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 = ®_(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