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/desc.h>
24 
25 #include "fpu_system.h"
26 #include "exception.h"
27 #include "fpu_emu.h"
28 
29 #define FPU_WRITE_BIT 0x10
30 
31 static 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 
44 static 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 
57 static 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 */
sib(int mod,unsigned long * fpu_eip)71 static 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 
vm86_segment(u_char segment,struct address * addr)122 static 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. */
pm_address(u_char FPU_modrm,u_char segment,struct address * addr,long offset)136 static 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 = LDT_DESCRIPTOR(PM_REG_(segment));
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 
FPU_get_address(u_char FPU_modrm,unsigned long * fpu_eip,struct address * addr,fpu_addr_modes addr_modes)208 void __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 
FPU_get_address_16(u_char FPU_modrm,unsigned long * fpu_eip,struct address * addr,fpu_addr_modes addr_modes)293 void __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