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