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
|
/* Operating system support for run-time dynamic linker. Generic Unix version.
Copyright (C) 1995, 1996, 1997 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. */
#include <elf.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <link.h>
#include <unistd.h>
extern int _dl_argc;
extern char **_dl_argv;
extern char **_environ;
extern size_t _dl_pagesize;
extern void _end;
extern void _start (void);
int __libc_enable_secure;
int __libc_multiple_libcs; /* Defining this here avoids the inclusion
of init-first. */
ElfW(Addr)
_dl_sysdep_start (void **start_argptr,
void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
ElfW(Addr) *user_entry))
{
const ElfW(Phdr) *phdr = NULL;
ElfW(Word) phnum = 0;
ElfW(Addr) user_entry;
ElfW(auxv_t) *av;
uid_t uid = 0;
uid_t euid = 0;
gid_t gid = 0;
gid_t egid = 0;
unsigned int seen;
user_entry = (ElfW(Addr)) &_start;
_dl_argc = *(long *) start_argptr;
_dl_argv = (char **) start_argptr + 1;
_environ = &_dl_argv[_dl_argc + 1];
start_argptr = (void **) _environ;
while (*start_argptr)
++start_argptr;
seen = 0;
#define M(type) (1 << (type))
for (av = (void *) ++start_argptr;
av->a_type != AT_NULL;
seen |= M ((++av)->a_type))
switch (av->a_type)
{
case AT_PHDR:
phdr = av->a_un.a_ptr;
break;
case AT_PHNUM:
phnum = av->a_un.a_val;
break;
case AT_PAGESZ:
_dl_pagesize = av->a_un.a_val;
break;
case AT_ENTRY:
user_entry = av->a_un.a_val;
break;
case AT_UID:
uid = av->a_un.a_val;
break;
case AT_GID:
gid = av->a_un.a_val;
break;
case AT_EUID:
euid = av->a_un.a_val;
break;
case AT_EGID:
egid = av->a_un.a_val;
break;
}
/* Linux doesn't provide us with any of these values on the stack
when the dynamic linker is run directly as a program. */
#define SEE(UID, uid) if ((seen & M (AT_##UID)) == 0) uid = __get##uid ()
SEE (UID, uid);
SEE (GID, gid);
SEE (EUID, euid);
SEE (EGID, egid);
__libc_enable_secure = uid != euid || gid != egid;
#ifdef DL_SYSDEP_INIT
DL_SYSDEP_INIT;
#endif
if (__sbrk (0) == &_end)
{
/* The dynamic linker was run as a program, and so the initial break
starts just after our bss, at &_end. The malloc in dl-minimal.c
will consume the rest of this page, so tell the kernel to move the
break up that far. When the user program examines its break, it
will see this new value and not clobber our data. */
size_t pg = __getpagesize ();
__sbrk (pg - ((&_end - (void *) 0) & (pg - 1)));
}
(*dl_main) (phdr, phnum, &user_entry);
return user_entry;
}
void
_dl_sysdep_start_cleanup (void)
{
}
|
