1 /* Machine-dependent ELF dynamic relocation inline functions. ARM version.
2 Copyright (C) 1995-2014 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. */
43 static inline Elf32_Addr
__attribute__ ((unused
))
44 elf_machine_dynamic (void)
46 /* Declaring this hidden ensures that a PC-relative reference is used. */
47 extern const Elf32_Addr _GLOBAL_OFFSET_TABLE_
[] attribute_hidden
;
48 return _GLOBAL_OFFSET_TABLE_
[0];
52 /* Return the run-time load address of the shared object. */
53 static inline Elf32_Addr
__attribute__ ((unused
))
54 elf_machine_load_address (void)
56 extern Elf32_Addr internal_function
__dl_start (void *) asm ("_dl_start");
57 Elf32_Addr got_addr
= (Elf32_Addr
) &__dl_start
;
58 Elf32_Addr pcrel_addr
;
60 /* Clear the low bit of the funciton address. */
61 got_addr
&= ~(Elf32_Addr
) 1;
63 asm ("adr %0, _dl_start" : "=r" (pcrel_addr
));
64 return pcrel_addr
- got_addr
;
68 /* Set up the loaded object described by L so its unrelocated PLT
69 entries will jump to the on-demand fixup code in dl-runtime.c. */
71 static inline int __attribute__ ((unused
))
72 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
75 extern void _dl_runtime_resolve (Elf32_Word
);
76 extern void _dl_runtime_profile (Elf32_Word
);
78 if (l
->l_info
[DT_JMPREL
] && lazy
)
80 /* patb: this is different than i386 */
81 /* The GOT entries for functions in the PLT have not yet been filled
82 in. Their initial contents will arrange when called to push an
83 index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
84 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
85 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
86 /* If a library is prelinked but we have to relocate anyway,
87 we have to be able to undo the prelinking of .got.plt.
88 The prelinker saved us here address of .plt. */
90 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
91 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
93 /* The got[2] entry contains the address of a function which gets
94 called to get the address of a so far unresolved function and
95 jump to it. The profiling extension of the dynamic linker allows
96 to intercept the calls to collect information. In this case we
97 don't store the address in the GOT so that all future calls also
98 end in this function. */
101 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
103 if (GLRO(dl_profile
) != NULL
104 && _dl_name_match_p (GLRO(dl_profile
), l
))
105 /* Say that we really want profiling and the timers are
107 GL(dl_profile_map
) = l
;
110 /* This function will get called to fix up the GOT entry indicated by
111 the offset on the stack, and then jump to the resolved address. */
112 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
115 if (l
->l_info
[ADDRIDX (DT_TLSDESC_GOT
)] && lazy
)
116 *(Elf32_Addr
*)(D_PTR (l
, l_info
[ADDRIDX (DT_TLSDESC_GOT
)]) + l
->l_addr
)
117 = (Elf32_Addr
) &_dl_tlsdesc_lazy_resolver
;
122 #if defined(ARCH_HAS_BX)
123 #define BX(x) "bx\t" #x
125 #define BX(x) "mov\tpc, " #x
128 /* Mask identifying addresses reserved for the user program,
129 where the dynamic linker should not map anything. */
130 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
132 /* Initial entry point code for the dynamic linker.
133 The C function `_dl_start' is the real entry point;
134 its return value is the user program's entry point. */
136 #define RTLD_START asm ("\
139 .type _start, %function\n\
140 .globl _dl_start_user\n\
141 .type _dl_start_user, %function\n\
143 @ we are PIC code, so get global offset table\n\
144 ldr sl, .L_GET_GOT\n\
145 @ See if we were run as a command with the executable file\n\
146 @ name as an extra leading argument.\n\
147 ldr r4, .L_SKIP_ARGS\n\
148 @ at start time, all the args are on the stack\n\
151 @ returns user entry point in r0\n\
153 adr r6, .L_GET_GOT\n\
156 @ save the entry point in another register\n\
158 @ get the original arg count\n\
160 @ get the argv address\n\
162 @ Fix up the stack if necessary.\n\
164 bne .L_fixup_stack\n\
167 add r3, r2, r1, lsl #2\n\
169 @ now we call _dl_init\n\
173 bl _dl_init_internal(PLT)\n\
174 @ load the finalizer function\n\
175 ldr r0, .L_FINI_PROC\n\
177 @ jump to the user_s entry point\n\
180 @ iWMMXt and EABI targets require the stack to be eight byte\n\
181 @ aligned - shuffle arguments etc.\n\
183 @ subtract _dl_skip_args from original arg count\n\
185 @ store the new argc in the new stack location\n\
187 @ find the first unskipped argument\n\
189 add r4, r2, r4, lsl #2\n\
190 @ shuffle argv down\n\
191 1: ldr r5, [r4], #4\n\
195 @ shuffle envp down\n\
196 1: ldr r5, [r4], #4\n\
200 @ shuffle auxv down\n\
201 1: ldmia r4!, {r0, r5}\n\
202 stmia r3!, {r0, r5}\n\
211 .word _GLOBAL_OFFSET_TABLE_ - .L_GET_GOT\n\
213 .word _dl_skip_args(GOTOFF)\n\
215 .word _dl_fini(GOTOFF)\n\
217 .word _dl_argv(GOTOFF)\n\
219 .word _rtld_local(GOTOFF)\n\
223 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
224 TLS variable, so undefined references should not be allowed to
226 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
227 of the main executable's symbols, as for a COPY reloc. */
228 #ifndef RTLD_BOOTSTRAP
229 # define elf_machine_type_class(type) \
230 ((((type) == R_ARM_JUMP_SLOT || (type) == R_ARM_TLS_DTPMOD32 \
231 || (type) == R_ARM_TLS_DTPOFF32 || (type) == R_ARM_TLS_TPOFF32 \
232 || (type) == R_ARM_TLS_DESC) \
233 * ELF_RTYPE_CLASS_PLT) \
234 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
236 #define elf_machine_type_class(type) \
237 ((((type) == R_ARM_JUMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
238 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
241 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
242 #define ELF_MACHINE_JMP_SLOT R_ARM_JUMP_SLOT
244 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
245 Prelinked libraries may use Elf32_Rela though. */
246 #define ELF_MACHINE_PLT_REL 1
248 /* We define an initialization functions. This is called very early in
250 #define DL_PLATFORM_INIT dl_platform_init ()
252 static inline void __attribute__ ((unused
))
253 dl_platform_init (void)
255 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
256 /* Avoid an empty string which would disturb us. */
257 GLRO(dl_platform
) = NULL
;
260 static inline Elf32_Addr
261 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
262 const Elf32_Rel
*reloc
,
263 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
265 return *reloc_addr
= value
;
268 /* Return the final value of a plt relocation. */
269 static inline Elf32_Addr
270 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
276 #endif /* !dl_machine_h */
279 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
280 Prelinked libraries may use Elf32_Rela though. */
281 #define ELF_MACHINE_NO_RELA defined RTLD_BOOTSTRAP
283 /* Names of the architecture-specific auditing callback functions. */
284 #define ARCH_LA_PLTENTER arm_gnu_pltenter
285 #define ARCH_LA_PLTEXIT arm_gnu_pltexit
288 /* Handle a PC24 reloc, including the out-of-range case. */
290 relocate_pc24 (struct link_map
*map
, Elf32_Addr value
,
291 Elf32_Addr
*const reloc_addr
, Elf32_Sword addend
)
293 Elf32_Addr new_value
;
295 /* Set NEW_VALUE based on V, and return true iff it overflows 24 bits. */
296 inline bool set_new_value (Elf32_Addr v
)
298 new_value
= v
+ addend
- (Elf32_Addr
) reloc_addr
;
299 Elf32_Addr topbits
= new_value
& 0xfe000000;
300 return topbits
!= 0xfe000000 && topbits
!= 0x00000000;
303 if (set_new_value (value
))
305 /* The PC-relative address doesn't fit in 24 bits! */
307 static void *fix_page
;
308 static size_t fix_offset
;
309 if (fix_page
== NULL
)
311 void *new_page
= __mmap (NULL
, GLRO(dl_pagesize
),
312 PROT_READ
| PROT_WRITE
| PROT_EXEC
,
313 MAP_PRIVATE
| MAP_ANON
, -1, 0);
314 if (new_page
== MAP_FAILED
)
315 _dl_signal_error (0, map
->l_name
, NULL
,
316 "could not map page for fixup");
318 assert (fix_offset
== 0);
321 Elf32_Word
*fix_address
= fix_page
+ fix_offset
;
322 fix_address
[0] = 0xe51ff004; /* ldr pc, [pc, #-4] */
323 fix_address
[1] = value
;
325 fix_offset
+= sizeof fix_address
[0] * 2;
326 if (fix_offset
>= GLRO(dl_pagesize
))
332 if (set_new_value ((Elf32_Addr
) fix_address
))
333 _dl_signal_error (0, map
->l_name
, NULL
,
334 "R_ARM_PC24 relocation out of range");
337 *reloc_addr
= (*reloc_addr
& 0xff000000) | ((new_value
>> 2) & 0x00ffffff);
340 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
341 MAP is the object containing the reloc. */
344 __attribute__ ((always_inline
))
345 elf_machine_rel (struct link_map
*map
, const Elf32_Rel
*reloc
,
346 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
347 void *const reloc_addr_arg
, int skip_ifunc
)
349 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
350 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
352 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
353 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
355 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
356 /* This is defined in rtld.c, but nowhere in the static libc.a;
357 make the reference weak so static programs can still link.
358 This declaration cannot be done when compiling rtld.c
359 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
360 common defn for _dl_rtld_map, which is incompatible with a
361 weak decl in the same file. */
363 weak_extern (_dl_rtld_map
);
365 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
367 *reloc_addr
+= map
->l_addr
;
369 # ifndef RTLD_BOOTSTRAP
370 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
376 const Elf32_Sym
*const refsym
= sym
;
377 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
378 Elf32_Addr value
= sym_map
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
381 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
382 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
383 && __builtin_expect (!skip_ifunc
, 1))
384 value
= elf_ifunc_invoke (value
);
390 /* This can happen in trace mode if an object could not be
393 if (sym
->st_size
> refsym
->st_size
394 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
398 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
400 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
401 RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
403 memcpy (reloc_addr_arg
, (void *) value
,
404 MIN (sym
->st_size
, refsym
->st_size
));
407 case R_ARM_JUMP_SLOT
:
408 # ifdef RTLD_BOOTSTRAP
409 /* Fix weak undefined references. */
410 if (sym
!= NULL
&& sym
->st_value
== 0)
421 } __attribute__ ((packed
, may_alias
));
422 # ifndef RTLD_BOOTSTRAP
423 /* This is defined in rtld.c, but nowhere in the static
424 libc.a; make the reference weak so static programs can
425 still link. This declaration cannot be done when
426 compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP) because
427 rtld.c contains the common defn for _dl_rtld_map, which
428 is incompatible with a weak decl in the same file. */
430 weak_extern (_dl_rtld_map
);
432 if (map
== &GL(dl_rtld_map
))
433 /* Undo the relocation done here during bootstrapping.
434 Now we will relocate it anew, possibly using a
435 binding found in the user program or a loaded library
436 rather than the dynamic linker's built-in definitions
437 used while loading those libraries. */
438 value
-= map
->l_addr
+ refsym
->st_value
;
440 /* Support relocations on mis-aligned offsets. */
441 ((struct unaligned
*) reloc_addr
)->x
+= value
;
446 struct tlsdesc
volatile *td
=
447 (struct tlsdesc
volatile *)reloc_addr
;
449 # ifndef RTLD_BOOTSTRAP
451 td
->entry
= _dl_tlsdesc_undefweak
;
455 value
= sym
->st_value
+ td
->argument
.value
;
457 # ifndef RTLD_BOOTSTRAP
459 CHECK_STATIC_TLS (map
, sym_map
);
461 if (!TRY_STATIC_TLS (map
, sym_map
))
464 = _dl_make_tlsdesc_dynamic (sym_map
, value
);
465 td
->entry
= _dl_tlsdesc_dynamic
;
471 td
->argument
.value
= value
+ sym_map
->l_tls_offset
;
472 td
->entry
= _dl_tlsdesc_return
;
478 relocate_pc24 (map
, value
, reloc_addr
,
479 /* Sign-extend the 24-bit addend in the
480 instruction (which counts instructions), and
481 then shift it up two so as to count bytes. */
482 (((Elf32_Sword
) *reloc_addr
<< 8) >> 8) << 2);
484 #if !defined RTLD_BOOTSTRAP
485 case R_ARM_TLS_DTPMOD32
:
486 /* Get the information from the link map returned by the
489 *reloc_addr
= sym_map
->l_tls_modid
;
492 case R_ARM_TLS_DTPOFF32
:
494 *reloc_addr
+= sym
->st_value
;
497 case R_ARM_TLS_TPOFF32
:
500 CHECK_STATIC_TLS (map
, sym_map
);
501 *reloc_addr
+= sym
->st_value
+ sym_map
->l_tls_offset
;
504 case R_ARM_IRELATIVE
:
505 value
= map
->l_addr
+ *reloc_addr
;
506 value
= ((Elf32_Addr (*) (int)) value
) (GLRO(dl_hwcap
));
511 _dl_reloc_bad_type (map
, r_type
, 0);
517 # ifndef RTLD_BOOTSTRAP
519 __attribute__ ((always_inline
))
520 elf_machine_rela (struct link_map
*map
, const Elf32_Rela
*reloc
,
521 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
522 void *const reloc_addr_arg
, int skip_ifunc
)
524 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
525 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
527 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
528 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
529 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
533 # ifndef RESOLVE_CONFLICT_FIND_MAP
534 const Elf32_Sym
*const refsym
= sym
;
536 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
537 Elf32_Addr value
= sym_map
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
540 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
541 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
542 && __builtin_expect (!skip_ifunc
, 1))
543 value
= elf_ifunc_invoke (value
);
547 # ifndef RESOLVE_CONFLICT_FIND_MAP
548 /* Not needed for dl-conflict.c. */
551 /* This can happen in trace mode if an object could not be
554 if (sym
->st_size
> refsym
->st_size
555 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
559 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
561 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
562 RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
564 memcpy (reloc_addr_arg
, (void *) value
,
565 MIN (sym
->st_size
, refsym
->st_size
));
567 # endif /* !RESOLVE_CONFLICT_FIND_MAP */
569 case R_ARM_JUMP_SLOT
:
571 *reloc_addr
= value
+ reloc
->r_addend
;
574 relocate_pc24 (map
, value
, reloc_addr
, reloc
->r_addend
);
576 #if !defined RTLD_BOOTSTRAP
577 case R_ARM_TLS_DTPMOD32
:
578 /* Get the information from the link map returned by the
581 *reloc_addr
= sym_map
->l_tls_modid
;
584 case R_ARM_TLS_DTPOFF32
:
585 *reloc_addr
= (sym
== NULL
? 0 : sym
->st_value
) + reloc
->r_addend
;
588 case R_ARM_TLS_TPOFF32
:
591 CHECK_STATIC_TLS (map
, sym_map
);
592 *reloc_addr
= (sym
->st_value
+ sym_map
->l_tls_offset
596 case R_ARM_IRELATIVE
:
597 value
= map
->l_addr
+ *reloc_addr
;
598 value
= ((Elf32_Addr (*) (int)) value
) (GLRO(dl_hwcap
));
603 _dl_reloc_bad_type (map
, r_type
, 0);
611 __attribute__ ((always_inline
))
612 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
613 void *const reloc_addr_arg
)
615 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
616 *reloc_addr
+= l_addr
;
619 # ifndef RTLD_BOOTSTRAP
621 __attribute__ ((always_inline
))
622 elf_machine_rela_relative (Elf32_Addr l_addr
, const Elf32_Rela
*reloc
,
623 void *const reloc_addr_arg
)
625 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
626 *reloc_addr
= l_addr
+ reloc
->r_addend
;
631 __attribute__ ((always_inline
))
632 elf_machine_lazy_rel (struct link_map
*map
,
633 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
636 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
637 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
638 /* Check for unexpected PLT reloc type. */
639 if (__builtin_expect (r_type
== R_ARM_JUMP_SLOT
, 1))
641 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
642 *reloc_addr
+= l_addr
;
644 *reloc_addr
= map
->l_mach
.plt
;
646 else if (__builtin_expect (r_type
== R_ARM_TLS_DESC
, 1))
648 struct tlsdesc
volatile *td
=
649 (struct tlsdesc
volatile *)reloc_addr
;
651 /* The linker must have given us the parameter we need in the
652 first GOT entry, and left the second one empty. We fill the
653 last with the resolver address */
654 assert (td
->entry
== 0);
655 td
->entry
= (void*)(D_PTR (map
, l_info
[ADDRIDX (DT_TLSDESC_PLT
)])
659 _dl_reloc_bad_type (map
, r_type
, 1);
662 #endif /* RESOLVE_MAP */