1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
/* Look up a symbol in the loaded objects.
Copyright (C) 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <stddef.h>
#include <libelf.h>
#include <link.h>
#include <assert.h>
/* Search loaded objects' symbol tables for a definition of the symbol
UNDEF_NAME. If NOPLT is nonzero, then a PLT entry cannot satisfy the
reference; some different binding must be found. */
Elf32_Addr
_dl_lookup_symbol (const char *undef_name, const Elf32_Sym **ref,
struct link_map *symbol_scope,
const char *reference_name,
int noplt)
{
unsigned long int hash = elf_hash (undef_name);
struct link_map *map;
struct
{
Elf32_Addr a;
const Elf32_Sym *s;
} weak_value = { 0, NULL };
/* Search the relevant loaded objects for a definition. */
for (map = symbol_scope; map; map = map->l_next)
{
const Elf32_Sym *symtab;
const char *strtab;
Elf32_Word symidx;
symtab = ((void *) map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
strtab = ((void *) map->l_addr + map->l_info[DT_STRTAB]->d_un.d_ptr);
/* Search the appropriate hash bucket in this object's symbol table
for a definition for the same symbol name. */
for (symidx = map->l_buckets[hash % map->l_nbuckets];
symidx != STN_UNDEF;
symidx = map->l_chain[symidx])
{
const Elf32_Sym *sym = &symtab[symidx];
if (sym->st_value == 0 || /* No value. */
(noplt && sym->st_shndx == SHN_UNDEF)) /* Unwanted PLT entry. */
continue;
switch (ELF32_ST_TYPE (sym->st_info))
{
case STT_NOTYPE:
case STT_FUNC:
case STT_OBJECT:
break;
default:
/* Not a code/data definition. */
continue;
}
if (sym != *ref && strcmp (strtab + sym->st_name, undef_name))
/* Not the symbol we are looking for. */
continue;
switch (ELF32_ST_BIND (sym->st_info))
{
case STB_GLOBAL:
/* Global definition. Just what we need. */
*ref = sym;
return map->l_addr;
case STB_WEAK:
/* Weak definition. Use this value if we don't find another. */
if (! weak_value.s)
{
weak_value.s = sym;
weak_value.a = map->l_addr;
}
break;
default:
/* Local symbols are ignored. */
break;
}
}
}
if (weak_value.s == NULL && ELF32_ST_BIND ((*ref)->st_info) != STB_WEAK)
{
const char msg[] = "undefined symbol: ";
char buf[sizeof msg + strlen (undef_name)];
memcpy (buf, msg, sizeof msg - 1);
memcpy (&buf[sizeof msg - 1], undef_name, sizeof buf - sizeof msg + 1);
_dl_signal_error (0, reference_name, buf);
}
*ref = weak_value.s;
return weak_value.a;
}
/* Cache the location of MAP's hash table. */
void
_dl_setup_hash (struct link_map *map)
{
Elf32_Word *hash = (void *) map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr;
Elf32_Word nchain;
map->l_nbuckets = *hash++;
nchain = *hash++;
map->l_buckets = hash;
hash += map->l_nbuckets;
map->l_chain = hash;
}
|
