#include <stdio.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <elf.h>

#define AT_SEC(ehdr, shdr) ((void *)(ehdr) + (shdr)->sh_offset)

int main(int argc, char **argv) {
  /* Open the file and get its size: */
  int fd = open(argv[1], O_RDONLY);
  size_t len = lseek(fd, 0, SEEK_END);

  /* Map the whole file into memory: */
  void *p = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);

  Elf64_Ehdr *ehdr = (Elf64_Ehdr *)p;

  if ((ehdr->e_ident[0] != 0x7F) || (ehdr->e_ident[1] != 'E')
      || (ehdr->e_ident[2] != 'L') || (ehdr->e_ident[3] != 'F'))
    printf("not an ELF file!\n");

  switch (ehdr->e_type) {
  case ET_REL: printf("object\n"); break;
  case ET_EXEC: printf("executable\n"); break;
  case ET_DYN: printf("shared library\n"); break;
  }

  printf("%d sections\n", ehdr->e_shnum);

  {
    Elf64_Shdr *shdrs = (void *)ehdr + ehdr->e_shoff;
    int i;
    char *strs = AT_SEC(ehdr, shdrs + ehdr->e_shstrndx);

    for (i = 0; i < ehdr->e_shnum; i++) {
      printf("%s %ld\n", strs + shdrs[i].sh_name, shdrs[i].sh_size);
    }
  }

  return 0;
}