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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
|
/* Machine-dependent ELF dynamic relocation inline functions. i386 version.
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.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#ifndef dl_machine_h
#define dl_machine_h
#define ELF_MACHINE_NAME "i386"
#include <assert.h>
/* Return nonzero iff E_MACHINE is compatible with the running host. */
static inline int __attribute__ ((unused))
elf_machine_matches_host (Elf32_Half e_machine)
{
switch (e_machine)
{
case EM_386:
case EM_486:
return 1;
default:
return 0;
}
}
/* Return the link-time address of _DYNAMIC. Conveniently, this is the
first element of the GOT. This must be inlined in a function which
uses global data. */
static inline Elf32_Addr
elf_machine_dynamic (void)
{
register Elf32_Addr *got asm ("%ebx");
return *got;
}
/* Return the run-time load address of the shared object. */
static inline Elf32_Addr __attribute__ ((unused))
elf_machine_load_address (void)
{
Elf32_Addr addr;
asm (" call here\n"
"here: popl %0\n"
" subl $here, %0"
: "=r" (addr));
return addr;
}
/* The `subl' insn above will contain an R_386_32 relocation entry
intended to insert the run-time address of the label `here'.
This will be the first relocation in the text of the dynamic linker;
we skip it to avoid trying to modify read-only text in this early stage. */
#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
++(const Elf32_Rel *) (dynamic_info)[DT_REL]->d_un.d_ptr; \
(dynamic_info)[DT_RELSZ]->d_un.d_val -= sizeof (Elf32_Rel);
/* Set up the loaded object described by L so its unrelocated PLT
entries will jump to the on-demand fixup code in dl-runtime.c. */
static inline void __attribute__ ((unused))
elf_machine_runtime_setup (struct link_map *l, int lazy)
{
Elf32_Addr *got;
extern void _dl_runtime_resolve (Elf32_Word);
if (l->l_info[DT_JMPREL] && lazy)
{
/* The GOT entries for functions in the PLT have not yet been filled
in. Their initial contents will arrange when called to push an
offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
and then jump to _GLOBAL_OFFSET_TABLE[2]. */
got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
got[1] = (Elf32_Addr) l; /* Identify this shared object. */
/* This function will get called to fix up the GOT entry indicated by
the offset on the stack, and then jump to the resolved address. */
got[2] = (Elf32_Addr) &_dl_runtime_resolve;
}
/* This code is used in dl-runtime.c to call the `fixup' function
and then redirect to the address it returns. */
#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
.globl _dl_runtime_resolve
.type _dl_runtime_resolve, @function
_dl_runtime_resolve:
call fixup # Args pushed by PLT.
addl $8, %esp # Pop args.
jmp *%eax # Jump to function address.
");
/* The PLT uses Elf32_Rel relocs. */
#define elf_machine_relplt elf_machine_rel
}
/* Mask identifying addresses reserved for the user program,
where the dynamic linker should not map anything. */
#define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
/* Initial entry point code for the dynamic linker.
The C function `_dl_start' is the real entry point;
its return value is the user program's entry point. */
#define RTLD_START asm ("\
.text\n\
.globl _start\n\
.globl _dl_start_user\n\
_start:\n\
pushl %esp\n\
call _dl_start\n\
popl %ebx\n\
_dl_start_user:\n\
# Save the user entry point address in %edi.\n\
movl %eax, %edi\n\
# Point %ebx at the GOT.
call 0f\n\
0: popl %ebx\n\
addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx\n\
# See if we were run as a command with the executable file\n\
# name as an extra leading argument.\n\
movl _dl_skip_args@GOT(%ebx), %eax\n\
movl (%eax), %eax\n\
# Pop the original argument count.\n\
popl %ecx\n\
# Subtract _dl_skip_args from it.\n\
subl %eax, %ecx\n\
# Adjust the stack pointer to skip _dl_skip_args words.\n\
leal (%esp,%eax,4), %esp\n\
# Push back the modified argument count.\n\
pushl %ecx\n\
# Push _dl_default_scope[2] as argument in _dl_init_next call below.\n\
movl _dl_default_scope@GOT(%ebx), %eax\n\
movl 8(%eax), %esi\n\
0: pushl %esi\n\
# Call _dl_init_next to return the address of an initializer\n\
# function to run.\n\
call _dl_init_next@PLT\n\
addl $4, %esp # Pop argument.\n\
# Check for zero return, when out of initializers.\n\
testl %eax, %eax\n\
jz 1f\n\
# Call the shared object initializer function.\n\
# NOTE: We depend only on the registers (%ebx, %esi and %edi)\n\
# and the return address pushed by this call;\n\
# the initializer is called with the stack just\n\
# as it appears on entry, and it is free to move\n\
# the stack around, as long as it winds up jumping to\n\
# the return address on the top of the stack.\n\
call *%eax\n\
# Loop to call _dl_init_next for the next initializer.\n\
jmp 0b\n\
1: # Clear the startup flag.\n\
movl _dl_starting_up@GOT(%ebx), %eax\n\
movl $0, (%eax)\n\
# Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
movl _dl_fini@GOT(%ebx), %edx\n\
# Jump to the user's entry point.\n\
jmp *%edi\n\
");
/* Nonzero iff TYPE describes relocation of a PLT entry, so
PLT entries should not be allowed to define the value. */
#define elf_machine_pltrel_p(type) ((type) == R_386_JMP_SLOT)
/* The i386 never uses Elf32_Rela relocations. */
#define ELF_MACHINE_NO_RELA 1
#endif /* !dl_machine_h */
#ifdef RESOLVE
/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
MAP is the object containing the reloc. */
static inline void
elf_machine_rel (struct link_map *map,
const Elf32_Rel *reloc, const Elf32_Sym *sym)
{
Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
Elf32_Addr loadbase;
switch (ELF32_R_TYPE (reloc->r_info))
{
case R_386_COPY:
loadbase = RESOLVE (&sym, DL_LOOKUP_NOEXEC);
memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
break;
case R_386_GLOB_DAT:
loadbase = RESOLVE (&sym, 0);
*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
break;
case R_386_JMP_SLOT:
loadbase = RESOLVE (&sym, DL_LOOKUP_NOPLT);
*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
break;
case R_386_32:
{
Elf32_Addr undo = 0;
#ifndef RTLD_BOOTSTRAP
/* This is defined in rtld.c, but nowhere in the static libc.a;
make the reference weak so static programs can still link. This
declaration cannot be done when compiling rtld.c (i.e. #ifdef
RTLD_BOOTSTRAP) because rtld.c contains the common defn for
_dl_rtld_map, which is incompatible with a weak decl in the same
file. */
weak_extern (_dl_rtld_map);
if (map == &_dl_rtld_map)
/* Undo the relocation done here during bootstrapping. Now we will
relocate it anew, possibly using a binding found in the user
program or a loaded library rather than the dynamic linker's
built-in definitions used while loading those libraries. */
undo = map->l_addr + sym->st_value;
#endif
loadbase = RESOLVE (&sym, 0);
*reloc_addr += (sym ? (loadbase + sym->st_value) : 0) - undo;
break;
}
case R_386_RELATIVE:
#ifndef RTLD_BOOTSTRAP
if (map != &_dl_rtld_map) /* Already done in rtld itself. */
#endif
*reloc_addr += map->l_addr;
break;
case R_386_PC32:
loadbase = RESOLVE (&sym, 0);
*reloc_addr += ((sym ? (loadbase + sym->st_value) : 0) -
(Elf32_Addr) reloc_addr);
break;
case R_386_NONE: /* Alright, Wilbur. */
break;
default:
assert (! "unexpected dynamic reloc type");
break;
}
}
static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf32_Rel *reloc)
{
Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
switch (ELF32_R_TYPE (reloc->r_info))
{
case R_386_JMP_SLOT:
*reloc_addr += map->l_addr;
break;
default:
assert (! "unexpected PLT reloc type");
break;
}
}
#endif /* RESOLVE */
|
