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
|
/* Check setcontext on the context from makecontext.
Copyright (C) 2018-2021 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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
#include <unistd.h>
#include <stdatomic.h>
static ucontext_t ctx[5];
static atomic_int done;
static void
__attribute__((noinline, noclone))
f2 (void)
{
done++;
puts ("swap contexts in f2");
if (swapcontext (&ctx[4], &ctx[2]) != 0)
{
printf ("%s: setcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
puts ("end f2");
exit (done == 2 ? EXIT_SUCCESS : EXIT_FAILURE);
}
static void
f1b (void)
{
if (done)
{
puts ("set context in f1b");
if (setcontext (&ctx[3]) != 0)
{
printf ("%s: setcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
}
exit (EXIT_FAILURE);
}
static void
f1a (void)
{
static char st2[32768];
puts ("start f1a");
if (getcontext (&ctx[2]) != 0)
{
printf ("%s: getcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
ctx[2].uc_stack.ss_sp = st2;
ctx[2].uc_stack.ss_size = sizeof st2;
ctx[2].uc_link = &ctx[0];
makecontext (&ctx[2], (void (*) (void)) f1b, 0);
f2 ();
}
/* The execution path through the test looks like this:
do_test (call)
-> "making contexts"
-> "swap contexts"
f1a (via swapcontext to ctx[1], with alternate stack)
-> "start f1a"
f2 (call)
-> "swap contexts in f2"
f1b (via swapcontext to ctx[2], with alternate stack)
-> "set context in f1b"
do_test (via setcontext to ctx[3], main stack)
-> "setcontext"
f2 (via setcontext to ctx[4], with alternate stack)
-> "end f2"
We must use an alternate stack for f1b, because if we don't then the
result of executing an earlier caller may overwrite registers
spilled to the stack in f2. */
static int
do_test (void)
{
static char st1[32768];
puts ("making contexts");
if (getcontext (&ctx[0]) != 0)
{
printf ("%s: getcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
if (getcontext (&ctx[1]) != 0)
{
printf ("%s: getcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
ctx[1].uc_stack.ss_sp = st1;
ctx[1].uc_stack.ss_size = sizeof st1;
ctx[1].uc_link = &ctx[0];
makecontext (&ctx[1], (void (*) (void)) f1a, 0);
puts ("swap contexts");
if (swapcontext (&ctx[3], &ctx[1]) != 0)
{
printf ("%s: setcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
if (done != 1)
exit (EXIT_FAILURE);
done++;
puts ("set context");
if (setcontext (&ctx[4]) != 0)
{
printf ("%s: setcontext: %m\n", __FUNCTION__);
exit (EXIT_FAILURE);
}
exit (EXIT_FAILURE);
}
#include <support/test-driver.c>
|
