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. */
19static 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 */
55asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
56{
57	struct thread_struct * t = &current->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
101asmlinkage 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