smart memcpy

[Michael Trimarchi]

Hi all,
is it possible to map a region on memory copy on write using this idea? 
I have an invalid argument in the mmap call.
Why?
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#define MAXPATH 255

int main (int argc, char **argv)
{
  char *s,*x;
  int i;
  int addr;
  int fd;   
  int size=40960; 
  char file_memory[MAXPATH];
  pid_t p=getpid();
  s=malloc(size);
  sprintf(file_memory,"/proc/%d/mem",(int)p);
  fd = open(file_memory,O_RDONLY);
  if (fd < 0) {
          perror(file_memory);
          exit(-1);
  }
  printf ("start %s\n",file_memory);
  printf("s = %p\n",s);
  memset(s, 'X', size);
  //lseek(fd,(int)s,SEEK_SET);
  //read(fd,&addr,1);
  //printf("%c", addr);
       
   x = mmap(0,size,PROT_READ|PROT_WRITE,MAP_PRIVATE,fd,(int)s);
   if ((int)(x)>0) {
       printf("x = %p\n",x);
       *x='P';
       for (i=0;i<40; i++)
          printf("sval=%c;xval=%c;",*(x+i),*(s+i));     
  } else {
        printf("%s\n",strerror(errno));
  }  
   return 0;
}