/*

   * This contains the io-permission bitmap code - written by obz, with changes

   * by Linus. 32/64 bits code unification by Miguel Botón.

   */
  
  #include <linux/sched.h>
  #include <linux/kernel.h>

  #include <linux/capability.h>

  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/ioport.h>
  #include <linux/smp.h>

  #include <linux/stddef.h>
  #include <linux/slab.h>
  #include <linux/thread_info.h>

  #include <linux/syscalls.h>

  #include <linux/bitmap.h>

  #include <asm/syscalls.h>

  /*
   * this changes the io permissions bitmap in the current task.
   */
  asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  {

  	struct thread_struct *t = &current->thread;
  	struct tss_struct *tss;

  	unsigned int i, max_long, bytes, bytes_updated;

  
  	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  		return -EINVAL;
  	if (turn_on && !capable(CAP_SYS_RAWIO))
  		return -EPERM;
  
  	/*
  	 * If it's the first ioperm() call in this thread's lifetime, set the
  	 * IO bitmap up. ioperm() is much less timing critical than clone(),
  	 * this is why we delay this operation until now:
  	 */
  	if (!t->io_bitmap_ptr) {

  		unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);

  		if (!bitmap)
  			return -ENOMEM;
  
  		memset(bitmap, 0xff, IO_BITMAP_BYTES);
  		t->io_bitmap_ptr = bitmap;

  		set_thread_flag(TIF_IO_BITMAP);

  	}
  
  	/*
  	 * do it in the per-thread copy and in the TSS ...
  	 *
  	 * Disable preemption via get_cpu() - we must not switch away
  	 * because the ->io_bitmap_max value must match the bitmap
  	 * contents:
  	 */
  	tss = &per_cpu(init_tss, get_cpu());

  	if (turn_on)
  		bitmap_clear(t->io_bitmap_ptr, from, num);
  	else
  		bitmap_set(t->io_bitmap_ptr, from, num);

  
  	/*
  	 * Search for a (possibly new) maximum. This is simple and stupid,
  	 * to keep it obviously correct:
  	 */
  	max_long = 0;
  	for (i = 0; i < IO_BITMAP_LONGS; i++)
  		if (t->io_bitmap_ptr[i] != ~0UL)
  			max_long = i;

  	bytes = (max_long + 1) * sizeof(unsigned long);
  	bytes_updated = max(bytes, t->io_bitmap_max);

  	t->io_bitmap_max = bytes;

  	/* Update the TSS: */
  	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);

  
  	put_cpu();
  
  	return 0;
  }
  
  /*
   * sys_iopl has to be used when you want to access the IO ports
   * beyond the 0x3ff range: to get the full 65536 ports bitmapped
   * you'd need 8kB of bitmaps/process, which is a bit excessive.
   *

   * Here we just change the flags value on the stack: we allow

   * only the super-user to do it. This depends on the stack-layout
   * on system-call entry - see also fork() and the signal handling
   * code.
   */

  long sys_iopl(unsigned int level, struct pt_regs *regs)

  {

  	unsigned int old = (regs->flags >> 12) & 3;

  	struct thread_struct *t = &current->thread;

  
  	if (level > 3)
  		return -EINVAL;
  	/* Trying to gain more privileges? */
  	if (level > old) {
  		if (!capable(CAP_SYS_RAWIO))
  			return -EPERM;
  	}

  	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);

  	t->iopl = level << 12;
  	set_iopl_mask(t->iopl);

  
  	return 0;
  }