2 * linux/arch/i386/kernel/ioport.c
4 * This contains the io-permission bitmap code - written by obz, with changes
8 #include <linux/sched.h>
9 #include <linux/kernel.h>
10 #include <linux/capability.h>
11 #include <linux/errno.h>
12 #include <linux/types.h>
13 #include <linux/ioport.h>
14 #include <linux/smp.h>
15 #include <linux/smp_lock.h>
16 #include <linux/stddef.h>
17 #include <linux/slab.h>
18 #include <linux/thread_info.h>
20 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
21 static void set_bitmap(unsigned long *bitmap
, unsigned int base
, unsigned int extent
, int new_value
)
24 unsigned long *bitmap_base
= bitmap
+ (base
/ BITS_PER_LONG
);
25 unsigned int low_index
= base
& (BITS_PER_LONG
-1);
26 int length
= low_index
+ extent
;
29 mask
= (~0UL << low_index
);
30 if (length
< BITS_PER_LONG
)
31 mask
&= ~(~0UL << length
);
33 *bitmap_base
++ |= mask
;
35 *bitmap_base
++ &= ~mask
;
36 length
-= BITS_PER_LONG
;
39 mask
= (new_value
? ~0UL : 0UL);
40 while (length
>= BITS_PER_LONG
) {
41 *bitmap_base
++ = mask
;
42 length
-= BITS_PER_LONG
;
46 mask
= ~(~0UL << length
);
48 *bitmap_base
++ |= mask
;
50 *bitmap_base
++ &= ~mask
;
56 * this changes the io permissions bitmap in the current task.
58 asmlinkage
long sys_ioperm(unsigned long from
, unsigned long num
, int turn_on
)
60 unsigned long i
, max_long
, bytes
, bytes_updated
;
61 struct thread_struct
* t
= ¤t
->thread
;
62 struct tss_struct
* tss
;
63 unsigned long *bitmap
;
65 if ((from
+ num
<= from
) || (from
+ num
> IO_BITMAP_BITS
))
67 if (turn_on
&& !capable(CAP_SYS_RAWIO
))
71 * If it's the first ioperm() call in this thread's lifetime, set the
72 * IO bitmap up. ioperm() is much less timing critical than clone(),
73 * this is why we delay this operation until now:
75 if (!t
->io_bitmap_ptr
) {
76 bitmap
= kmalloc(IO_BITMAP_BYTES
, GFP_KERNEL
);
80 memset(bitmap
, 0xff, IO_BITMAP_BYTES
);
81 t
->io_bitmap_ptr
= bitmap
;
85 * do it in the per-thread copy and in the TSS ...
87 * Disable preemption via get_cpu() - we must not switch away
88 * because the ->io_bitmap_max value must match the bitmap
91 tss
= &per_cpu(init_tss
, get_cpu());
93 set_bitmap(t
->io_bitmap_ptr
, from
, num
, !turn_on
);
96 * Search for a (possibly new) maximum. This is simple and stupid,
97 * to keep it obviously correct:
100 for (i
= 0; i
< IO_BITMAP_LONGS
; i
++)
101 if (t
->io_bitmap_ptr
[i
] != ~0UL)
104 bytes
= (max_long
+ 1) * sizeof(long);
105 bytes_updated
= max(bytes
, t
->io_bitmap_max
);
107 t
->io_bitmap_max
= bytes
;
110 * Sets the lazy trigger so that the next I/O operation will
111 * reload the correct bitmap.
112 * Reset the owner so that a process switch will not set
113 * tss->io_bitmap_base to IO_BITMAP_OFFSET.
115 tss
->io_bitmap_base
= INVALID_IO_BITMAP_OFFSET_LAZY
;
116 tss
->io_bitmap_owner
= NULL
;
124 * sys_iopl has to be used when you want to access the IO ports
125 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
126 * you'd need 8kB of bitmaps/process, which is a bit excessive.
128 * Here we just change the eflags value on the stack: we allow
129 * only the super-user to do it. This depends on the stack-layout
130 * on system-call entry - see also fork() and the signal handling
134 asmlinkage
long sys_iopl(unsigned long unused
)
136 volatile struct pt_regs
* regs
= (struct pt_regs
*) &unused
;
137 unsigned int level
= regs
->ebx
;
138 unsigned int old
= (regs
->eflags
>> 12) & 3;
139 struct thread_struct
*t
= ¤t
->thread
;
143 /* Trying to gain more privileges? */
145 if (!capable(CAP_SYS_RAWIO
))
148 t
->iopl
= level
<< 12;
149 regs
->eflags
= (regs
->eflags
& ~X86_EFLAGS_IOPL
) | t
->iopl
;
150 set_iopl_mask(t
->iopl
);