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
  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 int i, max_long, bytes, bytes_updated;
  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         bytes = (max_long + 1) * sizeof(unsigned long);
  83         bytes_updated = max(bytes, t->io_bitmap_max);
  84
  85         t->io_bitmap_max = bytes;
  86
  87 #ifdef CONFIG_X86_32
  88         /*
  89          * Sets the lazy trigger so that the next I/O operation will
  90          * reload the correct bitmap.
  91          * Reset the owner so that a process switch will not set
  92          * tss->io_bitmap_base to IO_BITMAP_OFFSET.
  93          */
  94         tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
  95         tss->io_bitmap_owner = NULL;
  96 #else
  97         /* Update the TSS: */
  98         memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
  99 #endif
 100
 101         put_cpu();
 102
 103         return 0;
 104 }
 105
 106 /*
 107  * sys_iopl has to be used when you want to access the IO ports
 108  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
 109  * you'd need 8kB of bitmaps/process, which is a bit excessive.
 110  *
 111  * Here we just change the flags value on the stack: we allow
 112  * only the super-user to do it. This depends on the stack-layout
 113  * on system-call entry - see also fork() and the signal handling
 114  * code.
 115  */
 116 static int do_iopl(unsigned int level, struct pt_regs *regs)
 117 {
 118         unsigned int old = (regs->flags >> 12) & 3;
 119
 120         if (level > 3)
 121                 return -EINVAL;
 122         /* Trying to gain more privileges? */
 123         if (level > old) {
 124                 if (!capable(CAP_SYS_RAWIO))
 125                         return -EPERM;
 126         }
 127         regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
 128
 129         return 0;
 130 }
 131
 132 #ifdef CONFIG_X86_32
 133 asmlinkage long sys_iopl(unsigned long regsp)
 134 {
 135         struct pt_regs *regs = (struct pt_regs *)&regsp;
 136         unsigned int level = regs->bx;
 137         struct thread_struct *t = &current->thread;
 138         int rc;
 139
 140         rc = do_iopl(level, regs);
 141         if (rc < 0)
 142                 goto out;
 143
 144         t->iopl = level << 12;
 145         set_iopl_mask(t->iopl);
 146 out:
 147         return rc;
 148 }
 149 #else
 150 asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
 151 {
 152         return do_iopl(level, regs);
 153 }
 154 #endif