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