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   1 /*
   2  * cp1emu.c: a MIPS coprocessor 1 (fpu) instruction emulator
   3  *
   4  * MIPS floating point support
   5  * Copyright (C) 1994-2000 Algorithmics Ltd.
   6  * http://www.algor.co.uk
   7  *
   8  * Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
   9  * Copyright (C) 2000  MIPS Technologies, Inc.
  10  *
  11  *  This program is free software; you can distribute it and/or modify it
  12  *  under the terms of the GNU General Public License (Version 2) as
  13  *  published by the Free Software Foundation.
  14  *
  15  *  This program is distributed in the hope it will be useful, but WITHOUT
  16  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  17  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  18  *  for more details.
  19  *
  20  *  You should have received a copy of the GNU General Public License along
  21  *  with this program; if not, write to the Free Software Foundation, Inc.,
  22  *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  23  *
  24  * A complete emulator for MIPS coprocessor 1 instructions.  This is
  25  * required for #float(switch) or #float(trap), where it catches all
  26  * COP1 instructions via the "CoProcessor Unusable" exception.
  27  *
  28  * More surprisingly it is also required for #float(ieee), to help out
  29  * the hardware fpu at the boundaries of the IEEE-754 representation
  30  * (denormalised values, infinities, underflow, etc).  It is made
  31  * quite nasty because emulation of some non-COP1 instructions is
  32  * required, e.g. in branch delay slots.
  33  *
  34  * Note if you know that you won't have an fpu, then you'll get much
  35  * better performance by compiling with -msoft-float!
  36  */
  37 #include <linux/sched.h>
  38
  39 #include <asm/inst.h>
  40 #include <asm/bootinfo.h>
  41 #include <asm/cpu.h>
  42 #include <asm/cpu-features.h>
  43 #include <asm/processor.h>
  44 #include <asm/ptrace.h>
  45 #include <asm/signal.h>
  46 #include <asm/mipsregs.h>
  47 #include <asm/fpu_emulator.h>
  48 #include <asm/uaccess.h>
  49 #include <asm/branch.h>
  50
  51 #include "ieee754.h"
  52 #include "dsemul.h"
  53
  54 /* Strap kernel emulator for full MIPS IV emulation */
  55
  56 #ifdef __mips
  57 #undef __mips
  58 #endif
  59 #define __mips 4
  60
  61 /* Function which emulates a floating point instruction. */
  62
  63 static int fpu_emu(struct pt_regs *, struct mips_fpu_soft_struct *,
  64         mips_instruction);
  65
  66 #if __mips >= 4 && __mips != 32
  67 static int fpux_emu(struct pt_regs *,
  68         struct mips_fpu_soft_struct *, mips_instruction);
  69 #endif
  70
  71 /* Further private data for which no space exists in mips_fpu_soft_struct */
  72
  73 struct mips_fpu_emulator_private fpuemuprivate;
  74
  75 /* Control registers */
  76
  77 #define FPCREG_RID      0       /* $0  = revision id */
  78 #define FPCREG_CSR      31      /* $31 = csr */
  79
  80 /* Convert Mips rounding mode (0..3) to IEEE library modes. */
  81 static const unsigned char ieee_rm[4] = {
  82         IEEE754_RN, IEEE754_RZ, IEEE754_RU, IEEE754_RD
  83 };
  84
  85 #if __mips >= 4
  86 /* convert condition code register number to csr bit */
  87 static const unsigned int fpucondbit[8] = {
  88         FPU_CSR_COND0,
  89         FPU_CSR_COND1,
  90         FPU_CSR_COND2,
  91         FPU_CSR_COND3,
  92         FPU_CSR_COND4,
  93         FPU_CSR_COND5,
  94         FPU_CSR_COND6,
  95         FPU_CSR_COND7
  96 };
  97 #endif
  98
  99
 100 /*
 101  * Redundant with logic already in kernel/branch.c,
 102  * embedded in compute_return_epc.  At some point,
 103  * a single subroutine should be used across both
 104  * modules.
 105  */
 106 static int isBranchInstr(mips_instruction * i)
 107 {
 108         switch (MIPSInst_OPCODE(*i)) {
 109         case spec_op:
 110                 switch (MIPSInst_FUNC(*i)) {
 111                 case jalr_op:
 112                 case jr_op:
 113                         return 1;
 114                 }
 115                 break;
 116
 117         case bcond_op:
 118                 switch (MIPSInst_RT(*i)) {
 119                 case bltz_op:
 120                 case bgez_op:
 121                 case bltzl_op:
 122                 case bgezl_op:
 123                 case bltzal_op:
 124                 case bgezal_op:
 125                 case bltzall_op:
 126                 case bgezall_op:
 127                         return 1;
 128                 }
 129                 break;
 130
 131         case j_op:
 132         case jal_op:
 133         case jalx_op:
 134         case beq_op:
 135         case bne_op:
 136         case blez_op:
 137         case bgtz_op:
 138         case beql_op:
 139         case bnel_op:
 140         case blezl_op:
 141         case bgtzl_op:
 142                 return 1;
 143
 144         case cop0_op:
 145         case cop1_op:
 146         case cop2_op:
 147         case cop1x_op:
 148                 if (MIPSInst_RS(*i) == bc_op)
 149                         return 1;
 150                 break;
 151         }
 152
 153         return 0;
 154 }
 155
 156 /*
 157  * In the Linux kernel, we support selection of FPR format on the
 158  * basis of the Status.FR bit.  This does imply that, if a full 32
 159  * FPRs are desired, there needs to be a flip-flop that can be written
 160  * to one at that bit position.  In any case, O32 MIPS ABI uses
 161  * only the even FPRs (Status.FR = 0).
 162  */
 163
 164 #define CP0_STATUS_FR_SUPPORT
 165
 166 #ifdef CP0_STATUS_FR_SUPPORT
 167 #define FR_BIT ST0_FR
 168 #else
 169 #define FR_BIT 0
 170 #endif
 171
 172 #define SIFROMREG(si,x) ((si) = \
 173                         (xcp->cp0_status & FR_BIT) || !(x & 1) ? \
 174                         (int)ctx->fpr[x] : \
 175                         (int)(ctx->fpr[x & ~1] >> 32 ))
 176 #define SITOREG(si,x)   (ctx->fpr[x & ~((xcp->cp0_status & FR_BIT) == 0)] = \
 177                         (xcp->cp0_status & FR_BIT) || !(x & 1) ? \
 178                         ctx->fpr[x & ~1] >> 32 << 32 | (u32)(si) : \
 179                         ctx->fpr[x & ~1] << 32 >> 32 | (u64)(si) << 32)
 180
 181 #define DIFROMREG(di,x) ((di) = \
 182                         ctx->fpr[x & ~((xcp->cp0_status & FR_BIT) == 0)])
 183 #define DITOREG(di,x)   (ctx->fpr[x & ~((xcp->cp0_status & FR_BIT) == 0)] \
 184                         = (di))
 185
 186 #define SPFROMREG(sp,x) SIFROMREG((sp).bits,x)
 187 #define SPTOREG(sp,x)   SITOREG((sp).bits,x)
 188 #define DPFROMREG(dp,x) DIFROMREG((dp).bits,x)
 189 #define DPTOREG(dp,x)   DITOREG((dp).bits,x)
 190
 191 /*
 192  * Emulate the single floating point instruction pointed at by EPC.
 193  * Two instructions if the instruction is in a branch delay slot.
 194  */
 195
 196 static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_soft_struct *ctx)
 197 {
 198         mips_instruction ir;
 199         vaddr_t emulpc, contpc;
 200         unsigned int cond;
 201
 202         if (get_user(ir, (mips_instruction *) xcp->cp0_epc)) {
 203                 fpuemuprivate.stats.errors++;
 204                 return SIGBUS;
 205         }
 206
 207         /* XXX NEC Vr54xx bug workaround */
 208         if ((xcp->cp0_cause & CAUSEF_BD) && !isBranchInstr(&ir))
 209                 xcp->cp0_cause &= ~CAUSEF_BD;
 210
 211         if (xcp->cp0_cause & CAUSEF_BD) {
 212                 /*
 213                  * The instruction to be emulated is in a branch delay slot
 214                  * which means that we have to  emulate the branch instruction
 215                  * BEFORE we do the cop1 instruction.
 216                  *
 217                  * This branch could be a COP1 branch, but in that case we
 218                  * would have had a trap for that instruction, and would not
 219                  * come through this route.
 220                  *
 221                  * Linux MIPS branch emulator operates on context, updating the
 222                  * cp0_epc.
 223                  */
 224                 emulpc = REG_TO_VA(xcp->cp0_epc + 4);   /* Snapshot emulation target */
 225
 226                 if (__compute_return_epc(xcp)) {
 227 #ifdef CP1DBG
 228                         printk("failed to emulate branch at %p\n",
 229                                 REG_TO_VA(xcp->cp0_epc));
 230 #endif
 231                         return SIGILL;
 232                 }
 233                 if (get_user(ir, (mips_instruction *) emulpc)) {
 234                         fpuemuprivate.stats.errors++;
 235                         return SIGBUS;
 236                 }
 237                 /* __compute_return_epc() will have updated cp0_epc */
 238                 contpc = REG_TO_VA xcp->cp0_epc;
 239                 /* In order not to confuse ptrace() et al, tweak context */
 240                 xcp->cp0_epc = VA_TO_REG emulpc - 4;
 241         }
 242         else {
 243                 emulpc = REG_TO_VA xcp->cp0_epc;
 244                 contpc = REG_TO_VA(xcp->cp0_epc + 4);
 245         }
 246
 247       emul:
 248         fpuemuprivate.stats.emulated++;
 249         switch (MIPSInst_OPCODE(ir)) {
 250 #ifndef SINGLE_ONLY_FPU
 251         case ldc1_op:{
 252                 u64 *va = REG_TO_VA(xcp->regs[MIPSInst_RS(ir)] +
 253                         MIPSInst_SIMM(ir));
 254                 u64 val;
 255
 256                 fpuemuprivate.stats.loads++;
 257                 if (get_user(val, va)) {
 258                         fpuemuprivate.stats.errors++;
 259                         return SIGBUS;
 260                 }
 261                 DITOREG(val, MIPSInst_RT(ir));
 262                 break;
 263         }
 264
 265         case sdc1_op:{
 266                 u64 *va = REG_TO_VA(xcp->regs[MIPSInst_RS(ir)] +
 267                         MIPSInst_SIMM(ir));
 268                 u64 val;
 269
 270                 fpuemuprivate.stats.stores++;
 271                 DIFROMREG(val, MIPSInst_RT(ir));
 272                 if (put_user(val, va)) {
 273                         fpuemuprivate.stats.errors++;
 274                         return SIGBUS;
 275                 }
 276                 break;
 277         }
 278 #endif
 279
 280         case lwc1_op:{
 281                 u32 *va = REG_TO_VA(xcp->regs[MIPSInst_RS(ir)] +
 282                         MIPSInst_SIMM(ir));
 283                 u32 val;
 284
 285                 fpuemuprivate.stats.loads++;
 286                 if (get_user(val, va)) {
 287                         fpuemuprivate.stats.errors++;
 288                         return SIGBUS;
 289                 }
 290 #ifdef SINGLE_ONLY_FPU
 291                 if (MIPSInst_RT(ir) & 1) {
 292                         /* illegal register in single-float mode */
 293                         return SIGILL;
 294                 }
 295 #endif
 296                 SITOREG(val, MIPSInst_RT(ir));
 297                 break;
 298         }
 299
 300         case swc1_op:{
 301                 u32 *va = REG_TO_VA(xcp->regs[MIPSInst_RS(ir)] +
 302                         MIPSInst_SIMM(ir));
 303                 u32 val;
 304
 305                 fpuemuprivate.stats.stores++;
 306 #ifdef SINGLE_ONLY_FPU
 307                 if (MIPSInst_RT(ir) & 1) {
 308                         /* illegal register in single-float mode */
 309                         return SIGILL;
 310                 }
 311 #endif
 312                 SIFROMREG(val, MIPSInst_RT(ir));
 313                 if (put_user(val, va)) {
 314                         fpuemuprivate.stats.errors++;
 315                         return SIGBUS;
 316                 }
 317                 break;
 318         }
 319
 320         case cop1_op:
 321                 switch (MIPSInst_RS(ir)) {
 322
 323 #if __mips64 && !defined(SINGLE_ONLY_FPU)
 324                 case dmfc_op:
 325                         /* copregister fs -> gpr[rt] */
 326                         if (MIPSInst_RT(ir) != 0) {
 327                                 DIFROMREG(xcp->regs[MIPSInst_RT(ir)],
 328                                         MIPSInst_RD(ir));
 329                         }
 330                         break;
 331
 332                 case dmtc_op:
 333                         /* copregister fs <- rt */
 334                         DITOREG(xcp->regs[MIPSInst_RT(ir)], MIPSInst_RD(ir));
 335                         break;
 336 #endif
 337
 338                 case mfc_op:
 339                         /* copregister rd -> gpr[rt] */
 340 #ifdef SINGLE_ONLY_FPU
 341                         if (MIPSInst_RD(ir) & 1) {
 342                                 /* illegal register in single-float mode */
 343                                 return SIGILL;
 344                         }
 345 #endif
 346                         if (MIPSInst_RT(ir) != 0) {
 347                                 SIFROMREG(xcp->regs[MIPSInst_RT(ir)],
 348                                         MIPSInst_RD(ir));
 349                         }
 350                         break;
 351
 352                 case mtc_op:
 353                         /* copregister rd <- rt */
 354 #ifdef SINGLE_ONLY_FPU
 355                         if (MIPSInst_RD(ir) & 1) {
 356                                 /* illegal register in single-float mode */
 357                                 return SIGILL;
 358                         }
 359 #endif
 360                         SITOREG(xcp->regs[MIPSInst_RT(ir)], MIPSInst_RD(ir));
 361                         break;
 362
 363                 case cfc_op:{
 364                         /* cop control register rd -> gpr[rt] */
 365                         u32 value;
 366
 367                         if (ir == CP1UNDEF) {
 368                                 return do_dsemulret(xcp);
 369                         }
 370                         if (MIPSInst_RD(ir) == FPCREG_CSR) {
 371                                 value = ctx->fcr31;
 372 #ifdef CSRTRACE
 373                                 printk("%p gpr[%d]<-csr=%08x\n",
 374                                         REG_TO_VA(xcp->cp0_epc),
 375                                         MIPSInst_RT(ir), value);
 376 #endif
 377                         }
 378                         else if (MIPSInst_RD(ir) == FPCREG_RID)
 379                                 value = 0;
 380                         else
 381                                 value = 0;
 382                         if (MIPSInst_RT(ir))
 383                                 xcp->regs[MIPSInst_RT(ir)] = value;
 384                         break;
 385                 }
 386
 387                 case ctc_op:{
 388                         /* copregister rd <- rt */
 389                         u32 value;
 390
 391                         if (MIPSInst_RT(ir) == 0)
 392                                 value = 0;
 393                         else
 394                                 value = xcp->regs[MIPSInst_RT(ir)];
 395
 396                         /* we only have one writable control reg
 397                          */
 398                         if (MIPSInst_RD(ir) == FPCREG_CSR) {
 399 #ifdef CSRTRACE
 400                                 printk("%p gpr[%d]->csr=%08x\n",
 401                                         REG_TO_VA(xcp->cp0_epc),
 402                                         MIPSInst_RT(ir), value);
 403 #endif
 404                                 ctx->fcr31 = value;
 405                                 /* copy new rounding mode and
 406                                    flush bit to ieee library state! */
 407                                 ieee754_csr.nod = (ctx->fcr31 & 0x1000000) != 0;
 408                                 ieee754_csr.rm = ieee_rm[value & 0x3];
 409                         }
 410                         if ((ctx->fcr31 >> 5) & ctx->fcr31 & FPU_CSR_ALL_E) {
 411                                 return SIGFPE;
 412                         }
 413                         break;
 414                 }
 415
 416                 case bc_op:{
 417                         int likely = 0;
 418
 419                         if (xcp->cp0_cause & CAUSEF_BD)
 420                                 return SIGILL;
 421
 422 #if __mips >= 4
 423                         cond = ctx->fcr31 & fpucondbit[MIPSInst_RT(ir) >> 2];
 424 #else
 425                         cond = ctx->fcr31 & FPU_CSR_COND;
 426 #endif
 427                         switch (MIPSInst_RT(ir) & 3) {
 428                         case bcfl_op:
 429                                 likely = 1;
 430                         case bcf_op:
 431                                 cond = !cond;
 432                                 break;
 433                         case bctl_op:
 434                                 likely = 1;
 435                         case bct_op:
 436                                 break;
 437                         default:
 438                                 /* thats an illegal instruction */
 439                                 return SIGILL;
 440                         }
 441
 442                         xcp->cp0_cause |= CAUSEF_BD;
 443                         if (cond) {
 444                                 /* branch taken: emulate dslot
 445                                  * instruction
 446                                  */
 447                                 xcp->cp0_epc += 4;
 448                                 contpc = REG_TO_VA
 449                                         (xcp->cp0_epc +
 450                                         (MIPSInst_SIMM(ir) << 2));
 451
 452                                 if (get_user(ir, (mips_instruction *)
 453                                                 REG_TO_VA xcp->cp0_epc)) {
 454                                         fpuemuprivate.stats.errors++;
 455                                         return SIGBUS;
 456                                 }
 457
 458                                 switch (MIPSInst_OPCODE(ir)) {
 459                                 case lwc1_op:
 460                                 case swc1_op:
 461 #if (__mips >= 2 || __mips64) && !defined(SINGLE_ONLY_FPU)
 462                                 case ldc1_op:
 463                                 case sdc1_op:
 464 #endif
 465                                 case cop1_op:
 466 #if __mips >= 4 && __mips != 32
 467                                 case cop1x_op:
 468 #endif
 469                                         /* its one of ours */
 470                                         goto emul;
 471 #if __mips >= 4
 472                                 case spec_op:
 473                                         if (MIPSInst_FUNC(ir) == movc_op)
 474                                                 goto emul;
 475                                         break;
 476 #endif
 477                                 }
 478
 479                                 /*
 480                                  * Single step the non-cp1
 481                                  * instruction in the dslot
 482                                  */
 483                                 return mips_dsemul(xcp, ir, VA_TO_REG contpc);
 484                         }
 485                         else {
 486                                 /* branch not taken */
 487                                 if (likely) {
 488                                         /*
 489                                          * branch likely nullifies
 490                                          * dslot if not taken
 491                                          */
 492                                         xcp->cp0_epc += 4;
 493                                         contpc += 4;
 494                                         /*
 495                                          * else continue & execute
 496                                          * dslot as normal insn
 497                                          */
 498                                 }
 499                         }
 500                         break;
 501                 }
 502
 503                 default:
 504                         if (!(MIPSInst_RS(ir) & 0x10))
 505                                 return SIGILL;
 506                         {
 507                                 int sig;
 508
 509                                 /* a real fpu computation instruction */
 510                                 if ((sig = fpu_emu(xcp, ctx, ir)))
 511                                         return sig;
 512                         }
 513                 }
 514                 break;
 515
 516 #if __mips >= 4 && __mips != 32
 517         case cop1x_op:{
 518                 int sig;
 519
 520                 if ((sig = fpux_emu(xcp, ctx, ir)))
 521                         return sig;
 522                 break;
 523         }
 524 #endif
 525
 526 #if __mips >= 4
 527         case spec_op:
 528                 if (MIPSInst_FUNC(ir) != movc_op)
 529                         return SIGILL;
 530                 cond = fpucondbit[MIPSInst_RT(ir) >> 2];
 531                 if (((ctx->fcr31 & cond) != 0) == ((MIPSInst_RT(ir) & 1) != 0))
 532                         xcp->regs[MIPSInst_RD(ir)] =
 533                                 xcp->regs[MIPSInst_RS(ir)];
 534                 break;
 535 #endif
 536
 537         default:
 538                 return SIGILL;
 539         }
 540
 541         /* we did it !! */
 542         xcp->cp0_epc = VA_TO_REG(contpc);
 543         xcp->cp0_cause &= ~CAUSEF_BD;
 544         return 0;
 545 }
 546
 547 /*
 548  * Conversion table from MIPS compare ops 48-63
 549  * cond = ieee754dp_cmp(x,y,IEEE754_UN,sig);
 550  */
 551 static const unsigned char cmptab[8] = {
 552         0,                      /* cmp_0 (sig) cmp_sf */
 553         IEEE754_CUN,            /* cmp_un (sig) cmp_ngle */
 554         IEEE754_CEQ,            /* cmp_eq (sig) cmp_seq */
 555         IEEE754_CEQ | IEEE754_CUN,      /* cmp_ueq (sig) cmp_ngl  */
 556         IEEE754_CLT,            /* cmp_olt (sig) cmp_lt */
 557         IEEE754_CLT | IEEE754_CUN,      /* cmp_ult (sig) cmp_nge */
 558         IEEE754_CLT | IEEE754_CEQ,      /* cmp_ole (sig) cmp_le */
 559         IEEE754_CLT | IEEE754_CEQ | IEEE754_CUN,        /* cmp_ule (sig) cmp_ngt */
 560 };
 561
 562
 563 #if __mips >= 4 && __mips != 32
 564
 565 /*
 566  * Additional MIPS4 instructions
 567  */
 568
 569 #define DEF3OP(name, p, f1, f2, f3) \
 570 static ieee754##p fpemu_##p##_##name (ieee754##p r, ieee754##p s, \
 571     ieee754##p t) \
 572 { \
 573         struct ieee754_csr ieee754_csr_save; \
 574         s = f1 (s, t); \
 575         ieee754_csr_save = ieee754_csr; \
 576         s = f2 (s, r); \
 577         ieee754_csr_save.cx |= ieee754_csr.cx; \
 578         ieee754_csr_save.sx |= ieee754_csr.sx; \
 579         s = f3 (s); \
 580         ieee754_csr.cx |= ieee754_csr_save.cx; \
 581         ieee754_csr.sx |= ieee754_csr_save.sx; \
 582         return s; \
 583 }
 584
 585 static ieee754dp fpemu_dp_recip(ieee754dp d)
 586 {
 587         return ieee754dp_div(ieee754dp_one(0), d);
 588 }
 589
 590 static ieee754dp fpemu_dp_rsqrt(ieee754dp d)
 591 {
 592         return ieee754dp_div(ieee754dp_one(0), ieee754dp_sqrt(d));
 593 }
 594
 595 static ieee754sp fpemu_sp_recip(ieee754sp s)
 596 {
 597         return ieee754sp_div(ieee754sp_one(0), s);
 598 }
 599
 600 static ieee754sp fpemu_sp_rsqrt(ieee754sp s)
 601 {
 602         return ieee754sp_div(ieee754sp_one(0), ieee754sp_sqrt(s));
 603 }
 604
 605 DEF3OP(madd, sp, ieee754sp_mul, ieee754sp_add,);
 606 DEF3OP(msub, sp, ieee754sp_mul, ieee754sp_sub,);
 607 DEF3OP(nmadd, sp, ieee754sp_mul, ieee754sp_add, ieee754sp_neg);
 608 DEF3OP(nmsub, sp, ieee754sp_mul, ieee754sp_sub, ieee754sp_neg);
 609 DEF3OP(madd, dp, ieee754dp_mul, ieee754dp_add,);
 610 DEF3OP(msub, dp, ieee754dp_mul, ieee754dp_sub,);
 611 DEF3OP(nmadd, dp, ieee754dp_mul, ieee754dp_add, ieee754dp_neg);
 612 DEF3OP(nmsub, dp, ieee754dp_mul, ieee754dp_sub, ieee754dp_neg);
 613
 614 static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_soft_struct *ctx,
 615         mips_instruction ir)
 616 {
 617         unsigned rcsr = 0;      /* resulting csr */
 618
 619         fpuemuprivate.stats.cp1xops++;
 620
 621         switch (MIPSInst_FMA_FFMT(ir)) {
 622         case s_fmt:{            /* 0 */
 623
 624                 ieee754sp(*handler) (ieee754sp, ieee754sp, ieee754sp);
 625                 ieee754sp fd, fr, fs, ft;
 626                 u32 *va;
 627                 u32 val;
 628
 629                 switch (MIPSInst_FUNC(ir)) {
 630                 case lwxc1_op:
 631                         va = REG_TO_VA(xcp->regs[MIPSInst_FR(ir)] +
 632                                 xcp->regs[MIPSInst_FT(ir)]);
 633
 634                         fpuemuprivate.stats.loads++;
 635                         if (get_user(val, va)) {
 636                                 fpuemuprivate.stats.errors++;
 637                                 return SIGBUS;
 638                         }
 639 #ifdef SINGLE_ONLY_FPU
 640                         if (MIPSInst_FD(ir) & 1) {
 641                                 /* illegal register in single-float
 642                                  * mode
 643                                  */
 644                                 return SIGILL;
 645                         }
 646 #endif
 647                         SITOREG(val, MIPSInst_FD(ir));
 648                         break;
 649
 650                 case swxc1_op:
 651                         va = REG_TO_VA(xcp->regs[MIPSInst_FR(ir)] +
 652                                 xcp->regs[MIPSInst_FT(ir)]);
 653
 654                         fpuemuprivate.stats.stores++;
 655 #ifdef SINGLE_ONLY_FPU
 656                         if (MIPSInst_FS(ir) & 1) {
 657                                 /* illegal register in single-float
 658                                  * mode
 659                                  */
 660                                 return SIGILL;
 661                         }
 662 #endif
 663
 664                         SIFROMREG(val, MIPSInst_FS(ir));
 665                         if (put_user(val, va)) {
 666                                 fpuemuprivate.stats.errors++;
 667                                 return SIGBUS;
 668                         }
 669                         break;
 670
 671                 case madd_s_op:
 672                         handler = fpemu_sp_madd;
 673                         goto scoptop;
 674                 case msub_s_op:
 675                         handler = fpemu_sp_msub;
 676                         goto scoptop;
 677                 case nmadd_s_op:
 678                         handler = fpemu_sp_nmadd;
 679                         goto scoptop;
 680                 case nmsub_s_op:
 681                         handler = fpemu_sp_nmsub;
 682                         goto scoptop;
 683
 684                       scoptop:
 685                         SPFROMREG(fr, MIPSInst_FR(ir));
 686                         SPFROMREG(fs, MIPSInst_FS(ir));
 687                         SPFROMREG(ft, MIPSInst_FT(ir));
 688                         fd = (*handler) (fr, fs, ft);
 689                         SPTOREG(fd, MIPSInst_FD(ir));
 690
 691                       copcsr:
 692                         if (ieee754_cxtest(IEEE754_INEXACT))
 693                                 rcsr |= FPU_CSR_INE_X | FPU_CSR_INE_S;
 694                         if (ieee754_cxtest(IEEE754_UNDERFLOW))
 695                                 rcsr |= FPU_CSR_UDF_X | FPU_CSR_UDF_S;
 696                         if (ieee754_cxtest(IEEE754_OVERFLOW))
 697                                 rcsr |= FPU_CSR_OVF_X | FPU_CSR_OVF_S;
 698                         if (ieee754_cxtest(IEEE754_INVALID_OPERATION))
 699                                 rcsr |= FPU_CSR_INV_X | FPU_CSR_INV_S;
 700
 701                         ctx->fcr31 = (ctx->fcr31 & ~FPU_CSR_ALL_X) | rcsr;
 702                         if (ieee754_csr.nod)
 703                                 ctx->fcr31 |= 0x1000000;
 704                         if ((ctx->fcr31 >> 5) & ctx->fcr31 & FPU_CSR_ALL_E) {
 705                                 /*printk ("SIGFPE: fpu csr = %08x\n",
 706                                    ctx->fcr31); */
 707                                 return SIGFPE;
 708                         }
 709
 710                         break;
 711
 712                 default:
 713                         return SIGILL;
 714                 }
 715                 break;
 716         }
 717
 718 #ifndef SINGLE_ONLY_FPU
 719         case d_fmt:{            /* 1 */
 720                 ieee754dp(*handler) (ieee754dp, ieee754dp, ieee754dp);
 721                 ieee754dp fd, fr, fs, ft;
 722                 u64 *va;
 723                 u64 val;
 724
 725                 switch (MIPSInst_FUNC(ir)) {
 726                 case ldxc1_op:
 727                         va = REG_TO_VA(xcp->regs[MIPSInst_FR(ir)] +
 728                                 xcp->regs[MIPSInst_FT(ir)]);
 729
 730                         fpuemuprivate.stats.loads++;
 731                         if (get_user(val, va)) {
 732                                 fpuemuprivate.stats.errors++;
 733                                 return SIGBUS;
 734                         }
 735                         DITOREG(val, MIPSInst_FD(ir));
 736                         break;
 737
 738                 case sdxc1_op:
 739                         va = REG_TO_VA(xcp->regs[MIPSInst_FR(ir)] +
 740                                 xcp->regs[MIPSInst_FT(ir)]);
 741
 742                         fpuemuprivate.stats.stores++;
 743                         DIFROMREG(val, MIPSInst_FS(ir));
 744                         if (put_user(val, va)) {
 745                                 fpuemuprivate.stats.errors++;
 746                                 return SIGBUS;
 747                         }
 748                         break;
 749
 750                 case madd_d_op:
 751                         handler = fpemu_dp_madd;
 752                         goto dcoptop;
 753                 case msub_d_op:
 754                         handler = fpemu_dp_msub;
 755                         goto dcoptop;
 756                 case nmadd_d_op:
 757                         handler = fpemu_dp_nmadd;
 758                         goto dcoptop;
 759                 case nmsub_d_op:
 760                         handler = fpemu_dp_nmsub;
 761                         goto dcoptop;
 762
 763                       dcoptop:
 764                         DPFROMREG(fr, MIPSInst_FR(ir));
 765                         DPFROMREG(fs, MIPSInst_FS(ir));
 766                         DPFROMREG(ft, MIPSInst_FT(ir));
 767                         fd = (*handler) (fr, fs, ft);
 768                         DPTOREG(fd, MIPSInst_FD(ir));
 769                         goto copcsr;
 770
 771                 default:
 772                         return SIGILL;
 773                 }
 774                 break;
 775         }
 776 #endif
 777
 778         case 0x7:               /* 7 */
 779                 if (MIPSInst_FUNC(ir) != pfetch_op) {
 780                         return SIGILL;
 781                 }
 782                 /* ignore prefx operation */
 783                 break;
 784
 785         default:
 786                 return SIGILL;
 787         }
 788
 789         return 0;
 790 }
 791 #endif
 792
 793
 794
 795 /*
 796  * Emulate a single COP1 arithmetic instruction.
 797  */
 798 static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_soft_struct *ctx,
 799         mips_instruction ir)
 800 {
 801         int rfmt;               /* resulting format */
 802         unsigned rcsr = 0;      /* resulting csr */
 803         unsigned cond;
 804         union {
 805                 ieee754dp d;
 806                 ieee754sp s;
 807                 int w;
 808 #if __mips64
 809                 s64 l;
 810 #endif
 811         } rv;                   /* resulting value */
 812
 813         fpuemuprivate.stats.cp1ops++;
 814         switch (rfmt = (MIPSInst_FFMT(ir) & 0xf)) {
 815         case s_fmt:{            /* 0 */
 816                 union {
 817                         ieee754sp(*b) (ieee754sp, ieee754sp);
 818                         ieee754sp(*u) (ieee754sp);
 819                 } handler;
 820
 821                 switch (MIPSInst_FUNC(ir)) {
 822                         /* binary ops */
 823                 case fadd_op:
 824                         handler.b = ieee754sp_add;
 825                         goto scopbop;
 826                 case fsub_op:
 827                         handler.b = ieee754sp_sub;
 828                         goto scopbop;
 829                 case fmul_op:
 830                         handler.b = ieee754sp_mul;
 831                         goto scopbop;
 832                 case fdiv_op:
 833                         handler.b = ieee754sp_div;
 834                         goto scopbop;
 835
 836                         /* unary  ops */
 837 #if __mips >= 2 || __mips64
 838                 case fsqrt_op:
 839                         handler.u = ieee754sp_sqrt;
 840                         goto scopuop;
 841 #endif
 842 #if __mips >= 4 && __mips != 32
 843                 case frsqrt_op:
 844                         handler.u = fpemu_sp_rsqrt;
 845                         goto scopuop;
 846                 case frecip_op:
 847                         handler.u = fpemu_sp_recip;
 848                         goto scopuop;
 849 #endif
 850 #if __mips >= 4
 851                 case fmovc_op:
 852                         cond = fpucondbit[MIPSInst_FT(ir) >> 2];
 853                         if (((ctx->fcr31 & cond) != 0) !=
 854                                 ((MIPSInst_FT(ir) & 1) != 0))
 855                                 return 0;
 856                         SPFROMREG(rv.s, MIPSInst_FS(ir));
 857                         break;
 858                 case fmovz_op:
 859                         if (xcp->regs[MIPSInst_FT(ir)] != 0)
 860                                 return 0;
 861                         SPFROMREG(rv.s, MIPSInst_FS(ir));
 862                         break;
 863                 case fmovn_op:
 864                         if (xcp->regs[MIPSInst_FT(ir)] == 0)
 865                                 return 0;
 866                         SPFROMREG(rv.s, MIPSInst_FS(ir));
 867                         break;
 868 #endif
 869                 case fabs_op:
 870                         handler.u = ieee754sp_abs;
 871                         goto scopuop;
 872                 case fneg_op:
 873                         handler.u = ieee754sp_neg;
 874                         goto scopuop;
 875                 case fmov_op:
 876                         /* an easy one */
 877                         SPFROMREG(rv.s, MIPSInst_FS(ir));
 878                         goto copcsr;
 879
 880                         /* binary op on handler */
 881                       scopbop:
 882                         {
 883                                 ieee754sp fs, ft;
 884
 885                                 SPFROMREG(fs, MIPSInst_FS(ir));
 886                                 SPFROMREG(ft, MIPSInst_FT(ir));
 887
 888                                 rv.s = (*handler.b) (fs, ft);
 889                                 goto copcsr;
 890                         }
 891                       scopuop:
 892                         {
 893                                 ieee754sp fs;
 894
 895                                 SPFROMREG(fs, MIPSInst_FS(ir));
 896                                 rv.s = (*handler.u) (fs);
 897                                 goto copcsr;
 898                         }
 899                       copcsr:
 900                         if (ieee754_cxtest(IEEE754_INEXACT))
 901                                 rcsr |= FPU_CSR_INE_X | FPU_CSR_INE_S;
 902                         if (ieee754_cxtest(IEEE754_UNDERFLOW))
 903                                 rcsr |= FPU_CSR_UDF_X | FPU_CSR_UDF_S;
 904                         if (ieee754_cxtest(IEEE754_OVERFLOW))
 905                                 rcsr |= FPU_CSR_OVF_X | FPU_CSR_OVF_S;
 906                         if (ieee754_cxtest(IEEE754_ZERO_DIVIDE))
 907                                 rcsr |= FPU_CSR_DIV_X | FPU_CSR_DIV_S;
 908                         if (ieee754_cxtest(IEEE754_INVALID_OPERATION))
 909                                 rcsr |= FPU_CSR_INV_X | FPU_CSR_INV_S;
 910                         break;
 911
 912                         /* unary conv ops */
 913                 case fcvts_op:
 914                         return SIGILL;  /* not defined */
 915                 case fcvtd_op:{
 916 #ifdef SINGLE_ONLY_FPU
 917                         return SIGILL;  /* not defined */
 918 #else
 919                         ieee754sp fs;
 920
 921                         SPFROMREG(fs, MIPSInst_FS(ir));
 922                         rv.d = ieee754dp_fsp(fs);
 923                         rfmt = d_fmt;
 924                         goto copcsr;
 925                 }
 926 #endif
 927                 case fcvtw_op:{
 928                         ieee754sp fs;
 929
 930                         SPFROMREG(fs, MIPSInst_FS(ir));
 931                         rv.w = ieee754sp_tint(fs);
 932                         rfmt = w_fmt;
 933                         goto copcsr;
 934                 }
 935
 936 #if __mips >= 2 || __mips64
 937                 case fround_op:
 938                 case ftrunc_op:
 939                 case fceil_op:
 940                 case ffloor_op:{
 941                         unsigned int oldrm = ieee754_csr.rm;
 942                         ieee754sp fs;
 943
 944                         SPFROMREG(fs, MIPSInst_FS(ir));
 945                         ieee754_csr.rm = ieee_rm[MIPSInst_FUNC(ir) & 0x3];
 946                         rv.w = ieee754sp_tint(fs);
 947                         ieee754_csr.rm = oldrm;
 948                         rfmt = w_fmt;
 949                         goto copcsr;
 950                 }
 951 #endif /* __mips >= 2 */
 952
 953 #if __mips64 && !defined(SINGLE_ONLY_FPU)
 954                 case fcvtl_op:{
 955                         ieee754sp fs;
 956
 957                         SPFROMREG(fs, MIPSInst_FS(ir));
 958                         rv.l = ieee754sp_tlong(fs);
 959                         rfmt = l_fmt;
 960                         goto copcsr;
 961                 }
 962
 963                 case froundl_op:
 964                 case ftruncl_op:
 965                 case fceill_op:
 966                 case ffloorl_op:{
 967                         unsigned int oldrm = ieee754_csr.rm;
 968                         ieee754sp fs;
 969
 970                         SPFROMREG(fs, MIPSInst_FS(ir));
 971                         ieee754_csr.rm = ieee_rm[MIPSInst_FUNC(ir) & 0x3];
 972                         rv.l = ieee754sp_tlong(fs);
 973                         ieee754_csr.rm = oldrm;
 974                         rfmt = l_fmt;
 975                         goto copcsr;
 976                 }
 977 #endif /* __mips64 && !fpu(single) */
 978
 979                 default:
 980                         if (MIPSInst_FUNC(ir) >= fcmp_op) {
 981                                 unsigned cmpop = MIPSInst_FUNC(ir) - fcmp_op;
 982                                 ieee754sp fs, ft;
 983
 984                                 SPFROMREG(fs, MIPSInst_FS(ir));
 985                                 SPFROMREG(ft, MIPSInst_FT(ir));
 986                                 rv.w = ieee754sp_cmp(fs, ft,
 987                                         cmptab[cmpop & 0x7], cmpop & 0x8);
 988                                 rfmt = -1;
 989                                 if ((cmpop & 0x8) && ieee754_cxtest
 990                                         (IEEE754_INVALID_OPERATION))
 991                                         rcsr = FPU_CSR_INV_X | FPU_CSR_INV_S;
 992                                 else
 993                                         goto copcsr;
 994
 995                         }
 996                         else {
 997                                 return SIGILL;
 998                         }
 999                         break;
1000                 }
1001                 break;
1002         }
1003
1004 #ifndef SINGLE_ONLY_FPU
1005         case d_fmt:{
1006                 union {
1007                         ieee754dp(*b) (ieee754dp, ieee754dp);
1008                         ieee754dp(*u) (ieee754dp);
1009                 } handler;
1010
1011                 switch (MIPSInst_FUNC(ir)) {
1012                         /* binary ops */
1013                 case fadd_op:
1014                         handler.b = ieee754dp_add;
1015                         goto dcopbop;
1016                 case fsub_op:
1017                         handler.b = ieee754dp_sub;
1018                         goto dcopbop;
1019                 case fmul_op:
1020                         handler.b = ieee754dp_mul;
1021                         goto dcopbop;
1022                 case fdiv_op:
1023                         handler.b = ieee754dp_div;
1024                         goto dcopbop;
1025
1026                         /* unary  ops */
1027 #if __mips >= 2 || __mips64
1028                 case fsqrt_op:
1029                         handler.u = ieee754dp_sqrt;
1030                         goto dcopuop;
1031 #endif
1032 #if __mips >= 4 && __mips != 32
1033                 case frsqrt_op:
1034                         handler.u = fpemu_dp_rsqrt;
1035                         goto dcopuop;
1036                 case frecip_op:
1037                         handler.u = fpemu_dp_recip;
1038                         goto dcopuop;
1039 #endif
1040 #if __mips >= 4
1041                 case fmovc_op:
1042                         cond = fpucondbit[MIPSInst_FT(ir) >> 2];
1043                         if (((ctx->fcr31 & cond) != 0) !=
1044                                 ((MIPSInst_FT(ir) & 1) != 0))
1045                                 return 0;
1046                         DPFROMREG(rv.d, MIPSInst_FS(ir));
1047                         break;
1048                 case fmovz_op:
1049                         if (xcp->regs[MIPSInst_FT(ir)] != 0)
1050                                 return 0;
1051                         DPFROMREG(rv.d, MIPSInst_FS(ir));
1052                         break;
1053                 case fmovn_op:
1054                         if (xcp->regs[MIPSInst_FT(ir)] == 0)
1055                                 return 0;
1056                         DPFROMREG(rv.d, MIPSInst_FS(ir));
1057                         break;
1058 #endif
1059                 case fabs_op:
1060                         handler.u = ieee754dp_abs;
1061                         goto dcopuop;
1062
1063                 case fneg_op:
1064                         handler.u = ieee754dp_neg;
1065                         goto dcopuop;
1066
1067                 case fmov_op:
1068                         /* an easy one */
1069                         DPFROMREG(rv.d, MIPSInst_FS(ir));
1070                         goto copcsr;
1071
1072                         /* binary op on handler */
1073                       dcopbop:{
1074                                 ieee754dp fs, ft;
1075
1076                                 DPFROMREG(fs, MIPSInst_FS(ir));
1077                                 DPFROMREG(ft, MIPSInst_FT(ir));
1078
1079                                 rv.d = (*handler.b) (fs, ft);
1080                                 goto copcsr;
1081                         }
1082                       dcopuop:{
1083                                 ieee754dp fs;
1084
1085                                 DPFROMREG(fs, MIPSInst_FS(ir));
1086                                 rv.d = (*handler.u) (fs);
1087                                 goto copcsr;
1088                         }
1089
1090                         /* unary conv ops */
1091                 case fcvts_op:{
1092                         ieee754dp fs;
1093
1094                         DPFROMREG(fs, MIPSInst_FS(ir));
1095                         rv.s = ieee754sp_fdp(fs);
1096                         rfmt = s_fmt;
1097                         goto copcsr;
1098                 }
1099                 case fcvtd_op:
1100                         return SIGILL;  /* not defined */
1101
1102                 case fcvtw_op:{
1103                         ieee754dp fs;
1104
1105                         DPFROMREG(fs, MIPSInst_FS(ir));
1106                         rv.w = ieee754dp_tint(fs);      /* wrong */
1107                         rfmt = w_fmt;
1108                         goto copcsr;
1109                 }
1110
1111 #if __mips >= 2 || __mips64
1112                 case fround_op:
1113                 case ftrunc_op:
1114                 case fceil_op:
1115                 case ffloor_op:{
1116                         unsigned int oldrm = ieee754_csr.rm;
1117                         ieee754dp fs;
1118
1119                         DPFROMREG(fs, MIPSInst_FS(ir));
1120                         ieee754_csr.rm = ieee_rm[MIPSInst_FUNC(ir) & 0x3];
1121                         rv.w = ieee754dp_tint(fs);
1122                         ieee754_csr.rm = oldrm;
1123                         rfmt = w_fmt;
1124                         goto copcsr;
1125                 }
1126 #endif
1127
1128 #if __mips64 && !defined(SINGLE_ONLY_FPU)
1129                 case fcvtl_op:{
1130                         ieee754dp fs;
1131
1132                         DPFROMREG(fs, MIPSInst_FS(ir));
1133                         rv.l = ieee754dp_tlong(fs);
1134                         rfmt = l_fmt;
1135                         goto copcsr;
1136                 }
1137
1138                 case froundl_op:
1139                 case ftruncl_op:
1140                 case fceill_op:
1141                 case ffloorl_op:{
1142                         unsigned int oldrm = ieee754_csr.rm;
1143                         ieee754dp fs;
1144
1145                         DPFROMREG(fs, MIPSInst_FS(ir));
1146                         ieee754_csr.rm = ieee_rm[MIPSInst_FUNC(ir) & 0x3];
1147                         rv.l = ieee754dp_tlong(fs);
1148                         ieee754_csr.rm = oldrm;
1149                         rfmt = l_fmt;
1150                         goto copcsr;
1151                 }
1152 #endif /* __mips >= 3 && !fpu(single) */
1153
1154                 default:
1155                         if (MIPSInst_FUNC(ir) >= fcmp_op) {
1156                                 unsigned cmpop = MIPSInst_FUNC(ir) - fcmp_op;
1157                                 ieee754dp fs, ft;
1158
1159                                 DPFROMREG(fs, MIPSInst_FS(ir));
1160                                 DPFROMREG(ft, MIPSInst_FT(ir));
1161                                 rv.w = ieee754dp_cmp(fs, ft,
1162                                         cmptab[cmpop & 0x7], cmpop & 0x8);
1163                                 rfmt = -1;
1164                                 if ((cmpop & 0x8)
1165                                         &&
1166                                         ieee754_cxtest
1167                                         (IEEE754_INVALID_OPERATION))
1168                                         rcsr = FPU_CSR_INV_X | FPU_CSR_INV_S;
1169                                 else
1170                                         goto copcsr;
1171
1172                         }
1173                         else {
1174                                 return SIGILL;
1175                         }
1176                         break;
1177                 }
1178                 break;
1179         }
1180 #endif /* ifndef SINGLE_ONLY_FPU */
1181
1182         case w_fmt:{
1183                 ieee754sp fs;
1184
1185                 switch (MIPSInst_FUNC(ir)) {
1186                 case fcvts_op:
1187                         /* convert word to single precision real */
1188                         SPFROMREG(fs, MIPSInst_FS(ir));
1189                         rv.s = ieee754sp_fint(fs.bits);
1190                         rfmt = s_fmt;
1191                         goto copcsr;
1192 #ifndef SINGLE_ONLY_FPU
1193                 case fcvtd_op:
1194                         /* convert word to double precision real */
1195                         SPFROMREG(fs, MIPSInst_FS(ir));
1196                         rv.d = ieee754dp_fint(fs.bits);
1197                         rfmt = d_fmt;
1198                         goto copcsr;
1199 #endif
1200                 default:
1201                         return SIGILL;
1202                 }
1203                 break;
1204         }
1205
1206 #if __mips64 && !defined(SINGLE_ONLY_FPU)
1207         case l_fmt:{
1208                 switch (MIPSInst_FUNC(ir)) {
1209                 case fcvts_op:
1210                         /* convert long to single precision real */
1211                         rv.s = ieee754sp_flong(ctx->fpr[MIPSInst_FS(ir)]);
1212                         rfmt = s_fmt;
1213                         goto copcsr;
1214                 case fcvtd_op:
1215                         /* convert long to double precision real */
1216                         rv.d = ieee754dp_flong(ctx->fpr[MIPSInst_FS(ir)]);
1217                         rfmt = d_fmt;
1218                         goto copcsr;
1219                 default:
1220                         return SIGILL;
1221                 }
1222                 break;
1223         }
1224 #endif
1225
1226         default:
1227                 return SIGILL;
1228         }
1229
1230         /*
1231          * Update the fpu CSR register for this operation.
1232          * If an exception is required, generate a tidy SIGFPE exception,
1233          * without updating the result register.
1234          * Note: cause exception bits do not accumulate, they are rewritten
1235          * for each op; only the flag/sticky bits accumulate.
1236          */
1237         ctx->fcr31 = (ctx->fcr31 & ~FPU_CSR_ALL_X) | rcsr;
1238         if ((ctx->fcr31 >> 5) & ctx->fcr31 & FPU_CSR_ALL_E) {
1239                 /*printk ("SIGFPE: fpu csr = %08x\n",ctx->fcr31); */
1240                 return SIGFPE;
1241         }
1242
1243         /*
1244          * Now we can safely write the result back to the register file.
1245          */
1246         switch (rfmt) {
1247         case -1:{
1248 #if __mips >= 4
1249                 cond = fpucondbit[MIPSInst_FD(ir) >> 2];
1250 #else
1251                 cond = FPU_CSR_COND;
1252 #endif
1253                 if (rv.w)
1254                         ctx->fcr31 |= cond;
1255                 else
1256                         ctx->fcr31 &= ~cond;
1257                 break;
1258         }
1259 #ifndef SINGLE_ONLY_FPU
1260         case d_fmt:
1261                 DPTOREG(rv.d, MIPSInst_FD(ir));
1262                 break;
1263 #endif
1264         case s_fmt:
1265                 SPTOREG(rv.s, MIPSInst_FD(ir));
1266                 break;
1267         case w_fmt:
1268                 SITOREG(rv.w, MIPSInst_FD(ir));
1269                 break;
1270 #if __mips64 && !defined(SINGLE_ONLY_FPU)
1271         case l_fmt:
1272                 DITOREG(rv.l, MIPSInst_FD(ir));
1273                 break;
1274 #endif
1275         default:
1276                 return SIGILL;
1277         }
1278
1279         return 0;
1280 }
1281
1282 int fpu_emulator_cop1Handler(int xcptno, struct pt_regs *xcp,
1283         struct mips_fpu_soft_struct *ctx)
1284 {
1285         gpreg_t oldepc, prevepc;
1286         mips_instruction insn;
1287         int sig = 0;
1288
1289         oldepc = xcp->cp0_epc;
1290         do {
1291                 prevepc = xcp->cp0_epc;
1292
1293                 if (get_user(insn, (mips_instruction *) xcp->cp0_epc)) {
1294                         fpuemuprivate.stats.errors++;
1295                         return SIGBUS;
1296                 }
1297                 if (insn == 0)
1298                         xcp->cp0_epc += 4;      /* skip nops */
1299                 else {
1300                         /* Update ieee754_csr. Only relevant if we have a
1301                            h/w FPU */
1302                         ieee754_csr.nod = (ctx->fcr31 & 0x1000000) != 0;
1303                         ieee754_csr.rm = ieee_rm[ctx->fcr31 & 0x3];
1304                         ieee754_csr.cx = (ctx->fcr31 >> 12) & 0x1f;
1305                         sig = cop1Emulate(xcp, ctx);
1306                 }
1307
1308                 if (cpu_has_fpu)
1309                         break;
1310                 if (sig)
1311                         break;
1312
1313                 cond_resched();
1314         } while (xcp->cp0_epc > prevepc);
1315
1316         /* SIGILL indicates a non-fpu instruction */
1317         if (sig == SIGILL && xcp->cp0_epc != oldepc)
1318                 /* but if epc has advanced, then ignore it */
1319                 sig = 0;
1320
1321         return sig;
1322 }