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
|
/* Copyright (C) 1998, 1999, 2000 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 <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <ldsodefs.h>
extern void __libc_init_first (int argc, char **argv, char **envp);
extern int _dl_starting_up;
weak_extern (_dl_starting_up)
extern int __libc_multiple_libcs;
extern void *__libc_stack_end;
/* Prototype for local function. */
static void check_standard_fds (void);
int
__libc_start_main (int (*main) (int, char **, char **), int argc,
char **argv, void (*init) (void), void (*fini) (void),
void (*rtld_fini) (void), void *stack_end)
{
#ifndef PIC
/* The next variable is only here to work around a bug in gcc <= 2.7.2.2.
If the address would be taken inside the expression the optimizer
would try to be too smart and throws it away. Grrr. */
int *dummy_addr = &_dl_starting_up;
__libc_multiple_libcs = dummy_addr && !_dl_starting_up;
#endif
/* Store the lowest stack address. */
__libc_stack_end = stack_end;
/* Set the global _environ variable correctly. */
__environ = &argv[argc + 1];
/* Some security at this point. Prevent starting a SUID binary where
the standard file descriptors are not opened. */
if (__libc_enable_secure)
check_standard_fds ();
/* Register the destructor of the dynamic linker if there is any. */
if (rtld_fini != NULL)
atexit (rtld_fini);
/* Call the initializer of the libc. */
#ifdef PIC
if (_dl_debug_impcalls)
_dl_debug_message (1, "\ninitialize libc\n\n", NULL);
#endif
__libc_init_first (argc, argv, __environ);
/* Register the destructor of the program, if any. */
if (fini)
atexit (fini);
/* Call the initializer of the program, if any. */
#ifdef PIC
if (_dl_debug_impcalls)
_dl_debug_message (1, "\ninitialize program: ", argv[0], "\n\n", NULL);
#endif
if (init)
(*init) ();
#ifdef PIC
if (_dl_debug_impcalls)
_dl_debug_message (1, "\ntransferring control: ", argv[0], "\n\n", NULL);
#endif
exit ((*main) (argc, argv, __environ));
}
/* Should other OSes (e.g., Hurd) have different versions which can
be written in a better way? */
static void
check_one_fd (int fd, int mode)
{
if (__libc_fcntl (fd, F_GETFD) == -1 && errno == EBADF)
{
/* Something is wrong with this descriptor, it's probably not
opened. Open /dev/null so that the SUID program we are
about to start does not accidently use this descriptor. */
int nullfd = __libc_open (_PATH_DEVNULL, mode);
if (nullfd == -1)
/* We cannot even give an error message here since it would
run into the same problems. */
abort ();
}
}
static void
check_standard_fds (void)
{
/* Check all three standard file descriptors. */
check_one_fd (STDIN_FILENO, O_RDONLY);
check_one_fd (STDOUT_FILENO, O_RDWR);
check_one_fd (STDERR_FILENO, O_RDWR);
}
|
