arch/i386/kernel/ioport.c

   1 /*
   2  *      linux/arch/i386/kernel/ioport.c
   3  *
   4  * This contains the io-permission bitmap code - written by obz, with changes
   5  * by Linus.
   6  */
   7
   8 #include <linux/sched.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/types.h>
  12 #include <linux/ioport.h>
  13 #include <linux/mm.h>
  14 #include <linux/smp.h>
  15 #include <linux/smp_lock.h>
  16 #include <linux/stddef.h>
  17
  18 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
  19 static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)
  20 {
  21         int mask;
  22         unsigned long *bitmap_base = bitmap + (base >> 5);
  23         unsigned short low_index = base & 0x1f;
  24         int length = low_index + extent;
  25
  26         if (low_index != 0) {
  27                 mask = (~0 << low_index);
  28                 if (length < 32)
  29                                 mask &= ~(~0 << length);
  30                 if (new_value)
  31                         *bitmap_base++ |= mask;
  32                 else
  33                         *bitmap_base++ &= ~mask;
  34                 length -= 32;
  35         }
  36
  37         mask = (new_value ? ~0 : 0);
  38         while (length >= 32) {
  39                 *bitmap_base++ = mask;
  40                 length -= 32;
  41         }
  42
  43         if (length > 0) {
  44                 mask = ~(~0 << length);
  45                 if (new_value)
  46                         *bitmap_base++ |= mask;
  47                 else
  48                         *bitmap_base++ &= ~mask;
  49         }
  50 }
  51
  52 /*
  53  * this changes the io permissions bitmap in the current task.
  54  */
  55 asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  56 {
  57         struct thread_struct * t = &current->thread;
  58         struct tss_struct * tss = init_tss + smp_processor_id();
  59
  60         if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32))
  61                 return -EINVAL;
  62         if (turn_on && !capable(CAP_SYS_RAWIO))
  63                 return -EPERM;
  64         /*
  65          * If it's the first ioperm() call in this thread's lifetime, set the
  66          * IO bitmap up. ioperm() is much less timing critical than clone(),
  67          * this is why we delay this operation until now:
  68          */
  69         if (!t->ioperm) {
  70                 /*
  71                  * just in case ...
  72                  */
  73                 memset(t->io_bitmap,0xff,(IO_BITMAP_SIZE+1)*4);
  74                 t->ioperm = 1;
  75                 /*
  76                  * this activates it in the TSS
  77                  */
  78                 tss->bitmap = IO_BITMAP_OFFSET;
  79         }
  80
  81         /*
  82          * do it in the per-thread copy and in the TSS ...
  83          */
  84         set_bitmap(t->io_bitmap, from, num, !turn_on);
  85         set_bitmap(tss->io_bitmap, from, num, !turn_on);
  86
  87         return 0;
  88 }
  89
  90 /*
  91  * sys_iopl has to be used when you want to access the IO ports
  92  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
  93  * you'd need 8kB of bitmaps/process, which is a bit excessive.
  94  *
  95  * Here we just change the eflags value on the stack: we allow
  96  * only the super-user to do it. This depends on the stack-layout
  97  * on system-call entry - see also fork() and the signal handling
  98  * code.
  99  */
 100
 101 asmlinkage int sys_iopl(unsigned long unused)
 102 {
 103         struct pt_regs * regs = (struct pt_regs *) &unused;
 104         unsigned int level = regs->ebx;
 105         unsigned int old = (regs->eflags >> 12) & 3;
 106
 107         if (level > 3)
 108                 return -EINVAL;
 109         /* Trying to gain more privileges? */
 110         if (level > old) {
 111                 if (!capable(CAP_SYS_RAWIO))
 112                         return -EPERM;
 113         }
 114         regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12);
 115         return 0;
 116 }