linux-bk/arch/i386/kernel/ioport.c
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   1/*
   2 *      linux/arch/i386/kernel/ioport.c
   3 *
   4 * This contains the io-permission bitmap code - written by obz, with changes
   5 * by Linus.
   6 */
   7
   8#include <linux/sched.h>
   9#include <linux/kernel.h>
  10#include <linux/errno.h>
  11#include <linux/types.h>
  12#include <linux/ioport.h>
  13#include <linux/smp.h>
  14#include <linux/smp_lock.h>
  15#include <linux/stddef.h>
  16#include <linux/slab.h>
  17#include <linux/thread_info.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, unsigned int extent, int new_value)
  21{
  22        unsigned long mask;
  23        unsigned long *bitmap_base = bitmap + (base / BITS_PER_LONG);
  24        unsigned int low_index = base & (BITS_PER_LONG-1);
  25        int length = low_index + extent;
  26
  27        if (low_index != 0) {
  28                mask = (~0UL << low_index);
  29                if (length < BITS_PER_LONG)
  30                        mask &= ~(~0UL << length);
  31                if (new_value)
  32                        *bitmap_base++ |= mask;
  33                else
  34                        *bitmap_base++ &= ~mask;
  35                length -= BITS_PER_LONG;
  36        }
  37
  38        mask = (new_value ? ~0UL : 0UL);
  39        while (length >= BITS_PER_LONG) {
  40                *bitmap_base++ = mask;
  41                length -= BITS_PER_LONG;
  42        }
  43
  44        if (length > 0) {
  45                mask = ~(~0UL << length);
  46                if (new_value)
  47                        *bitmap_base++ |= mask;
  48                else
  49                        *bitmap_base++ &= ~mask;
  50        }
  51}
  52
  53
  54/*
  55 * this changes the io permissions bitmap in the current task.
  56 */
  57asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  58{
  59        unsigned long i, max_long, bytes, bytes_updated;
  60        struct thread_struct * t = &current->thread;
  61        struct tss_struct * tss;
  62        unsigned long *bitmap;
  63
  64        if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  65                return -EINVAL;
  66        if (turn_on && !capable(CAP_SYS_RAWIO))
  67                return -EPERM;
  68
  69        /*
  70         * If it's the first ioperm() call in this thread's lifetime, set the
  71         * IO bitmap up. ioperm() is much less timing critical than clone(),
  72         * this is why we delay this operation until now:
  73         */
  74        if (!t->io_bitmap_ptr) {
  75                bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
  76                if (!bitmap)
  77                        return -ENOMEM;
  78
  79                memset(bitmap, 0xff, IO_BITMAP_BYTES);
  80                t->io_bitmap_ptr = bitmap;
  81        }
  82
  83        /*
  84         * do it in the per-thread copy and in the TSS ...
  85         *
  86         * Disable preemption via get_cpu() - we must not switch away
  87         * because the ->io_bitmap_max value must match the bitmap
  88         * contents:
  89         */
  90        tss = &per_cpu(init_tss, get_cpu());
  91
  92        set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
  93
  94        /*
  95         * Search for a (possibly new) maximum. This is simple and stupid,
  96         * to keep it obviously correct:
  97         */
  98        max_long = 0;
  99        for (i = 0; i < IO_BITMAP_LONGS; i++)
 100                if (t->io_bitmap_ptr[i] != ~0UL)
 101                        max_long = i;
 102
 103        bytes = (max_long + 1) * sizeof(long);
 104        bytes_updated = max(bytes, t->io_bitmap_max);
 105
 106        t->io_bitmap_max = bytes;
 107
 108        /*
 109         * Sets the lazy trigger so that the next I/O operation will
 110         * reload the correct bitmap.
 111         */
 112        tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
 113
 114        put_cpu();
 115
 116        return 0;
 117}
 118
 119/*
 120 * sys_iopl has to be used when you want to access the IO ports
 121 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
 122 * you'd need 8kB of bitmaps/process, which is a bit excessive.
 123 *
 124 * Here we just change the eflags value on the stack: we allow
 125 * only the super-user to do it. This depends on the stack-layout
 126 * on system-call entry - see also fork() and the signal handling
 127 * code.
 128 */
 129
 130asmlinkage long sys_iopl(unsigned long unused)
 131{
 132        volatile struct pt_regs * regs = (struct pt_regs *) &unused;
 133        unsigned int level = regs->ebx;
 134        unsigned int old = (regs->eflags >> 12) & 3;
 135
 136        if (level > 3)
 137                return -EINVAL;
 138        /* Trying to gain more privileges? */
 139        if (level > old) {
 140                if (!capable(CAP_SYS_RAWIO))
 141                        return -EPERM;
 142        }
 143        regs->eflags = (regs->eflags &~ 0x3000UL) | (level << 12);
 144        /* Make sure we return the long way (not sysenter) */
 145        set_thread_flag(TIF_IRET);
 146        return 0;
 147}
 148
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