riscv/processor.cc

   1 // See LICENSE for license details.
   2
   3 #include "processor.h"
   4 #include "extension.h"
   5 #include "common.h"
   6 #include "config.h"
   7 #include "sim.h"
   8 #include "mmu.h"
   9 #include "disasm.h"
  10 #include "gdbserver.h"
  11 #include <cinttypes>
  12 #include <cmath>
  13 #include <cstdlib>
  14 #include <iostream>
  15 #include <assert.h>
  16 #include <limits.h>
  17 #include <stdexcept>
  18 #include <algorithm>
  19
  20 #undef STATE
  21 #define STATE state
  22
  23 processor_t::processor_t(const char* isa, sim_t* sim, uint32_t id,
  24         bool halt_on_reset)
  25   : debug(false), sim(sim), ext(NULL), id(id), halt_on_reset(halt_on_reset)
  26 {
  27   parse_isa_string(isa);
  28   register_base_instructions();
  29
  30   mmu = new mmu_t(sim, this);
  31   disassembler = new disassembler_t(max_xlen);
  32
  33   reset();
  34 }
  35
  36 processor_t::~processor_t()
  37 {
  38 #ifdef RISCV_ENABLE_HISTOGRAM
  39   if (histogram_enabled)
  40   {
  41     fprintf(stderr, "PC Histogram size:%zu\n", pc_histogram.size());
  42     for (auto it : pc_histogram)
  43       fprintf(stderr, "%0" PRIx64 " %" PRIu64 "\n", it.first, it.second);
  44   }
  45 #endif
  46
  47   delete mmu;
  48   delete disassembler;
  49 }
  50
  51 static void bad_isa_string(const char* isa)
  52 {
  53   fprintf(stderr, "error: bad --isa option %s\n", isa);
  54   abort();
  55 }
  56
  57 void processor_t::parse_isa_string(const char* str)
  58 {
  59   std::string lowercase, tmp;
  60   for (const char *r = str; *r; r++)
  61     lowercase += std::tolower(*r);
  62
  63   const char* p = lowercase.c_str();
  64   const char* all_subsets = "imafdc";
  65
  66   max_xlen = 64;
  67   isa = reg_t(2) << 62;
  68
  69   if (strncmp(p, "rv32", 4) == 0)
  70     max_xlen = 32, isa = reg_t(1) << 30, p += 4;
  71   else if (strncmp(p, "rv64", 4) == 0)
  72     p += 4;
  73   else if (strncmp(p, "rv", 2) == 0)
  74     p += 2;
  75
  76   if (!*p) {
  77     p = all_subsets;
  78   } else if (*p == 'g') { // treat "G" as "IMAFD"
  79     tmp = std::string("imafd") + (p+1);
  80     p = &tmp[0];
  81   } else if (*p != 'i') {
  82     bad_isa_string(str);
  83   }
  84
  85   isa_string = "rv" + std::to_string(max_xlen) + p;
  86   isa |= 1L << ('s' - 'a'); // advertise support for supervisor mode
  87   isa |= 1L << ('u' - 'a'); // advertise support for user mode
  88
  89   while (*p) {
  90     isa |= 1L << (*p - 'a');
  91
  92     if (auto next = strchr(all_subsets, *p)) {
  93       all_subsets = next + 1;
  94       p++;
  95     } else if (*p == 'x') {
  96       const char* ext = p+1, *end = ext;
  97       while (islower(*end))
  98         end++;
  99       register_extension(find_extension(std::string(ext, end - ext).c_str())());
 100       p = end;
 101     } else {
 102       bad_isa_string(str);
 103     }
 104   }
 105
 106   if (supports_extension('D') && !supports_extension('F'))
 107     bad_isa_string(str);
 108
 109   // advertise support for supervisor and user modes
 110   isa |= 1L << ('s' - 'a');
 111   isa |= 1L << ('u' - 'a');
 112
 113   max_isa = isa;
 114 }
 115
 116 void state_t::reset()
 117 {
 118   memset(this, 0, sizeof(*this));
 119   prv = PRV_M;
 120   pc = DEFAULT_RSTVEC;
 121   mtvec = DEFAULT_MTVEC;
 122   load_reservation = -1;
 123   tselect = 0;
 124   for (unsigned int i = 0; i < num_triggers; i++)
 125     mcontrol[i].type = 2;
 126 }
 127
 128 void processor_t::set_debug(bool value)
 129 {
 130   debug = value;
 131   if (ext)
 132     ext->set_debug(value);
 133 }
 134
 135 void processor_t::set_histogram(bool value)
 136 {
 137   histogram_enabled = value;
 138 #ifndef RISCV_ENABLE_HISTOGRAM
 139   if (value) {
 140     fprintf(stderr, "PC Histogram support has not been properly enabled;");
 141     fprintf(stderr, " please re-build the riscv-isa-run project using \"configure --enable-histogram\".\n");
 142   }
 143 #endif
 144 }
 145
 146 void processor_t::reset()
 147 {
 148   state.reset();
 149   state.dcsr.halt = halt_on_reset;
 150   halt_on_reset = false;
 151   set_csr(CSR_MSTATUS, state.mstatus);
 152
 153   if (ext)
 154     ext->reset(); // reset the extension
 155 }
 156
 157 void processor_t::raise_interrupt(reg_t which)
 158 {
 159   throw trap_t(((reg_t)1 << (max_xlen-1)) | which);
 160 }
 161
 162 // Count number of contiguous 0 bits starting from the LSB.
 163 static int ctz(reg_t val)
 164 {
 165   int res = 0;
 166   if (val)
 167     while ((val & 1) == 0)
 168       val >>= 1, res++;
 169   return res;
 170 }
 171
 172 void processor_t::take_interrupt()
 173 {
 174   reg_t pending_interrupts = state.mip & state.mie;
 175
 176   reg_t mie = get_field(state.mstatus, MSTATUS_MIE);
 177   reg_t m_enabled = state.prv < PRV_M || (state.prv == PRV_M && mie);
 178   reg_t enabled_interrupts = pending_interrupts & ~state.mideleg & -m_enabled;
 179
 180   reg_t sie = get_field(state.mstatus, MSTATUS_SIE);
 181   reg_t s_enabled = state.prv < PRV_S || (state.prv == PRV_S && sie);
 182   enabled_interrupts |= pending_interrupts & state.mideleg & -s_enabled;
 183
 184   if (enabled_interrupts)
 185     raise_interrupt(ctz(enabled_interrupts));
 186 }
 187
 188 void processor_t::set_privilege(reg_t prv)
 189 {
 190   assert(prv <= PRV_M);
 191   if (prv == PRV_H)
 192     prv = PRV_U;
 193   mmu->flush_tlb();
 194   state.prv = prv;
 195 }
 196
 197 void processor_t::enter_debug_mode(uint8_t cause)
 198 {
 199   state.dcsr.cause = cause;
 200   state.dcsr.prv = state.prv;
 201   set_privilege(PRV_M);
 202   state.dpc = state.pc;
 203   state.pc = DEBUG_ROM_START;
 204 }
 205
 206 void processor_t::take_trap(trap_t& t, reg_t epc)
 207 {
 208   if (debug) {
 209     fprintf(stderr, "core %3d: exception %s, epc 0x%016" PRIx64 "\n",
 210             id, t.name(), epc);
 211     if (t.has_badaddr())
 212       fprintf(stderr, "core %3d:           badaddr 0x%016" PRIx64 "\n", id,
 213           t.get_badaddr());
 214   }
 215
 216   if (t.cause() == CAUSE_BREAKPOINT && (
 217               (state.prv == PRV_M && state.dcsr.ebreakm) ||
 218               (state.prv == PRV_H && state.dcsr.ebreakh) ||
 219               (state.prv == PRV_S && state.dcsr.ebreaks) ||
 220               (state.prv == PRV_U && state.dcsr.ebreaku))) {
 221     enter_debug_mode(DCSR_CAUSE_SWBP);
 222     return;
 223   }
 224
 225   if (state.dcsr.cause) {
 226     state.pc = DEBUG_ROM_EXCEPTION;
 227     return;
 228   }
 229
 230   // by default, trap to M-mode, unless delegated to S-mode
 231   reg_t bit = t.cause();
 232   reg_t deleg = state.medeleg;
 233   if (bit & ((reg_t)1 << (max_xlen-1)))
 234     deleg = state.mideleg, bit &= ~((reg_t)1 << (max_xlen-1));
 235   if (state.prv <= PRV_S && bit < max_xlen && ((deleg >> bit) & 1)) {
 236     // handle the trap in S-mode
 237     state.pc = state.stvec;
 238     state.scause = t.cause();
 239     state.sepc = epc;
 240     if (t.has_badaddr())
 241       state.sbadaddr = t.get_badaddr();
 242
 243     reg_t s = state.mstatus;
 244     s = set_field(s, MSTATUS_SPIE, get_field(s, MSTATUS_UIE << state.prv));
 245     s = set_field(s, MSTATUS_SPP, state.prv);
 246     s = set_field(s, MSTATUS_SIE, 0);
 247     set_csr(CSR_MSTATUS, s);
 248     set_privilege(PRV_S);
 249   } else {
 250     state.pc = state.mtvec;
 251     state.mepc = epc;
 252     state.mcause = t.cause();
 253     if (t.has_badaddr())
 254       state.mbadaddr = t.get_badaddr();
 255
 256     reg_t s = state.mstatus;
 257     s = set_field(s, MSTATUS_MPIE, get_field(s, MSTATUS_UIE << state.prv));
 258     s = set_field(s, MSTATUS_MPP, state.prv);
 259     s = set_field(s, MSTATUS_MIE, 0);
 260     set_csr(CSR_MSTATUS, s);
 261     set_privilege(PRV_M);
 262   }
 263
 264   yield_load_reservation();
 265 }
 266
 267 void processor_t::disasm(insn_t insn)
 268 {
 269   uint64_t bits = insn.bits() & ((1ULL << (8 * insn_length(insn.bits()))) - 1);
 270   fprintf(stderr, "core %3d: 0x%016" PRIx64 " (0x%08" PRIx64 ") %s\n",
 271           id, state.pc, bits, disassembler->disassemble(insn).c_str());
 272 }
 273
 274 static bool validate_vm(int max_xlen, reg_t vm)
 275 {
 276   if (max_xlen == 64 && (vm == VM_SV39 || vm == VM_SV48))
 277     return true;
 278   if (max_xlen == 32 && vm == VM_SV32)
 279     return true;
 280   return vm == VM_MBARE;
 281 }
 282
 283 int processor_t::paddr_bits()
 284 {
 285   assert(xlen == max_xlen);
 286   return max_xlen == 64 ? 50 : 34;
 287 }
 288
 289 void processor_t::set_csr(int which, reg_t val)
 290 {
 291   val = zext_xlen(val);
 292   reg_t delegable_ints = MIP_SSIP | MIP_STIP | MIP_SEIP | (1 << IRQ_COP);
 293   reg_t all_ints = delegable_ints | MIP_MSIP | MIP_MTIP;
 294   switch (which)
 295   {
 296     case CSR_FFLAGS:
 297       dirty_fp_state;
 298       state.fflags = val & (FSR_AEXC >> FSR_AEXC_SHIFT);
 299       break;
 300     case CSR_FRM:
 301       dirty_fp_state;
 302       state.frm = val & (FSR_RD >> FSR_RD_SHIFT);
 303       break;
 304     case CSR_FCSR:
 305       dirty_fp_state;
 306       state.fflags = (val & FSR_AEXC) >> FSR_AEXC_SHIFT;
 307       state.frm = (val & FSR_RD) >> FSR_RD_SHIFT;
 308       break;
 309     case CSR_MSTATUS: {
 310       if ((val ^ state.mstatus) &
 311           (MSTATUS_VM | MSTATUS_MPP | MSTATUS_MPRV | MSTATUS_PUM | MSTATUS_MXR))
 312         mmu->flush_tlb();
 313
 314       reg_t mask = MSTATUS_SIE | MSTATUS_SPIE | MSTATUS_MIE | MSTATUS_MPIE
 315                  | MSTATUS_SPP | MSTATUS_FS | MSTATUS_MPRV | MSTATUS_PUM
 316                  | MSTATUS_MPP | MSTATUS_MXR | (ext ? MSTATUS_XS : 0);
 317
 318       if (validate_vm(max_xlen, get_field(val, MSTATUS_VM)))
 319         mask |= MSTATUS_VM;
 320
 321       state.mstatus = (state.mstatus & ~mask) | (val & mask);
 322
 323       bool dirty = (state.mstatus & MSTATUS_FS) == MSTATUS_FS;
 324       dirty |= (state.mstatus & MSTATUS_XS) == MSTATUS_XS;
 325       if (max_xlen == 32)
 326         state.mstatus = set_field(state.mstatus, MSTATUS32_SD, dirty);
 327       else
 328         state.mstatus = set_field(state.mstatus, MSTATUS64_SD, dirty);
 329
 330       // spike supports the notion of xlen < max_xlen, but current priv spec
 331       // doesn't provide a mechanism to run RV32 software on an RV64 machine
 332       xlen = max_xlen;
 333       break;
 334     }
 335     case CSR_MIP: {
 336       reg_t mask = MIP_SSIP | MIP_STIP;
 337       state.mip = (state.mip & ~mask) | (val & mask);
 338       break;
 339     }
 340     case CSR_MIE:
 341       state.mie = (state.mie & ~all_ints) | (val & all_ints);
 342       break;
 343     case CSR_MIDELEG:
 344       state.mideleg = (state.mideleg & ~delegable_ints) | (val & delegable_ints);
 345       break;
 346     case CSR_MEDELEG: {
 347       reg_t mask = 0;
 348 #define DECLARE_CAUSE(name, value) mask |= 1ULL << (value);
 349 #include "encoding.h"
 350 #undef DECLARE_CAUSE
 351       state.medeleg = (state.medeleg & ~mask) | (val & mask);
 352       break;
 353     }
 354     case CSR_MINSTRET:
 355     case CSR_MCYCLE:
 356       if (xlen == 32)
 357         state.minstret = (state.minstret >> 32 << 32) | (val & 0xffffffffU);
 358       else
 359         state.minstret = val;
 360       break;
 361     case CSR_MINSTRETH:
 362     case CSR_MCYCLEH:
 363       state.minstret = (val << 32) | (state.minstret << 32 >> 32);
 364       break;
 365     case CSR_MUCOUNTEREN:
 366       state.mucounteren = val;
 367       break;
 368     case CSR_MSCOUNTEREN:
 369       state.mscounteren = val;
 370       break;
 371     case CSR_SSTATUS: {
 372       reg_t mask = SSTATUS_SIE | SSTATUS_SPIE | SSTATUS_SPP | SSTATUS_FS
 373                  | SSTATUS_XS | SSTATUS_PUM;
 374       return set_csr(CSR_MSTATUS, (state.mstatus & ~mask) | (val & mask));
 375     }
 376     case CSR_SIP: {
 377       reg_t mask = MIP_SSIP & state.mideleg;
 378       return set_csr(CSR_MIP, (state.mip & ~mask) | (val & mask));
 379     }
 380     case CSR_SIE:
 381       return set_csr(CSR_MIE,
 382                      (state.mie & ~state.mideleg) | (val & state.mideleg));
 383     case CSR_SPTBR: {
 384       // upper bits of sptbr are the ASID; we only support ASID = 0
 385       state.sptbr = val & (((reg_t)1 << (paddr_bits() - PGSHIFT)) - 1);
 386       break;
 387     }
 388     case CSR_SEPC: state.sepc = val; break;
 389     case CSR_STVEC: state.stvec = val >> 2 << 2; break;
 390     case CSR_SSCRATCH: state.sscratch = val; break;
 391     case CSR_SCAUSE: state.scause = val; break;
 392     case CSR_SBADADDR: state.sbadaddr = val; break;
 393     case CSR_MEPC: state.mepc = val; break;
 394     case CSR_MTVEC: state.mtvec = val >> 2 << 2; break;
 395     case CSR_MSCRATCH: state.mscratch = val; break;
 396     case CSR_MCAUSE: state.mcause = val; break;
 397     case CSR_MBADADDR: state.mbadaddr = val; break;
 398     case CSR_MISA: {
 399       if (!(val & (1L << ('F' - 'A'))))
 400         val &= ~(1L << ('D' - 'A'));
 401
 402       // allow MAFDC bits in MISA to be modified
 403       reg_t mask = 0;
 404       mask |= 1L << ('M' - 'A');
 405       mask |= 1L << ('A' - 'A');
 406       mask |= 1L << ('F' - 'A');
 407       mask |= 1L << ('D' - 'A');
 408       mask |= 1L << ('C' - 'A');
 409       mask &= max_isa;
 410
 411       isa = (val & mask) | (isa & ~mask);
 412       break;
 413     }
 414     case CSR_TSELECT:
 415       if (val < state.num_triggers) {
 416         state.tselect = val;
 417       }
 418       break;
 419     case CSR_TDATA1:
 420       {
 421         mcontrol_t *mc = &state.mcontrol[state.tselect];
 422         if (mc->dmode && !state.dcsr.cause) {
 423           break;
 424         }
 425         mc->dmode = get_field(val, MCONTROL_DMODE(xlen));
 426         mc->select = get_field(val, MCONTROL_SELECT);
 427         mc->timing = get_field(val, MCONTROL_TIMING);
 428         mc->action = (mcontrol_action_t) get_field(val, MCONTROL_ACTION);
 429         mc->chain = get_field(val, MCONTROL_CHAIN);
 430         mc->match = (mcontrol_match_t) get_field(val, MCONTROL_MATCH);
 431         mc->m = get_field(val, MCONTROL_M);
 432         mc->h = get_field(val, MCONTROL_H);
 433         mc->s = get_field(val, MCONTROL_S);
 434         mc->u = get_field(val, MCONTROL_U);
 435         mc->execute = get_field(val, MCONTROL_EXECUTE);
 436         mc->store = get_field(val, MCONTROL_STORE);
 437         mc->load = get_field(val, MCONTROL_LOAD);
 438         // Assume we're here because of csrw.
 439         if (mc->execute)
 440           mc->timing = 0;
 441         trigger_updated();
 442       }
 443       break;
 444     case CSR_TDATA2:
 445       if (state.mcontrol[state.tselect].dmode && !state.dcsr.cause) {
 446         break;
 447       }
 448       if (state.tselect < state.num_triggers) {
 449         state.tdata2[state.tselect] = val;
 450       }
 451       break;
 452     case CSR_DCSR:
 453       state.dcsr.prv = get_field(val, DCSR_PRV);
 454       state.dcsr.step = get_field(val, DCSR_STEP);
 455       // TODO: ndreset and fullreset
 456       state.dcsr.ebreakm = get_field(val, DCSR_EBREAKM);
 457       state.dcsr.ebreakh = get_field(val, DCSR_EBREAKH);
 458       state.dcsr.ebreaks = get_field(val, DCSR_EBREAKS);
 459       state.dcsr.ebreaku = get_field(val, DCSR_EBREAKU);
 460       state.dcsr.halt = get_field(val, DCSR_HALT);
 461       break;
 462     case CSR_DPC:
 463       state.dpc = val;
 464       break;
 465     case CSR_DSCRATCH:
 466       state.dscratch = val;
 467       break;
 468   }
 469 }
 470
 471 reg_t processor_t::get_csr(int which)
 472 {
 473   reg_t ctr_en = state.prv == PRV_U ? state.mucounteren :
 474                  state.prv == PRV_S ? state.mscounteren : -1U;
 475   bool ctr_ok = (ctr_en >> (which & 31)) & 1;
 476
 477   if (ctr_ok) {
 478     if (which >= CSR_HPMCOUNTER3 && which <= CSR_HPMCOUNTER31)
 479       return 0;
 480     if (xlen == 32 && which >= CSR_HPMCOUNTER3H && which <= CSR_HPMCOUNTER31H)
 481       return 0;
 482   }
 483   if (which >= CSR_MHPMCOUNTER3 && which <= CSR_MHPMCOUNTER31)
 484     return 0;
 485   if (xlen == 32 && which >= CSR_MHPMCOUNTER3 && which <= CSR_MHPMCOUNTER31)
 486     return 0;
 487   if (which >= CSR_MHPMEVENT3 && which <= CSR_MHPMEVENT31)
 488     return 0;
 489
 490   switch (which)
 491   {
 492     case CSR_FFLAGS:
 493       require_fp;
 494       if (!supports_extension('F'))
 495         break;
 496       return state.fflags;
 497     case CSR_FRM:
 498       require_fp;
 499       if (!supports_extension('F'))
 500         break;
 501       return state.frm;
 502     case CSR_FCSR:
 503       require_fp;
 504       if (!supports_extension('F'))
 505         break;
 506       return (state.fflags << FSR_AEXC_SHIFT) | (state.frm << FSR_RD_SHIFT);
 507     case CSR_INSTRET:
 508     case CSR_CYCLE:
 509       if (ctr_ok)
 510         return state.minstret;
 511       break;
 512     case CSR_MINSTRET:
 513     case CSR_MCYCLE:
 514       return state.minstret;
 515     case CSR_MINSTRETH:
 516     case CSR_MCYCLEH:
 517       if (xlen == 32)
 518         return state.minstret >> 32;
 519       break;
 520     case CSR_MUCOUNTEREN: return state.mucounteren;
 521     case CSR_MSCOUNTEREN: return state.mscounteren;
 522     case CSR_SSTATUS: {
 523       reg_t mask = SSTATUS_SIE | SSTATUS_SPIE | SSTATUS_SPP | SSTATUS_FS
 524                  | SSTATUS_XS | SSTATUS_PUM;
 525       reg_t sstatus = state.mstatus & mask;
 526       if ((sstatus & SSTATUS_FS) == SSTATUS_FS ||
 527           (sstatus & SSTATUS_XS) == SSTATUS_XS)
 528         sstatus |= (xlen == 32 ? SSTATUS32_SD : SSTATUS64_SD);
 529       return sstatus;
 530     }
 531     case CSR_SIP: return state.mip & state.mideleg;
 532     case CSR_SIE: return state.mie & state.mideleg;
 533     case CSR_SEPC: return state.sepc;
 534     case CSR_SBADADDR: return state.sbadaddr;
 535     case CSR_STVEC: return state.stvec;
 536     case CSR_SCAUSE:
 537       if (max_xlen > xlen)
 538         return state.scause | ((state.scause >> (max_xlen-1)) << (xlen-1));
 539       return state.scause;
 540     case CSR_SPTBR: return state.sptbr;
 541     case CSR_SSCRATCH: return state.sscratch;
 542     case CSR_MSTATUS: return state.mstatus;
 543     case CSR_MIP: return state.mip;
 544     case CSR_MIE: return state.mie;
 545     case CSR_MEPC: return state.mepc;
 546     case CSR_MSCRATCH: return state.mscratch;
 547     case CSR_MCAUSE: return state.mcause;
 548     case CSR_MBADADDR: return state.mbadaddr;
 549     case CSR_MISA: return isa;
 550     case CSR_MARCHID: return 0;
 551     case CSR_MIMPID: return 0;
 552     case CSR_MVENDORID: return 0;
 553     case CSR_MHARTID: return id;
 554     case CSR_MTVEC: return state.mtvec;
 555     case CSR_MEDELEG: return state.medeleg;
 556     case CSR_MIDELEG: return state.mideleg;
 557     case CSR_TSELECT: return state.tselect;
 558     case CSR_TDATA1:
 559       if (state.tselect < state.num_triggers) {
 560         reg_t v = 0;
 561         mcontrol_t *mc = &state.mcontrol[state.tselect];
 562         v = set_field(v, MCONTROL_TYPE(xlen), mc->type);
 563         v = set_field(v, MCONTROL_DMODE(xlen), mc->dmode);
 564         v = set_field(v, MCONTROL_MASKMAX(xlen), mc->maskmax);
 565         v = set_field(v, MCONTROL_SELECT, mc->select);
 566         v = set_field(v, MCONTROL_TIMING, mc->timing);
 567         v = set_field(v, MCONTROL_ACTION, mc->action);
 568         v = set_field(v, MCONTROL_CHAIN, mc->chain);
 569         v = set_field(v, MCONTROL_MATCH, mc->match);
 570         v = set_field(v, MCONTROL_M, mc->m);
 571         v = set_field(v, MCONTROL_H, mc->h);
 572         v = set_field(v, MCONTROL_S, mc->s);
 573         v = set_field(v, MCONTROL_U, mc->u);
 574         v = set_field(v, MCONTROL_EXECUTE, mc->execute);
 575         v = set_field(v, MCONTROL_STORE, mc->store);
 576         v = set_field(v, MCONTROL_LOAD, mc->load);
 577         return v;
 578       } else {
 579         return 0;
 580       }
 581       break;
 582     case CSR_TDATA2:
 583       if (state.tselect < state.num_triggers) {
 584         return state.tdata2[state.tselect];
 585       } else {
 586         return 0;
 587       }
 588       break;
 589     case CSR_TDATA3: return 0;
 590     case CSR_DCSR:
 591       {
 592         uint32_t v = 0;
 593         v = set_field(v, DCSR_XDEBUGVER, 1);
 594         v = set_field(v, DCSR_NDRESET, 0);
 595         v = set_field(v, DCSR_FULLRESET, 0);
 596         v = set_field(v, DCSR_PRV, state.dcsr.prv);
 597         v = set_field(v, DCSR_STEP, state.dcsr.step);
 598         v = set_field(v, DCSR_DEBUGINT, sim->debug_module.get_interrupt(id));
 599         v = set_field(v, DCSR_STOPCYCLE, 0);
 600         v = set_field(v, DCSR_STOPTIME, 0);
 601         v = set_field(v, DCSR_EBREAKM, state.dcsr.ebreakm);
 602         v = set_field(v, DCSR_EBREAKH, state.dcsr.ebreakh);
 603         v = set_field(v, DCSR_EBREAKS, state.dcsr.ebreaks);
 604         v = set_field(v, DCSR_EBREAKU, state.dcsr.ebreaku);
 605         v = set_field(v, DCSR_HALT, state.dcsr.halt);
 606         v = set_field(v, DCSR_CAUSE, state.dcsr.cause);
 607         return v;
 608       }
 609     case CSR_DPC:
 610       return state.dpc;
 611     case CSR_DSCRATCH:
 612       return state.dscratch;
 613   }
 614   throw trap_illegal_instruction();
 615 }
 616
 617 reg_t illegal_instruction(processor_t* p, insn_t insn, reg_t pc)
 618 {
 619   throw trap_illegal_instruction();
 620 }
 621
 622 insn_func_t processor_t::decode_insn(insn_t insn)
 623 {
 624   // look up opcode in hash table
 625   size_t idx = insn.bits() % OPCODE_CACHE_SIZE;
 626   insn_desc_t desc = opcode_cache[idx];
 627
 628   if (unlikely(insn.bits() != desc.match)) {
 629     // fall back to linear search
 630     insn_desc_t* p = &instructions[0];
 631     while ((insn.bits() & p->mask) != p->match)
 632       p++;
 633     desc = *p;
 634
 635     if (p->mask != 0 && p > &instructions[0]) {
 636       if (p->match != (p-1)->match && p->match != (p+1)->match) {
 637         // move to front of opcode list to reduce miss penalty
 638         while (--p >= &instructions[0])
 639           *(p+1) = *p;
 640         instructions[0] = desc;
 641       }
 642     }
 643
 644     opcode_cache[idx] = desc;
 645     opcode_cache[idx].match = insn.bits();
 646   }
 647
 648   return xlen == 64 ? desc.rv64 : desc.rv32;
 649 }
 650
 651 void processor_t::register_insn(insn_desc_t desc)
 652 {
 653   instructions.push_back(desc);
 654 }
 655
 656 void processor_t::build_opcode_map()
 657 {
 658   struct cmp {
 659     bool operator()(const insn_desc_t& lhs, const insn_desc_t& rhs) {
 660       if (lhs.match == rhs.match)
 661         return lhs.mask > rhs.mask;
 662       return lhs.match > rhs.match;
 663     }
 664   };
 665   std::sort(instructions.begin(), instructions.end(), cmp());
 666
 667   for (size_t i = 0; i < OPCODE_CACHE_SIZE; i++)
 668     opcode_cache[i] = {0, 0, &illegal_instruction, &illegal_instruction};
 669 }
 670
 671 void processor_t::register_extension(extension_t* x)
 672 {
 673   for (auto insn : x->get_instructions())
 674     register_insn(insn);
 675   build_opcode_map();
 676   for (auto disasm_insn : x->get_disasms())
 677     disassembler->add_insn(disasm_insn);
 678   if (ext != NULL)
 679     throw std::logic_error("only one extension may be registered");
 680   ext = x;
 681   x->set_processor(this);
 682 }
 683
 684 void processor_t::register_base_instructions()
 685 {
 686   #define DECLARE_INSN(name, match, mask) \
 687     insn_bits_t name##_match = (match), name##_mask = (mask);
 688   #include "encoding.h"
 689   #undef DECLARE_INSN
 690
 691   #define DEFINE_INSN(name) \
 692     REGISTER_INSN(this, name, name##_match, name##_mask)
 693   #include "insn_list.h"
 694   #undef DEFINE_INSN
 695
 696   register_insn({0, 0, &illegal_instruction, &illegal_instruction});
 697   build_opcode_map();
 698 }
 699
 700 bool processor_t::load(reg_t addr, size_t len, uint8_t* bytes)
 701 {
 702   return false;
 703 }
 704
 705 bool processor_t::store(reg_t addr, size_t len, const uint8_t* bytes)
 706 {
 707   switch (addr)
 708   {
 709     case 0:
 710       state.mip &= ~MIP_MSIP;
 711       if (bytes[0] & 1)
 712         state.mip |= MIP_MSIP;
 713       return true;
 714
 715     default:
 716       return false;
 717   }
 718 }
 719
 720 void processor_t::trigger_updated()
 721 {
 722   mmu->flush_tlb();
 723   mmu->check_triggers_fetch = false;
 724   mmu->check_triggers_load = false;
 725   mmu->check_triggers_store = false;
 726
 727   for (unsigned i = 0; i < state.num_triggers; i++) {
 728     if (state.mcontrol[i].execute) {
 729       mmu->check_triggers_fetch = true;
 730     }
 731     if (state.mcontrol[i].load) {
 732       mmu->check_triggers_load = true;
 733     }
 734     if (state.mcontrol[i].store) {
 735       mmu->check_triggers_store = true;
 736     }
 737   }
 738 }