aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86/math-emu/get_address.c
blob: 6ef5e99380f92134ba86a6a693b5ac6d3434e6d4 (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
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
/*---------------------------------------------------------------------------+
 |  get_address.c                                                            |
 |                                                                           |
 | Get the effective address from an FPU instruction.                        |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1997                                         |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail   billm@suburbia.net             |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | Note:                                                                     |
 |    The file contains code which accesses user memory.                     |
 |    Emulator static data may change when user memory is accessed, due to   |
 |    other processes using the emulator while swapping is in progress.      |
 +---------------------------------------------------------------------------*/

#include <linux/stddef.h>

#include <asm/uaccess.h>
#include <asm/desc.h>

#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"

#define FPU_WRITE_BIT 0x10

static int reg_offset[] = {
	offsetof(struct pt_regs, ax),
	offsetof(struct pt_regs, cx),
	offsetof(struct pt_regs, dx),
	offsetof(struct pt_regs, bx),
	offsetof(struct pt_regs, sp),
	offsetof(struct pt_regs, bp),
	offsetof(struct pt_regs, si),
	offsetof(struct pt_regs, di)
};

#define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))

static int reg_offset_vm86[] = {
	offsetof(struct pt_regs, cs),
	offsetof(struct kernel_vm86_regs, ds),
	offsetof(struct kernel_vm86_regs, es),
	offsetof(struct kernel_vm86_regs, fs),
	offsetof(struct kernel_vm86_regs, gs),
	offsetof(struct pt_regs, ss),
	offsetof(struct kernel_vm86_regs, ds)
};

#define VM86_REG_(x) (*(unsigned short *) \
		(reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))

static int reg_offset_pm[] = {
	offsetof(struct pt_regs, cs),
	offsetof(struct pt_regs, ds),
	offsetof(struct pt_regs, es),
	offsetof(struct pt_regs, fs),
	offsetof(struct pt_regs, ds),	/* dummy, not saved on stack */
	offsetof(struct pt_regs, ss),
	offsetof(struct pt_regs, ds)
};

#define PM_REG_(x) (*(unsigned short *) \
		(reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))

/* Decode the SIB byte. This function assumes mod != 0 */
static int sib(int mod, unsigned long *fpu_eip)
{
	u_char ss, index, base;
	long offset;

	RE_ENTRANT_CHECK_OFF;
	FPU_code_access_ok(1);
	FPU_get_user(base, (u_char __user *) (*fpu_eip));	/* The SIB byte */
	RE_ENTRANT_CHECK_ON;
	(*fpu_eip)++;
	ss = base >> 6;
	index = (base >> 3) & 7;
	base &= 7;

	if ((mod == 0) && (base == 5))
		offset = 0;	/* No base register */
	else
		offset = REG_(base);

	if (index == 4) {
		/* No index register */
		/* A non-zero ss is illegal */
		if (ss)
			EXCEPTION(EX_Invalid);
	} else {
		offset += (REG_(index)) << ss;
	}

	if (mod == 1) {
		/* 8 bit signed displacement */
		long displacement;
		RE_ENTRANT_CHECK_OFF;
		FPU_code_access_ok(1);
		FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
		offset += displacement;
		RE_ENTRANT_CHECK_ON;
		(*fpu_eip)++;
	} else if (mod == 2 || base == 5) {	/* The second condition also has mod==0 */
		/* 32 bit displacement */
		long displacement;
		RE_ENTRANT_CHECK_OFF;
		FPU_code_access_ok(4);
		FPU_get_user(displacement, (long __user *)(*fpu_eip));
		offset += displacement;
		RE_ENTRANT_CHECK_ON;
		(*fpu_eip) += 4;
	}

	return offset;
}

static unsigned long vm86_segment(u_char segment, struct address *addr)
{
	segment--;
#ifdef PARANOID
	if (segment > PREFIX_SS_) {
		EXCEPTION(EX_INTERNAL | 0x130);
		math_abort(FPU_info, SIGSEGV);
	}
#endif /* PARANOID */
	addr->selector = VM86_REG_(segment);
	return (unsigned long)VM86_REG_(segment) << 4;
}

/* This should work for 16 and 32 bit protected mode. */
static long pm_address(u_char FPU_modrm, u_char segment,
		       struct address *addr, long offset)
{
	struct desc_struct descriptor;
	unsigned long base_address, limit, address, seg_top;

	segment--;

#ifdef PARANOID
	/* segment is unsigned, so this also detects if segment was 0: */
	if (segment > PREFIX_SS_) {
		EXCEPTION(EX_INTERNAL | 0x132);
		math_abort(FPU_info, SIGSEGV);
	}
#endif /* PARANOID */

	switch (segment) {
	case PREFIX_GS_ - 1:
		/* user gs handling can be lazy, use special accessors */
		addr->selector = get_user_gs(FPU_info->regs);
		break;
	default:
		addr->selector = PM_REG_(segment);
	}

	descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
	base_address = SEG_BASE_ADDR(descriptor);
	address = base_address + offset;
	limit = base_address
	    + (SEG_LIMIT(descriptor) + 1) * SEG_GRANULARITY(descriptor) - 1;
	if (limit < base_address)
		limit = 0xffffffff;

	if (SEG_EXPAND_DOWN(descriptor)) {
		if (SEG_G_BIT(descriptor))
			seg_top = 0xffffffff;
		else {
			seg_top = base_address + (1 << 20);
			if (seg_top < base_address)
				seg_top = 0xffffffff;
		}
		access_limit =
		    (address <= limit) || (address >= seg_top) ? 0 :
		    ((seg_top - address) >= 255 ? 255 : seg_top - address);
	} else {
		access_limit =
		    (address > limit) || (address < base_address) ? 0 :
		    ((limit - address) >= 254 ? 255 : limit - address + 1);
	}
	if (SEG_EXECUTE_ONLY(descriptor) ||
	    (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
		access_limit = 0;
	}
	return address;
}

/*
       MOD R/M byte:  MOD == 3 has a special use for the FPU
                      SIB byte used iff R/M = 100b

       7   6   5   4   3   2   1   0
       .....   .........   .........
        MOD    OPCODE(2)     R/M

       SIB byte

       7   6   5   4   3   2   1   0
       .....   .........   .........
        SS      INDEX        BASE

*/

void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
			     struct address *addr, fpu_addr_modes addr_modes)
{
	u_char mod;
	unsigned rm = FPU_modrm & 7;
	long *cpu_reg_ptr;
	int address = 0;	/* Initialized just to stop compiler warnings. */

	/* Memory accessed via the cs selector is write protected
	   in `non-segmented' 32 bit protected mode. */
	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
	    && (addr_modes.override.segment == PREFIX_CS_)) {
		math_abort(FPU_info, SIGSEGV);
	}

	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */

	mod = (FPU_modrm >> 6) & 3;

	if (rm == 4 && mod != 3) {
		address = sib(mod, fpu_eip);
	} else {
		cpu_reg_ptr = &REG_(rm);
		switch (mod) {
		case 0:
			if (rm == 5) {
				/* Special case: disp32 */
				RE_ENTRANT_CHECK_OFF;
				FPU_code_access_ok(4);
				FPU_get_user(address,
					     (unsigned long __user
					      *)(*fpu_eip));
				(*fpu_eip) += 4;
				RE_ENTRANT_CHECK_ON;
				addr->offset = address;
				return (void __user *)address;
			} else {
				address = *cpu_reg_ptr;	/* Just return the contents
							   of the cpu register */
				addr->offset = address;
				return (void __user *)address;
			}
		case 1:
			/* 8 bit signed displacement */
			RE_ENTRANT_CHECK_OFF;
			FPU_code_access_ok(1);
			FPU_get_user(address, (signed char __user *)(*fpu_eip));
			RE_ENTRANT_CHECK_ON;
			(*fpu_eip)++;
			break;
		case 2:
			/* 32 bit displacement */
			RE_ENTRANT_CHECK_OFF;
			FPU_code_access_ok(4);
			FPU_get_user(address, (long __user *)(*fpu_eip));
			(*fpu_eip) += 4;
			RE_ENTRANT_CHECK_ON;
			break;
		case 3:
			/* Not legal for the FPU */
			EXCEPTION(EX_Invalid);
		}
		address += *cpu_reg_ptr;
	}

	addr->offset = address;

	switch (addr_modes.default_mode) {
	case 0:
		break;
	case VM86:
		address += vm86_segment(addr_modes.override.segment, addr);
		break;
	case PM16:
	case SEG32:
		address = pm_address(FPU_modrm, addr_modes.override.segment,
				     addr, address);
		break;
	default:
		EXCEPTION(EX_INTERNAL | 0x133);
	}

	return (void __user *)address;
}

void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
				struct address *addr, fpu_addr_modes addr_modes)
{
	u_char mod;
	unsigned rm = FPU_modrm & 7;
	int address = 0;	/* Default used for mod == 0 */

	/* Memory accessed via the cs selector is write protected
	   in `non-segmented' 32 bit protected mode. */
	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
	    && (addr_modes.override.segment == PREFIX_CS_)) {
		math_abort(FPU_info, SIGSEGV);
	}

	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */

	mod = (FPU_modrm >> 6) & 3;

	switch (mod) {
	case 0:
		if (rm == 6) {
			/* Special case: disp16 */
			RE_ENTRANT_CHECK_OFF;
			FPU_code_access_ok(2);
			FPU_get_user(address,
				     (unsigned short __user *)(*fpu_eip));
			(*fpu_eip) += 2;
			RE_ENTRANT_CHECK_ON;
			goto add_segment;
		}
		break;
	case 1:
		/* 8 bit signed displacement */
		RE_ENTRANT_CHECK_OFF;
		FPU_code_access_ok(1);
		FPU_get_user(address, (signed char __user *)(*fpu_eip));
		RE_ENTRANT_CHECK_ON;
		(*fpu_eip)++;
		break;
	case 2:
		/* 16 bit displacement */
		RE_ENTRANT_CHECK_OFF;
		FPU_code_access_ok(2);
		FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
		(*fpu_eip) += 2;
		RE_ENTRANT_CHECK_ON;
		break;
	case 3:
		/* Not legal for the FPU */
		EXCEPTION(EX_Invalid);
		break;
	}
	switch (rm) {
	case 0:
		address += FPU_info->regs->bx + FPU_info->regs->si;
		break;
	case 1:
		address += FPU_info->regs->bx + FPU_info->regs->di;
		break;
	case 2:
		address += FPU_info->regs->bp + FPU_info->regs->si;
		if (addr_modes.override.segment == PREFIX_DEFAULT)
			addr_modes.override.segment = PREFIX_SS_;
		break;
	case 3:
		address += FPU_info->regs->bp + FPU_info->regs->di;
		if (addr_modes.override.segment == PREFIX_DEFAULT)
			addr_modes.override.segment = PREFIX_SS_;
		break;
	case 4:
		address += FPU_info->regs->si;
		break;
	case 5:
		address += FPU_info->regs->di;
		break;
	case 6:
		address += FPU_info->regs->bp;
		if (addr_modes.override.segment == PREFIX_DEFAULT)
			addr_modes.override.segment = PREFIX_SS_;
		break;
	case 7:
		address += FPU_info->regs->bx;
		break;
	}

      add_segment:
	address &= 0xffff;

	addr->offset = address;

	switch (addr_modes.default_mode) {
	case 0:
		break;
	case VM86:
		address += vm86_segment(addr_modes.override.segment, addr);
		break;
	case PM16:
	case SEG32:
		address = pm_address(FPU_modrm, addr_modes.override.segment,
				     addr, address);
		break;
	default:
		EXCEPTION(EX_INTERNAL | 0x131);
	}

	return (void __user *)address;
}