1 /* On-demand PLT fixup for shared objects.
2 Copyright (C) 1995, 1996, 1997, 1998 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 Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 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 Library General Public License for more details.
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If not,
17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA. */
21 #include <elf/ldsodefs.h>
22 #include "dynamic-link.h"
24 #if !defined ELF_MACHINE_NO_RELA || ELF_MACHINE_NO_REL
25 # define PLTREL ElfW(Rela)
27 # define PLTREL ElfW(Rel)
31 # define VERSYMIDX(sym) (DT_NUM + DT_PROCNUM + DT_VERSIONTAGIDX (sym))
35 /* This function is called through a special trampoline from the PLT the
36 first time each PLT entry is called. We must perform the relocation
37 specified in the PLT of the given shared object, and return the resolved
38 function address to the trampoline, which will restart the original call
39 to that address. Future calls will bounce directly from the PLT to the
42 static ElfW(Addr
) __attribute__ ((unused
))
44 #ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
45 ELF_MACHINE_RUNTIME_FIXUP_ARGS
,
47 struct link_map
*l
, ElfW(Word
) reloc_offset
)
49 const ElfW(Sym
) *const symtab
50 = (const ElfW(Sym
) *) (l
->l_addr
+ l
->l_info
[DT_SYMTAB
]->d_un
.d_ptr
);
52 (const char *) (l
->l_addr
+ l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
);
54 const PLTREL
*const reloc
55 = (const void *) (l
->l_addr
+ l
->l_info
[DT_JMPREL
]->d_un
.d_ptr
+
57 const ElfW(Sym
) *sym
= &symtab
[ELFW(R_SYM
) (reloc
->r_info
)];
58 void *const rel_addr
= (void *)(l
->l_addr
+ reloc
->r_offset
);
61 /* Sanity check that we're really looking at a PLT relocation. */
62 assert (ELFW(R_TYPE
)(reloc
->r_info
) == ELF_MACHINE_JMP_SLOT
);
64 /* Look up the target symbol. */
65 switch (l
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
69 const ElfW(Half
) *vernum
= (const ElfW(Half
) *)
70 (l
->l_addr
+ l
->l_info
[VERSYMIDX (DT_VERSYM
)]->d_un
.d_ptr
);
71 ElfW(Half
) ndx
= vernum
[ELFW(R_SYM
) (reloc
->r_info
)];
72 const struct r_found_version
*version
= &l
->l_versions
[ndx
];
74 if (version
->hash
!= 0)
76 value
= _dl_lookup_versioned_symbol(strtab
+ sym
->st_name
,
77 &sym
, l
->l_scope
, l
->l_name
,
78 version
, ELF_MACHINE_JMP_SLOT
);
83 value
= _dl_lookup_symbol (strtab
+ sym
->st_name
, &sym
, l
->l_scope
,
84 l
->l_name
, ELF_MACHINE_JMP_SLOT
);
87 /* Currently value contains the base load address of the object
88 that defines sym. Now add in the symbol offset. */
89 value
= (sym
? value
+ sym
->st_value
: 0);
91 /* And now perhaps the relocation addend. */
92 value
= elf_machine_plt_value (l
, reloc
, value
);
94 /* Finally, fix up the plt itself. */
95 elf_machine_fixup_plt (l
, reloc
, rel_addr
, value
);
103 static ElfW(Addr
) __attribute__ ((unused
))
105 #ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
106 ELF_MACHINE_RUNTIME_FIXUP_ARGS
,
108 struct link_map
*l
, ElfW(Word
) reloc_offset
, ElfW(Addr
) retaddr
)
110 void (*mcount_fct
) (ElfW(Addr
), ElfW(Addr
)) = _dl_mcount
;
114 /* This is the address in the array where we store the result of previous
116 resultp
= &l
->l_reloc_result
[reloc_offset
/ sizeof (PLTREL
)];
121 /* This is the first time we have to relocate this object. */
122 const ElfW(Sym
) *const symtab
123 = (const ElfW(Sym
) *) (l
->l_addr
+ l
->l_info
[DT_SYMTAB
]->d_un
.d_ptr
);
125 (const char *) (l
->l_addr
+ l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
);
127 const PLTREL
*const reloc
128 = (const void *) (l
->l_addr
+ l
->l_info
[DT_JMPREL
]->d_un
.d_ptr
+
130 const ElfW(Sym
) *sym
= &symtab
[ELFW(R_SYM
) (reloc
->r_info
)];
132 /* Sanity check that we're really looking at a PLT relocation. */
133 assert (ELFW(R_TYPE
)(reloc
->r_info
) == ELF_MACHINE_JMP_SLOT
);
135 /* Look up the target symbol. */
136 switch (l
->l_info
[VERSYMIDX (DT_VERSYM
)] != NULL
)
140 const ElfW(Half
) *vernum
= (const ElfW(Half
) *)
141 (l
->l_addr
+ l
->l_info
[VERSYMIDX (DT_VERSYM
)]->d_un
.d_ptr
);
142 ElfW(Half
) ndx
= vernum
[ELFW(R_SYM
) (reloc
->r_info
)];
143 const struct r_found_version
*version
= &l
->l_versions
[ndx
];
145 if (version
->hash
!= 0)
147 value
= _dl_lookup_versioned_symbol(strtab
+ sym
->st_name
,
150 ELF_MACHINE_JMP_SLOT
);
155 value
= _dl_lookup_symbol (strtab
+ sym
->st_name
, &sym
, l
->l_scope
,
156 l
->l_name
, ELF_MACHINE_JMP_SLOT
);
159 /* Currently value contains the base load address of the object
160 that defines sym. Now add in the symbol offset. */
161 value
= (sym
? value
+ sym
->st_value
: 0);
163 /* And now perhaps the relocation addend. */
164 value
= elf_machine_plt_value (l
, reloc
, value
);
166 /* Store the result for later runs. */
170 (*mcount_fct
) (retaddr
, value
);
178 /* This macro is defined in dl-machine.h to define the entry point called
179 by the PLT. The `fixup' function above does the real work, but a little
180 more twiddling is needed to get the stack right and jump to the address
183 ELF_MACHINE_RUNTIME_TRAMPOLINE