arch/x86/kernel/ioport.c

   1 /*
   2  * This contains the io-permission bitmap code - written by obz, with changes
   3  * by Linus. 32/64 bits code unification by Miguel Botón.
   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 #include <asm/syscalls.h>
  18
  19 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
  20 static void set_bitmap(unsigned long *bitmap, unsigned int base,
  21                        unsigned int extent, int new_value)
  22 {
  23         unsigned int i;
  24
  25         for (i = base; i < base + extent; i++) {
  26                 if (new_value)
  27                         __set_bit(i, bitmap);
  28                 else
  29                         __clear_bit(i, bitmap);
  30         }
  31 }
  32
  33 /*
  34  * this changes the io permissions bitmap in the current task.
  35  */
  36 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  37 {
  38         struct thread_struct *t = &current->thread;
  39         struct tss_struct *tss;
  40         unsigned int i, max_long, bytes, bytes_updated;
  41
  42         if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  43                 return -EINVAL;
  44         if (turn_on && !capable(CAP_SYS_RAWIO))
  45                 return -EPERM;
  46
  47         /*
  48          * If it's the first ioperm() call in this thread's lifetime, set the
  49          * IO bitmap up. ioperm() is much less timing critical than clone(),
  50          * this is why we delay this operation until now:
  51          */
  52         if (!t->io_bitmap_ptr) {
  53                 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
  54
  55                 if (!bitmap)
  56                         return -ENOMEM;
  57
  58                 memset(bitmap, 0xff, IO_BITMAP_BYTES);
  59                 t->io_bitmap_ptr = bitmap;
  60                 set_thread_flag(TIF_IO_BITMAP);
  61         }
  62
  63         /*
  64          * do it in the per-thread copy and in the TSS ...
  65          *
  66          * Disable preemption via get_cpu() - we must not switch away
  67          * because the ->io_bitmap_max value must match the bitmap
  68          * contents:
  69          */
  70         tss = &per_cpu(init_tss, get_cpu());
  71
  72         set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
  73
  74         /*
  75          * Search for a (possibly new) maximum. This is simple and stupid,
  76          * to keep it obviously correct:
  77          */
  78         max_long = 0;
  79         for (i = 0; i < IO_BITMAP_LONGS; i++)
  80                 if (t->io_bitmap_ptr[i] != ~0UL)
  81                         max_long = i;
  82
  83         bytes = (max_long + 1) * sizeof(unsigned long);
  84         bytes_updated = max(bytes, t->io_bitmap_max);
  85
  86         t->io_bitmap_max = bytes;
  87
  88         /* Update the TSS: */
  89         memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
  90
  91         put_cpu();
  92
  93         return 0;
  94 }
  95
  96 /*
  97  * sys_iopl has to be used when you want to access the IO ports
  98  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
  99  * you'd need 8kB of bitmaps/process, which is a bit excessive.
 100  *
 101  * Here we just change the flags value on the stack: we allow
 102  * only the super-user to do it. This depends on the stack-layout
 103  * on system-call entry - see also fork() and the signal handling
 104  * code.
 105  */
 106 long sys_iopl(unsigned int level, struct pt_regs *regs)
 107 {
 108         unsigned int old = (regs->flags >> 12) & 3;
 109         struct thread_struct *t = &current->thread;
 110
 111         if (level > 3)
 112                 return -EINVAL;
 113         /* Trying to gain more privileges? */
 114         if (level > old) {
 115                 if (!capable(CAP_SYS_RAWIO))
 116                         return -EPERM;
 117         }
 118         regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
 119         t->iopl = level << 12;
 120         set_iopl_mask(t->iopl);
 121
 122         return 0;
 123 }