kernel/ioport.c

/*
 *	linux/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>

static unsigned long ioport_registrar[IO_BITMAP_SIZE] = {0, /* ... */};

#define _IODEBUG

#ifdef IODEBUG
static char * ios(unsigned long l)
{
	static char str[33] = { '\0' };
	int i;
	unsigned long mask;

	for (i = 0, mask = 0x80000000; i < 32; ++i, mask >>= 1)
		str[i] = (l & mask) ? '1' : '0';
	return str;
}

static void dump_io_bitmap(void)
{
	int i, j;
	int numl = sizeof(current->tss.io_bitmap) >> 2;

	for (i = j = 0; j < numl; ++i)
	{
		printk("%4d [%3x]: ", 64*i, 64*i);
		printk("%s ", ios(current->tss.io_bitmap[j++]));
		if (j < numl)
			printk("%s", ios(current->tss.io_bitmap[j++]));
		printk("\n");
	}
}
#endif

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

/* Check for set bits in BITMAP starting at BASE, going to EXTENT. */
asmlinkage int check_bitmap(unsigned long *bitmap, short base, short extent)
{
	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 (*bitmap_base++ & mask)
			return 1;
		length -= 32;
	}
	while (length >= 32) {
		if (*bitmap_base++ != 0)
			return 1;
		length -= 32;
	}

	if (length > 0) {
		mask = ~(~0 << length);
		if (*bitmap_base++ & mask)
			return 1;
	}
	return 0;
}

/*
 * 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())
		return -EPERM;

#ifdef IODEBUG
	printk("io: from=%d num=%d %s\n", from, num, (turn_on ? "on" : "off"));
#endif
	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())
		return -EPERM;
	*(&eflags) = (eflags & 0xffffcfff) | (level << 12);
	return 0;
}


void snarf_region(unsigned int from, unsigned int num)
{
	if (from > IO_BITMAP_SIZE*32)
		return;
	if (from + num > IO_BITMAP_SIZE*32)
		num = IO_BITMAP_SIZE*32 - from;
	set_bitmap(ioport_registrar, from, num, 1);
	return;
}

int check_region(unsigned int from, unsigned int num)
{
	if (from > IO_BITMAP_SIZE*32)
		return 0;
	if (from + num > IO_BITMAP_SIZE*32)
		num = IO_BITMAP_SIZE*32 - from;
	return check_bitmap(ioport_registrar, from, num);
}

/* Called from init/main.c to reserve IO ports. */
void reserve_setup(char *str, int *ints)
{
	int i;

	for (i = 1; i < ints[0]; i += 2)
		snarf_region(ints[i], ints[i+1]);
}