aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/ia32/fpu32.c
blob: ae80745f668fc37d95baa7e275bdd35433f4e6fc (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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
/*
 * Copyright 2002 Andi Kleen, SuSE Labs.
 * FXSAVE<->i387 conversion support. Based on code by Gareth Hughes.
 * This is used for ptrace, signals and coredumps in 32bit emulation.
 */

#include <linux/sched.h>
#include <asm/sigcontext32.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/i387.h>

static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
{
	unsigned int tmp; /* to avoid 16 bit prefixes in the code */

	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
	tmp = ~twd;
	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
	/* and move the valid bits to the lower byte. */
	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
	return tmp;
}

#define FPREG_ADDR(f, n)	((void *)&(f)->st_space + (n) * 16);
#define FP_EXP_TAG_VALID	0
#define FP_EXP_TAG_ZERO		1
#define FP_EXP_TAG_SPECIAL	2
#define FP_EXP_TAG_EMPTY	3

static inline unsigned long twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
{
	struct _fpxreg *st;
	unsigned long tos = (fxsave->swd >> 11) & 7;
	unsigned long twd = (unsigned long) fxsave->twd;
	unsigned long tag;
	unsigned long ret = 0xffff0000;
	int i;

	for (i = 0; i < 8; i++, twd >>= 1) {
		if (twd & 0x1) {
			st = FPREG_ADDR(fxsave, (i - tos) & 7);

			switch (st->exponent & 0x7fff) {
			case 0x7fff:
				tag = FP_EXP_TAG_SPECIAL;
				break;
			case 0x0000:
				if (!st->significand[0] &&
				    !st->significand[1] &&
				    !st->significand[2] &&
				    !st->significand[3])
					tag = FP_EXP_TAG_ZERO;
				else
					tag = FP_EXP_TAG_SPECIAL;
				break;
			default:
				if (st->significand[3] & 0x8000)
					tag = FP_EXP_TAG_VALID;
				else
					tag = FP_EXP_TAG_SPECIAL;
				break;
			}
		} else {
			tag = FP_EXP_TAG_EMPTY;
		}
		ret |= tag << (2 * i);
	}
	return ret;
}

#define G(num, val) err |= __get_user(val, num + (u32 __user *)buf)

static inline int convert_fxsr_from_user(struct i387_fxsave_struct *fxsave,
					 struct _fpstate_ia32 __user *buf)
{
	struct _fpxreg *to;
	struct _fpreg __user *from;
	int i, err = 0;
	u32 v;

	G(0, fxsave->cwd);
	G(1, fxsave->swd);
	G(2, fxsave->twd);
	fxsave->twd = twd_i387_to_fxsr(fxsave->twd);
	G(3, fxsave->rip);
	G(4, v);
	/* cs ignored */
	fxsave->fop = v>>16;
	G(5, fxsave->rdp);
	/* 6: ds ignored */
	if (err)
		return -1;

	to = (struct _fpxreg *)&fxsave->st_space[0];
	from = &buf->_st[0];
	for (i = 0; i < 8; i++, to++, from++) {
		if (__copy_from_user(to, from, sizeof(*from)))
			return -1;
	}
	return 0;
}

#define P(num, val) err |= __put_user(val, num + (u32 __user *)buf)

static inline int convert_fxsr_to_user(struct _fpstate_ia32 __user *buf,
				       struct i387_fxsave_struct *fxsave,
				       struct pt_regs *regs,
				       struct task_struct *tsk)
{
	struct _fpreg __user *to;
	struct _fpxreg *from;
	int i, err = 0;
	u16 cs, ds;

	if (tsk == current) {
		/*
		 * should be actually ds/cs at fpu exception time, but
		 * that information is not available in 64bit mode.
		 */
		asm("movw %%ds,%0 " : "=r" (ds));
		asm("movw %%cs,%0 " : "=r" (cs));
	} else {
		 /* ptrace. task has stopped. */
		ds = tsk->thread.ds;
		cs = regs->cs;
	}

	P(0, (u32)fxsave->cwd | 0xffff0000);
	P(1, (u32)fxsave->swd | 0xffff0000);
	P(2, twd_fxsr_to_i387(fxsave));
	P(3, (u32)fxsave->rip);
	P(4,  cs | ((u32)fxsave->fop) << 16);
	P(5, fxsave->rdp);
	P(6, 0xffff0000 | ds);

	if (err)
		return -1;

	to = &buf->_st[0];
	from = (struct _fpxreg *) &fxsave->st_space[0];
	for (i = 0; i < 8; i++, to++, from++) {
		if (__copy_to_user(to, from, sizeof(*to)))
			return -1;
	}
	return 0;
}

int restore_i387_ia32(struct task_struct *tsk,
		      struct _fpstate_ia32 __user *buf, int fsave)
{
	clear_fpu(tsk);
	if (!fsave) {
		if (__copy_from_user(&tsk->thread.i387.fxsave,
				     &buf->_fxsr_env[0],
				     sizeof(struct i387_fxsave_struct)))
			return -1;
		tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
		set_stopped_child_used_math(tsk);
	}
	return convert_fxsr_from_user(&tsk->thread.i387.fxsave, buf);
}

int save_i387_ia32(struct task_struct *tsk, struct _fpstate_ia32 __user *buf,
		   struct pt_regs *regs, int fsave)
{
	int err = 0;

	init_fpu(tsk);
	if (convert_fxsr_to_user(buf, &tsk->thread.i387.fxsave, regs, tsk))
		return -1;
	if (fsave)
		return 0;
	err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
	err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
	err |= __copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
			      sizeof(struct i387_fxsave_struct));
	return err ? -1 : 1;
}