summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/tls.c
blob: 74d2b65a82eb8e975e83e73f6ee86220bdaa7e78 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/user.h>

#include <asm/uaccess.h>
#include <asm/desc.h>
#include <asm/system.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/proto.h>

/*
 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
 */
static int get_free_idx(void)
{
	struct thread_struct *t = &current->thread;
	int idx;

	for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
		if (desc_empty(&t->tls_array[idx]))
			return idx + GDT_ENTRY_TLS_MIN;
	return -ESRCH;
}

/*
 * Set a given TLS descriptor:
 */
int do_set_thread_area(struct task_struct *p, int idx,
		       struct user_desc __user *u_info,
		       int can_allocate)
{
	struct thread_struct *t = &p->thread;
	struct user_desc info;
	u32 *desc;
	int cpu;

	if (copy_from_user(&info, u_info, sizeof(info)))
		return -EFAULT;

	if (idx == -1)
		idx = info.entry_number;

	/*
	 * index -1 means the kernel should try to find and
	 * allocate an empty descriptor:
	 */
	if (idx == -1 && can_allocate) {
		idx = get_free_idx();
		if (idx < 0)
			return idx;
		if (put_user(idx, &u_info->entry_number))
			return -EFAULT;
	}

	if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
		return -EINVAL;

	desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];

	/*
	 * We must not get preempted while modifying the TLS.
	 */
	cpu = get_cpu();

	if (LDT_empty(&info)) {
		desc[0] = 0;
		desc[1] = 0;
	} else
		fill_ldt((struct desc_struct *)desc, &info);

	if (t == &current->thread)
		load_TLS(t, cpu);

	put_cpu();
	return 0;
}

asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
{
	return do_set_thread_area(current, -1, u_info, 1);
}


/*
 * Get the current Thread-Local Storage area:
 */

#define GET_LIMIT(desc)		(((desc)[0] & 0x0ffff) | ((desc)[1] & 0xf0000))
#define GET_32BIT(desc)		(((desc)[1] >> 22) & 1)
#define GET_CONTENTS(desc)	(((desc)[1] >> 10) & 3)
#define GET_WRITABLE(desc)	(((desc)[1] >>  9) & 1)
#define GET_LIMIT_PAGES(desc)	(((desc)[1] >> 23) & 1)
#define GET_PRESENT(desc)	(((desc)[1] >> 15) & 1)
#define GET_USEABLE(desc)	(((desc)[1] >> 20) & 1)
#define GET_LONGMODE(desc)	(((desc)[1] >> 21) & 1)

int do_get_thread_area(struct task_struct *p, int idx,
		       struct user_desc __user *u_info)
{
	struct thread_struct *t = &p->thread;
	struct user_desc info;
	u32 *desc;

	if (idx == -1 && get_user(idx, &u_info->entry_number))
		return -EFAULT;
	if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
		return -EINVAL;

	desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];

	memset(&info, 0, sizeof(struct user_desc));
	info.entry_number = idx;
	info.base_addr = get_desc_base((void *)desc);
	info.limit = GET_LIMIT(desc);
	info.seg_32bit = GET_32BIT(desc);
	info.contents = GET_CONTENTS(desc);
	info.read_exec_only = !GET_WRITABLE(desc);
	info.limit_in_pages = GET_LIMIT_PAGES(desc);
	info.seg_not_present = !GET_PRESENT(desc);
	info.useable = GET_USEABLE(desc);
#ifdef CONFIG_X86_64
	info.lm = GET_LONGMODE(desc);
#endif

	if (copy_to_user(u_info, &info, sizeof(info)))
		return -EFAULT;
	return 0;
}

asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
{
	return do_get_thread_area(current, -1, u_info);
}