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
/*
* Copyright 2017, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This library's purpose is to hook the syscalls of the program
* built from test_clone_thread.c, and to check the
* intercept_hook_point_clone_child hook point while doing so.
*
* See also: examples/fork_ban.c about forking a new process.
*/
#ifdef NDEBUG
#undef NDEBUG
#endif
#include "libsyscall_intercept_hook_point.h"
#include <assert.h>
#include <syscall.h>
#include <stdio.h>
static long flags = -1;
static int
hook(long syscall_number,
long arg0, long arg1,
long arg2, long arg3,
long arg4, long arg5,
long *result)
{
(void) arg2;
(void) arg3;
(void) arg4;
(void) arg5;
(void) result;
/*
* One can not just simply issue a clone syscall that alters
* the stack pointer, as C compiler generates code that assumes
* the values pushed to the stack remain there. The only options
* are, to handle the situation in place (with some rather elaborate
* inline assembly tricks), or let libsyscall_intercept handle
* the details. This example returns 1, thus asks libsyscall_intercept
* to issue the actual syscall.
*
* So, such a clone syscall can be observed with a hook function
* before the syscall, and in the child process, after the syscall.
*
* At the moment, libsyscall_intercept does not provide a way to
* execute a hook function after the syscall in the parent process,
* therefore the return value (the child's pid) can not be observed,
* or modified.
*/
if (syscall_number == SYS_clone && (arg1 != 0))
flags = arg0;
return 1;
}
/*
* This function is executed in the child process right after the the
* actual syscall returned zero. The return value of clone can not
* be overridden, syscall_intercept returns zero to the syscall's caller.
*
* This function is executed on the stack associated with the new thread,
* the top of which was passed to the kernel as the second argument (arg1 above)
* of the clone syscall.
*/
static void
hook_child(void)
{
static const char msg[] = "clone_hook_child called\n";
assert(flags != -1);
syscall_no_intercept(SYS_write, 1, msg, sizeof(msg));
}
static __attribute__((constructor)) void
init(void)
{
intercept_hook_point = hook;
intercept_hook_point_clone_child = hook_child;
}