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/*

 *      linux/arch/i386/kernel/ioport.c

 *

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

 * by Linus.

 */

#include <linux/sched.h>

#include <linux/kernel.h>

#include <linux/errno.h>

#include <linux/types.h>

#include <linux/ioport.h>

/* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */

static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)

{

        int mask;

        unsigned long *bitmap_base = bitmap + (base >> 5);

        unsigned short low_index = base & 0x1f;

        int length = low_index + extent;

        if (low_index != 0) {

                mask = (~0 << low_index);

                if (length < 32)

                                mask &= ~(~0 << length);

                if (new_value)

                        *bitmap_base++ |= mask;

                else

                        *bitmap_base++ &= ~mask;

                length -= 32;

        }

        mask = (new_value ? ~0 : 0);

        while (length >= 32) {

                *bitmap_base++ = mask;

                length -= 32;

        }

        if (length > 0) {

                mask = ~(~0 << length);

                if (new_value)

                        *bitmap_base++ |= mask;

                else

                        *bitmap_base++ &= ~mask;

        }

}

/*

 * this changes the io permissions bitmap in the current task.

 */

asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)

{

        if (from + num <= from)

                return -EINVAL;

        if (from + num > IO_BITMAP_SIZE*32)

                return -EINVAL;

        if (!suser() || securelevel > 0)

                return -EPERM;

        set_bitmap((unsigned long *)current->tss.io_bitmap, from, num, !turn_on);

        return 0;

}

unsigned int *stack;

/*

 * 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 eflags 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.

 */

asmlinkage int sys_iopl(long ebx,long ecx,long edx,

             long esi, long edi, long ebp, long eax, long ds,

             long es, long fs, long gs, long orig_eax,

             long eip,long cs,long eflags,long esp,long ss)

{

        unsigned int level = ebx;

        if (level > 3)

                return -EINVAL;

        if (!suser() || securelevel > 0)

                return -EPERM;

        *(&eflags) = (eflags & 0xffffcfff) | (level << 12);

        return 0;

}