LXR linux/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. */
  20static 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 */
  36asmlinkage 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 */
 106long 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}
 124