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 #if !defined PROF && !__BOUNDED_POINTERS__
96 /* We add a declaration of this function here so that in dl-runtime.c
97 the ELF_MACHINE_RUNTIME_TRAMPOLINE macro really can pass the parameters
100 We cannot use this scheme for profiling because the _mcount call
101 destroys the passed register information. */
102 /* GKM FIXME: Fix trampoline to pass bounds so we can do
103 without the `__unbounded' qualifier. */
104 static ElfW(Addr
) fixup (struct link_map
*__unbounded l
, ElfW(Word
) reloc_offset
)
105 __attribute__ ((regparm (2), unused
));
106 static ElfW(Addr
) profile_fixup (struct link_map
*l
, ElfW(Word
) reloc_offset
,
108 __attribute__ ((regparm (3), unused
));
111 /* Set up the loaded object described by L so its unrelocated PLT
112 entries will jump to the on-demand fixup code in dl-runtime.c. */
114 static inline int __attribute__ ((unused
))
115 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
118 extern void _dl_runtime_resolve (Elf32_Word
) attribute_hidden
;
119 extern void _dl_runtime_profile (Elf32_Word
) attribute_hidden
;
121 if (l
->l_info
[DT_JMPREL
] && lazy
)
123 /* The GOT entries for functions in the PLT have not yet been filled
124 in. Their initial contents will arrange when called to push an
125 offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
126 and then jump to _GLOBAL_OFFSET_TABLE[2]. */
127 got
= (Elf32_Addr
*) D_PTR (l
, l_info
[DT_PLTGOT
]);
128 /* If a library is prelinked but we have to relocate anyway,
129 we have to be able to undo the prelinking of .got.plt.
130 The prelinker saved us here address of .plt + 0x16. */
133 l
->l_mach
.plt
= got
[1] + l
->l_addr
;
134 l
->l_mach
.gotplt
= (Elf32_Addr
) &got
[3];
136 got
[1] = (Elf32_Addr
) l
; /* Identify this shared object. */
138 /* The got[2] entry contains the address of a function which gets
139 called to get the address of a so far unresolved function and
140 jump to it. The profiling extension of the dynamic linker allows
141 to intercept the calls to collect information. In this case we
142 don't store the address in the GOT so that all future calls also
143 end in this function. */
144 if (__builtin_expect (profile
, 0))
146 got
[2] = (Elf32_Addr
) &_dl_runtime_profile
;
148 if (_dl_name_match_p (GL(dl_profile
), l
))
149 /* This is the object we are looking for. Say that we really
150 want profiling and the timers are started. */
151 GL(dl_profile_map
) = l
;
154 /* This function will get called to fix up the GOT entry indicated by
155 the offset on the stack, and then jump to the resolved address. */
156 got
[2] = (Elf32_Addr
) &_dl_runtime_resolve
;
162 /* This code is used in dl-runtime.c to call the `fixup' function
163 and then redirect to the address it returns. */
164 #if !defined PROF && !__BOUNDED_POINTERS__
165 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
167 .globl _dl_runtime_resolve\n\
168 .type _dl_runtime_resolve, @function\n\
170 _dl_runtime_resolve:\n\
171 pushl %eax # Preserve registers otherwise clobbered.\n\
174 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
175 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
176 call fixup # Call resolver.\n\
177 popl %edx # Get register content back.\n\
179 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
180 ret $8 # Jump to function address.\n\
181 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
183 .globl _dl_runtime_profile\n\
184 .type _dl_runtime_profile, @function\n\
186 _dl_runtime_profile:\n\
187 pushl %eax # Preserve registers otherwise clobbered.\n\
190 movl 20(%esp), %ecx # Load return address\n\
191 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
192 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
193 call profile_fixup # Call resolver.\n\
194 popl %edx # Get register content back.\n\
196 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
197 ret $8 # Jump to function address.\n\
198 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
202 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\n\
204 .globl _dl_runtime_resolve\n\
205 .globl _dl_runtime_profile\n\
206 .type _dl_runtime_resolve, @function\n\
207 .type _dl_runtime_profile, @function\n\
209 _dl_runtime_resolve:\n\
210 _dl_runtime_profile:\n\
211 pushl %eax # Preserve registers otherwise clobbered.\n\
214 movl 16(%esp), %edx # Push the arguments for `fixup'\n\
215 movl 12(%esp), %eax\n\
218 call fixup # Call resolver.\n\
219 popl %edx # Pop the parameters\n\
221 popl %edx # Get register content back.\n\
223 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
224 ret $8 # Jump to function address.\n\
225 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
226 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
231 /* Mask identifying addresses reserved for the user program,
232 where the dynamic linker should not map anything. */
233 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
235 /* Initial entry point code for the dynamic linker.
236 The C function `_dl_start' is the real entry point;
237 its return value is the user program's entry point. */
239 #define RTLD_START asm ("\n\
242 0: movl (%esp), %ebx\n\
246 .globl _dl_start_user\n\
248 # Note that _dl_start gets the parameter in %eax.\n\
252 # Save the user entry point address in %edi.\n\
254 # Point %ebx at the GOT.\n\
256 addl $_GLOBAL_OFFSET_TABLE_, %ebx\n\
257 # Store the highest stack address\n\
258 movl __libc_stack_end@GOT(%ebx), %eax\n\
260 # See if we were run as a command with the executable file\n\
261 # name as an extra leading argument.\n\
262 movl _dl_skip_args@GOTOFF(%ebx), %eax\n\
263 # Pop the original argument count.\n\
265 # Adjust the stack pointer to skip _dl_skip_args words.\n\
266 leal (%esp,%eax,4), %esp\n\
267 # Subtract _dl_skip_args from argc.\n\
269 # Push argc back on the stack.\n\
271 # The special initializer gets called with the stack just\n\
272 # as the application's entry point will see it; it can\n\
273 # switch stacks if it moves these contents over.\n\
274 " RTLD_START_SPECIAL_INIT "\n\
275 # Load the parameters again.\n\
276 # (eax, edx, ecx, *--esp) = (_dl_loaded, argc, argv, envp)\n\
277 movl _rtld_local@GOTOFF(%ebx), %eax\n\
278 leal 8(%esp,%edx,4), %esi\n\
279 leal 4(%esp), %ecx\n\
281 # Call the function to run the initializers.\n\
282 call _dl_init_internal@PLT\n\
283 # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
284 leal _dl_fini@GOTOFF(%ebx), %edx\n\
285 # Jump to the user's entry point.\n\
290 #ifndef RTLD_START_SPECIAL_INIT
291 # define RTLD_START_SPECIAL_INIT /* nothing */
294 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
295 TLS variable, so undefined references should not be allowed to
297 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
298 of the main executable's symbols, as for a COPY reloc. */
300 # define elf_machine_type_class(type) \
301 ((((type) == R_386_JMP_SLOT || (type) == R_386_TLS_DTPMOD32 \
302 || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32) \
303 * ELF_RTYPE_CLASS_PLT) \
304 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
306 # define elf_machine_type_class(type) \
307 ((((type) == R_386_JMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
308 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
311 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
312 #define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT
314 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
315 Prelinked libraries may use Elf32_Rela though. */
316 #define ELF_MACHINE_PLT_REL 1
318 /* We define an initialization functions. This is called very early in
320 #define DL_PLATFORM_INIT dl_platform_init ()
322 static inline void __attribute__ ((unused
))
323 dl_platform_init (void)
325 if (GL(dl_platform
) != NULL
&& *GL(dl_platform
) == '\0')
326 /* Avoid an empty string which would disturb us. */
327 GL(dl_platform
) = NULL
;
330 static inline Elf32_Addr
331 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
332 const Elf32_Rel
*reloc
,
333 Elf32_Addr
*reloc_addr
, Elf32_Addr value
)
335 return *reloc_addr
= value
;
338 /* Return the final value of a plt relocation. */
339 static inline Elf32_Addr
340 elf_machine_plt_value (struct link_map
*map
, const Elf32_Rel
*reloc
,
346 #endif /* !dl_machine_h */
350 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
351 Prelinked libraries may use Elf32_Rela though. */
352 #ifdef RTLD_BOOTSTRAP
353 # define ELF_MACHINE_NO_RELA 1
356 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
357 MAP is the object containing the reloc. */
360 elf_machine_rel (struct link_map
*map
, const Elf32_Rel
*reloc
,
361 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
362 Elf32_Addr
*const reloc_addr
)
364 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
366 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
367 if (__builtin_expect (r_type
== R_386_RELATIVE
, 0))
369 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
370 /* This is defined in rtld.c, but nowhere in the static libc.a;
371 make the reference weak so static programs can still link.
372 This declaration cannot be done when compiling rtld.c
373 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
374 common defn for _dl_rtld_map, which is incompatible with a
375 weak decl in the same file. */
377 weak_extern (_dl_rtld_map
);
379 if (map
!= &GL(dl_rtld_map
)) /* Already done in rtld itself. */
381 *reloc_addr
+= map
->l_addr
;
383 # ifndef RTLD_BOOTSTRAP
384 else if (__builtin_expect (r_type
== R_386_NONE
, 0))
390 const Elf32_Sym
*const refsym
= sym
;
391 #if defined USE_TLS && !defined RTLD_BOOTSTRAP
392 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
393 Elf32_Addr value
= sym
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
395 Elf32_Addr value
= RESOLVE (&sym
, version
, r_type
);
397 # ifndef RTLD_BOOTSTRAP
400 value
+= sym
->st_value
;
410 /* XXX Remove TLS relocations which are not needed. */
413 case R_386_TLS_DTPMOD32
:
414 # ifdef RTLD_BOOTSTRAP
415 /* During startup the dynamic linker is always the module
417 XXX If this relocation is necessary move before RESOLVE
421 /* Get the information from the link map returned by the
424 *reloc_addr
= sym_map
->l_tls_modid
;
427 case R_386_TLS_DTPOFF32
:
428 # ifndef RTLD_BOOTSTRAP
429 /* During relocation all TLS symbols are defined and used.
430 Therefore the offset is already correct. */
432 *reloc_addr
+= sym
->st_value
;
435 case R_386_TLS_TPOFF32
:
436 /* The offset is positive, backward from the thread pointer. */
437 # ifdef RTLD_BOOTSTRAP
438 *reloc_addr
+= map
->l_tls_offset
- sym
->st_value
;
440 /* We know the offset of object the symbol is contained in.
441 It is a positive value which will be subtracted from the
442 thread pointer. To get the variable position in the TLS
443 block we subtract the offset from that of the TLS block. */
444 if (sym_map
!= NULL
&& sym
!= NULL
)
445 *reloc_addr
+= sym_map
->l_tls_offset
- sym
->st_value
;
450 #ifndef RTLD_BOOTSTRAP
452 *reloc_addr
+= value
;
455 *reloc_addr
+= (value
- (Elf32_Addr
) reloc_addr
);
459 /* This can happen in trace mode if an object could not be
462 if (__builtin_expect (sym
->st_size
> refsym
->st_size
, 0)
463 || (__builtin_expect (sym
->st_size
< refsym
->st_size
, 0)
468 strtab
= (const char *) D_PTR (map
, l_info
[DT_STRTAB
]);
470 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
471 rtld_progname
?: "<program name unknown>",
472 strtab
+ refsym
->st_name
);
474 memcpy (reloc_addr
, (void *) value
, MIN (sym
->st_size
,
478 _dl_reloc_bad_type (map
, r_type
, 0);
485 #ifndef RTLD_BOOTSTRAP
487 elf_machine_rela (struct link_map
*map
, const Elf32_Rela
*reloc
,
488 const Elf32_Sym
*sym
, const struct r_found_version
*version
,
489 Elf32_Addr
*const reloc_addr
)
491 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
493 if (ELF32_R_TYPE (reloc
->r_info
) == R_386_RELATIVE
)
494 *reloc_addr
= map
->l_addr
+ reloc
->r_addend
;
495 else if (r_type
!= R_386_NONE
)
498 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
499 Elf32_Addr value
= sym
== NULL
? 0 : sym_map
->l_addr
+ sym
->st_value
;
501 Elf32_Addr value
= RESOLVE (&sym
, version
, ELF32_R_TYPE (reloc
->r_info
));
503 value
+= sym
->st_value
;
506 switch (ELF32_R_TYPE (reloc
->r_info
))
511 *reloc_addr
= value
+ reloc
->r_addend
;
514 *reloc_addr
= (value
+ reloc
->r_addend
- (Elf32_Addr
) reloc_addr
);
516 /* XXX Do we have to handle the TLS relocation here? */
518 /* We add these checks in the version to relocate ld.so only
519 if we are still debugging. */
520 _dl_reloc_bad_type (map
, r_type
, 0);
528 elf_machine_rel_relative (Elf32_Addr l_addr
, const Elf32_Rel
*reloc
,
529 Elf32_Addr
*const reloc_addr
)
531 assert (ELF32_R_TYPE (reloc
->r_info
) == R_386_RELATIVE
);
532 *reloc_addr
+= l_addr
;
535 #ifndef RTLD_BOOTSTRAP
537 elf_machine_rela_relative (Elf32_Addr l_addr
, const Elf32_Rela
*reloc
,
538 Elf32_Addr
*const reloc_addr
)
540 *reloc_addr
= l_addr
+ reloc
->r_addend
;
545 elf_machine_lazy_rel (struct link_map
*map
,
546 Elf32_Addr l_addr
, const Elf32_Rel
*reloc
)
548 Elf32_Addr
*const reloc_addr
= (void *) (l_addr
+ reloc
->r_offset
);
549 const unsigned int r_type
= ELF32_R_TYPE (reloc
->r_info
);
550 /* Check for unexpected PLT reloc type. */
551 if (__builtin_expect (r_type
== R_386_JMP_SLOT
, 1))
553 if (__builtin_expect (map
->l_mach
.plt
, 0) == 0)
554 *reloc_addr
+= l_addr
;
556 *reloc_addr
= (map
->l_mach
.plt
557 + (((Elf32_Addr
) reloc_addr
) - map
->l_mach
.gotplt
) * 4);
560 _dl_reloc_bad_type (map
, r_type
, 1);
563 #ifndef RTLD_BOOTSTRAP
566 elf_machine_lazy_rela (struct link_map
*map
,
567 Elf32_Addr l_addr
, const Elf32_Rela
*reloc
)