1 /* Machine-dependent ELF dynamic relocation inline functions. i386 version.
2 Copyright (C) 1995-2002, 2003, 2004 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, always_inline))
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 (GLRO(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 #define ARCH_FIXUP_ATTRIBUTE __attribute__ ((regparm (3), unused))
159 static ElfW(Addr) fixup (struct link_map *__unbounded l,
160 ElfW(Word) reloc_offset)
161 ARCH_FIXUP_ATTRIBUTE;
162 static ElfW(Addr) profile_fixup (struct link_map *l, ElfW(Word) reloc_offset,
164 ARCH_FIXUP_ATTRIBUTE;
167 /* This code is used in dl-runtime.c to call the `fixup' function
168 and then redirect to the address it returns. */
169 # if !defined PROF && !__BOUNDED_POINTERS__
170 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
172 .globl _dl_runtime_resolve\n\
173 .type _dl_runtime_resolve, @function\n\
176 _dl_runtime_resolve:\n\
177 " CFI_ADJUST_CFA_OFFSET (8) "\n\
178 pushl %eax # Preserve registers otherwise clobbered.\n\
179 " CFI_ADJUST_CFA_OFFSET (4) "\n\
181 " CFI_ADJUST_CFA_OFFSET (4) "\n\
183 " CFI_ADJUST_CFA_OFFSET (4) "\n\
184 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
185 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
186 call fixup # Call resolver.\n\
187 popl %edx # Get register content back.\n\
188 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
190 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
191 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
192 ret $8 # Jump to function address.\n\
194 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
196 .globl _dl_runtime_profile\n\
197 .type _dl_runtime_profile, @function\n\
200 _dl_runtime_profile:\n\
201 " CFI_ADJUST_CFA_OFFSET (8) "\n\
202 pushl %eax # Preserve registers otherwise clobbered.\n\
203 " CFI_ADJUST_CFA_OFFSET (4) "\n\
205 " CFI_ADJUST_CFA_OFFSET (4) "\n\
207 " CFI_ADJUST_CFA_OFFSET (4) "\n\
208 movl 20(%esp), %ecx # Load return address\n\
209 movl 16(%esp), %edx # Copy args pushed by PLT in register. Note\n\
210 movl 12(%esp), %eax # that `fixup' takes its parameters in regs.\n\
211 call profile_fixup # Call resolver.\n\
212 popl %edx # Get register content back.\n\
213 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
215 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
216 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
217 ret $8 # Jump to function address.\n\
219 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
223 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\n\
225 .globl _dl_runtime_resolve\n\
226 .globl _dl_runtime_profile\n\
227 .type _dl_runtime_resolve, @function\n\
228 .type _dl_runtime_profile, @function\n\
231 _dl_runtime_resolve:\n\
232 _dl_runtime_profile:\n\
233 " CFI_ADJUST_CFA_OFFSET (8) "\n\
234 pushl %eax # Preserve registers otherwise clobbered.\n\
235 " CFI_ADJUST_CFA_OFFSET (4) "\n\
237 " CFI_ADJUST_CFA_OFFSET (4) "\n\
239 " CFI_ADJUST_CFA_OFFSET (4) "\n\
240 movl 16(%esp), %edx # Push the arguments for `fixup'\n\
241 movl 12(%esp), %eax\n\
243 " CFI_ADJUST_CFA_OFFSET (4) "\n\
245 " CFI_ADJUST_CFA_OFFSET (4) "\n\
246 call fixup # Call resolver.\n\
247 popl %edx # Pop the parameters\n\
248 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
250 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
251 popl %edx # Get register content back.\n\
252 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
254 " CFI_ADJUST_CFA_OFFSET (-4) "\n\
255 xchgl %eax, (%esp) # Get %eax contents end store function address.\n\
256 ret $8 # Jump to function address.\n\
258 .size _dl_runtime_resolve, .-_dl_runtime_resolve\n\
259 .size _dl_runtime_profile, .-_dl_runtime_profile\n\
265 /* Mask identifying addresses reserved for the user program,
266 where the dynamic linker should not map anything. */
267 #define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
269 /* Initial entry point code for the dynamic linker.
270 The C function `_dl_start' is the real entry point;
271 its return value is the user program's entry point. */
273 #define RTLD_START asm ("\n\
276 0: movl (%esp), %ebx\n\
280 .globl _dl_start_user\n\
282 # Note that _dl_start gets the parameter in %eax.\n\
286 # Save the user entry point address in %edi.\n\
288 # Point %ebx at the GOT.\n\
290 addl $_GLOBAL_OFFSET_TABLE_, %ebx\n\
291 # See if we were run as a command with the executable file\n\
292 # name as an extra leading argument.\n\
293 movl _dl_skip_args@GOTOFF(%ebx), %eax\n\
294 # Pop the original argument count.\n\
296 # Adjust the stack pointer to skip _dl_skip_args words.\n\
297 leal (%esp,%eax,4), %esp\n\
298 # Subtract _dl_skip_args from argc.\n\
300 # Push argc back on the stack.\n\
302 # The special initializer gets called with the stack just\n\
303 # as the application's entry point will see it; it can\n\
304 # switch stacks if it moves these contents over.\n\
305 " RTLD_START_SPECIAL_INIT "\n\
306 # Load the parameters again.\n\
307 # (eax, edx, ecx, *--esp) = (_dl_loaded, argc, argv, envp)\n\
308 movl _rtld_local@GOTOFF(%ebx), %eax\n\
309 leal 8(%esp,%edx,4), %esi\n\
310 leal 4(%esp), %ecx\n\
312 # Call the function to run the initializers.\n\
313 call _dl_init_internal@PLT\n\
314 # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
315 leal _dl_fini@GOTOFF(%ebx), %edx\n\
316 # Jump to the user's entry point.\n\
321 #ifndef RTLD_START_SPECIAL_INIT
322 # define RTLD_START_SPECIAL_INIT /* nothing */
325 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
326 TLS variable, so undefined references should not be allowed to
328 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
329 of the main executable's symbols, as for a COPY reloc. */
330 #if defined USE_TLS && (!defined RTLD_BOOTSTRAP || USE___THREAD)
331 # define elf_machine_type_class(type) \
332 ((((type) == R_386_JMP_SLOT || (type) == R_386_TLS_DTPMOD32 \
333 || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32 \
334 || (type) == R_386_TLS_TPOFF) \
335 * ELF_RTYPE_CLASS_PLT) \
336 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
338 # define elf_machine_type_class(type) \
339 ((((type) == R_386_JMP_SLOT) * ELF_RTYPE_CLASS_PLT) \
340 | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY))
343 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
344 #define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT
346 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
347 Prelinked libraries may use Elf32_Rela though. */
348 #define ELF_MACHINE_PLT_REL 1
350 /* We define an initialization functions. This is called very early in
352 #define DL_PLATFORM_INIT dl_platform_init ()
354 static inline void __attribute__ ((unused))
355 dl_platform_init (void)
357 if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
358 /* Avoid an empty string which would disturb us. */
359 GLRO(dl_platform) = NULL;
362 static inline Elf32_Addr
363 elf_machine_fixup_plt (struct link_map *map, lookup_t t,
364 const Elf32_Rel *reloc,
365 Elf32_Addr *reloc_addr, Elf32_Addr value)
367 return *reloc_addr = value;
370 /* Return the final value of a plt relocation. */
371 static inline Elf32_Addr
372 elf_machine_plt_value (struct link_map *map, const Elf32_Rel *reloc,
378 #endif /* !dl_machine_h */
382 /* The i386 never uses Elf32_Rela relocations for the dynamic linker.
383 Prelinked libraries may use Elf32_Rela though. */
384 #ifdef RTLD_BOOTSTRAP
385 # define ELF_MACHINE_NO_RELA 1
388 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
389 MAP is the object containing the reloc. */
392 elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
393 const Elf32_Sym *sym, const struct r_found_version *version,
394 void *const reloc_addr_arg)
396 Elf32_Addr *const reloc_addr = reloc_addr_arg;
397 const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
399 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
400 if (__builtin_expect (r_type == R_386_RELATIVE, 0))
402 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
403 /* This is defined in rtld.c, but nowhere in the static libc.a;
404 make the reference weak so static programs can still link.
405 This declaration cannot be done when compiling rtld.c
406 (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
407 common defn for _dl_rtld_map, which is incompatible with a
408 weak decl in the same file. */
410 weak_extern (_dl_rtld_map);
412 if (map != &GL(dl_rtld_map)) /* Already done in rtld itself. */
414 *reloc_addr += map->l_addr;
416 # ifndef RTLD_BOOTSTRAP
417 else if (__builtin_expect (r_type == R_386_NONE, 0))
421 #endif /* !RTLD_BOOTSTRAP and have no -z combreloc */
423 const Elf32_Sym *const refsym = sym;
424 #if defined USE_TLS && !defined RTLD_BOOTSTRAP
425 struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
426 Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
428 Elf32_Addr value = RESOLVE (&sym, version, r_type);
430 # ifndef RTLD_BOOTSTRAP
433 value += sym->st_value;
434 #endif /* use TLS and !RTLD_BOOTSTRAP */
443 #if defined USE_TLS && (!defined RTLD_BOOTSTRAP || USE___THREAD)
444 case R_386_TLS_DTPMOD32:
445 # ifdef RTLD_BOOTSTRAP
446 /* During startup the dynamic linker is always the module
448 XXX If this relocation is necessary move before RESOLVE
452 /* Get the information from the link map returned by the
455 *reloc_addr = sym_map->l_tls_modid;
458 case R_386_TLS_DTPOFF32:
459 # ifndef RTLD_BOOTSTRAP
460 /* During relocation all TLS symbols are defined and used.
461 Therefore the offset is already correct. */
463 *reloc_addr = sym->st_value;
466 case R_386_TLS_TPOFF32:
467 /* The offset is positive, backward from the thread pointer. */
468 # ifdef RTLD_BOOTSTRAP
469 *reloc_addr += map->l_tls_offset - sym->st_value;
471 /* We know the offset of object the symbol is contained in.
472 It is a positive value which will be subtracted from the
473 thread pointer. To get the variable position in the TLS
474 block we subtract the offset from that of the TLS block. */
477 CHECK_STATIC_TLS (map, sym_map);
478 *reloc_addr += sym_map->l_tls_offset - sym->st_value;
482 case R_386_TLS_TPOFF:
483 /* The offset is negative, forward from the thread pointer. */
484 # ifdef RTLD_BOOTSTRAP
485 *reloc_addr += sym->st_value - map->l_tls_offset;
487 /* We know the offset of object the symbol is contained in.
488 It is a negative value which will be added to the
492 CHECK_STATIC_TLS (map, sym_map);
493 *reloc_addr += sym->st_value - sym_map->l_tls_offset;
499 #ifndef RTLD_BOOTSTRAP
501 *reloc_addr += value;
504 *reloc_addr += (value - (Elf32_Addr) reloc_addr);
508 /* This can happen in trace mode if an object could not be
511 if (__builtin_expect (sym->st_size > refsym->st_size, 0)
512 || (__builtin_expect (sym->st_size < refsym->st_size, 0)
513 && GLRO(dl_verbose)))
517 strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
519 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
520 rtld_progname ?: "<program name unknown>",
521 strtab + refsym->st_name);
523 memcpy (reloc_addr_arg, (void *) value,
524 MIN (sym->st_size, refsym->st_size));
527 _dl_reloc_bad_type (map, r_type, 0);
529 #endif /* !RTLD_BOOTSTRAP */
534 #ifndef RTLD_BOOTSTRAP
536 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
537 const Elf32_Sym *sym, const struct r_found_version *version,
538 void *const reloc_addr_arg)
540 Elf32_Addr *const reloc_addr = reloc_addr_arg;
541 const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
543 if (ELF32_R_TYPE (reloc->r_info) == R_386_RELATIVE)
544 *reloc_addr = map->l_addr + reloc->r_addend;
545 else if (r_type != R_386_NONE)
547 # ifndef RESOLVE_CONFLICT_FIND_MAP
548 const Elf32_Sym *const refsym = sym;
551 struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
552 Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
554 Elf32_Addr value = RESOLVE (&sym, version, r_type);
556 value += sym->st_value;
559 switch (ELF32_R_TYPE (reloc->r_info))
564 *reloc_addr = value + reloc->r_addend;
566 # ifndef RESOLVE_CONFLICT_FIND_MAP
567 /* Not needed for dl-conflict.c. */
569 *reloc_addr = (value + reloc->r_addend - (Elf32_Addr) reloc_addr);
573 case R_386_TLS_DTPMOD32:
574 /* Get the information from the link map returned by the
577 *reloc_addr = sym_map->l_tls_modid;
579 case R_386_TLS_DTPOFF32:
580 /* During relocation all TLS symbols are defined and used.
581 Therefore the offset is already correct. */
582 *reloc_addr = (sym == NULL ? 0 : sym->st_value) + reloc->r_addend;
584 case R_386_TLS_TPOFF32:
585 /* The offset is positive, backward from the thread pointer. */
586 /* We know the offset of object the symbol is contained in.
587 It is a positive value which will be subtracted from the
588 thread pointer. To get the variable position in the TLS
589 block we subtract the offset from that of the TLS block. */
590 CHECK_STATIC_TLS (map, sym_map);
592 = (sym == NULL ? 0 : sym_map->l_tls_offset - sym->st_value)
595 case R_386_TLS_TPOFF:
596 /* The offset is negative, forward from the thread pointer. */
597 /* We know the offset of object the symbol is contained in.
598 It is a negative value which will be added to the
600 CHECK_STATIC_TLS (map, sym_map);
602 = (sym == NULL ? 0 : sym->st_value - sym_map->l_tls_offset)
605 # endif /* use TLS */
608 /* This can happen in trace mode if an object could not be
611 if (__builtin_expect (sym->st_size > refsym->st_size, 0)
612 || (__builtin_expect (sym->st_size < refsym->st_size, 0)
613 && GLRO(dl_verbose)))
617 strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
619 %s: Symbol `%s' has different size in shared object, consider re-linking\n",
620 rtld_progname ?: "<program name unknown>",
621 strtab + refsym->st_name);
623 memcpy (reloc_addr_arg, (void *) value,
624 MIN (sym->st_size, refsym->st_size));
626 # endif /* !RESOLVE_CONFLICT_FIND_MAP */
628 /* We add these checks in the version to relocate ld.so only
629 if we are still debugging. */
630 _dl_reloc_bad_type (map, r_type, 0);
635 #endif /* !RTLD_BOOTSTRAP */
638 elf_machine_rel_relative (Elf32_Addr l_addr, const Elf32_Rel *reloc,
639 void *const reloc_addr_arg)
641 Elf32_Addr *const reloc_addr = reloc_addr_arg;
642 assert (ELF32_R_TYPE (reloc->r_info) == R_386_RELATIVE);
643 *reloc_addr += l_addr;
646 #ifndef RTLD_BOOTSTRAP
648 elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
649 void *const reloc_addr_arg)
651 Elf32_Addr *const reloc_addr = reloc_addr_arg;
652 *reloc_addr = l_addr + reloc->r_addend;
654 #endif /* !RTLD_BOOTSTRAP */
657 elf_machine_lazy_rel (struct link_map *map,
658 Elf32_Addr l_addr, const Elf32_Rel *reloc)
660 Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
661 const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
662 /* Check for unexpected PLT reloc type. */
663 if (__builtin_expect (r_type == R_386_JMP_SLOT, 1))
665 if (__builtin_expect (map->l_mach.plt, 0) == 0)
666 *reloc_addr += l_addr;
668 *reloc_addr = (map->l_mach.plt
669 + (((Elf32_Addr) reloc_addr) - map->l_mach.gotplt) * 4);
672 _dl_reloc_bad_type (map, r_type, 1);
675 #ifndef RTLD_BOOTSTRAP
678 elf_machine_lazy_rela (struct link_map *map,
679 Elf32_Addr l_addr, const Elf32_Rela *reloc)
683 #endif /* !RTLD_BOOTSTRAP */