1 /* Machine-dependent ELF dynamic relocation inline functions. i386 version.
2 Copyright (C) 1995,96,97,98,99,2000,2001,2002 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, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
23 #define ELF_MACHINE_NAME "i386"
25 #include <sys/param.h>
29 /* Return nonzero iff ELF header is compatible with the running host. */
30 static inline int __attribute__ ((unused
))
31 elf_machine_matches_host (const Elf32_Ehdr
*ehdr
)
33 return ehdr
->e_machine
== EM_386
;
37 #if defined PI_STATIC_AND_HIDDEN \
38 && defined HAVE_VISIBILITY_ATTRIBUTE && defined HAVE_HIDDEN \
39 && !defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
41 /* Return the link-time address of _DYNAMIC. Conveniently, this is the
42 first element of the GOT, a special entry that is never relocated. */
43 static inline Elf32_Addr
__attribute__ ((unused
, const))
44 elf_machine_dynamic (void)
46 /* This produces a GOTOFF reloc that resolves to zero at link time, so in
47 fact just loads from the GOT register directly. By doing it without
48 an asm we can let the compiler choose any register. */
49 extern const Elf32_Addr _GLOBAL_OFFSET_TABLE_
[] attribute_hidden
;
50 return _GLOBAL_OFFSET_TABLE_
[0];
53 /* Return the run-time load address of the shared object. */
54 static inline Elf32_Addr
__attribute__ ((unused
))
55 elf_machine_load_address (void)
57 /* Compute the difference between the runtime address of _DYNAMIC as seen
58 by a GOTOFF reference, and the link-time address found in the special
59 unrelocated first GOT entry. */
60 extern Elf32_Dyn bygotoff
[] asm ("_DYNAMIC") attribute_hidden
;
61 return (Elf32_Addr
) &bygotoff
- elf_machine_dynamic ();
64 #else /* Without .hidden support, we can't compile the code above. */
66 /* Return the link-time address of _DYNAMIC. Conveniently, this is the
67 first element of the GOT. This must be inlined in a function which
69 static inline Elf32_Addr
__attribute__ ((unused
))
70 elf_machine_dynamic (void)
72 register Elf32_Addr
*got
asm ("%ebx");
77 /* Return the run-time load address of the shared object. */
78 static inline Elf32_Addr
__attribute__ ((unused
))
79 elf_machine_load_address (void)
81 /* It doesn't matter what variable this is, the reference never makes
82 it to assembly. We need a dummy reference to some global variable
83 via the GOT to make sure the compiler initialized %ebx in time. */
86 asm ("leal _dl_start@GOTOFF(%%ebx), %0\n"
87 "subl _dl_start@GOT(%%ebx), %0"
88 : "=r" (addr
) : "m" (_dl_argc
) : "cc");
95 /* Set up the loaded object described by L so its unrelocated PLT
96 entries will jump to the on-demand fixup code in dl-runtime.c. */
98 static inline int __attribute__ ((unused
))
99 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
102 extern void _dl_runtime_resolve (Elf32_Word
) attribute_hidden
;
103 extern void _dl_runtime_profile (Elf32_Word
) attribute_hidden
;
105 if (l
->l_info
[DT_JMPREL
] && lazy
)
107 /* The GOT entries for functions in the PLT have not yet been filled
108 in. Their initial contents will arrange when called to push an
109 offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
110 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
111 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
112 /* If a library is prelinked but we have to relocate anyway,
113 we have to be able to undo the prelinking of .got.plt.
114 The prelinker saved us here address of .plt + 0x16. */
117 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
118 l
->l_mach
.gotplt
= (Elf32_Addr
) &got
[3];
120 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
122 /* The got[2] entry contains the address of a function which gets
123 called to get the address of a so far unresolved function and
124 jump to it. The profiling extension of the dynamic linker allows
125 to intercept the calls to collect information. In this case we
126 don't store the address in the GOT so that all future calls also
127 end in this function. */
128 if (__builtin_expect (profile
, 0))
130 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
132 if (_dl_name_match_p (GL(dl_profile
), l
))
133 /* This is the object we are looking for. Say that we really
134 want profiling and the timers are started. */
135 GL(dl_profile_map
) = l
;
138 /* This function will get called to fix up the GOT entry indicated by
139 the offset on the stack, and then jump to the resolved address. */
140 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
148 # if !defined PROF && !__BOUNDED_POINTERS__
149 /* We add a declaration of this function here so that in dl-runtime.c
150 the ELF_MACHINE_RUNTIME_TRAMPOLINE macro really can pass the parameters
153 We cannot use this scheme for profiling because the _mcount call
154 destroys the passed register information. */
155 /* GKM FIXME: Fix trampoline to pass bounds so we can do
156 without the `__unbounded' qualifier. */
157 static ElfW(Addr
) fixup (struct link_map
*__unbounded l
, ElfW(Word
) reloc_offset
)
158 __attribute__ ((regparm (2), unused
));
159 static ElfW(Addr
) profile_fixup (struct link_map
*l
, ElfW(Word
) reloc_offset
,
161 __attribute__ ((regparm (3), unused
));
164 /* This code is used in dl-runtime.c to call the `fixup' function
165 and then redirect to the address it returns. */
166 # if !defined PROF && !__BOUNDED_POINTERS__
167 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
169 .globl _dl_runtime_resolve\n\
170 .type _dl_runtime_resolve, @function\n\
172 _dl_runtime_resolve:\n\
173 pushl %eax # Preserve registers otherwise clobbered.\n\
176 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
177 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
178 call fixup # Call resolver.\n\
179 popl %edx # Get register content back.\n\
181 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
182 ret $8 # Jump to function address.\n\
183 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
185 .globl _dl_runtime_profile\n\
186 .type _dl_runtime_profile, @function\n\
188 _dl_runtime_profile:\n\
189 pushl %eax # Preserve registers otherwise clobbered.\n\
192 movl 20(%esp), %ecx # Load return address\n\
193 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
194 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
195 call profile_fixup # Call resolver.\n\
196 popl %edx # Get register content back.\n\
198 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
199 ret $8 # Jump to function address.\n\
200 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
204 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\n\
206 .globl _dl_runtime_resolve\n\
207 .globl _dl_runtime_profile\n\
208 .type _dl_runtime_resolve, @function\n\
209 .type _dl_runtime_profile, @function\n\
211 _dl_runtime_resolve:\n\
212 _dl_runtime_profile:\n\
213 pushl %eax # Preserve registers otherwise clobbered.\n\
216 movl 16(%esp), %edx # Push the arguments for `fixup'\n\
217 movl 12(%esp), %eax\n\
220 call fixup # Call resolver.\n\
221 popl %edx # Pop the parameters\n\
223 popl %edx # Get register content back.\n\
225 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
226 ret $8 # Jump to function address.\n\
227 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
228 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
234 /* Mask identifying addresses reserved for the user program,
235 where the dynamic linker should not map anything. */
236 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
238 /* Initial entry point code for the dynamic linker.
239 The C function `_dl_start' is the real entry point;
240 its return value is the user program's entry point. */
242 #define RTLD_START asm ("\n\
245 0: movl (%esp), %ebx\n\
249 .globl _dl_start_user\n\
251 # Note that _dl_start gets the parameter in %eax.\n\
255 # Save the user entry point address in %edi.\n\
257 # Point %ebx at the GOT.\n\
259 addl $_GLOBAL_OFFSET_TABLE_, %ebx\n\
260 # Store the highest stack address\n\
261 movl __libc_stack_end@GOT(%ebx), %eax\n\
263 # See if we were run as a command with the executable file\n\
264 # name as an extra leading argument.\n\
265 movl _dl_skip_args@GOTOFF(%ebx), %eax\n\
266 # Pop the original argument count.\n\
268 # Adjust the stack pointer to skip _dl_skip_args words.\n\
269 leal (%esp,%eax,4), %esp\n\
270 # Subtract _dl_skip_args from argc.\n\
272 # Push argc back on the stack.\n\
274 # The special initializer gets called with the stack just\n\
275 # as the application's entry point will see it; it can\n\
276 # switch stacks if it moves these contents over.\n\
277 " RTLD_START_SPECIAL_INIT "\n\
278 # Load the parameters again.\n\
279 # (eax, edx, ecx, *--esp) = (_dl_loaded, argc, argv, envp)\n\
280 movl _rtld_local@GOTOFF(%ebx), %eax\n\
281 leal 8(%esp,%edx,4), %esi\n\
282 leal 4(%esp), %ecx\n\
284 # Call the function to run the initializers.\n\
285 call _dl_init_internal@PLT\n\
286 # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
287 leal _dl_fini@GOTOFF(%ebx), %edx\n\
288 # Jump to the user's entry point.\n\
293 #ifndef RTLD_START_SPECIAL_INIT
294 # define RTLD_START_SPECIAL_INIT /* nothing */
297 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
298 TLS variable, so undefined references should not be allowed to
300 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
301 of the main executable's symbols, as for a COPY reloc. */
303 # define elf_machine_type_class(type) \
304 ((((type) == R_386_JMP_SLOT || (type) == R_386_TLS_DTPMOD32 \
305 || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32 \
306 || (type) == R_386_TLS_TPOFF) \
307 * ELF_RTYPE_CLASS_PLT) \
308 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
310 # define elf_machine_type_class(type) \
311 ((((type) == R_386_JMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
312 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
315 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
316 #define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT
318 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
319 Prelinked libraries may use Elf32_Rela though. */
320 #define ELF_MACHINE_PLT_REL 1
322 /* We define an initialization functions. This is called very early in
324 #define DL_PLATFORM_INIT dl_platform_init ()
326 static inline void __attribute__ ((unused
))
327 dl_platform_init (void)
329 if (GL(dl_platform
) != NULL
&& *GL(dl_platform
) == '\0')
330 /* Avoid an empty string which would disturb us. */
331 GL(dl_platform
) = NULL
;
334 static inline Elf32_Addr
335 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
336 const Elf32_Rel
*reloc
,
337 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
339 return *reloc_addr
= value
;
342 /* Return the final value of a plt relocation. */
343 static inline Elf32_Addr
344 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
350 #endif /* !dl_machine_h */
354 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
355 Prelinked libraries may use Elf32_Rela though. */
356 #ifdef RTLD_BOOTSTRAP
357 # define ELF_MACHINE_NO_RELA 1
360 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
361 MAP is the object containing the reloc. */
364 elf_machine_rel (struct link_map
*map
, const Elf32_Rel
*reloc
,
365 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
366 Elf32_Addr
*const reloc_addr
)
368 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
370 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
371 if (__builtin_expect (r_type
== R_386_RELATIVE
, 0))
373 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
374 /* This is defined in rtld.c, but nowhere in the static libc.a;
375 make the reference weak so static programs can still link.
376 This declaration cannot be done when compiling rtld.c
377 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
378 common defn for _dl_rtld_map, which is incompatible with a
379 weak decl in the same file. */
381 weak_extern (_dl_rtld_map
);
383 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
385 *reloc_addr
+= map
->l_addr
;
387 # ifndef RTLD_BOOTSTRAP
388 else if (__builtin_expect (r_type
== R_386_NONE
, 0))
394 const Elf32_Sym
*const refsym
= sym
;
395 #if defined USE_TLS && !defined RTLD_BOOTSTRAP
396 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
397 Elf32_Addr value
= sym
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
399 Elf32_Addr value
= RESOLVE (&sym
, version
, r_type
);
401 # ifndef RTLD_BOOTSTRAP
404 value
+= sym
->st_value
;
415 case R_386_TLS_DTPMOD32
:
416 # ifdef RTLD_BOOTSTRAP
417 /* During startup the dynamic linker is always the module
419 XXX If this relocation is necessary move before RESOLVE
423 /* Get the information from the link map returned by the
426 *reloc_addr
= sym_map
->l_tls_modid
;
429 case R_386_TLS_DTPOFF32
:
430 # ifndef RTLD_BOOTSTRAP
431 /* During relocation all TLS symbols are defined and used.
432 Therefore the offset is already correct. */
434 *reloc_addr
= sym
->st_value
;
437 case R_386_TLS_TPOFF32
:
438 /* The offset is positive, backward from the thread pointer. */
439 # ifdef RTLD_BOOTSTRAP
440 *reloc_addr
+= map
->l_tls_offset
- sym
->st_value
;
442 /* We know the offset of object the symbol is contained in.
443 It is a positive value which will be subtracted from the
444 thread pointer. To get the variable position in the TLS
445 block we subtract the offset from that of the TLS block. */
447 *reloc_addr
+= sym_map
->l_tls_offset
- sym
->st_value
;
450 case R_386_TLS_TPOFF
:
451 /* The offset is negative, forward from the thread pointer. */
452 # ifdef RTLD_BOOTSTRAP
453 *reloc_addr
+= sym
->st_value
- map
->l_tls_offset
;
455 /* We know the offset of object the symbol is contained in.
456 It is a negative value which will be added to the
459 *reloc_addr
+= sym
->st_value
- sym_map
->l_tls_offset
;
464 #ifndef RTLD_BOOTSTRAP
466 *reloc_addr
+= value
;
469 *reloc_addr
+= (value
- (Elf32_Addr
) reloc_addr
);
473 /* This can happen in trace mode if an object could not be
476 if (__builtin_expect (sym
->st_size
> refsym
->st_size
, 0)
477 || (__builtin_expect (sym
->st_size
< refsym
->st_size
, 0)
482 strtab
= (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
484 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
485 rtld_progname
?: "<program name unknown>",
486 strtab
+ refsym
->st_name
);
488 memcpy (reloc_addr
, (void *) value
, MIN (sym
->st_size
,
492 _dl_reloc_bad_type (map
, r_type
, 0);
499 #ifndef RTLD_BOOTSTRAP
501 elf_machine_rela (struct link_map
*map
, const Elf32_Rela
*reloc
,
502 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
503 Elf32_Addr
*const reloc_addr
)
505 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
507 if (ELF32_R_TYPE (reloc
->r_info
) == R_386_RELATIVE
)
508 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
509 else if (r_type
!= R_386_NONE
)
512 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
513 Elf32_Addr value
= sym
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
515 Elf32_Addr value
= RESOLVE (&sym
, version
, ELF32_R_TYPE (reloc
->r_info
));
517 value
+= sym
->st_value
;
520 switch (ELF32_R_TYPE (reloc
->r_info
))
525 *reloc_addr
= value
+ reloc
->r_addend
;
528 *reloc_addr
= (value
+ reloc
->r_addend
- (Elf32_Addr
) reloc_addr
);
532 case R_386_TLS_DTPMOD32
:
533 /* Get the information from the link map returned by the
536 *reloc_addr
= sym_map
->l_tls_modid
;
538 case R_386_TLS_DTPOFF32
:
539 /* During relocation all TLS symbols are defined and used.
540 Therefore the offset is already correct. */
541 *reloc_addr
= (sym
== NULL
? 0 : sym
->st_value
) + reloc
->r_addend
;
543 case R_386_TLS_TPOFF32
:
544 /* The offset is positive, backward from the thread pointer. */
545 /* We know the offset of object the symbol is contained in.
546 It is a positive value which will be subtracted from the
547 thread pointer. To get the variable position in the TLS
548 block we subtract the offset from that of the TLS block. */
550 = (sym
== NULL
? 0 : sym_map
->l_tls_offset
- sym
->st_value
)
553 case R_386_TLS_TPOFF
:
554 /* The offset is negative, forward from the thread pointer. */
555 /* We know the offset of object the symbol is contained in.
556 It is a negative value which will be added to the
559 = (sym
== NULL
? 0 : sym
->st_value
- sym_map
->l_tls_offset
)
564 /* We add these checks in the version to relocate ld.so only
565 if we are still debugging. */
566 _dl_reloc_bad_type (map
, r_type
, 0);
574 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
575 Elf32_Addr
*const reloc_addr
)
577 assert (ELF32_R_TYPE (reloc
->r_info
) == R_386_RELATIVE
);
578 *reloc_addr
+= l_addr
;
581 #ifndef RTLD_BOOTSTRAP
583 elf_machine_rela_relative (Elf32_Addr l_addr
, const Elf32_Rela
*reloc
,
584 Elf32_Addr
*const reloc_addr
)
586 *reloc_addr
= l_addr
+ reloc
->r_addend
;
591 elf_machine_lazy_rel (struct link_map
*map
,
592 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
)
594 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
595 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
596 /* Check for unexpected PLT reloc type. */
597 if (__builtin_expect (r_type
== R_386_JMP_SLOT
, 1))
599 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
600 *reloc_addr
+= l_addr
;
602 *reloc_addr
= (map
->l_mach
.plt
603 + (((Elf32_Addr
) reloc_addr
) - map
->l_mach
.gotplt
) * 4);
606 _dl_reloc_bad_type (map
, r_type
, 1);
609 #ifndef RTLD_BOOTSTRAP
612 elf_machine_lazy_rela (struct link_map
*map
,
613 Elf32_Addr l_addr
, const Elf32_Rela
*reloc
)