arch/x86/kernel/ioport_32.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,
  20                        unsigned int extent, int new_value)
  21 {
  22         unsigned int i;
  23
  24         for (i = base; i < base + extent; i++) {
  25                 if (new_value)
  26                         __set_bit(i, bitmap);
  27                 else
  28                         __clear_bit(i, bitmap);
  29         }
  30 }
  31
  32 /*
  33  * this changes the io permissions bitmap in the current task.
  34  */
  35 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  36 {
  37         struct thread_struct * t = &current->thread;
  38         struct tss_struct * tss;
  39         unsigned long i, max_long;
  40
  41         if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  42                 return -EINVAL;
  43         if (turn_on && !capable(CAP_SYS_RAWIO))
  44                 return -EPERM;
  45
  46         /*
  47          * If it's the first ioperm() call in this thread's lifetime, set the
  48          * IO bitmap up. ioperm() is much less timing critical than clone(),
  49          * this is why we delay this operation until now:
  50          */
  51         if (!t->io_bitmap_ptr) {
  52                 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
  53
  54                 if (!bitmap)
  55                         return -ENOMEM;
  56
  57                 memset(bitmap, 0xff, IO_BITMAP_BYTES);
  58                 t->io_bitmap_ptr = bitmap;
  59                 set_thread_flag(TIF_IO_BITMAP);
  60         }
  61
  62         /*
  63          * do it in the per-thread copy and in the TSS ...
  64          *
  65          * Disable preemption via get_cpu() - we must not switch away
  66          * because the ->io_bitmap_max value must match the bitmap
  67          * contents:
  68          */
  69         tss = &per_cpu(init_tss, get_cpu());
  70
  71         set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
  72
  73         /*
  74          * Search for a (possibly new) maximum. This is simple and stupid,
  75          * to keep it obviously correct:
  76          */
  77         max_long = 0;
  78         for (i = 0; i < IO_BITMAP_LONGS; i++)
  79                 if (t->io_bitmap_ptr[i] != ~0UL)
  80                         max_long = i;
  81
  82         t->io_bitmap_max = (max_long + 1) * sizeof(unsigned long);
  83
  84         /*
  85          * Sets the lazy trigger so that the next I/O operation will
  86          * reload the correct bitmap.
  87          * Reset the owner so that a process switch will not set
  88          * tss->io_bitmap_base to IO_BITMAP_OFFSET.
  89          */
  90         tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
  91         tss->io_bitmap_owner = NULL;
  92
  93         put_cpu();
  94
  95         return 0;
  96 }
  97
  98 /*
  99  * sys_iopl has to be used when you want to access the IO ports
 100  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
 101  * you'd need 8kB of bitmaps/process, which is a bit excessive.
 102  *
 103  * Here we just change the flags value on the stack: we allow
 104  * only the super-user to do it. This depends on the stack-layout
 105  * on system-call entry - see also fork() and the signal handling
 106  * code.
 107  */
 108
 109 asmlinkage long sys_iopl(unsigned long regsp)
 110 {
 111         volatile struct pt_regs *regs = (struct pt_regs *)&regsp;
 112         unsigned int level = regs->bx;
 113         unsigned int old = (regs->flags >> 12) & 3;
 114         struct thread_struct *t = &current->thread;
 115
 116         if (level > 3)
 117                 return -EINVAL;
 118         /* Trying to gain more privileges? */
 119         if (level > old) {
 120                 if (!capable(CAP_SYS_RAWIO))
 121                         return -EPERM;
 122         }
 123
 124         t->iopl = level << 12;
 125         regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | t->iopl;
 126         set_iopl_mask(t->iopl);
 127
 128         return 0;
 129 }