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#ifdef CONFIG_X86_32
  89        /*
  90         * Sets the lazy trigger so that the next I/O operation will
  91         * reload the correct bitmap.
  92         * Reset the owner so that a process switch will not set
  93         * tss->io_bitmap_base to IO_BITMAP_OFFSET.
  94         */
  95        tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
  96        tss->io_bitmap_owner = NULL;
  97#else
  98        /* Update the TSS: */
  99        memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
 100#endif
 101
 102        put_cpu();
 103
 104        return 0;
 105}
 106
 107/*
 108 * sys_iopl has to be used when you want to access the IO ports
 109 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
 110 * you'd need 8kB of bitmaps/process, which is a bit excessive.
 111 *
 112 * Here we just change the flags value on the stack: we allow
 113 * only the super-user to do it. This depends on the stack-layout
 114 * on system-call entry - see also fork() and the signal handling
 115 * code.
 116 */
 117static int do_iopl(unsigned int level, struct pt_regs *regs)
 118{
 119        unsigned int old = (regs->flags >> 12) & 3;
 120
 121        if (level > 3)
 122                return -EINVAL;
 123        /* Trying to gain more privileges? */
 124        if (level > old) {
 125                if (!capable(CAP_SYS_RAWIO))
 126                        return -EPERM;
 127        }
 128        regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
 129
 130        return 0;
 131}
 132
 133#ifdef CONFIG_X86_32
 134asmlinkage long sys_iopl(unsigned long regsp)
 135{
 136        struct pt_regs *regs = (struct pt_regs *)&regsp;
 137        unsigned int level = regs->bx;
 138        struct thread_struct *t = &current->thread;
 139        int rc;
 140
 141        rc = do_iopl(level, regs);
 142        if (rc < 0)
 143                goto out;
 144
 145        t->iopl = level << 12;
 146        set_iopl_mask(t->iopl);
 147out:
 148        return rc;
 149}
 150#else
 151asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
 152{
 153        return do_iopl(level, regs);
 154}
 155#endif
 156