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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>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.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)
{
struct thread_struct * t = ¤t->thread;
struct tss_struct * tss = init_tss + smp_processor_id();
if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32))
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->ioperm) {
/*
* just in case ...
*/
memset(t->io_bitmap,0xff,(IO_BITMAP_SIZE+1)*4);
t->ioperm = 1;
/*
* this activates it in the TSS
*/
tss->bitmap = IO_BITMAP_OFFSET;
}
/*
* do it in the per-thread copy and in the TSS ...
*/
set_bitmap(t->io_bitmap, from, num, !turn_on);
set_bitmap(tss->io_bitmap, from, num, !turn_on);
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 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(unsigned long unused)
{
struct pt_regs * regs = (struct pt_regs *) &unused;
unsigned int level = regs->ebx;
unsigned int old = (regs->eflags >> 12) & 3;
if (level > 3)
return -EINVAL;
/* Trying to gain more privileges? */
if (level > old) {
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
}
regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12);
return 0;
}
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