+#ifndef _RISCV_MMU_H
+#define _RISCV_MMU_H
+
#include "decode.h"
#include "trap.h"
+#include "common.h"
+#include "config.h"
+#include "processor.h"
+#include "memtracer.h"
+#include <vector>
+
+// virtual memory configuration
+typedef reg_t pte_t;
+const reg_t LEVELS = sizeof(pte_t) == sizeof(uint64_t) ? 3 : 2;
+const reg_t PGSHIFT = 13;
+const reg_t PGSIZE = 1 << PGSHIFT;
+const reg_t PTIDXBITS = PGSHIFT - (sizeof(pte_t) == 8 ? 3 : 2);
+const reg_t VPN_BITS = PTIDXBITS * LEVELS;
+const reg_t PPN_BITS = 8*sizeof(reg_t) - PGSHIFT;
+const reg_t VA_BITS = VPN_BITS + PGSHIFT;
+
+// page table entry (PTE) fields
+#define PTE_T 0x001 // Entry is a page Table descriptor
+#define PTE_E 0x002 // Entry is a page table Entry
+#define PTE_R 0x004 // Referenced
+#define PTE_D 0x008 // Dirty
+#define PTE_UX 0x010 // User eXecute permission
+#define PTE_UW 0x020 // User Read permission
+#define PTE_UR 0x040 // User Write permission
+#define PTE_SX 0x080 // Supervisor eXecute permission
+#define PTE_SW 0x100 // Supervisor Read permission
+#define PTE_SR 0x200 // Supervisor Write permission
+#define PTE_PERM (PTE_SR | PTE_SW | PTE_SX | PTE_UR | PTE_UW | PTE_UX)
+#define PTE_PPN_SHIFT 13 // LSB of physical page number in the PTE
+// this class implements a processor's port into the virtual memory system.
+// an MMU and instruction cache are maintained for simulator performance.
class mmu_t
{
public:
- mmu_t(char* _mem, size_t _memsz) : mem(_mem), memsz(_memsz), badvaddr(0) {}
+ mmu_t(char* _mem, size_t _memsz);
+ ~mmu_t();
+ // template for functions that load an aligned value from memory
#define load_func(type) \
type##_t load_##type(reg_t addr) { \
- check_align_and_bounds(addr, sizeof(type##_t), false, false); \
- return *(type##_t*)(mem+addr); \
+ if(unlikely(addr % sizeof(type##_t))) \
+ { \
+ badvaddr = addr; \
+ throw trap_load_address_misaligned; \
+ } \
+ reg_t paddr = translate(addr, sizeof(type##_t), false, false); \
+ return *(type##_t*)(mem + paddr); \
}
- #define store_func(type) \
- void store_##type(reg_t addr, type##_t val) { \
- check_align_and_bounds(addr, sizeof(type##_t), true, false); \
- *(type##_t*)(mem+addr) = val; \
- }
-
- insn_t load_insn(reg_t addr, bool rvc)
- {
- check_align_and_bounds(addr, rvc ? 2 : 4, false, true);
- uint16_t lo = *(uint16_t*)(mem+addr);
- uint16_t hi = *(uint16_t*)(mem+addr+2);
-
- insn_t insn;
- insn.bits = ((uint32_t)hi << 16) | lo;
- return insn;
- }
-
+ // load value from memory at aligned address; zero extend to register width
load_func(uint8)
load_func(uint16)
load_func(uint32)
load_func(uint64)
+ // load value from memory at aligned address; sign extend to register width
load_func(int8)
load_func(int16)
load_func(int32)
load_func(int64)
+ // template for functions that store an aligned value to memory
+ #define store_func(type) \
+ void store_##type(reg_t addr, type##_t val) { \
+ if(unlikely(addr % sizeof(type##_t))) \
+ { \
+ badvaddr = addr; \
+ throw trap_store_address_misaligned; \
+ } \
+ reg_t paddr = translate(addr, sizeof(type##_t), true, false); \
+ *(type##_t*)(mem + paddr) = val; \
+ }
+
+ // store value to memory at aligned address
store_func(uint8)
store_func(uint16)
store_func(uint32)
store_func(uint64)
+ struct insn_fetch_t
+ {
+ insn_t insn;
+ insn_func_t func;
+ };
+
+ // load instruction from memory at aligned address.
+ // (needed because instruction alignment requirement is variable
+ // if RVC is supported)
+ // returns the instruction at the specified address, given the current
+ // RVC mode. func is set to a pointer to a function that knows how to
+ // execute the returned instruction.
+ inline insn_fetch_t load_insn(reg_t addr, bool rvc)
+ {
+ #ifdef RISCV_ENABLE_RVC
+ if(addr % 4 == 2 && rvc) // fetch across word boundary
+ {
+ reg_t addr_lo = translate(addr, 2, false, true);
+ insn_fetch_t fetch;
+ fetch.insn.bits = *(uint16_t*)(mem + addr_lo);
+ fetch.func = get_insn_func(fetch.insn, sr);
+
+ if(!INSN_IS_RVC(fetch.insn.bits))
+ {
+ reg_t addr_hi = translate(addr+2, 2, false, true);
+ fetch.insn.bits |= (uint32_t)*(uint16_t*)(mem + addr_hi) << 16;
+ }
+ return fetch;
+ }
+ else
+ #endif
+ {
+ reg_t idx = (addr/sizeof(insn_t)) % ICACHE_ENTRIES;
+ insn_fetch_t fetch;
+ if (unlikely(icache_tag[idx] != addr))
+ {
+ reg_t paddr = translate(addr, sizeof(insn_t), false, true);
+ fetch.insn = *(insn_t*)(mem + paddr);
+ fetch.func = get_insn_func(fetch.insn, sr);
+
+ reg_t idx = (paddr/sizeof(insn_t)) % ICACHE_ENTRIES;
+ icache_tag[idx] = addr;
+ icache_data[idx] = fetch.insn;
+ icache_func[idx] = fetch.func;
+
+ if (tracer.interested_in_range(paddr, paddr + sizeof(insn_t), false, true))
+ {
+ icache_tag[idx] = -1;
+ tracer.trace(paddr, sizeof(insn_t), false, true);
+ }
+ }
+ fetch.insn = icache_data[idx];;
+ fetch.func = icache_func[idx];
+ return fetch;
+ }
+ }
+
+ // get the virtual address that caused a fault
reg_t get_badvaddr() { return badvaddr; }
+ // get/set the page table base register
+ reg_t get_ptbr() { return ptbr; }
+ void set_ptbr(reg_t addr) { ptbr = addr & ~(PGSIZE-1); flush_tlb(); }
+ // keep the MMU in sync with processor mode
+ void set_sr(uint32_t _sr) { sr = _sr; }
+
+ // flush the TLB and instruction cache
+ void flush_tlb();
+ void flush_icache();
+
+ void register_memtracer(memtracer_t*);
+
private:
char* mem;
size_t memsz;
reg_t badvaddr;
+ reg_t ptbr;
+ uint32_t sr;
+ memtracer_list_t tracer;
- void check_align(reg_t addr, int size, bool fetch)
- {
- if(addr & (size-1))
- {
- badvaddr = addr;
- if(fetch)
- throw trap_instruction_address_misaligned;
- throw trap_data_address_misaligned;
- }
- }
+ // implement a TLB for simulator performance
+ static const reg_t TLB_ENTRIES = 256;
+ reg_t tlb_data[TLB_ENTRIES];
+ reg_t tlb_insn_tag[TLB_ENTRIES];
+ reg_t tlb_load_tag[TLB_ENTRIES];
+ reg_t tlb_store_tag[TLB_ENTRIES];
- void check_bounds(reg_t addr, int size, bool store, bool fetch)
- {
- if(addr >= memsz || addr + size > memsz)
- {
- badvaddr = addr;
- if(fetch)
- throw trap_instruction_access_fault;
- throw store ? trap_store_access_fault : trap_load_access_fault;
- }
- }
+ // implement an instruction cache for simulator performance
+ static const reg_t ICACHE_ENTRIES = 256;
+ insn_t icache_data[ICACHE_ENTRIES];
+ insn_func_t icache_func[ICACHE_ENTRIES];
+ reg_t icache_tag[ICACHE_ENTRIES];
- void check_align_and_bounds(reg_t addr, int size, bool store, bool fetch)
+ // finish translation on a TLB miss and upate the TLB
+ reg_t refill_tlb(reg_t addr, reg_t bytes, bool store, bool fetch);
+
+ // perform a page table walk for a given virtual address
+ pte_t walk(reg_t addr);
+
+ // translate a virtual address to a physical address
+ reg_t translate(reg_t addr, reg_t bytes, bool store, bool fetch)
{
- check_align(addr, size, fetch);
- check_bounds(addr, size, store, fetch);
+ reg_t idx = (addr >> PGSHIFT) % TLB_ENTRIES;
+
+ reg_t* tlb_tag = fetch ? tlb_insn_tag : store ? tlb_store_tag :tlb_load_tag;
+ reg_t expected_tag = addr & ~(PGSIZE-1);
+ if(likely(tlb_tag[idx] == expected_tag))
+ return ((uintptr_t)addr & (PGSIZE-1)) + tlb_data[idx];
+
+ return refill_tlb(addr, bytes, store, fetch);
}
+
+ friend class processor_t;
};
+
+#endif
projects / riscv-isa-sim.git / blobdiff