1 /* Machine-dependent ELF dynamic relocation inline functions. ARM version.
2 Copyright (C) 1995-2024 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"
25 #include <sys/param.h>
27 #include <dl-tlsdesc.h>
29 #include <dl-static-tls.h>
30 #include <dl-machine-rel.h>
33 # error CLEAR_CACHE definition required to handle TEXTREL
36 /* Return nonzero iff ELF header is compatible with the running host. */
37 static inline int __attribute__ ((unused
))
38 elf_machine_matches_host (const Elf32_Ehdr
*ehdr
)
40 return ehdr
->e_machine
== EM_ARM
;
43 /* Return the run-time load address of the shared object. */
44 static inline ElfW(Addr
) __attribute__ ((unused
))
45 elf_machine_load_address (void)
47 extern const ElfW(Ehdr
) __ehdr_start attribute_hidden
;
48 return (ElfW(Addr
)) &__ehdr_start
;
51 /* Return the link-time address of _DYNAMIC. */
52 static inline ElfW(Addr
) __attribute__ ((unused
))
53 elf_machine_dynamic (void)
55 extern ElfW(Dyn
) _DYNAMIC
[] attribute_hidden
;
56 return (ElfW(Addr
)) _DYNAMIC
- elf_machine_load_address ();
59 /* Set up the loaded object described by L so its unrelocated PLT
60 entries will jump to the on-demand fixup code in dl-runtime.c. */
62 static inline int __attribute__ ((unused
))
63 elf_machine_runtime_setup (struct link_map
*l
, struct r_scope_elem
*scope
[],
64 int lazy
, int profile
)
67 extern void _dl_runtime_resolve (Elf32_Word
);
69 if (l
->l_info
[DT_JMPREL
] && lazy
)
71 /* patb: this is different than i386 */
72 /* The GOT entries for functions in the PLT have not yet been filled
73 in. Their initial contents will arrange when called to push an
74 index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
75 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
76 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
77 /* If a library is prelinked but we have to relocate anyway,
78 we have to be able to undo the prelinking of .got.plt.
79 The prelinker saved us here address of .plt. */
81 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
82 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
84 /* The got[2] entry contains the address of a function which gets
85 called to get the address of a so far unresolved function and
86 jump to it. The profiling extension of the dynamic linker allows
87 to intercept the calls to collect information. In this case we
88 don't store the address in the GOT so that all future calls also
89 end in this function. */
91 extern void _dl_runtime_profile (Elf32_Word
);
94 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
96 if (GLRO(dl_profile
) != NULL
97 && _dl_name_match_p (GLRO(dl_profile
), l
))
98 /* Say that we really want profiling and the timers are
100 GL(dl_profile_map
) = l
;
104 /* This function will get called to fix up the GOT entry indicated by
105 the offset on the stack, and then jump to the resolved address. */
106 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
112 #if defined(ARCH_HAS_BX)
113 #define BX(x) "bx\t" #x
115 #define BX(x) "mov\tpc, " #x
118 /* Mask identifying addresses reserved for the user program,
119 where the dynamic linker should not map anything. */
120 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
122 /* Initial entry point code for the dynamic linker.
123 The C function `_dl_start' is the real entry point;
124 its return value is the user program's entry point. */
126 #define RTLD_START asm ("\
129 .type _start, %function\n\
130 .globl _dl_start_user\n\
131 .type _dl_start_user, %function\n\
133 @ we are PIC code, so get global offset table\n\
134 ldr sl, .L_GET_GOT\n\
135 @ at start time, all the args are on the stack\n\
138 @ returns user entry point in r0\n\
140 adr r6, .L_GET_GOT\n\
142 @ save the entry point in another register\n\
144 @ get the original arg count\n\
146 @ get the argv address\n\
149 add r3, r2, r1, lsl #2\n\
151 @ now we call _dl_init\n\
156 @ load the finalizer function\n\
157 ldr r0, .L_FINI_PROC\n\
159 @ jump to the user_s entry point\n\
163 .word _GLOBAL_OFFSET_TABLE_ - .L_GET_GOT\n\
165 .word _dl_fini(GOTOFF)\n\
167 .word __GI__dl_argv(GOTOFF)\n\
169 .word _rtld_local(GOTOFF)\n\
173 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
174 TLS variable, so undefined references should not be allowed to
176 ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one
177 of the main executable's symbols, as for a COPY reloc. */
178 #ifndef RTLD_BOOTSTRAP
179 # define elf_machine_type_class(type) \
180 ((((type) == R_ARM_JUMP_SLOT || (type) == R_ARM_TLS_DTPMOD32 \
181 || (type) == R_ARM_TLS_DTPOFF32 || (type) == R_ARM_TLS_TPOFF32 \
182 || (type) == R_ARM_TLS_DESC) \
183 * ELF_RTYPE_CLASS_PLT) \
184 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
186 #define elf_machine_type_class(type) \
187 ((((type) == R_ARM_JUMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
188 | (((type) == R_ARM_COPY) * ELF_RTYPE_CLASS_COPY))
191 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
192 #define ELF_MACHINE_JMP_SLOT R_ARM_JUMP_SLOT
194 /* We define an initialization functions. This is called very early in
196 #define DL_PLATFORM_INIT dl_platform_init ()
198 static inline void __attribute__ ((unused
))
199 dl_platform_init (void)
201 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
202 /* Avoid an empty string which would disturb us. */
203 GLRO(dl_platform
) = NULL
;
206 static inline Elf32_Addr
207 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
208 const ElfW(Sym
) *refsym
, const ElfW(Sym
) *sym
,
209 const Elf32_Rel
*reloc
,
210 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
212 return *reloc_addr
= value
;
215 /* Return the final value of a plt relocation. */
216 static inline Elf32_Addr
217 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
223 #endif /* !dl_machine_h */
226 /* Names of the architecture-specific auditing callback functions. */
227 #define ARCH_LA_PLTENTER arm_gnu_pltenter
228 #define ARCH_LA_PLTEXIT arm_gnu_pltexit
231 /* Set NEW_VALUE based on V, and return true iff it overflows 24 bits. */
232 static inline bool set_new_value (Elf32_Addr
*new_value
, Elf32_Addr v
,
233 Elf32_Addr
*const reloc_addr
,
236 *new_value
= v
+ addend
- (Elf32_Addr
) reloc_addr
;
237 Elf32_Addr topbits
= *new_value
& 0xfe000000;
238 return topbits
!= 0xfe000000 && topbits
!= 0x00000000;
241 /* Handle a PC24 reloc, including the out-of-range case. */
243 relocate_pc24 (struct link_map
*map
, Elf32_Addr value
,
244 Elf32_Addr
*const reloc_addr
, Elf32_Sword addend
)
246 Elf32_Addr new_value
;
248 if (set_new_value (&new_value
, value
, reloc_addr
, addend
))
250 /* The PC-relative address doesn't fit in 24 bits! */
252 static void *fix_page
;
253 static size_t fix_offset
;
254 if (fix_page
== NULL
)
256 void *new_page
= __mmap (NULL
, GLRO(dl_pagesize
),
257 PROT_READ
| PROT_WRITE
| PROT_EXEC
,
258 MAP_PRIVATE
| MAP_ANON
, -1, 0);
259 if (new_page
== MAP_FAILED
)
260 _dl_signal_error (0, map
->l_name
, NULL
,
261 "could not map page for fixup");
263 assert (fix_offset
== 0);
266 Elf32_Word
*fix_address
= fix_page
+ fix_offset
;
267 fix_address
[0] = 0xe51ff004; /* ldr pc, [pc, #-4] */
268 fix_address
[1] = value
;
270 fix_offset
+= sizeof fix_address
[0] * 2;
271 if (fix_offset
>= GLRO(dl_pagesize
))
277 if (set_new_value (&new_value
, (Elf32_Addr
) fix_address
, reloc_addr
,
279 _dl_signal_error (0, map
->l_name
, NULL
,
280 "R_ARM_PC24 relocation out of range");
283 *reloc_addr
= (*reloc_addr
& 0xff000000) | ((new_value
>> 2) & 0x00ffffff);
286 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
287 MAP is the object containing the reloc. */
290 __attribute__ ((always_inline
))
291 elf_machine_rel (struct link_map
*map
, struct r_scope_elem
*scope
[],
292 const Elf32_Rel
*reloc
, const Elf32_Sym
*sym
,
293 const struct r_found_version
*version
,
294 void *const reloc_addr_arg
, int skip_ifunc
)
296 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
297 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
299 #if !defined RTLD_BOOTSTRAP
300 if (__builtin_expect (r_type
== R_ARM_RELATIVE
, 0))
301 *reloc_addr
+= map
->l_addr
;
302 # ifndef RTLD_BOOTSTRAP
303 else if (__builtin_expect (r_type
== R_ARM_NONE
, 0))
309 const Elf32_Sym
*const refsym
= sym
;
310 struct link_map
*sym_map
= RESOLVE_MAP (map
, scope
, &sym
, version
,
312 Elf32_Addr value
= SYMBOL_ADDRESS (sym_map
, sym
, true);
315 && __builtin_expect (ELFW(ST_TYPE
) (sym
->st_info
) == STT_GNU_IFUNC
, 0)
316 && __builtin_expect (sym
->st_shndx
!= SHN_UNDEF
, 1)
317 && __builtin_expect (!skip_ifunc
, 1))
318 value
= elf_ifunc_invoke (value
);
324 /* This can happen in trace mode if an object could not be
327 if (sym
->st_size
> refsym
->st_size
328 || (GLRO(dl_verbose
) && sym
->st_size
< refsym
->st_size
))
332 strtab
= (const void *) D_PTR (map
, l_info
[DT_STRTAB
]);
334 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
335 RTLD_PROGNAME
, strtab
+ refsym
->st_name
);
337 memcpy (reloc_addr_arg
, (void *) value
,
338 MIN (sym
->st_size
, refsym
->st_size
));
341 case R_ARM_JUMP_SLOT
:
342 # ifdef RTLD_BOOTSTRAP
343 /* Fix weak undefined references. */
344 if (sym
!= NULL
&& sym
->st_value
== 0)
355 } __attribute__ ((packed
, may_alias
));
356 # ifndef RTLD_BOOTSTRAP
357 /* This is defined in rtld.c, but nowhere in the static
358 libc.a; make the reference weak so static programs can
359 still link. This declaration cannot be done when
360 compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP) because
361 rtld.c contains the common defn for _dl_rtld_map, which
362 is incompatible with a weak decl in the same file. */
364 weak_extern (_dl_rtld_map
);
366 if (map
== &GL(dl_rtld_map
))
367 /* Undo the relocation done here during bootstrapping.
368 Now we will relocate it anew, possibly using a
369 binding found in the user program or a loaded library
370 rather than the dynamic linker's built-in definitions
371 used while loading those libraries. */
372 value
-= SYMBOL_ADDRESS (map
, refsym
, true);
374 /* Support relocations on mis-aligned offsets. */
375 ((struct unaligned
*) reloc_addr
)->x
+= value
;
380 struct tlsdesc
*td
= (struct tlsdesc
*)reloc_addr
;
382 # ifndef RTLD_BOOTSTRAP
384 td
->entry
= _dl_tlsdesc_undefweak
;
388 if (ELF32_R_SYM (reloc
->r_info
) == STN_UNDEF
)
389 value
= td
->argument
.value
;
391 value
= sym
->st_value
;
393 # ifndef RTLD_BOOTSTRAP
395 CHECK_STATIC_TLS (map
, sym_map
);
397 if (!TRY_STATIC_TLS (map
, sym_map
))
400 = _dl_make_tlsdesc_dynamic (sym_map
, value
);
401 td
->entry
= _dl_tlsdesc_dynamic
;
407 td
->argument
.value
= value
+ sym_map
->l_tls_offset
;
408 td
->entry
= _dl_tlsdesc_return
;
414 relocate_pc24 (map
, value
, reloc_addr
,
415 /* Sign-extend the 24-bit addend in the
416 instruction (which counts instructions), and
417 then shift it up two so as to count bytes. */
418 (((Elf32_Sword
) *reloc_addr
<< 8) >> 8) << 2);
420 #if !defined RTLD_BOOTSTRAP
421 case R_ARM_TLS_DTPMOD32
:
422 /* Get the information from the link map returned by the
425 *reloc_addr
= sym_map
->l_tls_modid
;
428 case R_ARM_TLS_DTPOFF32
:
430 *reloc_addr
+= sym
->st_value
;
433 case R_ARM_TLS_TPOFF32
:
436 CHECK_STATIC_TLS (map
, sym_map
);
437 *reloc_addr
+= sym
->st_value
+ sym_map
->l_tls_offset
;
440 case R_ARM_IRELATIVE
:
441 value
= map
->l_addr
+ *reloc_addr
;
442 if (__glibc_likely (!skip_ifunc
))
443 value
= ((Elf32_Addr (*) (int)) value
) (GLRO(dl_hwcap
));
448 _dl_reloc_bad_type (map
, r_type
, 0);
456 __attribute__ ((always_inline
))
457 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
458 void *const reloc_addr_arg
)
460 Elf32_Addr
*const reloc_addr
= reloc_addr_arg
;
461 *reloc_addr
+= l_addr
;
466 __attribute__ ((always_inline
))
467 elf_machine_lazy_rel (struct link_map
*map
, struct r_scope_elem
*scope
[],
468 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
471 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
472 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
473 /* Check for unexpected PLT reloc type. */
474 if (__builtin_expect (r_type
== R_ARM_JUMP_SLOT
, 1))
476 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
477 *reloc_addr
+= l_addr
;
479 *reloc_addr
= map
->l_mach
.plt
;
481 else if (__builtin_expect (r_type
== R_ARM_TLS_DESC
, 1))
483 const Elf_Symndx symndx
= ELFW (R_SYM
) (reloc
->r_info
);
484 const ElfW (Sym
) *symtab
= (const void *)D_PTR (map
, l_info
[DT_SYMTAB
]);
485 const ElfW (Sym
) *sym
= &symtab
[symndx
];
486 const struct r_found_version
*version
= NULL
;
488 if (map
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
490 const ElfW (Half
) *vernum
=
491 (const void *)D_PTR (map
, l_info
[VERSYMIDX (DT_VERSYM
)]);
492 version
= &map
->l_versions
[vernum
[symndx
] & 0x7fff];
495 /* Always initialize TLS descriptors completely, because lazy
496 initialization requires synchronization at every TLS access. */
497 elf_machine_rel (map
, scope
, reloc
, sym
, version
, reloc_addr
, skip_ifunc
);
500 _dl_reloc_bad_type (map
, r_type
, 1);
503 #endif /* RESOLVE_MAP */