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#define _GNU_SOURCE
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
#define STACK_SIZE (1024 * 1024) /* Stack size for cloned child */
struct clone_args {
char **argv;
};
// child_exec is the func that will be executed as the result of clone
static int child_exec(void *stuff)
{
struct clone_args *args = (struct clone_args *)stuff;
if (execvp(args->argv[0], args->argv) != 0) {
fprintf(stderr, "failed to execvp arguments %s\n",
strerror(errno));
exit(-1);
}
// we should never reach here!
exit(EXIT_FAILURE);
}
int main(int argc, char **argv)
{
struct clone_args args;
args.argv = &argv[1];
int clone_flags = CLONE_NEWUSER | SIGCHLD;
// allocate stack for child
char *stack; /* Start of stack buffer */
char *child_stack; /* End of stack buffer */
stack =
mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANON | MAP_STACK, -1, 0);
if (stack == MAP_FAILED) {
fprintf(stderr, "mmap failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
child_stack = stack + STACK_SIZE; /* Assume stack grows downward */
// the result of this call is that our child_exec will be run in another
// process returning its pid
pid_t pid = clone(child_exec, child_stack, clone_flags, &args);
if (pid < 0) {
fprintf(stderr, "clone failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
// lets wait on our child process here before we, the parent, exits
if (waitpid(pid, NULL, 0) == -1) {
fprintf(stderr, "failed to wait pid %d\n", pid);
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
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