arch/x86/kernel/ioport_64.c

   1 /*
   2  * This contains the io-permission bitmap code - written by obz, with changes
   3  * by Linus.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/kernel.h>
   8 #include <linux/capability.h>
   9 #include <linux/errno.h>
  10 #include <linux/types.h>
  11 #include <linux/ioport.h>
  12 #include <linux/smp.h>
  13 #include <linux/stddef.h>
  14 #include <linux/slab.h>
  15 #include <linux/thread_info.h>
  16 #include <linux/syscalls.h>
  17
  18 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
  19 static void set_bitmap(unsigned long *bitmap, unsigned int base, unsigned int extent, int new_value)
  20 {
  21         int i;
  22                 if (new_value)
  23                 for (i = base; i < base + extent; i++)
  24                         __set_bit(i, bitmap);
  25                 else
  26                 for (i = base; i < base + extent; i++)
  27                         clear_bit(i, bitmap);
  28 }
  29
  30 /*
  31  * this changes the io permissions bitmap in the current task.
  32  */
  33 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  34 {
  35         unsigned int i, max_long, bytes, bytes_updated;
  36         struct thread_struct * t = &current->thread;
  37         struct tss_struct * tss;
  38         unsigned long *bitmap;
  39
  40         if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  41                 return -EINVAL;
  42         if (turn_on && !capable(CAP_SYS_RAWIO))
  43                 return -EPERM;
  44
  45         /*
  46          * If it's the first ioperm() call in this thread's lifetime, set the
  47          * IO bitmap up. ioperm() is much less timing critical than clone(),
  48          * this is why we delay this operation until now:
  49          */
  50         if (!t->io_bitmap_ptr) {
  51                 bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
  52                 if (!bitmap)
  53                         return -ENOMEM;
  54
  55                 memset(bitmap, 0xff, IO_BITMAP_BYTES);
  56                 t->io_bitmap_ptr = bitmap;
  57                 set_thread_flag(TIF_IO_BITMAP);
  58         }
  59
  60         /*
  61          * do it in the per-thread copy and in the TSS ...
  62          *
  63          * Disable preemption via get_cpu() - we must not switch away
  64          * because the ->io_bitmap_max value must match the bitmap
  65          * contents:
  66          */
  67         tss = &per_cpu(init_tss, get_cpu());
  68
  69         set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
  70
  71         /*
  72          * Search for a (possibly new) maximum. This is simple and stupid,
  73          * to keep it obviously correct:
  74          */
  75         max_long = 0;
  76         for (i = 0; i < IO_BITMAP_LONGS; i++)
  77                 if (t->io_bitmap_ptr[i] != ~0UL)
  78                         max_long = i;
  79
  80         bytes = (max_long + 1) * sizeof(long);
  81         bytes_updated = max(bytes, t->io_bitmap_max);
  82
  83         t->io_bitmap_max = bytes;
  84
  85         /* Update the TSS: */
  86         memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
  87
  88         put_cpu();
  89
  90         return 0;
  91 }
  92
  93 /*
  94  * sys_iopl has to be used when you want to access the IO ports
  95  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
  96  * you'd need 8kB of bitmaps/process, which is a bit excessive.
  97  *
  98  * Here we just change the eflags value on the stack: we allow
  99  * only the super-user to do it. This depends on the stack-layout
 100  * on system-call entry - see also fork() and the signal handling
 101  * code.
 102  */
 103
 104 asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
 105 {
 106         unsigned int old = (regs->eflags >> 12) & 3;
 107
 108         if (level > 3)
 109                 return -EINVAL;
 110         /* Trying to gain more privileges? */
 111         if (level > old) {
 112                 if (!capable(CAP_SYS_RAWIO))
 113                         return -EPERM;
 114         }
 115         regs->eflags = (regs->eflags &~ X86_EFLAGS_IOPL) | (level << 12);
 116         return 0;
 117 }