File: /usr/src/linux/arch/i386/kernel/ioport.c
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/mm.h>
14 #include <linux/smp.h>
15 #include <linux/smp_lock.h>
16 #include <linux/stddef.h>
17
18 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
19 static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)
20 {
21 int mask;
22 unsigned long *bitmap_base = bitmap + (base >> 5);
23 unsigned short low_index = base & 0x1f;
24 int length = low_index + extent;
25
26 if (low_index != 0) {
27 mask = (~0 << low_index);
28 if (length < 32)
29 mask &= ~(~0 << length);
30 if (new_value)
31 *bitmap_base++ |= mask;
32 else
33 *bitmap_base++ &= ~mask;
34 length -= 32;
35 }
36
37 mask = (new_value ? ~0 : 0);
38 while (length >= 32) {
39 *bitmap_base++ = mask;
40 length -= 32;
41 }
42
43 if (length > 0) {
44 mask = ~(~0 << length);
45 if (new_value)
46 *bitmap_base++ |= mask;
47 else
48 *bitmap_base++ &= ~mask;
49 }
50 }
51
52 /*
53 * this changes the io permissions bitmap in the current task.
54 */
55 asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
56 {
57 struct thread_struct * t = ¤t->thread;
58 struct tss_struct * tss = init_tss + smp_processor_id();
59
60 if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32))
61 return -EINVAL;
62 if (turn_on && !capable(CAP_SYS_RAWIO))
63 return -EPERM;
64 /*
65 * If it's the first ioperm() call in this thread's lifetime, set the
66 * IO bitmap up. ioperm() is much less timing critical than clone(),
67 * this is why we delay this operation until now:
68 */
69 if (!t->ioperm) {
70 /*
71 * just in case ...
72 */
73 memset(t->io_bitmap,0xff,(IO_BITMAP_SIZE+1)*4);
74 t->ioperm = 1;
75 /*
76 * this activates it in the TSS
77 */
78 tss->bitmap = IO_BITMAP_OFFSET;
79 }
80
81 /*
82 * do it in the per-thread copy and in the TSS ...
83 */
84 set_bitmap(t->io_bitmap, from, num, !turn_on);
85 set_bitmap(tss->io_bitmap, from, num, !turn_on);
86
87 return 0;
88 }
89
90 /*
91 * sys_iopl has to be used when you want to access the IO ports
92 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
93 * you'd need 8kB of bitmaps/process, which is a bit excessive.
94 *
95 * Here we just change the eflags value on the stack: we allow
96 * only the super-user to do it. This depends on the stack-layout
97 * on system-call entry - see also fork() and the signal handling
98 * code.
99 */
100
101 asmlinkage int sys_iopl(unsigned long unused)
102 {
103 struct pt_regs * regs = (struct pt_regs *) &unused;
104 unsigned int level = regs->ebx;
105 unsigned int old = (regs->eflags >> 12) & 3;
106
107 if (level > 3)
108 return -EINVAL;
109 /* Trying to gain more privileges? */
110 if (level > old) {
111 if (!capable(CAP_SYS_RAWIO))
112 return -EPERM;
113 }
114 regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12);
115 return 0;
116 }
117