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
| | #include <stddef.h>
#include "dynlink.h"
#ifdef SHARED
#ifndef START
#define START "_dlstart"
#endif
#include "crt_arch.h"
__attribute__((__visibility__("hidden")))
void _dlstart_c(size_t *sp, size_t *dynv)
{
size_t i, aux[AUX_CNT], dyn[DYN_CNT];
int argc = *sp;
char **argv = (void *)(sp+1);
for (i=argc+1; argv[i]; i++);
size_t *auxv = (void *)(argv+i+1);
for (i=0; i<AUX_CNT; i++) aux[i] = 0;
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT)
aux[auxv[i]] = auxv[i+1];
for (i=0; i<DYN_CNT; i++) dyn[i] = 0;
for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT)
dyn[dynv[i]] = dynv[i+1];
/* If the dynamic linker is invoked as a command, its load
* address is not available in the aux vector. Instead, compute
* the load address as the difference between &_DYNAMIC and the
* virtual address in the PT_DYNAMIC program header. */
unsigned char *base = (void *)aux[AT_BASE];
if (!base) {
size_t phnum = aux[AT_PHNUM];
size_t phentsize = aux[AT_PHENT];
Phdr *ph = (void *)aux[AT_PHDR];
for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) {
if (ph->p_type == PT_DYNAMIC) {
base = (void *)((size_t)dynv - ph->p_vaddr);
break;
}
}
}
/* MIPS uses an ugly packed form for GOT relocations. Since we
* can't make function calls yet and the code is tiny anyway,
* it's simply inlined here. */
if (NEED_MIPS_GOT_RELOCS) {
size_t local_cnt = 0;
size_t *got = (void *)(base + dyn[DT_PLTGOT]);
for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO)
local_cnt = dynv[i+1];
for (i=0; i<local_cnt; i++) got[i] += (size_t)base;
}
size_t *rel, rel_size, symbolic_rel_cnt=0;
rel = (void *)(base+dyn[DT_REL]);
rel_size = dyn[DT_RELSZ];
for (; rel_size; rel+=2, rel_size-=2*sizeof(size_t)) {
if (!IS_RELATIVE(rel[1])) {
symbolic_rel_cnt++;
continue;
}
size_t *rel_addr = (void *)(base + rel[0]);
*rel_addr += (size_t)base;
}
rel = (void *)(base+dyn[DT_RELA]);
rel_size = dyn[DT_RELASZ];
for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) {
if (!IS_RELATIVE(rel[1])) continue;
size_t *rel_addr = (void *)(base + rel[0]);
*rel_addr = (size_t)base + rel[2];
}
/* Prepare storage for stages 2 to save clobbered REL
* addends so they can be reused in stage 3. There should
* be very few. If something goes wrong and there are a
* huge number, pass a null pointer to trigger stage 2
* to abort instead of risking stack overflow. */
int too_many_addends = symbolic_rel_cnt > 4096;
size_t naddends = too_many_addends ? 1 : symbolic_rel_cnt;
size_t addends[naddends];
size_t *paddends = too_many_addends ? 0 : addends;
const char *strings = (void *)(base + dyn[DT_STRTAB]);
const Sym *syms = (void *)(base + dyn[DT_SYMTAB]);
/* Call dynamic linker stage-2, __dls2 */
for (i=0; ;i++) {
const char *s = strings + syms[i].st_name;
if (s[0]=='_' && s[1]=='_' && s[2]=='d'
&& s[3]=='l' && s[4]=='s' && s[5]=='2' && !s[6])
break;
}
((stage2_func)(base + syms[i].st_value))(base, paddends);
/* Call dynamic linker stage-3, __dls3 */
for (i=0; ;i++) {
const char *s = strings + syms[i].st_name;
if (s[0]=='_' && s[1]=='_' && s[2]=='d'
&& s[3]=='l' && s[4]=='s' && s[5]=='3' && !s[6])
break;
}
((stage3_func)(base + syms[i].st_value))(sp);
}
#endif
|