1 /* Machine-dependent ELF dynamic relocation inline functions. ARM version.
2 Copyright (C) 1995-2020 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 <https://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 Elf32_Addr pcrel_addr
;
58 extern Elf32_Addr
__dl_start (void *) asm ("_dl_start");
59 Elf32_Addr got_addr
= (Elf32_Addr
) &__dl_start
;
60 asm ("adr %0, _dl_start" : "=r" (pcrel_addr
));
62 extern Elf32_Addr
__dl_relocate_static_pie (void *)
63 asm ("_dl_relocate_static_pie") attribute_hidden
;
64 Elf32_Addr got_addr
= (Elf32_Addr
) &__dl_relocate_static_pie
;
65 asm ("adr %0, _dl_relocate_static_pie" : "=r" (pcrel_addr
));
68 /* Clear the low bit of the function address.
70 NOTE: got_addr is from GOT table whose lsb is always set by linker if it's
71 Thumb function address. PCREL_ADDR comes from PC-relative calculation
72 which will finish during assembling. GAS assembler before the fix for
73 PR gas/21458 was not setting the lsb but does after that. Always do the
74 strip for both, so the code works with various combinations of glibc and
76 got_addr
&= ~(Elf32_Addr
) 1;
77 pcrel_addr
&= ~(Elf32_Addr
) 1;
79 return pcrel_addr
- got_addr
;
83 /* Set up the loaded object described by L so its unrelocated PLT
84 entries will jump to the on-demand fixup code in dl-runtime.c. */
86 static inline int __attribute__ ((unused
))
87 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
90 extern void _dl_runtime_resolve (Elf32_Word
);
91 extern void _dl_runtime_profile (Elf32_Word
);
93 if (l
->l_info
[DT_JMPREL
] && lazy
)
95 /* patb: this is different than i386 */
96 /* The GOT entries for functions in the PLT have not yet been filled
97 in. Their initial contents will arrange when called to push an
98 index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
99 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
100 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
101 /* If a library is prelinked but we have to relocate anyway,
102 we have to be able to undo the prelinking of .got.plt.
103 The prelinker saved us here address of .plt. */
105 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
106 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
108 /* The got[2] entry contains the address of a function which gets
109 called to get the address of a so far unresolved function and
110 jump to it. The profiling extension of the dynamic linker allows
111 to intercept the calls to collect information. In this case we
112 don't store the address in the GOT so that all future calls also
113 end in this function. */
116 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
118 if (GLRO(dl_profile
) != NULL
119 && _dl_name_match_p (GLRO(dl_profile
), l
))
120 /* Say that we really want profiling and the timers are
122 GL(dl_profile_map
) = l
;
125 /* This function will get called to fix up the GOT entry indicated by
126 the offset on the stack, and then jump to the resolved address. */
127 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
133 #if defined(ARCH_HAS_BX)
134 #define BX(x) "bx\t" #x
136 #define BX(x) "mov\tpc, " #x
139 /* Mask identifying addresses reserved for the user program,
140 where the dynamic linker should not map anything. */
141 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
143 /* Initial entry point code for the dynamic linker.
144 The C function `_dl_start' is the real entry point;
145 its return value is the user program's entry point. */
147 #define RTLD_START asm ("\
150 .type _start, %function\n\
151 .globl _dl_start_user\n\
152 .type _dl_start_user, %function\n\
154 @ we are PIC code, so get global offset table\n\
155 ldr sl, .L_GET_GOT\n\
156 @ See if we were run as a command with the executable file\n\
157 @ name as an extra leading argument.\n\
158 ldr r4, .L_SKIP_ARGS\n\
159 @ at start time, all the args are on the stack\n\
162 @ returns user entry point in r0\n\
164 adr r6, .L_GET_GOT\n\
167 @ save the entry point in another register\n\
169 @ get the original arg count\n\
171 @ get the argv address\n\
173 @ Fix up the stack if necessary.\n\
175 bne .L_fixup_stack\n\
178 add r3, r2, r1, lsl #2\n\
180 @ now we call _dl_init\n\
185 @ load the finalizer function\n\
186 ldr r0, .L_FINI_PROC\n\
188 @ jump to the user_s entry point\n\
191 @ iWMMXt and EABI targets require the stack to be eight byte\n\
192 @ aligned - shuffle arguments etc.\n\
194 @ subtract _dl_skip_args from original arg count\n\
196 @ store the new argc in the new stack location\n\
198 @ find the first unskipped argument\n\
200 add r4, r2, r4, lsl #2\n\
201 @ shuffle argv down\n\
202 1: ldr r5, [r4], #4\n\
206 @ shuffle envp down\n\
207 1: ldr r5, [r4], #4\n\
211 @ shuffle auxv down\n\
212 1: ldmia r4!, {r0, r5}\n\
213 stmia r3!, {r0, r5}\n\
222 .word _GLOBAL_OFFSET_TABLE_ - .L_GET_GOT\n\
224 .word _dl_skip_args(GOTOFF)\n\
226 .word _dl_fini(GOTOFF)\n\
228 .word _dl_argv(GOTOFF)\n\
230 .word _rtld_local(GOTOFF)\n\
234 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
235 TLS variable, so undefined references should not be allowed to
237 ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one
238 of the main executable's symbols, as for a COPY reloc.
239 ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation against
240 protected data whose address may be external due to copy relocation. */
241 #ifndef RTLD_BOOTSTRAP
242 # define elf_machine_type_class(type) \
243 ((((type) == R_ARM_JUMP_SLOT || (type) == R_ARM_TLS_DTPMOD32 \
244 || (type) == R_ARM_TLS_DTPOFF32 || (type) == R_ARM_TLS_TPOFF32 \
245 || (type) == R_ARM_TLS_DESC) \
246 * ELF_RTYPE_CLASS_PLT) \
247 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY) \
248 | (((type) == R_ARM_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
250 #define elf_machine_type_class(type) \
251 ((((type) == R_ARM_JUMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
252 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY) \
253 | (((type) == R_ARM_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
256 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
257 #define ELF_MACHINE_JMP_SLOT R_ARM_JUMP_SLOT
259 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
260 Prelinked libraries may use Elf32_Rela though. */
261 #define ELF_MACHINE_PLT_REL 1
263 /* We define an initialization functions. This is called very early in
265 #define DL_PLATFORM_INIT dl_platform_init ()
267 static inline void __attribute__ ((unused
))
268 dl_platform_init (void)
270 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
271 /* Avoid an empty string which would disturb us. */
272 GLRO(dl_platform
) = NULL
;
275 static inline Elf32_Addr
276 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
277 const ElfW(Sym
) *refsym
, const ElfW(Sym
) *sym
,
278 const Elf32_Rel
*reloc
,
279 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
281 return *reloc_addr
= value
;
284 /* Return the final value of a plt relocation. */
285 static inline Elf32_Addr
286 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
292 #endif /* !dl_machine_h */
295 /* ARM never uses Elf32_Rela relocations for the dynamic linker.
296 Prelinked libraries may use Elf32_Rela though. */
297 #define ELF_MACHINE_NO_RELA defined RTLD_BOOTSTRAP
298 #define ELF_MACHINE_NO_REL 0
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
= SYMBOL_ADDRESS (sym_map
, sym
, true);
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
, strtab
+ refsym
->st_name
);
420 memcpy (reloc_addr_arg
, (void *) value
,
421 MIN (sym
->st_size
, refsym
->st_size
));
424 case R_ARM_JUMP_SLOT
:
425 # ifdef RTLD_BOOTSTRAP
426 /* Fix weak undefined references. */
427 if (sym
!= NULL
&& sym
->st_value
== 0)
438 } __attribute__ ((packed
, may_alias
));
439 # ifndef RTLD_BOOTSTRAP
440 /* This is defined in rtld.c, but nowhere in the static
441 libc.a; make the reference weak so static programs can
442 still link. This declaration cannot be done when
443 compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP) because
444 rtld.c contains the common defn for _dl_rtld_map, which
445 is incompatible with a weak decl in the same file. */
447 weak_extern (_dl_rtld_map
);
449 if (map
== &GL(dl_rtld_map
))
450 /* Undo the relocation done here during bootstrapping.
451 Now we will relocate it anew, possibly using a
452 binding found in the user program or a loaded library
453 rather than the dynamic linker's built-in definitions
454 used while loading those libraries. */
455 value
-= SYMBOL_ADDRESS (map
, refsym
, true);
457 /* Support relocations on mis-aligned offsets. */
458 ((struct unaligned
*) reloc_addr
)->x
+= value
;
463 struct tlsdesc
*td
= (struct tlsdesc
*)reloc_addr
;
465 # ifndef RTLD_BOOTSTRAP
467 td
->entry
= _dl_tlsdesc_undefweak
;
471 if (ELF32_R_SYM (reloc
->r_info
) == STN_UNDEF
)
472 value
= td
->argument
.value
;
474 value
= sym
->st_value
;
476 # ifndef RTLD_BOOTSTRAP
478 CHECK_STATIC_TLS (map
, sym_map
);
480 if (!TRY_STATIC_TLS (map
, sym_map
))
483 = _dl_make_tlsdesc_dynamic (sym_map
, value
);
484 td
->entry
= _dl_tlsdesc_dynamic
;
490 td
->argument
.value
= value
+ sym_map
->l_tls_offset
;
491 td
->entry
= _dl_tlsdesc_return
;
497 relocate_pc24 (map
, value
, reloc_addr
,
498 /* Sign-extend the 24-bit addend in the
499 instruction (which counts instructions), and
500 then shift it up two so as to count bytes. */
501 (((Elf32_Sword
) *reloc_addr
<< 8) >> 8) << 2);
503 #if !defined RTLD_BOOTSTRAP
504 case R_ARM_TLS_DTPMOD32
:
505 /* Get the information from the link map returned by the
508 *reloc_addr
= sym_map
->l_tls_modid
;
511 case R_ARM_TLS_DTPOFF32
:
513 *reloc_addr
+= sym
->st_value
;
516 case R_ARM_TLS_TPOFF32
:
519 CHECK_STATIC_TLS (map
, sym_map
);
520 *reloc_addr
+= sym
->st_value
+ sym_map
->l_tls_offset
;
523 case R_ARM_IRELATIVE
:
524 value
= map
->l_addr
+ *reloc_addr
;
525 if (__glibc_likely (!skip_ifunc
))
526 value
= ((Elf32_Addr (*) (int)) value
) (GLRO(dl_hwcap
));
531 _dl_reloc_bad_type (map
, r_type
, 0);
537 # ifndef RTLD_BOOTSTRAP
539 __attribute__ ((always_inline
))
540 elf_machine_rela (struct link_map
*map
, const Elf32_Rela
*reloc
,
541 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
542 void *const reloc_addr_arg
, int skip_ifunc
)
544 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
545 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
547 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
548 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
549 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
553 # ifndef RESOLVE_CONFLICT_FIND_MAP
554 const Elf32_Sym
*const refsym
= sym
;
556 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
557 Elf32_Addr value
= SYMBOL_ADDRESS (sym_map
, sym
, true);
560 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
561 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
562 && __builtin_expect (!skip_ifunc
, 1))
563 value
= elf_ifunc_invoke (value
);
567 # ifndef RESOLVE_CONFLICT_FIND_MAP
568 /* Not needed for dl-conflict.c. */
571 /* This can happen in trace mode if an object could not be
574 if (sym
->st_size
> refsym
->st_size
575 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
579 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
581 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
582 RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
584 memcpy (reloc_addr_arg
, (void *) value
,
585 MIN (sym
->st_size
, refsym
->st_size
));
587 # endif /* !RESOLVE_CONFLICT_FIND_MAP */
589 case R_ARM_JUMP_SLOT
:
591 *reloc_addr
= value
+ reloc
->r_addend
;
594 relocate_pc24 (map
, value
, reloc_addr
, reloc
->r_addend
);
596 #if !defined RTLD_BOOTSTRAP
597 case R_ARM_TLS_DTPMOD32
:
598 /* Get the information from the link map returned by the
601 *reloc_addr
= sym_map
->l_tls_modid
;
604 case R_ARM_TLS_DTPOFF32
:
605 *reloc_addr
= (sym
== NULL
? 0 : sym
->st_value
) + reloc
->r_addend
;
608 case R_ARM_TLS_TPOFF32
:
611 CHECK_STATIC_TLS (map
, sym_map
);
612 *reloc_addr
= (sym
->st_value
+ sym_map
->l_tls_offset
616 case R_ARM_IRELATIVE
:
617 value
= map
->l_addr
+ reloc
->r_addend
;
618 if (__glibc_likely (!skip_ifunc
))
619 value
= ((Elf32_Addr (*) (int)) value
) (GLRO(dl_hwcap
));
624 _dl_reloc_bad_type (map
, r_type
, 0);
632 __attribute__ ((always_inline
))
633 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
634 void *const reloc_addr_arg
)
636 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
637 *reloc_addr
+= l_addr
;
640 # ifndef RTLD_BOOTSTRAP
642 __attribute__ ((always_inline
))
643 elf_machine_rela_relative (Elf32_Addr l_addr
, const Elf32_Rela
*reloc
,
644 void *const reloc_addr_arg
)
646 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
647 *reloc_addr
= l_addr
+ reloc
->r_addend
;
652 __attribute__ ((always_inline
))
653 elf_machine_lazy_rel (struct link_map
*map
,
654 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
657 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
658 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
659 /* Check for unexpected PLT reloc type. */
660 if (__builtin_expect (r_type
== R_ARM_JUMP_SLOT
, 1))
662 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
663 *reloc_addr
+= l_addr
;
665 *reloc_addr
= map
->l_mach
.plt
;
667 else if (__builtin_expect (r_type
== R_ARM_TLS_DESC
, 1))
669 const Elf_Symndx symndx
= ELFW (R_SYM
) (reloc
->r_info
);
670 const ElfW (Sym
) *symtab
= (const void *)D_PTR (map
, l_info
[DT_SYMTAB
]);
671 const ElfW (Sym
) *sym
= &symtab
[symndx
];
672 const struct r_found_version
*version
= NULL
;
674 if (map
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
676 const ElfW (Half
) *vernum
=
677 (const void *)D_PTR (map
, l_info
[VERSYMIDX (DT_VERSYM
)]);
678 version
= &map
->l_versions
[vernum
[symndx
] & 0x7fff];
681 /* Always initialize TLS descriptors completely, because lazy
682 initialization requires synchronization at every TLS access. */
683 elf_machine_rel (map
, reloc
, sym
, version
, reloc_addr
, skip_ifunc
);
686 _dl_reloc_bad_type (map
, r_type
, 1);
689 #endif /* RESOLVE_MAP */