main.c

#include <dirent.h>
#include <dlfcn.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>

int main() {
  /* Open the .so */
  int file_fd = open("module.so", O_RDONLY, O_RDONLY);
  if (file_fd < 0) {
    perror("open");
    return 10;
  }
  printf("Open module.so: %i\n", file_fd);

  /* Get the siez of the .so */
  int file_size = lseek(file_fd, 0, SEEK_END);
  printf("File size: %i\n", file_size);
  lseek(file_fd, 0, SEEK_SET);
  /* Allocate a buffer */
  char *buffer = malloc(file_size);
  if (buffer == NULL) {
    perror("malloc");
    return 20;
  }

  /* Open the shm_file to write on */
  int shm_fd = shm_open("shm_module.so", O_RDWR | O_CREAT, 0644);
  if (shm_fd < 0) {
    perror("shm_open");
    return 4;
  }
  printf("Open shm module.so: %i\n", shm_fd);

  /* Read the .so to the buffer and Write the buffer to the shm */
  int read_size = read(file_fd, buffer, file_size);
  printf("Read size: %i\n", read_size);
  int write_size = write(shm_fd, buffer, file_size);
  printf("Write size: %i\n", write_size);

  /* Free the buffer */
  free(buffer);
  /* Close the file */
  close(file_fd);

  /* Prepare the shm .so to be read */
  #define shm_path_size sizeof("/proc/self/fd/65536")
  char shm_path[shm_path_size] = {0};
  snprintf(shm_path, shm_path_size, "/proc/self/fd/%i", shm_fd);
  printf("shm path: %s\n", shm_path);

  /* Load the .so */
  void *module_so = dlopen(shm_path, RTLD_NOW);
  if (module_so == NULL) {
    perror("dlopen");
    return 1;
  }
  int (*module_run)(int*) = dlsym(module_so, "run");
  if (module_run == NULL) {
    perror("dlsym");
    return 2;
  }

  /* Execute some sym from the .so */
  int var = 4;
  module_run(&var);
  printf("var = %i\n", var);

  /* remove the shm */
  if (shm_unlink("shm_module.so") < 0) {
    perror("shm_error");
    return 5;
  }

  return 0;
}