memfd_create file less practice

fileless-practice.c

#include <stdio.h>
#include <stdlib.h>

// for syscall()
#include <sys/syscall.h>

// for getpid()
#include <sys/types.h>
// for read() and execl()
#include <unistd.h>

int main(void) {
  // init
  pid_t pid;
  pid = getpid();
  
  printf("start memfd_create\n");

  // create virtual fd
  int virtual_fd;
  virtual_fd = syscall(SYS_memfd_create, "kingyo", 0);
  // error handling
  if (virtual_fd == -1) {
    perror("memdf_create fail\n");
    exit(1);
  }

  // display fd and proc info, and wait
  printf("fd is %d\n", virtual_fd);
  printf("check command:\n ls -l /proc/%d/fd\n", pid);
  char ch;
  ch = getchar();

  // write data want to execute
  int r;
  char *bin = "/bin/date";
  r = write(virtual_fd, bin, strlen(bin));
  if (r == -1) {
    perror("write fail\n");
    exit(1);
  }

  // display fd info and wait
  printf("data is written to fd\n", virtual_fd);
  printf("check command:\n cat /proc/%d/fd/%d\n", pid, virtual_fd);
  ch = getchar();

  // execute written data
  char path[128] = {'\0'};
  sprintf(path, "/proc/%d/fd/%d", pid, virtual_fd);
  int pfd;
  pfd = open(path, 0);
  if (pfd == -1) {
    perror("open fail\n");
  }
  
  char *buf[128] = {'\0'};
  //r = read(virtual_fd, buf, strlen(bin))
  r = read(pfd, buf, strlen(bin));
  if (r == -1) {
    perror("read fail\n");
    exit(1);
  }

  execl(buf, buf, NULL);

  perror("exec fail\n");
  return -1;
}