riscv/mmu.cc

   1 // See LICENSE for license details.
   2
   3 #include "mmu.h"
   4 #include "sim.h"
   5 #include "processor.h"
   6
   7 mmu_t::mmu_t(sim_t* sim, processor_t* proc)
   8  : sim(sim), proc(proc),
   9   check_triggers_fetch(false),
  10   check_triggers_load(false),
  11   check_triggers_store(false),
  12   matched_trigger(NULL)
  13 {
  14   flush_tlb();
  15 }
  16
  17 mmu_t::~mmu_t()
  18 {
  19 }
  20
  21 void mmu_t::flush_icache()
  22 {
  23   for (size_t i = 0; i < ICACHE_ENTRIES; i++)
  24     icache[i].tag = -1;
  25 }
  26
  27 void mmu_t::flush_tlb()
  28 {
  29   memset(tlb_insn_tag, -1, sizeof(tlb_insn_tag));
  30   memset(tlb_load_tag, -1, sizeof(tlb_load_tag));
  31   memset(tlb_store_tag, -1, sizeof(tlb_store_tag));
  32
  33   flush_icache();
  34 }
  35
  36 reg_t mmu_t::translate(reg_t addr, access_type type)
  37 {
  38   if (!proc)
  39     return addr;
  40
  41   reg_t mode = proc->state.prv;
  42   if (type != FETCH) {
  43     if (!proc->state.dcsr.cause && get_field(proc->state.mstatus, MSTATUS_MPRV))
  44       mode = get_field(proc->state.mstatus, MSTATUS_MPP);
  45   }
  46
  47   return walk(addr, type, mode) | (addr & (PGSIZE-1));
  48 }
  49
  50 const uint16_t* mmu_t::fetch_slow_path(reg_t vaddr)
  51 {
  52   reg_t paddr = translate(vaddr, FETCH);
  53
  54   if (sim->addr_is_mem(paddr)) {
  55     refill_tlb(vaddr, paddr, FETCH);
  56     return (const uint16_t*)sim->addr_to_mem(paddr);
  57   } else {
  58     if (!sim->mmio_load(paddr, sizeof fetch_temp, (uint8_t*)&fetch_temp))
  59       throw trap_instruction_access_fault(vaddr);
  60     return &fetch_temp;
  61   }
  62 }
  63
  64 reg_t reg_from_bytes(size_t len, const uint8_t* bytes)
  65 {
  66   switch (len) {
  67     case 1:
  68       return bytes[0];
  69     case 2:
  70       return bytes[0] |
  71         (((reg_t) bytes[1]) << 8);
  72     case 4:
  73       return bytes[0] |
  74         (((reg_t) bytes[1]) << 8) |
  75         (((reg_t) bytes[2]) << 16) |
  76         (((reg_t) bytes[3]) << 24);
  77     case 8:
  78       return bytes[0] |
  79         (((reg_t) bytes[1]) << 8) |
  80         (((reg_t) bytes[2]) << 16) |
  81         (((reg_t) bytes[3]) << 24) |
  82         (((reg_t) bytes[4]) << 32) |
  83         (((reg_t) bytes[5]) << 40) |
  84         (((reg_t) bytes[6]) << 48) |
  85         (((reg_t) bytes[7]) << 56);
  86   }
  87   abort();
  88 }
  89
  90 void mmu_t::load_slow_path(reg_t addr, reg_t len, uint8_t* bytes)
  91 {
  92   reg_t paddr = translate(addr, LOAD);
  93
  94   if (sim->addr_is_mem(paddr)) {
  95     memcpy(bytes, sim->addr_to_mem(paddr), len);
  96     if (tracer.interested_in_range(paddr, paddr + PGSIZE, LOAD))
  97       tracer.trace(paddr, len, LOAD);
  98     else
  99       refill_tlb(addr, paddr, LOAD);
 100   } else if (!sim->mmio_load(paddr, len, bytes)) {
 101     throw trap_load_access_fault(addr);
 102   }
 103
 104   if (!matched_trigger) {
 105     reg_t data = reg_from_bytes(len, bytes);
 106     matched_trigger = trigger_exception(OPERATION_LOAD, addr, data);
 107     if (matched_trigger)
 108       throw *matched_trigger;
 109   }
 110 }
 111
 112 void mmu_t::store_slow_path(reg_t addr, reg_t len, const uint8_t* bytes)
 113 {
 114   reg_t paddr = translate(addr, STORE);
 115
 116   if (!matched_trigger) {
 117     reg_t data = reg_from_bytes(len, bytes);
 118     matched_trigger = trigger_exception(OPERATION_STORE, addr, data);
 119     if (matched_trigger)
 120       throw *matched_trigger;
 121   }
 122
 123   if (sim->addr_is_mem(paddr)) {
 124     memcpy(sim->addr_to_mem(paddr), bytes, len);
 125     if (tracer.interested_in_range(paddr, paddr + PGSIZE, STORE))
 126       tracer.trace(paddr, len, STORE);
 127     else
 128       refill_tlb(addr, paddr, STORE);
 129   } else if (!sim->mmio_store(paddr, len, bytes)) {
 130     throw trap_store_access_fault(addr);
 131   }
 132 }
 133
 134 void mmu_t::refill_tlb(reg_t vaddr, reg_t paddr, access_type type)
 135 {
 136   reg_t idx = (vaddr >> PGSHIFT) % TLB_ENTRIES;
 137   reg_t expected_tag = vaddr >> PGSHIFT;
 138
 139   if ((tlb_load_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
 140     tlb_load_tag[idx] = -1;
 141   if ((tlb_store_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
 142     tlb_store_tag[idx] = -1;
 143   if ((tlb_insn_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
 144     tlb_insn_tag[idx] = -1;
 145
 146   if ((check_triggers_fetch && type == FETCH) ||
 147       (check_triggers_load && type == LOAD) ||
 148       (check_triggers_store && type == STORE))
 149     expected_tag |= TLB_CHECK_TRIGGERS;
 150
 151   if (type == FETCH) tlb_insn_tag[idx] = expected_tag;
 152   else if (type == STORE) tlb_store_tag[idx] = expected_tag;
 153   else tlb_load_tag[idx] = expected_tag;
 154
 155   tlb_data[idx] = sim->addr_to_mem(paddr) - vaddr;
 156 }
 157
 158 reg_t mmu_t::walk(reg_t addr, access_type type, reg_t mode)
 159 {
 160   vm_info vm = decode_vm_info(proc->max_xlen, mode, proc->get_state()->sptbr);
 161   if (vm.levels == 0)
 162     return addr & ((reg_t(2) << (proc->xlen-1))-1); // zero-extend from xlen
 163
 164   bool supervisor = mode == PRV_S;
 165   bool sum = get_field(proc->state.mstatus, MSTATUS_SUM);
 166   bool mxr = get_field(proc->state.mstatus, MSTATUS_MXR);
 167
 168   // verify bits xlen-1:va_bits-1 are all equal
 169   int va_bits = PGSHIFT + vm.levels * vm.idxbits;
 170   reg_t mask = (reg_t(1) << (proc->xlen - (va_bits-1))) - 1;
 171   reg_t masked_msbs = (addr >> (va_bits-1)) & mask;
 172   if (masked_msbs != 0 && masked_msbs != mask)
 173     vm.levels = 0;
 174
 175   reg_t base = vm.ptbase;
 176   for (int i = vm.levels - 1; i >= 0; i--) {
 177     int ptshift = i * vm.idxbits;
 178     reg_t idx = (addr >> (PGSHIFT + ptshift)) & ((1 << vm.idxbits) - 1);
 179
 180     // check that physical address of PTE is legal
 181     reg_t pte_addr = base + idx * vm.ptesize;
 182     if (!sim->addr_is_mem(pte_addr))
 183       break;
 184
 185     void* ppte = sim->addr_to_mem(pte_addr);
 186     reg_t pte = vm.ptesize == 4 ? *(uint32_t*)ppte : *(uint64_t*)ppte;
 187     reg_t ppn = pte >> PTE_PPN_SHIFT;
 188
 189     if (PTE_TABLE(pte)) { // next level of page table
 190       base = ppn << PGSHIFT;
 191     } else if ((pte & PTE_U) ? supervisor && !sum : !supervisor) {
 192       break;
 193     } else if (!(pte & PTE_V) || (!(pte & PTE_R) && (pte & PTE_W))) {
 194       break;
 195     } else if (type == FETCH ? !(pte & PTE_X) :
 196                type == LOAD ?  !(pte & PTE_R) && !(mxr && (pte & PTE_X)) :
 197                                !((pte & PTE_R) && (pte & PTE_W))) {
 198       break;
 199     } else {
 200       reg_t ad = PTE_A | ((type == STORE) * PTE_D);
 201 #ifdef RISCV_ENABLE_DIRTY
 202       // set accessed and possibly dirty bits.
 203       *(uint32_t*)ppte |= ad;
 204 #else
 205       // take exception if access or possibly dirty bit is not set.
 206       if ((pte & ad) != ad)
 207         break;
 208 #endif
 209       // for superpage mappings, make a fake leaf PTE for the TLB's benefit.
 210       reg_t vpn = addr >> PGSHIFT;
 211       reg_t value = (ppn | (vpn & ((reg_t(1) << ptshift) - 1))) << PGSHIFT;
 212       return value;
 213     }
 214   }
 215
 216 fail:
 217   switch (type) {
 218     case FETCH: throw trap_instruction_access_fault(addr);
 219     case LOAD: throw trap_load_access_fault(addr);
 220     case STORE: throw trap_store_access_fault(addr);
 221     default: abort();
 222   }
 223 }
 224
 225 void mmu_t::register_memtracer(memtracer_t* t)
 226 {
 227   flush_tlb();
 228   tracer.hook(t);
 229 }