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 <linux/bitmap.h>
  18#include <linux/security.h>
  19#include <asm/syscalls.h>
  20
  21/*
  22 * this changes the io permissions bitmap in the current task.
  23 */
  24asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
  25{
  26        struct thread_struct *t = &current->thread;
  27        struct tss_struct *tss;
  28        unsigned int i, max_long, bytes, bytes_updated;
  29
  30        if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
  31                return -EINVAL;
  32        if (turn_on && (!capable(CAP_SYS_RAWIO) || (get_securelevel() > 0)))
  33                return -EPERM;
  34
  35        /*
  36         * If it's the first ioperm() call in this thread's lifetime, set the
  37         * IO bitmap up. ioperm() is much less timing critical than clone(),
  38         * this is why we delay this operation until now:
  39         */
  40        if (!t->io_bitmap_ptr) {
  41                unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
  42
  43                if (!bitmap)
  44                        return -ENOMEM;
  45
  46                memset(bitmap, 0xff, IO_BITMAP_BYTES);
  47                t->io_bitmap_ptr = bitmap;
  48                set_thread_flag(TIF_IO_BITMAP);
  49        }
  50
  51        /*
  52         * do it in the per-thread copy and in the TSS ...
  53         *
  54         * Disable preemption via get_cpu() - we must not switch away
  55         * because the ->io_bitmap_max value must match the bitmap
  56         * contents:
  57         */
  58        tss = &per_cpu(init_tss, get_cpu());
  59
  60        if (turn_on)
  61                bitmap_clear(t->io_bitmap_ptr, from, num);
  62        else
  63                bitmap_set(t->io_bitmap_ptr, from, num);
  64
  65        /*
  66         * Search for a (possibly new) maximum. This is simple and stupid,
  67         * to keep it obviously correct:
  68         */
  69        max_long = 0;
  70        for (i = 0; i < IO_BITMAP_LONGS; i++)
  71                if (t->io_bitmap_ptr[i] != ~0UL)
  72                        max_long = i;
  73
  74        bytes = (max_long + 1) * sizeof(unsigned long);
  75        bytes_updated = max(bytes, t->io_bitmap_max);
  76
  77        t->io_bitmap_max = bytes;
  78
  79        /* Update the TSS: */
  80        memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
  81
  82        put_cpu();
  83
  84        return 0;
  85}
  86
  87/*
  88 * sys_iopl has to be used when you want to access the IO ports
  89 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
  90 * you'd need 8kB of bitmaps/process, which is a bit excessive.
  91 *
  92 * Here we just change the flags value on the stack: we allow
  93 * only the super-user to do it. This depends on the stack-layout
  94 * on system-call entry - see also fork() and the signal handling
  95 * code.
  96 */
  97SYSCALL_DEFINE1(iopl, unsigned int, level)
  98{
  99        struct pt_regs *regs = current_pt_regs();
 100        unsigned int old = (regs->flags >> 12) & 3;
 101        struct thread_struct *t = &current->thread;
 102
 103        if (level > 3)
 104                return -EINVAL;
 105        /* Trying to gain more privileges? */
 106        if (level > old) {
 107                if (!capable(CAP_SYS_RAWIO) || (get_securelevel() > 0))
 108                        return -EPERM;
 109        }
 110        regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
 111        t->iopl = level << 12;
 112        set_iopl_mask(t->iopl);
 113
 114        return 0;
 115}
 116