1 /* Machine-dependent ELF dynamic relocation inline functions. ARM version.
2 Copyright (C) 1995-2012 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
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.
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/>. */
22 #define ELF_MACHINE_NAME "ARM"
24 #include <sys/param.h>
26 #include <dl-tlsdesc.h>
30 # error CLEAR_CACHE definition required to handle TEXTREL
33 /* Return nonzero iff ELF header is compatible with the running host. */
34 static inline int __attribute__ ((unused
))
35 elf_machine_matches_host (const Elf32_Ehdr
*ehdr
)
37 return ehdr
->e_machine
== EM_ARM
;
41 /* Return the link-time address of _DYNAMIC. Conveniently, this is the
42 first element of the GOT. We used to use the PIC register to do this
43 without a constant pool reference, but GCC 4.2 will use a pseudo-register
44 for the PIC base, so it may not be in r10. */
45 static inline Elf32_Addr
__attribute__ ((unused
))
46 elf_machine_dynamic (void)
51 asm ("ldr\t%0, 1f\n\t"
53 "ldr\t%0, [%0, %1]\n\t"
56 "1: .word _GLOBAL_OFFSET_TABLE_ - 1b\n"
57 "2:" : "=r" (dynamic
), "=r"(tmp
));
60 "1: ldr %0, [pc, %0]\n"
62 "2: .word _GLOBAL_OFFSET_TABLE_ - (1b+8)\n"
63 "3:" : "=r" (dynamic
));
69 /* Return the run-time load address of the shared object. */
70 static inline Elf32_Addr
__attribute__ ((unused
))
71 elf_machine_load_address (void)
73 extern Elf32_Addr internal_function
__dl_start (void *) asm ("_dl_start");
74 Elf32_Addr got_addr
= (Elf32_Addr
) &__dl_start
;
75 Elf32_Addr pcrel_addr
;
77 /* Clear the low bit of the funciton address. */
78 got_addr
&= ~(Elf32_Addr
) 1;
80 asm ("adr %0, _dl_start" : "=r" (pcrel_addr
));
81 return pcrel_addr
- got_addr
;
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
))
89 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
92 extern void _dl_runtime_resolve (Elf32_Word
);
93 extern void _dl_runtime_profile (Elf32_Word
);
95 if (l
->l_info
[DT_JMPREL
] && lazy
)
97 /* patb: this is different than i386 */
98 /* The GOT entries for functions in the PLT have not yet been filled
99 in. Their initial contents will arrange when called to push an
100 index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
101 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
102 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
103 /* If a library is prelinked but we have to relocate anyway,
104 we have to be able to undo the prelinking of .got.plt.
105 The prelinker saved us here address of .plt. */
107 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
108 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
110 /* The got[2] entry contains the address of a function which gets
111 called to get the address of a so far unresolved function and
112 jump to it. The profiling extension of the dynamic linker allows
113 to intercept the calls to collect information. In this case we
114 don't store the address in the GOT so that all future calls also
115 end in this function. */
118 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
120 if (GLRO(dl_profile
) != NULL
121 && _dl_name_match_p (GLRO(dl_profile
), l
))
122 /* Say that we really want profiling and the timers are
124 GL(dl_profile_map
) = l
;
127 /* This function will get called to fix up the GOT entry indicated by
128 the offset on the stack, and then jump to the resolved address. */
129 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
132 if (l
->l_info
[ADDRIDX (DT_TLSDESC_GOT
)] && lazy
)
133 *(Elf32_Addr
*)(D_PTR (l
, l_info
[ADDRIDX (DT_TLSDESC_GOT
)]) + l
->l_addr
)
134 = (Elf32_Addr
) &_dl_tlsdesc_lazy_resolver
;
139 #if defined(__USE_BX__)
140 #define BX(x) "bx\t" #x
142 #define BX(x) "mov\tpc, " #x
145 /* Mask identifying addresses reserved for the user program,
146 where the dynamic linker should not map anything. */
147 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
149 /* Initial entry point code for the dynamic linker.
150 The C function `_dl_start' is the real entry point;
151 its return value is the user program's entry point. */
153 #define RTLD_START asm ("\
156 .type _start, %function\n\
157 .globl _dl_start_user\n\
158 .type _dl_start_user, %function\n\
160 @ we are PIC code, so get global offset table\n\
161 ldr sl, .L_GET_GOT\n\
162 @ See if we were run as a command with the executable file\n\
163 @ name as an extra leading argument.\n\
164 ldr r4, .L_SKIP_ARGS\n\
165 @ at start time, all the args are on the stack\n\
168 @ returns user entry point in r0\n\
170 adr r6, .L_GET_GOT\n\
173 @ save the entry point in another register\n\
175 @ get the original arg count\n\
177 @ get the argv address\n\
179 @ Fix up the stack if necessary.\n\
181 bne .L_fixup_stack\n\
184 add r3, r2, r1, lsl #2\n\
186 @ now we call _dl_init\n\
190 bl _dl_init_internal(PLT)\n\
191 @ load the finalizer function\n\
192 ldr r0, .L_FINI_PROC\n\
194 @ jump to the user_s entry point\n\
197 @ iWMMXt and EABI targets require the stack to be eight byte\n\
198 @ aligned - shuffle arguments etc.\n\
200 @ subtract _dl_skip_args from original arg count\n\
202 @ store the new argc in the new stack location\n\
204 @ find the first unskipped argument\n\
206 add r4, r2, r4, lsl #2\n\
207 @ shuffle argv down\n\
208 1: ldr r5, [r4], #4\n\
212 @ shuffle envp down\n\
213 1: ldr r5, [r4], #4\n\
217 @ shuffle auxv down\n\
218 1: ldmia r4!, {r0, r5}\n\
219 stmia r3!, {r0, r5}\n\
228 .word _GLOBAL_OFFSET_TABLE_ - .L_GET_GOT\n\
230 .word _dl_skip_args(GOTOFF)\n\
232 .word _dl_fini(GOTOFF)\n\
234 .word _dl_argv(GOTOFF)\n\
236 .word _rtld_local(GOTOFF)\n\
240 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
241 TLS variable, so undefined references should not be allowed to
243 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
244 of the main executable's symbols, as for a COPY reloc. */
245 #ifndef RTLD_BOOTSTRAP
246 # define elf_machine_type_class(type) \
247 ((((type) == R_ARM_JUMP_SLOT || (type) == R_ARM_TLS_DTPMOD32 \
248 || (type) == R_ARM_TLS_DTPOFF32 || (type) == R_ARM_TLS_TPOFF32 \
249 || (type) == R_ARM_TLS_DESC) \
250 * ELF_RTYPE_CLASS_PLT) \
251 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
253 #define elf_machine_type_class(type) \
254 ((((type) == R_ARM_JUMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
255 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
258 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
259 #define ELF_MACHINE_JMP_SLOT R_ARM_JUMP_SLOT
261 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
262 Prelinked libraries may use Elf32_Rela though. */
263 #define ELF_MACHINE_PLT_REL 1
265 /* We define an initialization functions. This is called very early in
267 #define DL_PLATFORM_INIT dl_platform_init ()
269 static inline void __attribute__ ((unused
))
270 dl_platform_init (void)
272 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
273 /* Avoid an empty string which would disturb us. */
274 GLRO(dl_platform
) = NULL
;
277 static inline Elf32_Addr
278 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
279 const Elf32_Rel
*reloc
,
280 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
282 return *reloc_addr
= value
;
285 /* Return the final value of a plt relocation. */
286 static inline Elf32_Addr
287 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
293 #endif /* !dl_machine_h */
296 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
297 Prelinked libraries may use Elf32_Rela though. */
298 #define ELF_MACHINE_NO_RELA defined RTLD_BOOTSTRAP
300 /* Names of the architecture-specific auditing callback functions. */
301 #define ARCH_LA_PLTENTER arm_gnu_pltenter
302 #define ARCH_LA_PLTEXIT arm_gnu_pltexit
305 /* Handle a PC24 reloc, including the out-of-range case. */
307 relocate_pc24 (struct link_map
*map
, Elf32_Addr value
,
308 Elf32_Addr
*const reloc_addr
, Elf32_Sword addend
)
310 Elf32_Addr new_value
;
312 /* Set NEW_VALUE based on V, and return true iff it overflows 24 bits. */
313 inline bool set_new_value (Elf32_Addr v
)
315 new_value
= v
+ addend
- (Elf32_Addr
) reloc_addr
;
316 Elf32_Addr topbits
= new_value
& 0xfe000000;
317 return topbits
!= 0xfe000000 && topbits
!= 0x00000000;
320 if (set_new_value (value
))
322 /* The PC-relative address doesn't fit in 24 bits! */
324 static void *fix_page
;
325 static size_t fix_offset
;
326 if (fix_page
== NULL
)
328 void *new_page
= __mmap (NULL
, GLRO(dl_pagesize
),
329 PROT_READ
| PROT_WRITE
| PROT_EXEC
,
330 MAP_PRIVATE
| MAP_ANON
, -1, 0);
331 if (new_page
== MAP_FAILED
)
332 _dl_signal_error (0, map
->l_name
, NULL
,
333 "could not map page for fixup");
335 assert (fix_offset
== 0);
338 Elf32_Word
*fix_address
= fix_page
+ fix_offset
;
339 fix_address
[0] = 0xe51ff004; /* ldr pc, [pc, #-4] */
340 fix_address
[1] = value
;
342 fix_offset
+= sizeof fix_address
[0] * 2;
343 if (fix_offset
>= GLRO(dl_pagesize
))
349 if (set_new_value ((Elf32_Addr
) fix_address
))
350 _dl_signal_error (0, map
->l_name
, NULL
,
351 "R_ARM_PC24 relocation out of range");
354 *reloc_addr
= (*reloc_addr
& 0xff000000) | ((new_value
>> 2) & 0x00ffffff);
357 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
358 MAP is the object containing the reloc. */
361 __attribute__ ((always_inline
))
362 elf_machine_rel (struct link_map
*map
, const Elf32_Rel
*reloc
,
363 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
364 void *const reloc_addr_arg
, int skip_ifunc
)
366 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
367 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
369 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
370 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
372 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
373 /* This is defined in rtld.c, but nowhere in the static libc.a;
374 make the reference weak so static programs can still link.
375 This declaration cannot be done when compiling rtld.c
376 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
377 common defn for _dl_rtld_map, which is incompatible with a
378 weak decl in the same file. */
380 weak_extern (_dl_rtld_map
);
382 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
384 *reloc_addr
+= map
->l_addr
;
386 # ifndef RTLD_BOOTSTRAP
387 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
393 const Elf32_Sym
*const refsym
= sym
;
394 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
395 Elf32_Addr value
= sym_map
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
398 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
399 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
400 && __builtin_expect (!skip_ifunc
, 1))
401 value
= elf_ifunc_invoke (value
);
407 /* This can happen in trace mode if an object could not be
410 if (sym
->st_size
> refsym
->st_size
411 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
415 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
417 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
418 rtld_progname
?: "<program name unknown>",
419 strtab
+ refsym
->st_name
);
421 memcpy (reloc_addr_arg
, (void *) value
,
422 MIN (sym
->st_size
, refsym
->st_size
));
425 case R_ARM_JUMP_SLOT
:
426 # ifdef RTLD_BOOTSTRAP
427 /* Fix weak undefined references. */
428 if (sym
!= NULL
&& sym
->st_value
== 0)
439 } __attribute__ ((packed
, may_alias
));
440 # ifndef RTLD_BOOTSTRAP
441 /* This is defined in rtld.c, but nowhere in the static
442 libc.a; make the reference weak so static programs can
443 still link. This declaration cannot be done when
444 compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP) because
445 rtld.c contains the common defn for _dl_rtld_map, which
446 is incompatible with a weak decl in the same file. */
448 weak_extern (_dl_rtld_map
);
450 if (map
== &GL(dl_rtld_map
))
451 /* Undo the relocation done here during bootstrapping.
452 Now we will relocate it anew, possibly using a
453 binding found in the user program or a loaded library
454 rather than the dynamic linker's built-in definitions
455 used while loading those libraries. */
456 value
-= map
->l_addr
+ refsym
->st_value
;
458 /* Support relocations on mis-aligned offsets. */
459 ((struct unaligned
*) reloc_addr
)->x
+= value
;
464 struct tlsdesc
volatile *td
=
465 (struct tlsdesc
volatile *)reloc_addr
;
467 # ifndef RTLD_BOOTSTRAP
469 td
->entry
= _dl_tlsdesc_undefweak
;
473 value
= sym
->st_value
+ td
->argument
.value
;
475 # ifndef RTLD_BOOTSTRAP
477 CHECK_STATIC_TLS (map
, sym_map
);
479 if (!TRY_STATIC_TLS (map
, sym_map
))
482 = _dl_make_tlsdesc_dynamic (sym_map
, value
);
483 td
->entry
= _dl_tlsdesc_dynamic
;
489 td
->argument
.value
= value
+ sym_map
->l_tls_offset
;
490 td
->entry
= _dl_tlsdesc_return
;
496 relocate_pc24 (map
, value
, reloc_addr
,
497 /* Sign-extend the 24-bit addend in the
498 instruction (which counts instructions), and
499 then shift it up two so as to count bytes. */
500 (((Elf32_Sword
) *reloc_addr
<< 8) >> 8) << 2);
502 #if !defined RTLD_BOOTSTRAP
503 case R_ARM_TLS_DTPMOD32
:
504 /* Get the information from the link map returned by the
507 *reloc_addr
= sym_map
->l_tls_modid
;
510 case R_ARM_TLS_DTPOFF32
:
512 *reloc_addr
+= sym
->st_value
;
515 case R_ARM_TLS_TPOFF32
:
518 CHECK_STATIC_TLS (map
, sym_map
);
519 *reloc_addr
+= sym
->st_value
+ sym_map
->l_tls_offset
;
522 case R_ARM_IRELATIVE
:
523 value
= map
->l_addr
+ *reloc_addr
;
524 value
= ((Elf32_Addr (*) (void)) value
) ();
529 _dl_reloc_bad_type (map
, r_type
, 0);
535 # ifndef RTLD_BOOTSTRAP
537 __attribute__ ((always_inline
))
538 elf_machine_rela (struct link_map
*map
, const Elf32_Rela
*reloc
,
539 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
540 void *const reloc_addr_arg
, int skip_ifunc
)
542 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
543 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
545 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
546 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
547 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
551 # ifndef RESOLVE_CONFLICT_FIND_MAP
552 const Elf32_Sym
*const refsym
= sym
;
554 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
555 Elf32_Addr value
= sym_map
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
558 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
559 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
560 && __builtin_expect (!skip_ifunc
, 1))
561 value
= elf_ifunc_invoke (value
);
565 # ifndef RESOLVE_CONFLICT_FIND_MAP
566 /* Not needed for dl-conflict.c. */
569 /* This can happen in trace mode if an object could not be
572 if (sym
->st_size
> refsym
->st_size
573 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
577 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
579 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
580 rtld_progname
?: "<program name unknown>",
581 strtab
+ refsym
->st_name
);
583 memcpy (reloc_addr_arg
, (void *) value
,
584 MIN (sym
->st_size
, refsym
->st_size
));
586 # endif /* !RESOLVE_CONFLICT_FIND_MAP */
588 case R_ARM_JUMP_SLOT
:
590 *reloc_addr
= value
+ reloc
->r_addend
;
593 relocate_pc24 (map
, value
, reloc_addr
, reloc
->r_addend
);
595 #if !defined RTLD_BOOTSTRAP
596 case R_ARM_TLS_DTPMOD32
:
597 /* Get the information from the link map returned by the
600 *reloc_addr
= sym_map
->l_tls_modid
;
603 case R_ARM_TLS_DTPOFF32
:
604 *reloc_addr
= (sym
== NULL
? 0 : sym
->st_value
) + reloc
->r_addend
;
607 case R_ARM_TLS_TPOFF32
:
610 CHECK_STATIC_TLS (map
, sym_map
);
611 *reloc_addr
= (sym
->st_value
+ sym_map
->l_tls_offset
615 case R_ARM_IRELATIVE
:
616 value
= map
->l_addr
+ *reloc_addr
;
617 value
= ((Elf32_Addr (*) (void)) value
) ();
622 _dl_reloc_bad_type (map
, r_type
, 0);
630 __attribute__ ((always_inline
))
631 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
632 void *const reloc_addr_arg
)
634 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
635 *reloc_addr
+= l_addr
;
638 # ifndef RTLD_BOOTSTRAP
640 __attribute__ ((always_inline
))
641 elf_machine_rela_relative (Elf32_Addr l_addr
, const Elf32_Rela
*reloc
,
642 void *const reloc_addr_arg
)
644 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
645 *reloc_addr
= l_addr
+ reloc
->r_addend
;
650 __attribute__ ((always_inline
))
651 elf_machine_lazy_rel (struct link_map
*map
,
652 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
655 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
656 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
657 /* Check for unexpected PLT reloc type. */
658 if (__builtin_expect (r_type
== R_ARM_JUMP_SLOT
, 1))
660 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
661 *reloc_addr
+= l_addr
;
663 *reloc_addr
= map
->l_mach
.plt
;
665 else if (__builtin_expect (r_type
== R_ARM_TLS_DESC
, 1))
667 struct tlsdesc
volatile *td
=
668 (struct tlsdesc
volatile *)reloc_addr
;
670 /* The linker must have given us the parameter we need in the
671 first GOT entry, and left the second one empty. We fill the
672 last with the resolver address */
673 assert (td
->entry
== 0);
674 td
->entry
= (void*)(D_PTR (map
, l_info
[ADDRIDX (DT_TLSDESC_PLT
)])
678 _dl_reloc_bad_type (map
, r_type
, 1);
681 #endif /* RESOLVE_MAP */