1/*---------------------------------------------------------------------------+
2 |  get_address.c                                                            |
3 |                                                                           |
4 | Get the effective address from an FPU instruction.                        |
5 |                                                                           |
6 | Copyright (C) 1992,1993,1994,1997                                         |
7 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
8 |                       Australia.  E-mail   billm@suburbia.net             |
9 |                                                                           |
10 |                                                                           |
11 +---------------------------------------------------------------------------*/
12
13/*---------------------------------------------------------------------------+
14 | Note:                                                                     |
15 |    The file contains code which accesses user memory.                     |
16 |    Emulator static data may change when user memory is accessed, due to   |
17 |    other processes using the emulator while swapping is in progress.      |
18 +---------------------------------------------------------------------------*/
19
20#include <linux/stddef.h>
21
22#include <asm/uaccess.h>
23#include <asm/vm86.h>
24
25#include "fpu_system.h"
26#include "exception.h"
27#include "fpu_emu.h"
28
29#define FPU_WRITE_BIT 0x10
30
31static int reg_offset[] = {
32	offsetof(struct pt_regs, ax),
33	offsetof(struct pt_regs, cx),
34	offsetof(struct pt_regs, dx),
35	offsetof(struct pt_regs, bx),
36	offsetof(struct pt_regs, sp),
37	offsetof(struct pt_regs, bp),
38	offsetof(struct pt_regs, si),
39	offsetof(struct pt_regs, di)
40};
41
42#define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))
43
44static int reg_offset_vm86[] = {
45	offsetof(struct pt_regs, cs),
46	offsetof(struct kernel_vm86_regs, ds),
47	offsetof(struct kernel_vm86_regs, es),
48	offsetof(struct kernel_vm86_regs, fs),
49	offsetof(struct kernel_vm86_regs, gs),
50	offsetof(struct pt_regs, ss),
51	offsetof(struct kernel_vm86_regs, ds)
52};
53
54#define VM86_REG_(x) (*(unsigned short *) \
55		(reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))
56
57static int reg_offset_pm[] = {
58	offsetof(struct pt_regs, cs),
59	offsetof(struct pt_regs, ds),
60	offsetof(struct pt_regs, es),
61	offsetof(struct pt_regs, fs),
62	offsetof(struct pt_regs, ds),	/* dummy, not saved on stack */
63	offsetof(struct pt_regs, ss),
64	offsetof(struct pt_regs, ds)
65};
66
67#define PM_REG_(x) (*(unsigned short *) \
68		(reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))
69
70/* Decode the SIB byte. This function assumes mod != 0 */
71static int sib(int mod, unsigned long *fpu_eip)
72{
73	u_char ss, index, base;
74	long offset;
75
76	RE_ENTRANT_CHECK_OFF;
77	FPU_code_access_ok(1);
78	FPU_get_user(base, (u_char __user *) (*fpu_eip));	/* The SIB byte */
79	RE_ENTRANT_CHECK_ON;
80	(*fpu_eip)++;
81	ss = base >> 6;
82	index = (base >> 3) & 7;
83	base &= 7;
84
85	if ((mod == 0) && (base == 5))
86		offset = 0;	/* No base register */
87	else
88		offset = REG_(base);
89
90	if (index == 4) {
91		/* No index register */
92		/* A non-zero ss is illegal */
93		if (ss)
94			EXCEPTION(EX_Invalid);
95	} else {
96		offset += (REG_(index)) << ss;
97	}
98
99	if (mod == 1) {
100		/* 8 bit signed displacement */
101		long displacement;
102		RE_ENTRANT_CHECK_OFF;
103		FPU_code_access_ok(1);
104		FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
105		offset += displacement;
106		RE_ENTRANT_CHECK_ON;
107		(*fpu_eip)++;
108	} else if (mod == 2 || base == 5) {	/* The second condition also has mod==0 */
109		/* 32 bit displacement */
110		long displacement;
111		RE_ENTRANT_CHECK_OFF;
112		FPU_code_access_ok(4);
113		FPU_get_user(displacement, (long __user *)(*fpu_eip));
114		offset += displacement;
115		RE_ENTRANT_CHECK_ON;
116		(*fpu_eip) += 4;
117	}
118
119	return offset;
120}
121
122static unsigned long vm86_segment(u_char segment, struct address *addr)
123{
124	segment--;
125#ifdef PARANOID
126	if (segment > PREFIX_SS_) {
127		EXCEPTION(EX_INTERNAL | 0x130);
128		math_abort(FPU_info, SIGSEGV);
129	}
130#endif /* PARANOID */
131	addr->selector = VM86_REG_(segment);
132	return (unsigned long)VM86_REG_(segment) << 4;
133}
134
135/* This should work for 16 and 32 bit protected mode. */
136static long pm_address(u_char FPU_modrm, u_char segment,
137		       struct address *addr, long offset)
138{
139	struct desc_struct descriptor;
140	unsigned long base_address, limit, address, seg_top;
141
142	segment--;
143
144#ifdef PARANOID
145	/* segment is unsigned, so this also detects if segment was 0: */
146	if (segment > PREFIX_SS_) {
147		EXCEPTION(EX_INTERNAL | 0x132);
148		math_abort(FPU_info, SIGSEGV);
149	}
150#endif /* PARANOID */
151
152	switch (segment) {
153	case PREFIX_GS_ - 1:
154		/* user gs handling can be lazy, use special accessors */
155		addr->selector = get_user_gs(FPU_info->regs);
156		break;
157	default:
158		addr->selector = PM_REG_(segment);
159	}
160
161	descriptor = FPU_get_ldt_descriptor(addr->selector);
162	base_address = SEG_BASE_ADDR(descriptor);
163	address = base_address + offset;
164	limit = base_address
165	    + (SEG_LIMIT(descriptor) + 1) * SEG_GRANULARITY(descriptor) - 1;
166	if (limit < base_address)
167		limit = 0xffffffff;
168
169	if (SEG_EXPAND_DOWN(descriptor)) {
170		if (SEG_G_BIT(descriptor))
171			seg_top = 0xffffffff;
172		else {
173			seg_top = base_address + (1 << 20);
174			if (seg_top < base_address)
175				seg_top = 0xffffffff;
176		}
177		access_limit =
178		    (address <= limit) || (address >= seg_top) ? 0 :
179		    ((seg_top - address) >= 255 ? 255 : seg_top - address);
180	} else {
181		access_limit =
182		    (address > limit) || (address < base_address) ? 0 :
183		    ((limit - address) >= 254 ? 255 : limit - address + 1);
184	}
185	if (SEG_EXECUTE_ONLY(descriptor) ||
186	    (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
187		access_limit = 0;
188	}
189	return address;
190}
191
192/*
193       MOD R/M byte:  MOD == 3 has a special use for the FPU
194                      SIB byte used iff R/M = 100b
195
196       7   6   5   4   3   2   1   0
197       .....   .........   .........
198        MOD    OPCODE(2)     R/M
199
200       SIB byte
201
202       7   6   5   4   3   2   1   0
203       .....   .........   .........
204        SS      INDEX        BASE
205
206*/
207
208void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
209			     struct address *addr, fpu_addr_modes addr_modes)
210{
211	u_char mod;
212	unsigned rm = FPU_modrm & 7;
213	long *cpu_reg_ptr;
214	int address = 0;	/* Initialized just to stop compiler warnings. */
215
216	/* Memory accessed via the cs selector is write protected
217	   in `non-segmented' 32 bit protected mode. */
218	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
219	    && (addr_modes.override.segment == PREFIX_CS_)) {
220		math_abort(FPU_info, SIGSEGV);
221	}
222
223	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */
224
225	mod = (FPU_modrm >> 6) & 3;
226
227	if (rm == 4 && mod != 3) {
228		address = sib(mod, fpu_eip);
229	} else {
230		cpu_reg_ptr = &REG_(rm);
231		switch (mod) {
232		case 0:
233			if (rm == 5) {
234				/* Special case: disp32 */
235				RE_ENTRANT_CHECK_OFF;
236				FPU_code_access_ok(4);
237				FPU_get_user(address,
238					     (unsigned long __user
239					      *)(*fpu_eip));
240				(*fpu_eip) += 4;
241				RE_ENTRANT_CHECK_ON;
242				addr->offset = address;
243				return (void __user *)address;
244			} else {
245				address = *cpu_reg_ptr;	/* Just return the contents
246							   of the cpu register */
247				addr->offset = address;
248				return (void __user *)address;
249			}
250		case 1:
251			/* 8 bit signed displacement */
252			RE_ENTRANT_CHECK_OFF;
253			FPU_code_access_ok(1);
254			FPU_get_user(address, (signed char __user *)(*fpu_eip));
255			RE_ENTRANT_CHECK_ON;
256			(*fpu_eip)++;
257			break;
258		case 2:
259			/* 32 bit displacement */
260			RE_ENTRANT_CHECK_OFF;
261			FPU_code_access_ok(4);
262			FPU_get_user(address, (long __user *)(*fpu_eip));
263			(*fpu_eip) += 4;
264			RE_ENTRANT_CHECK_ON;
265			break;
266		case 3:
267			/* Not legal for the FPU */
268			EXCEPTION(EX_Invalid);
269		}
270		address += *cpu_reg_ptr;
271	}
272
273	addr->offset = address;
274
275	switch (addr_modes.default_mode) {
276	case 0:
277		break;
278	case VM86:
279		address += vm86_segment(addr_modes.override.segment, addr);
280		break;
281	case PM16:
282	case SEG32:
283		address = pm_address(FPU_modrm, addr_modes.override.segment,
284				     addr, address);
285		break;
286	default:
287		EXCEPTION(EX_INTERNAL | 0x133);
288	}
289
290	return (void __user *)address;
291}
292
293void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
294				struct address *addr, fpu_addr_modes addr_modes)
295{
296	u_char mod;
297	unsigned rm = FPU_modrm & 7;
298	int address = 0;	/* Default used for mod == 0 */
299
300	/* Memory accessed via the cs selector is write protected
301	   in `non-segmented' 32 bit protected mode. */
302	if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
303	    && (addr_modes.override.segment == PREFIX_CS_)) {
304		math_abort(FPU_info, SIGSEGV);
305	}
306
307	addr->selector = FPU_DS;	/* Default, for 32 bit non-segmented mode. */
308
309	mod = (FPU_modrm >> 6) & 3;
310
311	switch (mod) {
312	case 0:
313		if (rm == 6) {
314			/* Special case: disp16 */
315			RE_ENTRANT_CHECK_OFF;
316			FPU_code_access_ok(2);
317			FPU_get_user(address,
318				     (unsigned short __user *)(*fpu_eip));
319			(*fpu_eip) += 2;
320			RE_ENTRANT_CHECK_ON;
321			goto add_segment;
322		}
323		break;
324	case 1:
325		/* 8 bit signed displacement */
326		RE_ENTRANT_CHECK_OFF;
327		FPU_code_access_ok(1);
328		FPU_get_user(address, (signed char __user *)(*fpu_eip));
329		RE_ENTRANT_CHECK_ON;
330		(*fpu_eip)++;
331		break;
332	case 2:
333		/* 16 bit displacement */
334		RE_ENTRANT_CHECK_OFF;
335		FPU_code_access_ok(2);
336		FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
337		(*fpu_eip) += 2;
338		RE_ENTRANT_CHECK_ON;
339		break;
340	case 3:
341		/* Not legal for the FPU */
342		EXCEPTION(EX_Invalid);
343		break;
344	}
345	switch (rm) {
346	case 0:
347		address += FPU_info->regs->bx + FPU_info->regs->si;
348		break;
349	case 1:
350		address += FPU_info->regs->bx + FPU_info->regs->di;
351		break;
352	case 2:
353		address += FPU_info->regs->bp + FPU_info->regs->si;
354		if (addr_modes.override.segment == PREFIX_DEFAULT)
355			addr_modes.override.segment = PREFIX_SS_;
356		break;
357	case 3:
358		address += FPU_info->regs->bp + FPU_info->regs->di;
359		if (addr_modes.override.segment == PREFIX_DEFAULT)
360			addr_modes.override.segment = PREFIX_SS_;
361		break;
362	case 4:
363		address += FPU_info->regs->si;
364		break;
365	case 5:
366		address += FPU_info->regs->di;
367		break;
368	case 6:
369		address += FPU_info->regs->bp;
370		if (addr_modes.override.segment == PREFIX_DEFAULT)
371			addr_modes.override.segment = PREFIX_SS_;
372		break;
373	case 7:
374		address += FPU_info->regs->bx;
375		break;
376	}
377
378      add_segment:
379	address &= 0xffff;
380
381	addr->offset = address;
382
383	switch (addr_modes.default_mode) {
384	case 0:
385		break;
386	case VM86:
387		address += vm86_segment(addr_modes.override.segment, addr);
388		break;
389	case PM16:
390	case SEG32:
391		address = pm_address(FPU_modrm, addr_modes.override.segment,
392				     addr, address);
393		break;
394	default:
395		EXCEPTION(EX_INTERNAL | 0x131);
396	}
397
398	return (void __user *)address;
399}
400