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
|
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <sched.h>
#include <signal.h>
#include <string.h>
#define STKS 4096
#ifndef CLONE_NEWPID
#define CLONE_NEWPID 0x20000000
#endif
static int do_test(void *logf)
{
int fd, i = 0;
// Detach from the parent terminal
setsid();
// Close standard file descriptors
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
// Open /dev/null as stdin
fd = open("/dev/null", O_RDONLY);
if (fd != STDIN_FILENO) {
dup2(fd, STDIN_FILENO);
close(fd);
}
// Open the log file and redirect stdout and stderr to it
fd = open(logf, O_WRONLY | O_TRUNC | O_CREAT, 0600);
dup2(fd, STDOUT_FILENO);
dup2(fd, STDERR_FILENO);
if (fd != STDOUT_FILENO && fd != STDERR_FILENO)
close(fd);
while (1) {
printf("%d\n", i++);
fflush(stdout);
sleep(1);
}
return 0;
}
int main(int argc, char *argv[])
{
int pid;
size_t size;
void *stk;
int flags = 0;
int fd = 0;
if (argc < 4) {
fprintf(stderr, "Usage: %s <size> <mapping_flags (s|p[a])> <log_file>\n", argv[0]);
fprintf(stderr, "Example: %s 4096 sp /tmp/mmapper.log\n", argv[0]);
return 1;
}
size = atoi(argv[1]);
if (size <= 0) {
fprintf(stderr, "Invalid input size\n");
return 1;
}
char *mapping_flags = argv[2];
// Parse mapping flags argument
for (int i = 0; i < strlen(mapping_flags); i++) {
switch (mapping_flags[i]) {
case 's':
flags |= MAP_SHARED;
break;
case 'p':
flags |= MAP_PRIVATE;
break;
case 'a':
flags |= MAP_ANONYMOUS;
break;
}
}
// If using MAP_PRIVATE or MAP_SHARED without MAP_ANONYMOUS, create a temporary file
if (flags == MAP_SHARED || flags == MAP_PRIVATE) {
char filename[] = "/tmp/crit-mmapper.XXXXXX";
fd = mkstemp(filename);
if (fd == -1) {
perror("mkstemp() failed");
return 1;
}
ftruncate(fd, size);
// Clean-up the temporary file
unlink(filename);
}
// Create the memory mapping
stk = mmap(NULL, size, PROT_READ | PROT_WRITE, flags, fd, 0);
if (stk == MAP_FAILED) {
perror("mmap() failed");
return 1;
}
// Create a child process
pid = clone(do_test, stk + STKS, SIGCHLD | CLONE_NEWPID, argv[3]);
if (pid < 0) {
perror("clone() failed");
return 1;
}
printf("%d\n", pid);
return 0;
}
|
