#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <elf.h>
#include <link.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>


int main (int argc, char *argv[])
{
  const char *filename = argv[1];
  ElfW(Ehdr) header;
  int fd = open (filename, O_RDWR);

  ssize_t bytes_read = read (fd, &header, sizeof (header));
  if (bytes_read != sizeof (header))
    {
      return -1;
    }

  ElfW(Phdr) *ph = malloc (header.e_phnum * header.e_phentsize);
  if (ph == 0)
    {
      return -2;
    }
  if (lseek (fd, header.e_phoff, SEEK_SET) == -1)
    {
      return -3;
    }
  if (read (fd, ph, header.e_phnum * header.e_phentsize) != header.e_phnum * header.e_phentsize)
    {
      return -4;
    }
  int i;
  for (i = 0; i < header.e_phnum; i++)
    {
      if (ph[i].p_type == PT_INTERP)
	{
	  if (strlen (argv[2]) + 1> ph[i].p_filesz)
	    {
	      return -5;
	    }
	  if (lseek (fd, ph[i].p_offset, SEEK_SET) == -1)
	    {
	      return -6;
	    }
	  char *interp = malloc (ph[i].p_filesz);
	  memset (interp, 0, ph[i].p_filesz);
	  memcpy (interp, argv[2], strlen (argv[2]));
	  if (write (fd, argv[2], ph[i].p_filesz) != ph[i].p_filesz)
	    {
	      return -7;
	    }
	  if (lseek (fd, header.e_phoff + ((long)&ph[i].p_filesz - (long)ph), SEEK_SET) == -1)
	    {
	      return -8;
	    }
	  ElfW(Xword) filesz = strlen (argv[2])+1;
	  if (write (fd, &filesz, sizeof(filesz)) != sizeof(filesz))
	    {
	      return -9;
	    }
	  if (lseek (fd, header.e_phoff + ((long)&ph[i].p_memsz-(long)ph), SEEK_SET) == -1)
	    {
	      return -10;
	    }
	  ElfW(Xword) memsz = strlen (argv[2])+1;
	  if (write (fd, &memsz, sizeof(memsz)) != sizeof(memsz))
	    {
	      return -11;
	    }
	  return 0;
	}
    }
  

  return 0;
}