diff --git a/src/isa/mips32/diff-test.c b/src/isa/mips32/diff-test.c
index 303f2119847298ffd162ac0cdeb3266487641462..b24f3c4bc6a5ea350fe77c0bebccebb699697572 100644
--- a/src/isa/mips32/diff-test.c
+++ b/src/isa/mips32/diff-test.c
@@ -5,6 +5,8 @@ void isa_difftest_syncregs() {
   ref_difftest_setregs(&cpu);
 }
 
+#define check_reg(r) same = same && difftest_check_reg(str(r), pc, ref_r->r, cpu.r)
+
 bool isa_difftest_checkregs(CPU_state *ref_r, vaddr_t pc) {
   bool same = true;
   if (memcmp(&cpu, ref_r, sizeof(cpu.gpr))) {
@@ -14,7 +16,11 @@ bool isa_difftest_checkregs(CPU_state *ref_r, vaddr_t pc) {
     }
     same = false;
   }
-  same = same && difftest_check_reg("pc", pc, ref_r->pc, cpu.pc);
+  check_reg(pc);
+  check_reg(lo);
+  check_reg(hi);
+  check_reg(status);
+
   return same;
 }
 
diff --git a/src/isa/mips32/exec/all-instr.h b/src/isa/mips32/exec/all-instr.h
index 09643edbe3056c1569c1bc14c2ec842165df9226..42aeec3497be1494d6db2bad5c3b9fa120e4188e 100644
--- a/src/isa/mips32/exec/all-instr.h
+++ b/src/isa/mips32/exec/all-instr.h
@@ -25,6 +25,8 @@ make_EHelper(lwr);
 
 make_EHelper(mfhi);
 make_EHelper(mflo);
+make_EHelper(mthi);
+make_EHelper(mtlo);
 make_EHelper(mul);
 make_EHelper(mult);
 make_EHelper(multu);
@@ -44,3 +46,8 @@ make_EHelper(bgez);
 
 make_EHelper(inv);
 make_EHelper(nemu_trap);
+
+make_EHelper(syscall);
+make_EHelper(eret);
+make_EHelper(mfc0);
+make_EHelper(mtc0);
diff --git a/src/isa/mips32/exec/exec.c b/src/isa/mips32/exec/exec.c
index 3133bb38b3430a9fa43428b9f1e33bf83bc9df4e..d506721a56993738e28516dc8d02ff35e3c1ecb6 100644
--- a/src/isa/mips32/exec/exec.c
+++ b/src/isa/mips32/exec/exec.c
@@ -3,8 +3,8 @@
 
 static OpcodeEntry special_table [64] = {
   /* b000 */ IDEX(shift, sll), EMPTY, IDEX(shift, srl), IDEX(shift, sra), IDEX(R, sll), EMPTY, IDEX(R, srl), IDEX(R, sra),
-  /* b001 */ IDEX(R, jr), IDEX(R, jalr), IDEX(cmov, movz), IDEX(cmov, movn), EMPTY, EMPTY, EMPTY, EMPTY,
-  /* b010 */ IDEX(R, mfhi), EMPTY, IDEX(R, mflo), EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b001 */ IDEX(R, jr), IDEX(R, jalr), IDEX(cmov, movz), IDEX(cmov, movn), EX(syscall), EMPTY, EMPTY, EMPTY,
+  /* b010 */ IDEX(R, mfhi), IDEX(R, mthi), IDEX(R, mflo), IDEX(R, mtlo), EMPTY, EMPTY, EMPTY, EMPTY,
   /* b011 */ IDEX(R, mult), IDEX(R, multu), IDEX(R, div), IDEX(R, divu), EMPTY, EMPTY, EMPTY, EMPTY,
   /* b100 */ EMPTY, IDEX(R, add), EMPTY, IDEX(R, sub), IDEX(R, and), IDEX(R, or), IDEX(R, xor), IDEX(R, nor),
   /* b101 */ EMPTY, EMPTY, IDEX(R, slt), IDEX(R, sltu), EMPTY, EMPTY, EMPTY, EMPTY,
@@ -42,10 +42,35 @@ static make_EHelper(regimm) {
   idex(eip, &regimm_table[decinfo.isa.instr.rt]);
 }
 
+static OpcodeEntry cop0_table [16] = {
+  /* b00 */ IDEX(R, mfc0), EMPTY, EMPTY, EMPTY, IDEX(R, mtc0), EMPTY, EMPTY, EMPTY,
+  /* b01 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+};
+
+static OpcodeEntry cop0co_table [64] = {
+  /* b000 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b001 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b010 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b011 */ EX(eret), EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b100 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b101 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b110 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b111 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+};
+
+static make_EHelper(cop0) {
+  if (decinfo.isa.instr.rs & 0x10) {
+    idex(eip, &cop0co_table[decinfo.isa.instr.func]);
+  }
+  else {
+    idex(eip, &cop0_table[decinfo.isa.instr.rs]);
+  }
+}
+
 static OpcodeEntry opcode_table [64] = {
   /* b000 */ EX(special), EX(regimm), IDEX(J, j), IDEX(J, jal), IDEX(B, beq), IDEX(B, bne), IDEX(B, blez), IDEX(B, bgtz),
   /* b001 */ EMPTY, IDEX(I, add), IDEX(I, slt), IDEX(I, sltu), IDEX(IU, and), IDEX(IU, or), IDEX(IU, xor), IDEX(IU, lui),
-  /* b010 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
+  /* b010 */ EX(cop0), EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
   /* b011 */ EMPTY, EMPTY, EMPTY, EMPTY, EX(special2), EMPTY, EMPTY, EMPTY,
   /* b100 */ IDEXW(ld, lds, 1), IDEXW(ld, lds, 2), IDEX(st, lwl), IDEXW(ld, ld, 4), IDEXW(ld, ld, 1), IDEXW(ld, ld, 2), IDEX(st, lwr), EMPTY,
   /* b101 */ IDEXW(st, st, 1), IDEXW(st, st, 2), IDEX(st, swl), IDEXW(st, st, 4), EMPTY, EMPTY, IDEX(st, swr), EMPTY,
diff --git a/src/isa/mips32/exec/muldiv.c b/src/isa/mips32/exec/muldiv.c
index 0a7640d643660ebf5b8a2c706b35148497943953..e5e263c5b42963487b77af6d21c9c547593b85ae 100644
--- a/src/isa/mips32/exec/muldiv.c
+++ b/src/isa/mips32/exec/muldiv.c
@@ -12,6 +12,18 @@ make_EHelper(mflo) {
   print_asm_template3(mflo);
 }
 
+make_EHelper(mthi) {
+  rtl_mv(&cpu.hi, &id_src->val);
+
+  print_asm_template2(mthi);
+}
+
+make_EHelper(mtlo) {
+  rtl_mv(&cpu.lo, &id_src->val);
+
+  print_asm_template2(mtlo);
+}
+
 make_EHelper(mul) {
   rtl_imul_lo(&s0, &id_src->val, &id_src2->val);
   rtl_sr(id_dest->reg, &s0, 4);
diff --git a/src/isa/mips32/exec/system.c b/src/isa/mips32/exec/system.c
new file mode 100644
index 0000000000000000000000000000000000000000..99b70516d2a6881a631e4e0be638e46a07b18fd6
--- /dev/null
+++ b/src/isa/mips32/exec/system.c
@@ -0,0 +1,61 @@
+#include "cpu/exec.h"
+
+void raise_intr(uint8_t, vaddr_t);
+#define EX_SYSCALL 8
+
+make_EHelper(syscall) {
+#if defined(DIFF_TEST)
+  difftest_skip_ref();
+#endif
+
+  raise_intr(EX_SYSCALL, cpu.pc);
+
+  print_asm("syscall");
+}
+
+make_EHelper(eret) {
+#if defined(DIFF_TEST)
+  difftest_skip_ref();
+#endif
+
+  rtl_li(&s0, cpu.epc);
+  rtl_jr(&s0);
+
+  print_asm("eret");
+}
+
+make_EHelper(mfc0) {
+#if defined(DIFF_TEST)
+  difftest_skip_ref();
+#endif
+
+  uint32_t val;
+  char *name;
+  switch (id_dest->reg) {
+    case 12: val = cpu.status; name = "status"; break;
+    case 13: val = cpu.cause; name = "cause"; break;
+    case 14: val = cpu.epc; name = "epc"; break;
+    default: assert(0);
+  }
+
+  rtl_li(&s0, val);
+  rtl_sr(id_src2->reg, &s0, 4);
+
+  print_asm("mfc0 %s, %s", id_src2->str, name);
+}
+
+make_EHelper(mtc0) {
+#if defined(DIFF_TEST)
+  difftest_skip_ref();
+#endif
+
+  char *name;
+  switch (id_dest->reg) {
+    case 12: cpu.status = id_src2->val; name = "status"; break;
+    case 13: cpu.cause = id_src2->val; name = "cause"; break;
+    case 14: cpu.epc = id_src2->val; name = "epc"; break;
+    default: assert(0);
+  }
+
+  print_asm("mtc0 %s, %s", id_src2->str, name);
+}
diff --git a/src/isa/mips32/include/isa/reg.h b/src/isa/mips32/include/isa/reg.h
index 26a333908d86d9c3fd375dc964fd10f364e1a1d6..876d405d048d3dfe5a7ca4b894375431c79932e7 100644
--- a/src/isa/mips32/include/isa/reg.h
+++ b/src/isa/mips32/include/isa/reg.h
@@ -17,6 +17,7 @@ typedef struct {
   uint32_t badvaddr;
   uint32_t cause;
   vaddr_t pc;
+  uint32_t epc;
 
   bool INTR;
 } CPU_state;
diff --git a/src/isa/mips32/intr.c b/src/isa/mips32/intr.c
index 8828e32474d65ed824661d78ae374a471182e21b..44dc6817f17284b81d6ea4c8fe55af2af7b13d06 100644
--- a/src/isa/mips32/intr.c
+++ b/src/isa/mips32/intr.c
@@ -1,10 +1,16 @@
 #include "cpu/rtl.h"
 //#include "isa/mmu.h"
 
-void raise_intr(uint8_t NO, vaddr_t ret_addr) {
+#define EX_ENTRY 0x180
+
+void raise_intr(uint8_t NO, vaddr_t epc) {
   /* TODO: Trigger an interrupt/exception with ``NO''.
    * That is, use ``NO'' to index the IDT.
    */
 
   //TODO();
+  cpu.cause = NO << 2;
+  cpu.epc = epc;
+
+  rtl_j(EX_ENTRY);
 }