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 
21 #include <linux/stddef.h>
22 
23 #include <asm/uaccess.h>
24 #include <asm/desc.h>
25 
26 #include "fpu_system.h"
27 #include "exception.h"
28 #include "fpu_emu.h"
29 
30 
31 #define FPU_WRITE_BIT 0x10
32 
33 static int reg_offset[] = {
34 	offsetof(struct info,___eax),
35 	offsetof(struct info,___ecx),
36 	offsetof(struct info,___edx),
37 	offsetof(struct info,___ebx),
38 	offsetof(struct info,___esp),
39 	offsetof(struct info,___ebp),
40 	offsetof(struct info,___esi),
41 	offsetof(struct info,___edi)
42 };
43 
44 #define REG_(x) (*(long *)(reg_offset[(x)]+(u_char *) FPU_info))
45 
46 static int reg_offset_vm86[] = {
47 	offsetof(struct info,___cs),
48 	offsetof(struct info,___vm86_ds),
49 	offsetof(struct info,___vm86_es),
50 	offsetof(struct info,___vm86_fs),
51 	offsetof(struct info,___vm86_gs),
52 	offsetof(struct info,___ss),
53 	offsetof(struct info,___vm86_ds)
54       };
55 
56 #define VM86_REG_(x) (*(unsigned short *) \
57 		      (reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
58 
59 /* These are dummy, fs and gs are not saved on the stack. */
60 #define ___FS ___ds
61 #define ___GS ___ds
62 
63 static int reg_offset_pm[] = {
64 	offsetof(struct info,___cs),
65 	offsetof(struct info,___ds),
66 	offsetof(struct info,___es),
67 	offsetof(struct info,___FS),
68 	offsetof(struct info,___GS),
69 	offsetof(struct info,___ss),
70 	offsetof(struct info,___ds)
71       };
72 
73 #define PM_REG_(x) (*(unsigned short *) \
74 		      (reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
75 
76 
77 /* Decode the SIB byte. This function assumes mod != 0 */
sib(int mod,unsigned long * fpu_eip)78 static int sib(int mod, unsigned long *fpu_eip)
79 {
80   u_char ss,index,base;
81   long offset;
82 
83   RE_ENTRANT_CHECK_OFF;
84   FPU_code_verify_area(1);
85   FPU_get_user(base, (u_char *) (*fpu_eip));   /* The SIB byte */
86   RE_ENTRANT_CHECK_ON;
87   (*fpu_eip)++;
88   ss = base >> 6;
89   index = (base >> 3) & 7;
90   base &= 7;
91 
92   if ((mod == 0) && (base == 5))
93     offset = 0;              /* No base register */
94   else
95     offset = REG_(base);
96 
97   if (index == 4)
98     {
99       /* No index register */
100       /* A non-zero ss is illegal */
101       if ( ss )
102 	EXCEPTION(EX_Invalid);
103     }
104   else
105     {
106       offset += (REG_(index)) << ss;
107     }
108 
109   if (mod == 1)
110     {
111       /* 8 bit signed displacement */
112       long displacement;
113       RE_ENTRANT_CHECK_OFF;
114       FPU_code_verify_area(1);
115       FPU_get_user(displacement, (signed char *) (*fpu_eip));
116       offset += displacement;
117       RE_ENTRANT_CHECK_ON;
118       (*fpu_eip)++;
119     }
120   else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
121     {
122       /* 32 bit displacement */
123       long displacement;
124       RE_ENTRANT_CHECK_OFF;
125       FPU_code_verify_area(4);
126       FPU_get_user(displacement, (long *) (*fpu_eip));
127       offset += displacement;
128       RE_ENTRANT_CHECK_ON;
129       (*fpu_eip) += 4;
130     }
131 
132   return offset;
133 }
134 
135 
vm86_segment(u_char segment,struct address * addr)136 static unsigned long vm86_segment(u_char segment,
137 				  struct address *addr)
138 {
139   segment--;
140 #ifdef PARANOID
141   if ( segment > PREFIX_SS_ )
142     {
143       EXCEPTION(EX_INTERNAL|0x130);
144       math_abort(FPU_info,SIGSEGV);
145     }
146 #endif /* PARANOID */
147   addr->selector = VM86_REG_(segment);
148   return (unsigned long)VM86_REG_(segment) << 4;
149 }
150 
151 
152 /* This should work for 16 and 32 bit protected mode. */
pm_address(u_char FPU_modrm,u_char segment,struct address * addr,long offset)153 static long pm_address(u_char FPU_modrm, u_char segment,
154 		       struct address *addr, long offset)
155 {
156   struct desc_struct descriptor;
157   unsigned long base_address, limit, address, seg_top;
158   unsigned short selector;
159 
160   segment--;
161 
162 #ifdef PARANOID
163   /* segment is unsigned, so this also detects if segment was 0: */
164   if ( segment > PREFIX_SS_ )
165     {
166       EXCEPTION(EX_INTERNAL|0x132);
167       math_abort(FPU_info,SIGSEGV);
168     }
169 #endif /* PARANOID */
170 
171   switch ( segment )
172     {
173       /* fs and gs aren't used by the kernel, so they still have their
174 	 user-space values. */
175     case PREFIX_FS_-1:
176       /* The cast is needed here to get gcc 2.8.0 to use a 16 bit register
177 	 in the assembler statement. */
178 
179       __asm__("mov %%fs,%0":"=r" (selector));
180       addr->selector = selector;
181       break;
182     case PREFIX_GS_-1:
183       /* The cast is needed here to get gcc 2.8.0 to use a 16 bit register
184 	 in the assembler statement. */
185       __asm__("mov %%gs,%0":"=r" (selector));
186       addr->selector = selector;
187       break;
188     default:
189       addr->selector = PM_REG_(segment);
190     }
191 
192   descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
193   base_address = SEG_BASE_ADDR(descriptor);
194   address = base_address + offset;
195   limit = base_address
196 	+ (SEG_LIMIT(descriptor)+1) * SEG_GRANULARITY(descriptor) - 1;
197   if ( limit < base_address ) limit = 0xffffffff;
198 
199   if ( SEG_EXPAND_DOWN(descriptor) )
200     {
201       if ( SEG_G_BIT(descriptor) )
202 	seg_top = 0xffffffff;
203       else
204 	{
205 	  seg_top = base_address + (1 << 20);
206 	  if ( seg_top < base_address ) seg_top = 0xffffffff;
207 	}
208       access_limit =
209 	(address <= limit) || (address >= seg_top) ? 0 :
210 	  ((seg_top-address) >= 255 ? 255 : seg_top-address);
211     }
212   else
213     {
214       access_limit =
215 	(address > limit) || (address < base_address) ? 0 :
216 	  ((limit-address) >= 254 ? 255 : limit-address+1);
217     }
218   if ( SEG_EXECUTE_ONLY(descriptor) ||
219       (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT)) )
220     {
221       access_limit = 0;
222     }
223   return address;
224 }
225 
226 
227 /*
228        MOD R/M byte:  MOD == 3 has a special use for the FPU
229                       SIB byte used iff R/M = 100b
230 
231        7   6   5   4   3   2   1   0
232        .....   .........   .........
233         MOD    OPCODE(2)     R/M
234 
235 
236        SIB byte
237 
238        7   6   5   4   3   2   1   0
239        .....   .........   .........
240         SS      INDEX        BASE
241 
242 */
243 
FPU_get_address(u_char FPU_modrm,unsigned long * fpu_eip,struct address * addr,fpu_addr_modes addr_modes)244 void *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
245 		  struct address *addr,
246 		  fpu_addr_modes addr_modes)
247 {
248   u_char mod;
249   unsigned rm = FPU_modrm & 7;
250   long *cpu_reg_ptr;
251   int address = 0;     /* Initialized just to stop compiler warnings. */
252 
253   /* Memory accessed via the cs selector is write protected
254      in `non-segmented' 32 bit protected mode. */
255   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
256       && (addr_modes.override.segment == PREFIX_CS_) )
257     {
258       math_abort(FPU_info,SIGSEGV);
259     }
260 
261   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
262 
263   mod = (FPU_modrm >> 6) & 3;
264 
265   if (rm == 4 && mod != 3)
266     {
267       address = sib(mod, fpu_eip);
268     }
269   else
270     {
271       cpu_reg_ptr = & REG_(rm);
272       switch (mod)
273 	{
274 	case 0:
275 	  if (rm == 5)
276 	    {
277 	      /* Special case: disp32 */
278 	      RE_ENTRANT_CHECK_OFF;
279 	      FPU_code_verify_area(4);
280 	      FPU_get_user(address, (unsigned long *) (*fpu_eip));
281 	      (*fpu_eip) += 4;
282 	      RE_ENTRANT_CHECK_ON;
283 	      addr->offset = address;
284 	      return (void *) address;
285 	    }
286 	  else
287 	    {
288 	      address = *cpu_reg_ptr;  /* Just return the contents
289 					  of the cpu register */
290 	      addr->offset = address;
291 	      return (void *) address;
292 	    }
293 	case 1:
294 	  /* 8 bit signed displacement */
295 	  RE_ENTRANT_CHECK_OFF;
296 	  FPU_code_verify_area(1);
297 	  FPU_get_user(address, (signed char *) (*fpu_eip));
298 	  RE_ENTRANT_CHECK_ON;
299 	  (*fpu_eip)++;
300 	  break;
301 	case 2:
302 	  /* 32 bit displacement */
303 	  RE_ENTRANT_CHECK_OFF;
304 	  FPU_code_verify_area(4);
305 	  FPU_get_user(address, (long *) (*fpu_eip));
306 	  (*fpu_eip) += 4;
307 	  RE_ENTRANT_CHECK_ON;
308 	  break;
309 	case 3:
310 	  /* Not legal for the FPU */
311 	  EXCEPTION(EX_Invalid);
312 	}
313       address += *cpu_reg_ptr;
314     }
315 
316   addr->offset = address;
317 
318   switch ( addr_modes.default_mode )
319     {
320     case 0:
321       break;
322     case VM86:
323       address += vm86_segment(addr_modes.override.segment, addr);
324       break;
325     case PM16:
326     case SEG32:
327       address = pm_address(FPU_modrm, addr_modes.override.segment,
328 			   addr, address);
329       break;
330     default:
331       EXCEPTION(EX_INTERNAL|0x133);
332     }
333 
334   return (void *)address;
335 }
336 
337 
FPU_get_address_16(u_char FPU_modrm,unsigned long * fpu_eip,struct address * addr,fpu_addr_modes addr_modes)338 void *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
339 		     struct address *addr,
340 		     fpu_addr_modes addr_modes)
341 {
342   u_char mod;
343   unsigned rm = FPU_modrm & 7;
344   int address = 0;     /* Default used for mod == 0 */
345 
346   /* Memory accessed via the cs selector is write protected
347      in `non-segmented' 32 bit protected mode. */
348   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
349       && (addr_modes.override.segment == PREFIX_CS_) )
350     {
351       math_abort(FPU_info,SIGSEGV);
352     }
353 
354   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
355 
356   mod = (FPU_modrm >> 6) & 3;
357 
358   switch (mod)
359     {
360     case 0:
361       if (rm == 6)
362 	{
363 	  /* Special case: disp16 */
364 	  RE_ENTRANT_CHECK_OFF;
365 	  FPU_code_verify_area(2);
366 	  FPU_get_user(address, (unsigned short *) (*fpu_eip));
367 	  (*fpu_eip) += 2;
368 	  RE_ENTRANT_CHECK_ON;
369 	  goto add_segment;
370 	}
371       break;
372     case 1:
373       /* 8 bit signed displacement */
374       RE_ENTRANT_CHECK_OFF;
375       FPU_code_verify_area(1);
376       FPU_get_user(address, (signed char *) (*fpu_eip));
377       RE_ENTRANT_CHECK_ON;
378       (*fpu_eip)++;
379       break;
380     case 2:
381       /* 16 bit displacement */
382       RE_ENTRANT_CHECK_OFF;
383       FPU_code_verify_area(2);
384       FPU_get_user(address, (unsigned short *) (*fpu_eip));
385       (*fpu_eip) += 2;
386       RE_ENTRANT_CHECK_ON;
387       break;
388     case 3:
389       /* Not legal for the FPU */
390       EXCEPTION(EX_Invalid);
391       break;
392     }
393   switch ( rm )
394     {
395     case 0:
396       address += FPU_info->___ebx + FPU_info->___esi;
397       break;
398     case 1:
399       address += FPU_info->___ebx + FPU_info->___edi;
400       break;
401     case 2:
402       address += FPU_info->___ebp + FPU_info->___esi;
403       if ( addr_modes.override.segment == PREFIX_DEFAULT )
404 	addr_modes.override.segment = PREFIX_SS_;
405       break;
406     case 3:
407       address += FPU_info->___ebp + FPU_info->___edi;
408       if ( addr_modes.override.segment == PREFIX_DEFAULT )
409 	addr_modes.override.segment = PREFIX_SS_;
410       break;
411     case 4:
412       address += FPU_info->___esi;
413       break;
414     case 5:
415       address += FPU_info->___edi;
416       break;
417     case 6:
418       address += FPU_info->___ebp;
419       if ( addr_modes.override.segment == PREFIX_DEFAULT )
420 	addr_modes.override.segment = PREFIX_SS_;
421       break;
422     case 7:
423       address += FPU_info->___ebx;
424       break;
425     }
426 
427  add_segment:
428   address &= 0xffff;
429 
430   addr->offset = address;
431 
432   switch ( addr_modes.default_mode )
433     {
434     case 0:
435       break;
436     case VM86:
437       address += vm86_segment(addr_modes.override.segment, addr);
438       break;
439     case PM16:
440     case SEG32:
441       address = pm_address(FPU_modrm, addr_modes.override.segment,
442 			   addr, address);
443       break;
444     default:
445       EXCEPTION(EX_INTERNAL|0x131);
446     }
447 
448   return (void *)address ;
449 }
450