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
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
|
/* Run an ELF binary on a linux system.
Copyright (C) 1993, Eric Youngdale.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#ifndef VERBOSE_DLINKER
#define VERBOSE_DLINKER
#endif
#ifdef VERBOSE_DLINKER
static const char *_dl_reltypes[] =
{ "R_ARM_NONE", "R_ARM_PC24", "R_ARM_ABS32", "R_ARM_REL32",
"R_ARM_PC13", "R_ARM_ABS16", "R_ARM_ABS12", "R_ARM_THM_ABS5",
"R_ARM_ABS8", "R_ARM_SBREL32", "R_ARM_THM_PC22", "R_ARM_THM_PC8",
"R_ARM_AMP_VCALL9", "R_ARM_SWI24", "R_ARM_THM_SWI8", "R_ARM_XPC25",
"R_ARM_THM_XPC22", "R_ARM_COPY", "R_ARM_GLOB_DAT", "R_ARM_JUMP_SLOT",
"R_ARM_RELATIVE", "R_ARM_GOTOFF", "R_ARM_GOTPC", "R_ARM_GOT32",
"R_ARM_PLT32", "R_ARM_ALU_PCREL_7_0", "R_ARM_ALU_PCREL_15_8",
"R_ARM_ALU_PCREL_23_15", "R_ARM_LDR_SBREL_11_0", "R_ARM_ALU_SBREL_19_12",
"R_ARM_ALU_SBREL_27_20", "R_ARM_GNU_VTENTRY", "R_ARM_GNU_VTINHERIT",
"R_ARM_THM_PC11", "R_ARM_THM_PC9", "R_ARM_RXPC25", "R_ARM_RSBREL32",
"R_ARM_THM_RPC22", "R_ARM_RREL32", "R_ARM_RABS22", "R_ARM_RPC24",
"R_ARM_RBASE", "R_ARM_NUM"
};
#endif
/* Program to load an ELF binary on a linux system, and run it.
References to symbols in sharable libraries can be resolved by either
an ELF sharable library or a linux style of shared library. */
/* Disclaimer: I have never seen any AT&T source code for SVr4, nor have
I ever taken any courses on internals. This program was developed using
information available through the book "UNIX SYSTEM V RELEASE 4,
Programmers guide: Ansi C and Programming Support Tools", which did
a more than adequate job of explaining everything required to get this
working. */
extern int _dl_linux_resolve(void);
unsigned long _dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
{
int reloc_type;
Elf32_Rel *this_reloc;
char *strtab;
Elf32_Sym *symtab;
Elf32_Rel *rel_addr;
int symtab_index;
char *new_addr;
char **got_addr;
unsigned long instr_addr;
rel_addr = (Elf32_Rel *) (tpnt->dynamic_info[DT_JMPREL] + tpnt->loadaddr);
this_reloc = rel_addr + (reloc_entry >> 3);
reloc_type = ELF32_R_TYPE(this_reloc->r_info);
symtab_index = ELF32_R_SYM(this_reloc->r_info);
symtab = (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
if (reloc_type != R_ARM_JUMP_SLOT) {
_dl_dprintf(2, "%s: Incorrect relocation type in jump relocations\n",
_dl_progname);
_dl_exit(1);
};
/* Address of jump instruction to fix up */
instr_addr = ((unsigned long) this_reloc->r_offset +
(unsigned long) tpnt->loadaddr);
got_addr = (char **) instr_addr;
#ifdef DL_DEBUG_SYMBOLS
_dl_dprintf(2, "Resolving symbol %s\n",
strtab + symtab[symtab_index].st_name);
#endif
/* Get the address of the GOT entry */
new_addr = _dl_find_hash(strtab + symtab[symtab_index].st_name,
tpnt->symbol_scope, tpnt, 0);
if (!new_addr) {
_dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
_dl_progname, strtab + symtab[symtab_index].st_name);
_dl_exit(1);
};
#ifdef DL_NEVER_FIXUP_SYMBOLS
if ((unsigned long) got_addr < 0x40000000) {
_dl_dprintf(2, "Calling library function: %s\n",
strtab + symtab[symtab_index].st_name);
} else {
*got_addr = new_addr;
}
#else
*got_addr = new_addr;
#endif
return (unsigned long) new_addr;
}
void _dl_parse_lazy_relocation_information(struct elf_resolve *tpnt,
unsigned long rel_addr, unsigned long rel_size, int type)
{
int i;
char *strtab;
int reloc_type;
int symtab_index;
Elf32_Sym *symtab;
Elf32_Rel *rpnt;
unsigned long *reloc_addr;
/* Now parse the relocation information */
rpnt = (Elf32_Rel *) (rel_addr + tpnt->loadaddr);
rel_size = rel_size / sizeof(Elf32_Rel);
symtab =
(Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
for (i = 0; i < rel_size; i++, rpnt++) {
reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
reloc_type = ELF32_R_TYPE(rpnt->r_info);
symtab_index = ELF32_R_SYM(rpnt->r_info);
/* When the dynamic linker bootstrapped itself, it resolved some symbols.
Make sure we do not do them again */
if (!symtab_index && tpnt->libtype == program_interpreter)
continue;
if (symtab_index && tpnt->libtype == program_interpreter &&
_dl_symbol(strtab + symtab[symtab_index].st_name))
continue;
switch (reloc_type) {
case R_ARM_NONE:
break;
case R_ARM_JUMP_SLOT:
*reloc_addr += (unsigned long) tpnt->loadaddr;
break;
default:
_dl_dprintf(2, "%s: (LAZY) can't handle reloc type ",
_dl_progname);
#ifdef VERBOSE_DLINKER
_dl_dprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
if (symtab_index)
_dl_dprintf(2, "'%s'\n", strtab + symtab[symtab_index].st_name);
_dl_exit(1);
};
};
}
static unsigned long
fix_bad_pc24 (unsigned long *const reloc_addr, unsigned long value)
{
static void *fix_page;
static unsigned int fix_offset;
unsigned int *fix_address;
if (! fix_page)
{
fix_page = _dl_mmap (NULL, 4096 , PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
fix_offset = 0;
}
fix_address = (unsigned int *)(fix_page + fix_offset);
fix_address[0] = 0xe51ff004; /* ldr pc, [pc, #-4] */
fix_address[1] = value;
fix_offset += 8;
if (fix_offset >= 4096)
fix_page = NULL;
return (unsigned long)fix_address;
}
int _dl_parse_relocation_information(struct elf_resolve *tpnt,
unsigned long rel_addr, unsigned long rel_size, int type)
{
int i;
char *strtab;
int reloc_type;
int goof = 0;
Elf32_Sym *symtab;
Elf32_Rel *rpnt;
unsigned long *reloc_addr;
unsigned long symbol_addr;
int symtab_index;
/* Now parse the relocation information */
rpnt = (Elf32_Rel *) (rel_addr + tpnt->loadaddr);
rel_size = rel_size / sizeof(Elf32_Rel);
symtab = (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
for (i = 0; i < rel_size; i++, rpnt++) {
reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
reloc_type = ELF32_R_TYPE(rpnt->r_info);
symtab_index = ELF32_R_SYM(rpnt->r_info);
symbol_addr = 0;
if (!symtab_index && tpnt->libtype == program_interpreter)
continue;
if (symtab_index) {
if (tpnt->libtype == program_interpreter &&
_dl_symbol(strtab + symtab[symtab_index].st_name))
continue;
symbol_addr = (unsigned long) _dl_find_hash(strtab + symtab[symtab_index].st_name,
tpnt->symbol_scope,
(reloc_type == R_ARM_JUMP_SLOT ? tpnt : NULL), 0);
/*
* We want to allow undefined references to weak symbols - this might
* have been intentional. We should not be linking local symbols
* here, so all bases should be covered.
*/
if (!symbol_addr && ELF32_ST_BIND(symtab[symtab_index].st_info) == STB_GLOBAL) {
_dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
_dl_progname, strtab + symtab[symtab_index].st_name);
goof++;
}
}
switch (reloc_type) {
case R_ARM_NONE:
break;
case R_ARM_ABS32:
*reloc_addr += symbol_addr;
break;
case R_ARM_PC24:
{
unsigned long addend;
long newvalue, topbits;
addend = *reloc_addr & 0x00ffffff;
if (addend & 0x00800000) addend |= 0xff000000;
newvalue = symbol_addr - (unsigned long)reloc_addr + (addend << 2);
topbits = newvalue & 0xfe000000;
if (topbits != 0xfe000000 && topbits != 0x00000000)
{
newvalue = fix_bad_pc24(reloc_addr, symbol_addr)
- (unsigned long)reloc_addr + (addend << 2);
topbits = newvalue & 0xfe000000;
if (topbits != 0xfe000000 && topbits != 0x00000000)
{
_dl_dprintf(2,"symbol '%s': R_ARM_PC24 relocation out of range.",
symtab[symtab_index].st_name);
_dl_exit(1);
}
}
newvalue >>= 2;
symbol_addr = (*reloc_addr & 0xff000000) | (newvalue & 0x00ffffff);
*reloc_addr = symbol_addr;
break;
}
case R_ARM_GLOB_DAT:
case R_ARM_JUMP_SLOT:
*reloc_addr = symbol_addr;
break;
case R_ARM_RELATIVE:
*reloc_addr += (unsigned long) tpnt->loadaddr;
break;
case R_ARM_COPY:
#if 0
/* Do this later */
_dl_dprintf(2, "Doing copy for symbol ");
if (symtab_index) _dl_dprintf(2, strtab + symtab[symtab_index].st_name);
_dl_dprintf(2, "\n");
_dl_memcpy((void *) symtab[symtab_index].st_value,
(void *) symbol_addr, symtab[symtab_index].st_size);
#endif
break;
default:
_dl_dprintf(2, "%s: can't handle reloc type ", _dl_progname);
#ifdef VERBOSE_DLINKER
_dl_dprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
if (symtab_index)
_dl_dprintf(2, "'%s'\n", strtab + symtab[symtab_index].st_name);
_dl_exit(1);
};
};
return goof;
}
/* This is done as a separate step, because there are cases where
information is first copied and later initialized. This results in
the wrong information being copied. Someone at Sun was complaining about
a bug in the handling of _COPY by SVr4, and this may in fact be what he
was talking about. Sigh. */
/* No, there are cases where the SVr4 linker fails to emit COPY relocs
at all */
int _dl_parse_copy_information(struct dyn_elf *xpnt, unsigned long rel_addr,
unsigned long rel_size, int type)
{
int i;
char *strtab;
int reloc_type;
int goof = 0;
Elf32_Sym *symtab;
Elf32_Rel *rpnt;
unsigned long *reloc_addr;
unsigned long symbol_addr;
struct elf_resolve *tpnt;
int symtab_index;
/* Now parse the relocation information */
tpnt = xpnt->dyn;
rpnt = (Elf32_Rel *) (rel_addr + tpnt->loadaddr);
rel_size = rel_size / sizeof(Elf32_Rel);
symtab = (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
for (i = 0; i < rel_size; i++, rpnt++) {
reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
reloc_type = ELF32_R_TYPE(rpnt->r_info);
if (reloc_type != R_ARM_COPY)
continue;
symtab_index = ELF32_R_SYM(rpnt->r_info);
symbol_addr = 0;
if (!symtab_index && tpnt->libtype == program_interpreter)
continue;
if (symtab_index) {
if (tpnt->libtype == program_interpreter &&
_dl_symbol(strtab + symtab[symtab_index].st_name))
continue;
symbol_addr = (unsigned long) _dl_find_hash(strtab +
symtab[symtab_index].st_name, xpnt->next,
NULL, 1);
if (!symbol_addr) {
_dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
_dl_progname, strtab + symtab[symtab_index].st_name);
goof++;
};
};
if (!goof) {
_dl_memcpy((char *) symtab[symtab_index].st_value,
(char *) symbol_addr, symtab[symtab_index].st_size);
}
};
return goof;
}
|
