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(cpu_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	struct thread_struct *t = &current->thread;
100
101	/*
102	 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
103	 * and changing them has no effect.
104	 */
105	unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
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->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
115		(level << X86_EFLAGS_IOPL_BIT);
116	t->iopl = level << X86_EFLAGS_IOPL_BIT;
117	set_iopl_mask(t->iopl);
118
119	return 0;
120}
121