#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Fortune Cookie Kernel Module");
MODULE_AUTHOR("M. Tim Jones, modified by Tom Kelliher");

#define MAX_COOKIE_LENGTH       PAGE_SIZE

ssize_t fortune_write( struct file *filp, const char __user *buff,
                       unsigned long len, void *data );
int fortune_read( char *page, char **start, off_t off,
                  int count, int *eof, void *data );

static struct proc_dir_entry *proc_entry;

static char *cookie_pot;  // Space for fortune strings
static int cookie_index;  // Index to write next fortune
static int next_fortune;  // Index to read next fortune

int init_fortune_module( void )
{
  int ret = 0;
  cookie_pot = (char *)vmalloc( MAX_COOKIE_LENGTH );

  if (!cookie_pot)
     ret = -ENOMEM;
  else
  {
     memset( cookie_pot, 0, MAX_COOKIE_LENGTH );
     proc_entry = create_proc_entry( "fortune", 0666, NULL );

     if (proc_entry == NULL)
     {
        ret = -ENOMEM;
        vfree(cookie_pot);
        printk(KERN_INFO "fortune: Couldn't create proc entry\n");
     }
     else
     {
        cookie_index = 0;
        next_fortune = 0;

        proc_entry->read_proc = fortune_read;
        proc_entry->write_proc = fortune_write;
        proc_entry->owner = THIS_MODULE;
        printk(KERN_INFO "fortune: Module loaded.\n");
     }
  }
  return ret;
}


void cleanup_fortune_module( void )
{
   remove_proc_entry("fortune", &proc_root);
   vfree(cookie_pot);
   printk(KERN_INFO "fortune: Module unloaded.\n");
}


module_init( init_fortune_module );
module_exit( cleanup_fortune_module );


ssize_t fortune_write( struct file *filp, const char __user *buff,
                       unsigned long len, void *data )
{
   int space_available = (MAX_COOKIE_LENGTH-cookie_index)+1;

   if (len > space_available)
   {
      printk(KERN_INFO "fortune: cookie pot is full!\n");
      return -ENOSPC;
   }

   if (copy_from_user( &cookie_pot[cookie_index], buff, len ))
      return -EFAULT;

   cookie_index += len;
   cookie_pot[cookie_index-1] = 0;

   return len;
}


int fortune_read( char *page, char **start, off_t off,
                  int count, int *eof, void *data )
{
   int len;

   if (off > 0)
   {
      *eof = 1;
      return 0;
   }

   /* Wrap-around */

   if (next_fortune >= cookie_index)
      next_fortune = 0;

   len = sprintf(page, "%s\n", &cookie_pot[next_fortune]);
   next_fortune += len;

   return len;
}