1 #define _GNU_SOURCE
2 #include <errno.h>
3 #include <sched.h>
4 #include <signal.h>
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8 #include <sys/mman.h>
9 #include <sys/wait.h>
10 #include <unistd.h>
11
12 #define STACK_SIZE (1024 * 1024) /* Stack size for cloned child */
13
14 struct clone_args {
15 char **argv;
16 };
17
18 // child_exec is the func that will be executed as the result of clone
child_exec(void * stuff)19 static int child_exec(void *stuff)
20 {
21 struct clone_args *args = (struct clone_args *)stuff;
22 if (execvp(args->argv[0], args->argv) != 0) {
23 fprintf(stderr, "failed to execvp arguments %s\n",
24 strerror(errno));
25 exit(-1);
26 }
27 // we should never reach here!
28 exit(EXIT_FAILURE);
29 }
30
main(int argc,char ** argv)31 int main(int argc, char **argv)
32 {
33 struct clone_args args;
34 args.argv = &argv[1];
35
36 int clone_flags = CLONE_NEWUSER | SIGCHLD;
37
38 // allocate stack for child
39 char *stack; /* Start of stack buffer */
40 char *child_stack; /* End of stack buffer */
41 stack =
42 mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE,
43 MAP_SHARED | MAP_ANON | MAP_STACK, -1, 0);
44 if (stack == MAP_FAILED) {
45 fprintf(stderr, "mmap failed: %s\n", strerror(errno));
46 exit(EXIT_FAILURE);
47 }
48 child_stack = stack + STACK_SIZE; /* Assume stack grows downward */
49
50 // the result of this call is that our child_exec will be run in another
51 // process returning its pid
52 pid_t pid = clone(child_exec, child_stack, clone_flags, &args);
53 if (pid < 0) {
54 fprintf(stderr, "clone failed: %s\n", strerror(errno));
55 exit(EXIT_FAILURE);
56 }
57 // lets wait on our child process here before we, the parent, exits
58 if (waitpid(pid, NULL, 0) == -1) {
59 fprintf(stderr, "failed to wait pid %d\n", pid);
60 exit(EXIT_FAILURE);
61 }
62 exit(EXIT_SUCCESS);
63 }
64