1 /* On-demand PLT fixup for shared objects.
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
20 #define IN_DL_RUNTIME 1 /* This can be tested in dl-machine.h. */
26 #include "dynamic-link.h"
28 #if (!defined ELF_MACHINE_NO_RELA && !defined ELF_MACHINE_PLT_REL) \
30 # define PLTREL ElfW(Rela)
32 # define PLTREL ElfW(Rel)
36 # define VERSYMIDX(sym) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (sym))
40 /* This function is called through a special trampoline from the PLT the
41 first time each PLT entry is called. We must perform the relocation
42 specified in the PLT of the given shared object, and return the resolved
43 function address to the trampoline, which will restart the original call
44 to that address. Future calls will bounce directly from the PLT to the
47 #ifndef ELF_MACHINE_NO_PLT
49 __attribute ((used
, noinline
))
51 # ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
52 ELF_MACHINE_RUNTIME_FIXUP_ARGS
,
54 /* GKM FIXME: Fix trampoline to pass bounds so we can do
55 without the `__unbounded' qualifier. */
56 struct link_map
*__unbounded l
, ElfW(Word
) reloc_offset
)
58 const ElfW(Sym
) *const symtab
59 = (const void *) D_PTR (l
, l_info
[DT_SYMTAB
]);
60 const char *strtab
= (const void *) D_PTR (l
, l_info
[DT_STRTAB
]);
62 const PLTREL
*const reloc
63 = (const void *) (D_PTR (l
, l_info
[DT_JMPREL
]) + reloc_offset
);
64 const ElfW(Sym
) *sym
= &symtab
[ELFW(R_SYM
) (reloc
->r_info
)];
65 void *const rel_addr
= (void *)(l
->l_addr
+ reloc
->r_offset
);
69 /* Sanity check that we're really looking at a PLT relocation. */
70 assert (ELFW(R_TYPE
)(reloc
->r_info
) == ELF_MACHINE_JMP_SLOT
);
72 /* Look up the target symbol. If the normal lookup rules are not
73 used don't look in the global scope. */
74 if (__builtin_expect (ELFW(ST_VISIBILITY
) (sym
->st_other
), 0) == 0)
76 switch (l
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
80 const ElfW(Half
) *vernum
=
81 (const void *) D_PTR (l
, l_info
[VERSYMIDX (DT_VERSYM
)]);
82 ElfW(Half
) ndx
= vernum
[ELFW(R_SYM
) (reloc
->r_info
)] & 0x7fff;
83 const struct r_found_version
*version
= &l
->l_versions
[ndx
];
85 if (version
->hash
!= 0)
87 result
= INTUSE(_dl_lookup_versioned_symbol
) (strtab
97 result
= INTUSE(_dl_lookup_symbol
) (strtab
+ sym
->st_name
, l
, &sym
,
98 l
->l_scope
, ELF_RTYPE_CLASS_PLT
,
99 DL_LOOKUP_ADD_DEPENDENCY
);
102 /* Currently result contains the base load address (or link map)
103 of the object that defines sym. Now add in the symbol
105 value
= (sym
? LOOKUP_VALUE_ADDRESS (result
) + sym
->st_value
: 0);
109 /* We already found the symbol. The module (and therefore its load
110 address) is also known. */
111 value
= l
->l_addr
+ sym
->st_value
;
112 #ifdef DL_LOOKUP_RETURNS_MAP
117 /* And now perhaps the relocation addend. */
118 value
= elf_machine_plt_value (l
, reloc
, value
);
120 /* Finally, fix up the plt itself. */
121 if (__builtin_expect (GL(dl_bind_not
), 0))
124 return elf_machine_fixup_plt (l
, result
, reloc
, rel_addr
, value
);
128 #if !defined PROF && !defined ELF_MACHINE_NO_PLT && !__BOUNDED_POINTERS__
131 __attribute ((used
, noinline
))
133 #ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
134 ELF_MACHINE_RUNTIME_FIXUP_ARGS
,
136 struct link_map
*l
, ElfW(Word
) reloc_offset
, ElfW(Addr
) retaddr
)
138 void (*mcount_fct
) (ElfW(Addr
), ElfW(Addr
)) = INTUSE(_dl_mcount
);
143 /* This is the address in the array where we store the result of previous
145 resultp
= &l
->l_reloc_result
[reloc_offset
/ sizeof (PLTREL
)];
150 /* This is the first time we have to relocate this object. */
151 const ElfW(Sym
) *const symtab
152 = (const void *) D_PTR (l
, l_info
[DT_SYMTAB
]);
153 const char *strtab
= (const void *) D_PTR (l
, l_info
[DT_STRTAB
]);
155 const PLTREL
*const reloc
156 = (const void *) (D_PTR (l
, l_info
[DT_JMPREL
]) + reloc_offset
);
157 const ElfW(Sym
) *sym
= &symtab
[ELFW(R_SYM
) (reloc
->r_info
)];
159 /* Sanity check that we're really looking at a PLT relocation. */
160 assert (ELFW(R_TYPE
)(reloc
->r_info
) == ELF_MACHINE_JMP_SLOT
);
162 /* Look up the target symbol. If the symbol is marked STV_PROTECTED
163 don't look in the global scope. */
164 if (__builtin_expect (ELFW(ST_VISIBILITY
) (sym
->st_other
), 0) == 0)
166 switch (l
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
170 const ElfW(Half
) *vernum
=
171 (const void *) D_PTR (l
,l_info
[VERSYMIDX (DT_VERSYM
)]);
172 ElfW(Half
) ndx
= vernum
[ELFW(R_SYM
) (reloc
->r_info
)] & 0x7fff;
173 const struct r_found_version
*version
= &l
->l_versions
[ndx
];
175 if (version
->hash
!= 0)
177 result
= INTUSE(_dl_lookup_versioned_symbol
) (strtab
188 result
= INTUSE(_dl_lookup_symbol
) (strtab
+ sym
->st_name
, l
,
191 DL_LOOKUP_ADD_DEPENDENCY
);
194 /* Currently result contains the base load address (or link map)
195 of the object that defines sym. Now add in the symbol
197 value
= (sym
? LOOKUP_VALUE_ADDRESS (result
) + sym
->st_value
: 0);
201 /* We already found the symbol. The module (and therefore its load
202 address) is also known. */
203 value
= l
->l_addr
+ sym
->st_value
;
204 #ifdef DL_LOOKUP_RETURNS_MAP
208 /* And now perhaps the relocation addend. */
209 value
= elf_machine_plt_value (l
, reloc
, value
);
211 /* Store the result for later runs. */
212 if (__builtin_expect (! GL(dl_bind_not
), 1))
216 (*mcount_fct
) (retaddr
, value
);
221 #endif /* PROF && ELF_MACHINE_NO_PLT */
224 /* This macro is defined in dl-machine.h to define the entry point called
225 by the PLT. The `fixup' function above does the real work, but a little
226 more twiddling is needed to get the stack right and jump to the address
229 ELF_MACHINE_RUNTIME_TRAMPOLINE