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// See LICENSE for license details.
#include "mmu.h"
#include "sim.h"
#include "processor.h"
mmu_t::mmu_t(simif_t* sim, processor_t* proc)
: sim(sim), proc(proc),
check_triggers_fetch(false),
check_triggers_load(false),
check_triggers_store(false),
matched_trigger(NULL)
{
flush_tlb();
}
mmu_t::~mmu_t()
{
}
void mmu_t::flush_icache()
{
for (size_t i = 0; i < ICACHE_ENTRIES; i++)
icache[i].tag = -1;
}
void mmu_t::flush_tlb()
{
memset(tlb_insn_tag, -1, sizeof(tlb_insn_tag));
memset(tlb_load_tag, -1, sizeof(tlb_load_tag));
memset(tlb_store_tag, -1, sizeof(tlb_store_tag));
flush_icache();
}
reg_t mmu_t::translate(reg_t addr, access_type type)
{
if (!proc)
return addr;
reg_t mode = proc->state.prv;
if (type != FETCH) {
if (!proc->state.dcsr.cause && get_field(proc->state.mstatus, MSTATUS_MPRV))
mode = get_field(proc->state.mstatus, MSTATUS_MPP);
}
return walk(addr, type, mode) | (addr & (PGSIZE-1));
}
tlb_entry_t mmu_t::fetch_slow_path(reg_t vaddr)
{
reg_t paddr = translate(vaddr, FETCH);
if (auto host_addr = sim->addr_to_mem(paddr)) {
return refill_tlb(vaddr, paddr, host_addr, FETCH);
} else {
if (!sim->mmio_load(paddr, sizeof fetch_temp, (uint8_t*)&fetch_temp))
throw trap_instruction_access_fault(vaddr);
tlb_entry_t entry = {(char*)&fetch_temp - vaddr, paddr - vaddr};
return entry;
}
}
reg_t reg_from_bytes(size_t len, const uint8_t* bytes)
{
switch (len) {
case 1:
return bytes[0];
case 2:
return bytes[0] |
(((reg_t) bytes[1]) << 8);
case 4:
return bytes[0] |
(((reg_t) bytes[1]) << 8) |
(((reg_t) bytes[2]) << 16) |
(((reg_t) bytes[3]) << 24);
case 8:
return bytes[0] |
(((reg_t) bytes[1]) << 8) |
(((reg_t) bytes[2]) << 16) |
(((reg_t) bytes[3]) << 24) |
(((reg_t) bytes[4]) << 32) |
(((reg_t) bytes[5]) << 40) |
(((reg_t) bytes[6]) << 48) |
(((reg_t) bytes[7]) << 56);
}
abort();
}
void mmu_t::load_slow_path(reg_t addr, reg_t len, uint8_t* bytes)
{
reg_t paddr = translate(addr, LOAD);
if (auto host_addr = sim->addr_to_mem(paddr)) {
memcpy(bytes, host_addr, len);
if (tracer.interested_in_range(paddr, paddr + PGSIZE, LOAD))
tracer.trace(paddr, len, LOAD);
else
refill_tlb(addr, paddr, host_addr, LOAD);
} else if (!sim->mmio_load(paddr, len, bytes)) {
throw trap_load_access_fault(addr);
}
if (!matched_trigger) {
reg_t data = reg_from_bytes(len, bytes);
matched_trigger = trigger_exception(OPERATION_LOAD, addr, data);
if (matched_trigger)
throw *matched_trigger;
}
}
void mmu_t::store_slow_path(reg_t addr, reg_t len, const uint8_t* bytes)
{
reg_t paddr = translate(addr, STORE);
if (!matched_trigger) {
reg_t data = reg_from_bytes(len, bytes);
matched_trigger = trigger_exception(OPERATION_STORE, addr, data);
if (matched_trigger)
throw *matched_trigger;
}
if (auto host_addr = sim->addr_to_mem(paddr)) {
memcpy(host_addr, bytes, len);
if (tracer.interested_in_range(paddr, paddr + PGSIZE, STORE))
tracer.trace(paddr, len, STORE);
else
refill_tlb(addr, paddr, host_addr, STORE);
} else if (!sim->mmio_store(paddr, len, bytes)) {
throw trap_store_access_fault(addr);
}
}
tlb_entry_t mmu_t::refill_tlb(reg_t vaddr, reg_t paddr, char* host_addr, access_type type)
{
reg_t idx = (vaddr >> PGSHIFT) % TLB_ENTRIES;
reg_t expected_tag = vaddr >> PGSHIFT;
if ((tlb_load_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
tlb_load_tag[idx] = -1;
if ((tlb_store_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
tlb_store_tag[idx] = -1;
if ((tlb_insn_tag[idx] & ~TLB_CHECK_TRIGGERS) != expected_tag)
tlb_insn_tag[idx] = -1;
if ((check_triggers_fetch && type == FETCH) ||
(check_triggers_load && type == LOAD) ||
(check_triggers_store && type == STORE))
expected_tag |= TLB_CHECK_TRIGGERS;
if (type == FETCH) tlb_insn_tag[idx] = expected_tag;
else if (type == STORE) tlb_store_tag[idx] = expected_tag;
else tlb_load_tag[idx] = expected_tag;
tlb_entry_t entry = {host_addr - vaddr, paddr - vaddr};
tlb_data[idx] = entry;
return entry;
}
reg_t mmu_t::walk(reg_t addr, access_type type, reg_t mode)
{
vm_info vm = decode_vm_info(proc->max_xlen, mode, proc->get_state()->satp);
if (vm.levels == 0)
return addr & ((reg_t(2) << (proc->xlen-1))-1); // zero-extend from xlen
bool s_mode = mode == PRV_S;
bool sum = get_field(proc->state.mstatus, MSTATUS_SUM);
bool mxr = get_field(proc->state.mstatus, MSTATUS_MXR);
// verify bits xlen-1:va_bits-1 are all equal
int va_bits = PGSHIFT + vm.levels * vm.idxbits;
reg_t mask = (reg_t(1) << (proc->xlen - (va_bits-1))) - 1;
reg_t masked_msbs = (addr >> (va_bits-1)) & mask;
if (masked_msbs != 0 && masked_msbs != mask)
vm.levels = 0;
reg_t base = vm.ptbase;
for (int i = vm.levels - 1; i >= 0; i--) {
int ptshift = i * vm.idxbits;
reg_t idx = (addr >> (PGSHIFT + ptshift)) & ((1 << vm.idxbits) - 1);
// check that physical address of PTE is legal
auto ppte = sim->addr_to_mem(base + idx * vm.ptesize);
if (!ppte)
goto fail_access;
reg_t pte = vm.ptesize == 4 ? *(uint32_t*)ppte : *(uint64_t*)ppte;
reg_t ppn = pte >> PTE_PPN_SHIFT;
if (PTE_TABLE(pte)) { // next level of page table
base = ppn << PGSHIFT;
} else if ((pte & PTE_U) ? s_mode && (type == FETCH || !sum) : !s_mode) {
break;
} else if (!(pte & PTE_V) || (!(pte & PTE_R) && (pte & PTE_W))) {
break;
} else if (type == FETCH ? !(pte & PTE_X) :
type == LOAD ? !(pte & PTE_R) && !(mxr && (pte & PTE_X)) :
!((pte & PTE_R) && (pte & PTE_W))) {
break;
} else if ((ppn & ((reg_t(1) << ptshift) - 1)) != 0) {
break;
} else {
reg_t ad = PTE_A | ((type == STORE) * PTE_D);
#ifdef RISCV_ENABLE_DIRTY
// set accessed and possibly dirty bits.
*(uint32_t*)ppte |= ad;
#else
// take exception if access or possibly dirty bit is not set.
if ((pte & ad) != ad)
break;
#endif
// for superpage mappings, make a fake leaf PTE for the TLB's benefit.
reg_t vpn = addr >> PGSHIFT;
reg_t value = (ppn | (vpn & ((reg_t(1) << ptshift) - 1))) << PGSHIFT;
return value;
}
}
fail:
switch (type) {
case FETCH: throw trap_instruction_page_fault(addr);
case LOAD: throw trap_load_page_fault(addr);
case STORE: throw trap_store_page_fault(addr);
default: abort();
}
fail_access:
switch (type) {
case FETCH: throw trap_instruction_access_fault(addr);
case LOAD: throw trap_load_access_fault(addr);
case STORE: throw trap_store_access_fault(addr);
default: abort();
}
}
void mmu_t::register_memtracer(memtracer_t* t)
{
flush_tlb();
tracer.hook(t);
}
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