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(seg: addr->selector); |
163 | base_address = seg_get_base(d: &descriptor); |
164 | address = base_address + offset; |
165 | limit = seg_get_limit(d: &descriptor) + 1; |
166 | limit *= seg_get_granularity(d: &descriptor); |
167 | limit += base_address - 1; |
168 | if (limit < base_address) |
169 | limit = 0xffffffff; |
170 | |
171 | if (seg_expands_down(d: &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(d: &descriptor) || |
188 | (!seg_writable(d: &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(segment: addr_modes.override.segment, addr); |
282 | break; |
283 | case PM16: |
284 | case SEG32: |
285 | address = pm_address(FPU_modrm, segment: addr_modes.override.segment, |
286 | addr, offset: 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(segment: addr_modes.override.segment, addr); |
390 | break; |
391 | case PM16: |
392 | case SEG32: |
393 | address = pm_address(FPU_modrm, segment: addr_modes.override.segment, |
394 | addr, offset: address); |
395 | break; |
396 | default: |
397 | EXCEPTION(EX_INTERNAL | 0x131); |
398 | } |
399 | |
400 | return (void __user *)address; |
401 | } |
402 | |