1 // SPDX-License-Identifier: GPL-2.0
2 /*---------------------------------------------------------------------------+
3 | get_address.c |
4 | |
5 | Get the effective address from an FPU instruction. |
6 | |
7 | Copyright (C) 1992,1993,1994,1997 |
8 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
9 | Australia. E-mail billm@suburbia.net |
10 | |
11 | |
12 +---------------------------------------------------------------------------*/
13
14 /*---------------------------------------------------------------------------+
15 | Note: |
16 | The file contains code which accesses user memory. |
17 | Emulator static data may change when user memory is accessed, due to |
18 | other processes using the emulator while swapping is in progress. |
19 +---------------------------------------------------------------------------*/
20
21 #include <linux/stddef.h>
22
23 #include <linux/uaccess.h>
24 #include <asm/vm86.h>
25
26 #include "fpu_system.h"
27 #include "exception.h"
28 #include "fpu_emu.h"
29
30 #define FPU_WRITE_BIT 0x10
31
32 static int reg_offset[] = {
33 offsetof(struct pt_regs, ax),
34 offsetof(struct pt_regs, cx),
35 offsetof(struct pt_regs, dx),
36 offsetof(struct pt_regs, bx),
37 offsetof(struct pt_regs, sp),
38 offsetof(struct pt_regs, bp),
39 offsetof(struct pt_regs, si),
40 offsetof(struct pt_regs, di)
41 };
42
43 #define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))
44
45 static int reg_offset_vm86[] = {
46 offsetof(struct pt_regs, cs),
47 offsetof(struct kernel_vm86_regs, ds),
48 offsetof(struct kernel_vm86_regs, es),
49 offsetof(struct kernel_vm86_regs, fs),
50 offsetof(struct kernel_vm86_regs, gs),
51 offsetof(struct pt_regs, ss),
52 offsetof(struct kernel_vm86_regs, ds)
53 };
54
55 #define VM86_REG_(x) (*(unsigned short *) \
56 (reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))
57
58 static int reg_offset_pm[] = {
59 offsetof(struct pt_regs, cs),
60 offsetof(struct pt_regs, ds),
61 offsetof(struct pt_regs, es),
62 offsetof(struct pt_regs, fs),
63 offsetof(struct pt_regs, ds), /* dummy, not saved on stack */
64 offsetof(struct pt_regs, ss),
65 offsetof(struct pt_regs, ds)
66 };
67
68 #define PM_REG_(x) (*(unsigned short *) \
69 (reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))
70
71 /* Decode the SIB byte. This function assumes mod != 0 */
72 static int sib(int mod, unsigned long *fpu_eip)
73 {
74 u_char ss, index, base;
75 long offset;
76
77 RE_ENTRANT_CHECK_OFF;
78 FPU_code_access_ok(1);
79 FPU_get_user(base, (u_char __user *) (*fpu_eip)); /* The SIB byte */
80 RE_ENTRANT_CHECK_ON;
81 (*fpu_eip)++;
82 ss = base >> 6;
83 index = (base >> 3) & 7;
84 base &= 7;
85
86 if ((mod == 0) && (base == 5))
87 offset = 0; /* No base register */
88 else
89 offset = REG_(base);
90
91 if (index == 4) {
92 /* No index register */
93 /* A non-zero ss is illegal */
94 if (ss)
95 EXCEPTION(EX_Invalid);
96 } else {
97 offset += (REG_(index)) << ss;
98 }
99
100 if (mod == 1) {
101 /* 8 bit signed displacement */
102 long displacement;
103 RE_ENTRANT_CHECK_OFF;
104 FPU_code_access_ok(1);
105 FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
106 offset += displacement;
107 RE_ENTRANT_CHECK_ON;
108 (*fpu_eip)++;
109 } else if (mod == 2 || base == 5) { /* The second condition also has mod==0 */
110 /* 32 bit displacement */
111 long displacement;
112 RE_ENTRANT_CHECK_OFF;
113 FPU_code_access_ok(4);
114 FPU_get_user(displacement, (long __user *)(*fpu_eip));
115 offset += displacement;
116 RE_ENTRANT_CHECK_ON;
117 (*fpu_eip) += 4;
118 }
119
120 return offset;
121 }
122
123 static unsigned long vm86_segment(u_char segment, struct address *addr)
124 {
125 segment--;
126 #ifdef PARANOID
127 if (segment > PREFIX_SS_) {
128 EXCEPTION(EX_INTERNAL | 0x130);
129 math_abort(FPU_info, SIGSEGV);
130 }
131 #endif /* PARANOID */
132 addr->selector = VM86_REG_(segment);
133 return (unsigned long)VM86_REG_(segment) << 4;
134 }
135
136 /* This should work for 16 and 32 bit protected mode. */
137 static long pm_address(u_char FPU_modrm, u_char segment,
138 struct address *addr, long offset)
139 {
140 struct desc_struct descriptor;
141 unsigned long base_address, limit, address, seg_top;
142
143 segment--;
144
145 #ifdef PARANOID
146 /* segment is unsigned, so this also detects if segment was 0: */
147 if (segment > PREFIX_SS_) {
148 EXCEPTION(EX_INTERNAL | 0x132);
149 math_abort(FPU_info, SIGSEGV);
150 }
151 #endif /* PARANOID */
152
153 switch (segment) {
154 case PREFIX_GS_ - 1:
155 /* user gs handling can be lazy, use special accessors */
156 savesegment(gs, addr->selector);
157 break;
158 default:
159 addr->selector = PM_REG_(segment);
160 }
161
162 descriptor = FPU_get_ldt_descriptor(addr->selector);
163 base_address = seg_get_base(&descriptor);
164 address = base_address + offset;
165 limit = seg_get_limit(&descriptor) + 1;
166 limit *= seg_get_granularity(&descriptor);
167 limit += base_address - 1;
168 if (limit < base_address)
169 limit = 0xffffffff;
170
171 if (seg_expands_down(&descriptor)) {
172 if (descriptor.g) {
173 seg_top = 0xffffffff;
174 } else {
175 seg_top = base_address + (1 << 20);
176 if (seg_top < base_address)
177 seg_top = 0xffffffff;
178 }
179 access_limit =
180 (address <= limit) || (address >= seg_top) ? 0 :
181 ((seg_top - address) >= 255 ? 255 : seg_top - address);
182 } else {
183 access_limit =
184 (address > limit) || (address < base_address) ? 0 :
185 ((limit - address) >= 254 ? 255 : limit - address + 1);
186 }
187 if (seg_execute_only(&descriptor) ||
188 (!seg_writable(&descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
189 access_limit = 0;
190 }
191 return address;
192 }
193
194 /*
195 MOD R/M byte: MOD == 3 has a special use for the FPU
196 SIB byte used iff R/M = 100b
197
198 7 6 5 4 3 2 1 0
199 ..... ......... .........
200 MOD OPCODE(2) R/M
201
202 SIB byte
203
204 7 6 5 4 3 2 1 0
205 ..... ......... .........
206 SS INDEX BASE
207
208 */
209
210 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
211 struct address *addr, fpu_addr_modes addr_modes)
212 {
213 u_char mod;
214 unsigned rm = FPU_modrm & 7;
215 long *cpu_reg_ptr;
216 int address = 0; /* Initialized just to stop compiler warnings. */
217
218 /* Memory accessed via the cs selector is write protected
219 in `non-segmented' 32 bit protected mode. */
220 if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
221 && (addr_modes.override.segment == PREFIX_CS_)) {
222 math_abort(FPU_info, SIGSEGV);
223 }
224
225 addr->selector = FPU_DS; /* Default, for 32 bit non-segmented mode. */
226
227 mod = (FPU_modrm >> 6) & 3;
228
229 if (rm == 4 && mod != 3) {
230 address = sib(mod, fpu_eip);
231 } else {
232 cpu_reg_ptr = ®_(rm);
233 switch (mod) {
234 case 0:
235 if (rm == 5) {
236 /* Special case: disp32 */
237 RE_ENTRANT_CHECK_OFF;
238 FPU_code_access_ok(4);
239 FPU_get_user(address,
240 (unsigned long __user
241 *)(*fpu_eip));
242 (*fpu_eip) += 4;
243 RE_ENTRANT_CHECK_ON;
244 addr->offset = address;
245 return (void __user *)address;
246 } else {
247 address = *cpu_reg_ptr; /* Just return the contents
248 of the cpu register */
249 addr->offset = address;
250 return (void __user *)address;
251 }
252 case 1:
253 /* 8 bit signed displacement */
254 RE_ENTRANT_CHECK_OFF;
255 FPU_code_access_ok(1);
256 FPU_get_user(address, (signed char __user *)(*fpu_eip));
257 RE_ENTRANT_CHECK_ON;
258 (*fpu_eip)++;
259 break;
260 case 2:
261 /* 32 bit displacement */
262 RE_ENTRANT_CHECK_OFF;
263 FPU_code_access_ok(4);
264 FPU_get_user(address, (long __user *)(*fpu_eip));
265 (*fpu_eip) += 4;
266 RE_ENTRANT_CHECK_ON;
267 break;
268 case 3:
269 /* Not legal for the FPU */
270 EXCEPTION(EX_Invalid);
271 }
272 address += *cpu_reg_ptr;
273 }
274
275 addr->offset = address;
276
277 switch (addr_modes.default_mode) {
278 case 0:
279 break;
280 case VM86:
281 address += vm86_segment(addr_modes.override.segment, addr);
282 break;
283 case PM16:
284 case SEG32:
285 address = pm_address(FPU_modrm, addr_modes.override.segment,
286 addr, address);
287 break;
288 default:
289 EXCEPTION(EX_INTERNAL | 0x133);
290 }
291
292 return (void __user *)address;
293 }
294
295 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
296 struct address *addr, fpu_addr_modes addr_modes)
297 {
298 u_char mod;
299 unsigned rm = FPU_modrm & 7;
300 int address = 0; /* Default used for mod == 0 */
301
302 /* Memory accessed via the cs selector is write protected
303 in `non-segmented' 32 bit protected mode. */
304 if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
305 && (addr_modes.override.segment == PREFIX_CS_)) {
306 math_abort(FPU_info, SIGSEGV);
307 }
308
309 addr->selector = FPU_DS; /* Default, for 32 bit non-segmented mode. */
310
311 mod = (FPU_modrm >> 6) & 3;
312
313 switch (mod) {
314 case 0:
315 if (rm == 6) {
316 /* Special case: disp16 */
317 RE_ENTRANT_CHECK_OFF;
318 FPU_code_access_ok(2);
319 FPU_get_user(address,
320 (unsigned short __user *)(*fpu_eip));
321 (*fpu_eip) += 2;
322 RE_ENTRANT_CHECK_ON;
323 goto add_segment;
324 }
325 break;
326 case 1:
327 /* 8 bit signed displacement */
328 RE_ENTRANT_CHECK_OFF;
329 FPU_code_access_ok(1);
330 FPU_get_user(address, (signed char __user *)(*fpu_eip));
331 RE_ENTRANT_CHECK_ON;
332 (*fpu_eip)++;
333 break;
334 case 2:
335 /* 16 bit displacement */
336 RE_ENTRANT_CHECK_OFF;
337 FPU_code_access_ok(2);
338 FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
339 (*fpu_eip) += 2;
340 RE_ENTRANT_CHECK_ON;
341 break;
342 case 3:
343 /* Not legal for the FPU */
344 EXCEPTION(EX_Invalid);
345 break;
346 }
347 switch (rm) {
348 case 0:
349 address += FPU_info->regs->bx + FPU_info->regs->si;
350 break;
351 case 1:
352 address += FPU_info->regs->bx + FPU_info->regs->di;
353 break;
354 case 2:
355 address += FPU_info->regs->bp + FPU_info->regs->si;
356 if (addr_modes.override.segment == PREFIX_DEFAULT)
357 addr_modes.override.segment = PREFIX_SS_;
358 break;
359 case 3:
360 address += FPU_info->regs->bp + FPU_info->regs->di;
361 if (addr_modes.override.segment == PREFIX_DEFAULT)
362 addr_modes.override.segment = PREFIX_SS_;
363 break;
364 case 4:
365 address += FPU_info->regs->si;
366 break;
367 case 5:
368 address += FPU_info->regs->di;
369 break;
370 case 6:
371 address += FPU_info->regs->bp;
372 if (addr_modes.override.segment == PREFIX_DEFAULT)
373 addr_modes.override.segment = PREFIX_SS_;
374 break;
375 case 7:
376 address += FPU_info->regs->bx;
377 break;
378 }
379
380 add_segment:
381 address &= 0xffff;
382
383 addr->offset = address;
384
385 switch (addr_modes.default_mode) {
386 case 0:
387 break;
388 case VM86:
389 address += vm86_segment(addr_modes.override.segment, addr);
390 break;
391 case PM16:
392 case SEG32:
393 address = pm_address(FPU_modrm, addr_modes.override.segment,
394 addr, address);
395 break;
396 default:
397 EXCEPTION(EX_INTERNAL | 0x131);
398 }
399
400 return (void __user *)address;
401 }
402
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