb us. */
225 GLRO(dl_platform) = NULL;
226
227#ifdef SHARED
228 /* init_cpu_features has been called early from __libc_start_main in
229 static executable. */
230 init_cpu_features (&GLRO(dl_x86_cpu_features));
231#endif
232}
233
234static inline ElfW(Addr)
235elf_machine_fixup_plt (struct link_map *map, lookup_t t,
236 const ElfW(Rela) *reloc,
237 ElfW(Addr) *reloc_addr, ElfW(Addr) value)
238{
239 return *reloc_addr = value;
240}
241
242/* Return the final value of a PLT relocation. On x86-64 the
243 JUMP_SLOT relocation ignores the addend. */
244static inline ElfW(Addr)
245elf_machine_plt_value (struct link_map *map, const ElfW(Rela) *reloc,
246 ElfW(Addr) value)
247{
248 return value;
249}
250
251
252/* Names of the architecture-specific auditing callback functions. */
253#define ARCH_LA_PLTENTER x86_64_gnu_pltenter
254#define ARCH_LA_PLTEXIT x86_64_gnu_pltexit
255
256#endif /* !dl_machine_h */
257
258#ifdef RESOLVE_MAP
259
260/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
261 MAP is the object containing the reloc. */
262
263auto inline void
264__attribute__ ((always_inline))
265elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
266 const ElfW(Sym) *sym, const struct r_found_version *version,
267 void *const reloc_addr_arg, int skip_ifunc)
268{
269 ElfW(Addr) *const reloc_addr = reloc_addr_arg;
270 const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);
271
272# if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
273 if (__glibc_unlikely (r_type == R_X86_64_RELATIVE))
274 {
275# if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
276 /* This is defined in rtld.c, but nowhere in the static libc.a;
277 make the reference weak so static programs can still link.
278 This declaration cannot be done when compiling rtld.c
279 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
280 common defn for _dl_rtld_map, which is incompatible with a
281 weak decl in the same file. */
282# ifndef SHARED
283 weak_extern (GL(dl_rtld_map));
284# endif
285 if (map != &GL(dl_rtld_map)) /* Already done in rtld itself. */
286# endif
287 *reloc_addr = map->l_addr + reloc->r_addend;
288 }
289 else
290# endif
291# if !defined RTLD_BOOTSTRAP
292 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
293 relocation updates the whole 64-bit entry. */
294 if (__glibc_unlikely (r_type == R_X86_64_RELATIVE64))
295 *(Elf64_Addr *) reloc_addr = (Elf64_Addr) map->l_addr + reloc->r_addend;
296 else
297# endif
298 if (__glibc_unlikely (r_type == R_X86_64_NONE))
299 return;
300 else
301 {
302# ifndef RTLD_BOOTSTRAP
303 const ElfW(Sym) *const refsym = sym;
304# endif
305 struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
306 ElfW(Addr) value = (sym == NULL ? 0
307 : (ElfW(Addr)) sym_map->l_addr + sym->st_value);
308
309 if (sym != NULL
310 && __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC,
311 0)
312 && __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
313 && __builtin_expect (!skip_ifunc, 1))
314 value = ((ElfW(Addr) (*) (void)) value) ();
315
316 switch (r_type)
317 {
318# ifndef RTLD_BOOTSTRAP
319# ifdef __ILP32__
320 case R_X86_64_SIZE64:
321 /* Set to symbol size plus addend. */
322 *(Elf64_Addr *) (uintptr_t) reloc_addr
323 = (Elf64_Addr) sym->st_size + reloc->r_addend;
324 break;
325
326 case R_X86_64_SIZE32:
327# else
328 case R_X86_64_SIZE64:
329# endif
330 /* Set to symbol size plus addend. */
331 value = sym->st_size;
332# endif
333 case R_X86_64_GLOB_DAT:
334 case R_X86_64_JUMP_SLOT:
335 *reloc_addr = value + reloc->r_addend;
336 break;
337
338# ifndef RESOLVE_CONFLICT_FIND_MAP
339 case R_X86_64_DTPMOD64:
340# ifdef RTLD_BOOTSTRAP
341 /* During startup the dynamic linker is always the module
342 with index 1.
343 XXX If this relocation is necessary move before RESOLVE
344 call. */
345 *reloc_addr = 1;
346# else
347 /* Get the information from the link map returned by the
348 resolve function. */
349 if (sym_map != NULL)
350 *reloc_addr = sym_map->l_tls_modid;
351# endif
352 break;
353 case R_X86_64_DTPOFF64:
354# ifndef RTLD_BOOTSTRAP
355 /* During relocation all TLS symbols are defined and used.
356 Therefore the offset is already correct. */
357 if (sym != NULL)
358 {
359 value = sym->st_value + reloc->r_addend;
360# ifdef __ILP32__
361 /* This relocation type computes a signed offset that is
362 usually negative. The symbol and addend values are 32
363 bits but the GOT entry is 64 bits wide and the whole
364 64-bit entry is used as a signed quantity, so we need
365 to sign-extend the computed value to 64 bits. */
366 *(Elf64_Sxword *) reloc_addr = (Elf64_Sxword) (Elf32_Sword) value;
367# else
368 *reloc_addr = value;
369# endif
370 }
371# endif
372 break;
373 case R_X86_64_TLSDESC:
374 {
375 struct tlsdesc volatile *td =
376 (struct tlsdesc volatile *)reloc_addr;
377
378# ifndef RTLD_BOOTSTRAP
379 if (! sym)
380 {
381 td->arg = (void*)reloc->r_addend;
382 td->entry = _dl_tlsdesc_undefweak;
383 }
384 else
385# endif
386 {
387# ifndef RTLD_BOOTSTRAP
388# ifndef SHARED
389 CHECK_STATIC_TLS (map, sym_map);
390# else
391 if (!TRY_STATIC_TLS (map, sym_map))
392 {
393 td->arg = _dl_make_tlsdesc_dynamic
394 (sym_map, sym->st_value + reloc->r_addend);
395 td->entry = _dl_tlsdesc_dynamic;
396 }
397 else
398# endif
399# endif
400 {
401 td->arg = (void*)(sym->st_value - sym_map->l_tls_offset
402 + reloc->r_addend);
403 td->entry = _dl_tlsdesc_return;
404 }
405 }
406 break;
407 }
408 case R_X86_64_TPOFF64:
409 /* The offset is negative, forward from the thread pointer. */
410# ifndef RTLD_BOOTSTRAP
411 if (sym != NULL)
412# endif
413 {
414# ifndef RTLD_BOOTSTRAP
415 CHECK_STATIC_TLS (map, sym_map);
416# endif
417 /* We know the offset of the object the symbol is contained in.
418 It is a negative value which will be added to the
419 thread pointer. */
420 value = (sym->st_value + reloc->r_addend
421 - sym_map->l_tls_offset);
422# ifdef __ILP32__
423 /* The symbol and addend values are 32 bits but the GOT
424 entry is 64 bits wide and the whole 64-bit entry is used
425 as a signed quantity, so we need to sign-extend the
426 computed value to 64 bits. */
427 *(Elf64_Sxword *) reloc_addr = (Elf64_Sxword) (Elf32_Sword) value;
428# else
429 *reloc_addr = value;
430# endif
431 }
432 break;
433# endif
434
435# ifndef RTLD_BOOTSTRAP
436 case R_X86_64_64:
437 /* value + r_addend may be > 0xffffffff and R_X86_64_64
438 relocation updates the whole 64-bit entry. */
439 *(Elf64_Addr *) reloc_addr = (Elf64_Addr) value + reloc->r_addend;
440 break;
441# ifndef __ILP32__
442 case R_X86_64_SIZE32:
443 /* Set to symbol size plus addend. */
444 value = sym->st_size;
445# endif
446 case R_X86_64_32:
447 value += reloc->r_addend;
448 *(unsigned int *) reloc_addr = value;
449
450 const char *fmt;
451 if (__glibc_unlikely (value > UINT_MAX))
452 {
453 const char *strtab;
454
455 fmt = "\
456%s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
457# ifndef RESOLVE_CONFLICT_FIND_MAP
458 print_err:
459# endif
460 strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
461
462 _dl_error_printf (fmt, RTLD_PROGNAME, strtab + refsym->st_name);
463 }
464 break;
465# ifndef RESOLVE_CONFLICT_FIND_MAP
466 /* Not needed for dl-conflict.c. */
467 case R_X86_64_PC32:
468 value += reloc->r_addend - (ElfW(Addr)) reloc_addr;
469 *(unsigned int *) reloc_addr = value;
470 if (__glibc_unlikely (value != (int) value))
471 {
472 fmt = "\
473%s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
474 goto print_err;
475 }
476 break;
477 case R_X86_64_COPY:
478 if (sym == NULL)
479 /* This can happen in trace mode if an object could not be
480 found. */
481 break;
482 memcpy (reloc_addr_arg, (void *) value,
483 MIN (sym->st_size, refsym->st_size));
484 if (__builtin_expect (sym->st_size > refsym->st_size, 0)
485 || (__builtin_expect (sym->st_size < refsym->st_size, 0)
486 && GLRO(dl_verbose)))
487 {
488 fmt = "\
489%s: Symbol `%s' has different size in shared object, consider re-linking\n";
490 goto print_err;
491 }
492 break;
493# endif
494 case R_X86_64_IRELATIVE:
495 value = map->l_addr + reloc->r_addend;
496 value = ((ElfW(Addr) (*) (void)) value) ();
497 *reloc_addr = value;
498 break;
499 default:
500 _dl_reloc_bad_type (map, r_type, 0);
501 break;
502# endif
503 }
504 }
505}
506
507auto inline void
508__attribute ((always_inline))
509elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
510 void *const reloc_addr_arg)
511{
512 ElfW(Addr) *const reloc_addr = reloc_addr_arg;
513#if !defined RTLD_BOOTSTRAP
514 /* l_addr + r_addend may be > 0xffffffff and R_X86_64_RELATIVE64
515 relocation updates the whole 64-bit entry. */
516 if (__glibc_unlikely (ELFW(R_TYPE) (reloc->r_info) == R_X86_64_RELATIVE64))
517 *(Elf64_Addr *) reloc_addr = (Elf64_Addr) l_addr + reloc->r_addend;
518 else
519#endif
520 {
521 assert (ELFW(R_TYPE) (reloc->r_info) == R_X86_64_RELATIVE);
522 *reloc_addr = l_addr + reloc->r_addend;
523 }
524}
525
526auto inline void
527__attribute ((always_inline))
528elf_machine_lazy_rel (struct link_map *map,
529 ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
530 int skip_ifunc)
531{
532 ElfW(Addr) *const reloc_addr = (void *) (l_addr + reloc->r_offset);
533 const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);
534
535 /* Check for unexpected PLT reloc type. */
536 if (__glibc_likely (r_type == R_X86_64_JUMP_SLOT))
537 {
538 if (__builtin_expect (map->l_mach.plt, 0) == 0)
539 *reloc_addr += l_addr;
540 else
541 *reloc_addr =
542 map->l_mach.plt
543 + (((ElfW(Addr)) reloc_addr) - map->l_mach.gotplt) * 2;
544 }
545 else if (__glibc_likely (r_type == R_X86_64_TLSDESC))
546 {
547 struct tlsdesc volatile * __attribute__((__unused__)) td =
548 (struct tlsdesc volatile *)reloc_addr;
549
550 td->arg = (void*)reloc;
551 td->entry = (void*)(D_PTR (map, l_info[ADDRIDX (DT_TLSDESC_PLT)])
552 + map->l_addr);
553 }
554 else if (__glibc_unlikely (r_type == R_X86_64_IRELATIVE))
555 {
556 ElfW(Addr) value = map->l_addr + reloc->r_addend;
557 if (__glibc_likely (!skip_ifunc))
558 value = ((ElfW(Addr) (*) (void)) value) ();
559 *reloc_addr = value;
560 }
561 else
562 _dl_reloc_bad_type (map, r_type, 1);
563}
564
565#endif /* RESOLVE_MAP */
566