diff --git a/.gitmodules b/.gitmodules
index e4ce605..7e43040 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,4 +4,4 @@
 	branch = dev
 [submodule "diffu"]
 	path = diffu
-	url = https://git.xinyang.life/xin/diffu.git
+	url = git@github.com:xinyangli/diffu.git
diff --git a/abstract-machine/CMakeLists.txt b/abstract-machine/CMakeLists.txt
index 659bb84..b6e660c 100644
--- a/abstract-machine/CMakeLists.txt
+++ b/abstract-machine/CMakeLists.txt
@@ -76,7 +76,8 @@ target_include_directories(
   INTERFACE $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/am/include>
             $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/am/src>
             $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-target_compile_definitions(am_interface INTERFACE ARCH_H=<arch/${ISA}.h>)
+target_compile_definitions(am_interface INTERFACE ARCH_H=<arch/${ISA}.h>
+                                                  "__ISA__=\"${ISA}\"")
 file(GLOB_RECURSE AM_HEADERS "${CMAKE_SOURCE_DIR}/am/include/*.h")
 target_sources(
   am_interface
diff --git a/abstract-machine/am/include/arch/riscv.h b/abstract-machine/am/include/arch/riscv.h
index 9709050..cb6ecc1 100644
--- a/abstract-machine/am/include/arch/riscv.h
+++ b/abstract-machine/am/include/arch/riscv.h
@@ -1,5 +1,6 @@
 #ifndef ARCH_H__
 #define ARCH_H__
+#include <stdint.h>
 
 #ifdef __riscv_e
 #define NR_REGS 16
@@ -9,10 +10,13 @@
 
 struct Context {
   // TODO: fix the order of these members to match trap.S
-  uintptr_t mepc, mcause, gpr[NR_REGS], mstatus;
+  uintptr_t gpr[NR_REGS];
+  uintptr_t mcause, mstatus, mepc;
   void *pdir;
 };
 
+enum Cause { CauseEnvironmentCallFromMMode = 11 };
+
 #ifdef __riscv_e
 #define GPR1 gpr[15] // a5
 #else
diff --git a/abstract-machine/am/src/platform/nemu/trm.c b/abstract-machine/am/src/platform/nemu/trm.c
index c4287c5..5d08a48 100644
--- a/abstract-machine/am/src/platform/nemu/trm.c
+++ b/abstract-machine/am/src/platform/nemu/trm.c
@@ -6,7 +6,7 @@ int main(const char *args);
 
 Area heap = RANGE(&_heap_start, PMEM_END);
 #ifndef MAINARGS
-#define MAINARGS "5"
+#define MAINARGS "i"
 #endif
 static const char mainargs[] = MAINARGS;
 
diff --git a/abstract-machine/am/src/riscv/nemu/cte.c b/abstract-machine/am/src/riscv/nemu/cte.c
index 77a357c..12a9d32 100644
--- a/abstract-machine/am/src/riscv/nemu/cte.c
+++ b/abstract-machine/am/src/riscv/nemu/cte.c
@@ -1,14 +1,20 @@
+#include "arch/riscv.h"
 #include <am.h>
-#include <riscv/riscv.h>
 #include <klib.h>
+#include <riscv/riscv.h>
 
-static Context* (*user_handler)(Event, Context*) = NULL;
+static Context *(*user_handler)(Event, Context *) = NULL;
 
-Context* __am_irq_handle(Context *c) {
+Context *__am_irq_handle(Context *c) {
   if (user_handler) {
     Event ev = {0};
     switch (c->mcause) {
-      default: ev.event = EVENT_ERROR; break;
+    case CauseEnvironmentCallFromMMode:
+      ev.event = EVENT_YIELD;
+      break;
+    default:
+      ev.event = EVENT_ERROR;
+      break;
     }
 
     c = user_handler(ev, c);
@@ -20,7 +26,7 @@ Context* __am_irq_handle(Context *c) {
 
 extern void __am_asm_trap(void);
 
-bool cte_init(Context*(*handler)(Event, Context*)) {
+bool cte_init(Context *(*handler)(Event, Context *)) {
   // initialize exception entry
   asm volatile("csrw mtvec, %0" : : "r"(__am_asm_trap));
 
@@ -42,9 +48,6 @@ void yield() {
 #endif
 }
 
-bool ienabled() {
-  return false;
-}
+bool ienabled() { return false; }
 
-void iset(bool enable) {
-}
+void iset(bool enable) {}
diff --git a/abstract-machine/default.nix b/abstract-machine/default.nix
index ef21cf2..4e3fb1c 100644
--- a/abstract-machine/default.nix
+++ b/abstract-machine/default.nix
@@ -15,6 +15,9 @@ stdenv.mkDerivation {
     (lib.cmakeFeature "ISA" isa)
   ] ++ map (p: (lib.cmakeBool "__PLATFORM_${lib.strings.toUpper p}__" true)) platform;
 
+  cmakeBuildType = "Debug";
+  dontStrip = true;
+
   nativeBuildInputs = [
     cmake
   ];
diff --git a/am-kernels b/am-kernels
index 02b38e7..8c4ea04 160000
--- a/am-kernels
+++ b/am-kernels
@@ -1 +1 @@
-Subproject commit 02b38e7b44f673f808abcb3bf9464811f8c58d4b
+Subproject commit 8c4ea046225e2dce599dc36aeef6c4c857996d00
diff --git a/nemu/.gitignore b/nemu/.gitignore
index 36e223b..5bea786 100644
--- a/nemu/.gitignore
+++ b/nemu/.gitignore
@@ -9,6 +9,7 @@ build/
 .envrc
 .metals/
 .vscode/
+.zed/
 compile_commands.json
 
 ### C ###
diff --git a/nemu/include/utils.h b/nemu/include/utils.h
index f974584..43c30ad 100644
--- a/nemu/include/utils.h
+++ b/nemu/include/utils.h
@@ -20,7 +20,14 @@
 
 // ----------- state -----------
 
-enum { NEMU_RUNNING, NEMU_STOP, NEMU_END, NEMU_ABORT, NEMU_QUIT };
+enum {
+  NEMU_RUNNING,
+  NEMU_GDB_INTERRUPT,
+  NEMU_STOP,
+  NEMU_END,
+  NEMU_ABORT,
+  NEMU_QUIT
+};
 
 typedef struct {
   int state;
@@ -36,42 +43,41 @@ uint64_t get_time();
 
 // ----------- log -----------
 
-#define ANSI_FG_BLACK   "\33[1;30m"
-#define ANSI_FG_RED     "\33[1;31m"
-#define ANSI_FG_GREEN   "\33[1;32m"
-#define ANSI_FG_YELLOW  "\33[1;33m"
-#define ANSI_FG_BLUE    "\33[1;34m"
+#define ANSI_FG_BLACK "\33[1;30m"
+#define ANSI_FG_RED "\33[1;31m"
+#define ANSI_FG_GREEN "\33[1;32m"
+#define ANSI_FG_YELLOW "\33[1;33m"
+#define ANSI_FG_BLUE "\33[1;34m"
 #define ANSI_FG_MAGENTA "\33[1;35m"
-#define ANSI_FG_CYAN    "\33[1;36m"
-#define ANSI_FG_WHITE   "\33[1;37m"
-#define ANSI_BG_BLACK   "\33[1;40m"
-#define ANSI_BG_RED     "\33[1;41m"
-#define ANSI_BG_GREEN   "\33[1;42m"
-#define ANSI_BG_YELLOW  "\33[1;43m"
-#define ANSI_BG_BLUE    "\33[1;44m"
+#define ANSI_FG_CYAN "\33[1;36m"
+#define ANSI_FG_WHITE "\33[1;37m"
+#define ANSI_BG_BLACK "\33[1;40m"
+#define ANSI_BG_RED "\33[1;41m"
+#define ANSI_BG_GREEN "\33[1;42m"
+#define ANSI_BG_YELLOW "\33[1;43m"
+#define ANSI_BG_BLUE "\33[1;44m"
 #define ANSI_BG_MAGENTA "\33[1;35m"
-#define ANSI_BG_CYAN    "\33[1;46m"
-#define ANSI_BG_WHITE   "\33[1;47m"
-#define ANSI_NONE       "\33[0m"
+#define ANSI_BG_CYAN "\33[1;46m"
+#define ANSI_BG_WHITE "\33[1;47m"
+#define ANSI_NONE "\33[0m"
 
 #define ANSI_FMT(str, fmt) fmt str ANSI_NONE
 
-#define log_write(...) IFDEF(CONFIG_TARGET_NATIVE_ELF, \
-  do { \
-    extern FILE* log_fp; \
-    extern bool log_enable(); \
-    if (log_enable()) { \
-      fprintf(log_fp, __VA_ARGS__); \
-      fflush(log_fp); \
-    } \
-  } while (0) \
-)
+#define log_write(...)                                                         \
+  IFDEF(                                                                       \
+      CONFIG_TARGET_NATIVE_ELF, do {                                           \
+        extern FILE *log_fp;                                                   \
+        extern bool log_enable();                                              \
+        if (log_enable()) {                                                    \
+          fprintf(log_fp, __VA_ARGS__);                                        \
+          fflush(log_fp);                                                      \
+        }                                                                      \
+      } while (0))
 
-#define _Log(...) \
-  do { \
-    printf(__VA_ARGS__); \
-    log_write(__VA_ARGS__); \
+#define _Log(...)                                                              \
+  do {                                                                         \
+    printf(__VA_ARGS__);                                                       \
+    log_write(__VA_ARGS__);                                                    \
   } while (0)
 
-
 #endif
diff --git a/nemu/src/device/keyboard.c b/nemu/src/device/keyboard.c
index da699b5..2ae5d17 100644
--- a/nemu/src/device/keyboard.c
+++ b/nemu/src/device/keyboard.c
@@ -13,7 +13,10 @@
 * See the Mulan PSL v2 for more details.
 ***************************************************************************************/
 
+#include <assert.h>
+#include <debug.h>
 #include <device/map.h>
+#include <generated/autoconf.h>
 #include <utils.h>
 
 #define KEYDOWN_MASK 0x8000
@@ -22,28 +25,27 @@
 #include <SDL2/SDL.h>
 
 // Note that this is not the standard
-#define NEMU_KEYS(f) \
-  f(ESCAPE) f(F1) f(F2) f(F3) f(F4) f(F5) f(F6) f(F7) f(F8) f(F9) f(F10) f(F11) f(F12) \
-f(GRAVE) f(1) f(2) f(3) f(4) f(5) f(6) f(7) f(8) f(9) f(0) f(MINUS) f(EQUALS) f(BACKSPACE) \
-f(TAB) f(Q) f(W) f(E) f(R) f(T) f(Y) f(U) f(I) f(O) f(P) f(LEFTBRACKET) f(RIGHTBRACKET) f(BACKSLASH) \
-f(CAPSLOCK) f(A) f(S) f(D) f(F) f(G) f(H) f(J) f(K) f(L) f(SEMICOLON) f(APOSTROPHE) f(RETURN) \
-f(LSHIFT) f(Z) f(X) f(C) f(V) f(B) f(N) f(M) f(COMMA) f(PERIOD) f(SLASH) f(RSHIFT) \
-f(LCTRL) f(APPLICATION) f(LALT) f(SPACE) f(RALT) f(RCTRL) \
-f(UP) f(DOWN) f(LEFT) f(RIGHT) f(INSERT) f(DELETE) f(HOME) f(END) f(PAGEUP) f(PAGEDOWN)
+#define NEMU_KEYS(f)                                                           \
+  f(ESCAPE) f(F1) f(F2) f(F3) f(F4) f(F5) f(F6) f(F7) f(F8) f(F9) f(F10)       \
+      f(F11) f(F12) f(GRAVE) f(1) f(2) f(3) f(4) f(5) f(6) f(7) f(8) f(9) f(0) \
+          f(MINUS) f(EQUALS) f(BACKSPACE) f(TAB) f(Q) f(W) f(E) f(R) f(T) f(Y) \
+              f(U) f(I) f(O) f(P) f(LEFTBRACKET) f(RIGHTBRACKET) f(BACKSLASH)  \
+                  f(CAPSLOCK) f(A) f(S) f(D) f(F) f(G) f(H) f(J) f(K) f(L)     \
+                      f(SEMICOLON) f(APOSTROPHE) f(RETURN) f(LSHIFT) f(Z) f(X) \
+                          f(C) f(V) f(B) f(N) f(M) f(COMMA) f(PERIOD) f(SLASH) \
+                              f(RSHIFT) f(LCTRL) f(APPLICATION) f(LALT)        \
+                                  f(SPACE) f(RALT) f(RCTRL) f(UP) f(DOWN)      \
+                                      f(LEFT) f(RIGHT) f(INSERT) f(DELETE)     \
+                                          f(HOME) f(END) f(PAGEUP) f(PAGEDOWN)
 
-#define NEMU_KEY_NAME(k) NEMU_KEY_ ## k,
+#define NEMU_KEY_NAME(k) NEMU_KEY_##k,
 
-enum {
-  NEMU_KEY_NONE = 0,
-  MAP(NEMU_KEYS, NEMU_KEY_NAME)
-};
+enum { NEMU_KEY_NONE = 0, MAP(NEMU_KEYS, NEMU_KEY_NAME) };
 
-#define SDL_KEYMAP(k) keymap[SDL_SCANCODE_ ## k] = NEMU_KEY_ ## k;
+#define SDL_KEYMAP(k) keymap[SDL_SCANCODE_##k] = NEMU_KEY_##k;
 static uint32_t keymap[256] = {};
 
-static void init_keymap() {
-  MAP(NEMU_KEYS, SDL_KEYMAP)
-}
+static void init_keymap() { MAP(NEMU_KEYS, SDL_KEYMAP) }
 
 #define KEY_QUEUE_LEN 1024
 static int key_queue[KEY_QUEUE_LEN] = {};
@@ -92,9 +94,11 @@ void init_i8042() {
   i8042_data_port_base = (uint32_t *)new_space(4);
   i8042_data_port_base[0] = NEMU_KEY_NONE;
 #ifdef CONFIG_HAS_PORT_IO
-  add_pio_map ("keyboard", CONFIG_I8042_DATA_PORT, i8042_data_port_base, 4, i8042_data_io_handler);
+  add_pio_map("keyboard", CONFIG_I8042_DATA_PORT, i8042_data_port_base, 4,
+              i8042_data_io_handler);
 #else
-  add_mmio_map("keyboard", CONFIG_I8042_DATA_MMIO, i8042_data_port_base, 4, i8042_data_io_handler);
+  add_mmio_map("keyboard", CONFIG_I8042_DATA_MMIO, i8042_data_port_base, 4,
+               i8042_data_io_handler);
 #endif
   IFNDEF(CONFIG_TARGET_AM, init_keymap());
 }
diff --git a/nemu/src/device/serial.c b/nemu/src/device/serial.c
index ad437e8..dba02f6 100644
--- a/nemu/src/device/serial.c
+++ b/nemu/src/device/serial.c
@@ -16,6 +16,7 @@
 #include <assert.h>
 #include <debug.h>
 #include <device/map.h>
+#include <generated/autoconf.h>
 #include <utils.h>
 
 /* http://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Programming */
diff --git a/nemu/src/device/timer.c b/nemu/src/device/timer.c
index 23c2d49..886ecd6 100644
--- a/nemu/src/device/timer.c
+++ b/nemu/src/device/timer.c
@@ -16,6 +16,7 @@
 #include <assert.h>
 #include <device/alarm.h>
 #include <device/map.h>
+#include <generated/autoconf.h>
 #include <utils.h>
 
 static uint32_t *rtc_port_base = NULL;
diff --git a/nemu/src/isa/riscv32/csr.c b/nemu/src/isa/riscv32/csr.c
new file mode 100644
index 0000000..5b9a298
--- /dev/null
+++ b/nemu/src/isa/riscv32/csr.c
@@ -0,0 +1,18 @@
+#include <csr.h>
+
+void init_csr(csr_t csr) { memset(csr, 0, sizeof(word_t)); }
+
+void write_csr(csr_t csr, csr_addr_t csrnum, word_t value) {
+  switch (csrnum) {
+  default:
+    csr[csrnum] = value;
+  }
+}
+
+word_t read_csr(csr_t csr, csr_addr_t csrnum) {
+  switch (csrnum) {
+  // TODO: Implement csr read checks
+  default:
+    return csr[csrnum];
+  }
+}
diff --git a/nemu/src/isa/riscv32/include/isa-def.h b/nemu/src/isa/riscv32/include/isa-def.h
index 524cb4e..e3f514a 100644
--- a/nemu/src/isa/riscv32/include/isa-def.h
+++ b/nemu/src/isa/riscv32/include/isa-def.h
@@ -18,9 +18,13 @@
 
 #include <common.h>
 
+#define CSR_SIZE (0x1000)
+
+typedef word_t csr_t[CSR_SIZE];
+
 typedef struct {
   word_t gpr[MUXDEF(CONFIG_RVE, 16, 32)];
-  // word_t csr[MUXDEF(CONFIG_RVE, )]
+  csr_t csr;
   vaddr_t pc;
 } MUXDEF(CONFIG_RV64, riscv64_CPU_state, riscv32_CPU_state);
 
diff --git a/nemu/src/isa/riscv32/inst.c b/nemu/src/isa/riscv32/inst.c
index dc65f47..75a5fa2 100644
--- a/nemu/src/isa/riscv32/inst.c
+++ b/nemu/src/isa/riscv32/inst.c
@@ -13,6 +13,7 @@
  * See the Mulan PSL v2 for more details.
  ***************************************************************************************/
 
+#include "isa.h"
 #include "local-include/reg.h"
 #include "macro.h"
 #include "types.h"
@@ -20,6 +21,7 @@
 #include <cpu/cpu.h>
 #include <cpu/decode.h>
 #include <cpu/ifetch.h>
+#include <csr.h>
 #include <ftrace.h>
 #include <utils.h>
 
@@ -33,6 +35,8 @@ enum {
   TYPE_S,
   TYPE_B,
   TYPE_J,
+  TYPE_CSR,
+  TYPE_CSRI,
   TYPE_N, // none
 };
 
@@ -66,6 +70,14 @@ enum {
     *imm = SEXT(BITS(i, 31, 31), 1) << 20 | BITS(i, 30, 21) << 1 |             \
            BITS(i, 20, 20) << 11 | BITS(i, 19, 12) << 12;                      \
   } while (0)
+#define csr()                                                                  \
+  do {                                                                         \
+    *src2 = BITS(i, 31, 20);                                                   \
+  } while (0)
+#define uimm()                                                                 \
+  do {                                                                         \
+    *imm = BITS(i, 19, 15);                                                    \
+  } while (0)
 
 static void decode_operand(Decode *s, int *rd, word_t *src1, word_t *src2,
                            word_t *imm, int type) {
@@ -98,6 +110,14 @@ static void decode_operand(Decode *s, int *rd, word_t *src1, word_t *src2,
     src2R();
     immB();
     break;
+  case TYPE_CSR:
+    src1R();
+    csr();
+    break;
+  case TYPE_CSRI:
+    csr();
+    uimm();
+    break;
   }
 }
 
@@ -249,6 +269,44 @@ static int decode_exec(Decode *s) {
   INSTPAT("0000001 ????? ????? 111 ????? 01100 11", remu, R,
           R(rd) = src1 % src2);
 
+  // "Previledge"
+  // -- CSR instructions
+  INSTPAT(
+      "??????? ????? ????? 001 ????? 11100 11", csrrw, CSR, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        write_csr(cpu.csr, src2, src1);
+      } while (0););
+  INSTPAT(
+      "??????? ????? ????? 010 ????? 11100 11", csrrs, CSR, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        set_csr_bits(cpu.csr, src2, src1);
+      } while (0););
+  INSTPAT(
+      "??????? ????? ????? 011 ????? 11100 11", csrrc, CSR, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        clear_csr_bits(cpu.csr, src2, src1);
+      } while (0););
+  INSTPAT(
+      "??????? ????? ????? 101 ????? 11100 11", csrrwi, CSRI, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        write_csr(cpu.csr, src2, imm);
+      } while (0););
+  INSTPAT(
+      "??????? ????? ????? 110 ????? 11100 11", csrrsi, CSRI, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        set_csr_bits(cpu.csr, src2, imm);
+      } while (0););
+  INSTPAT(
+      "??????? ????? ????? 111 ????? 11100 11", csrrci, CSRI, do {
+        R(rd) = read_csr(cpu.csr, src2);
+        clear_csr_bits(cpu.csr, src2, imm);
+      } while (0););
+  // -- Machine level
+  INSTPAT("0000000 00000 00000 000 00000 11100 11", ecall, N,
+          s->dnpc = isa_raise_intr(CauseEnvironmentCallFromMMode, cpu.pc));
+  INSTPAT("0011000 00010 00000 000 00000 11100 11", mret, N,
+          s->dnpc = read_csr(cpu.csr, MEPC));
+
   INSTPAT("??????? ????? ????? ??? ????? ????? ??", inv, N, INV(s->pc));
   INSTPAT_END();
 
diff --git a/nemu/src/isa/riscv32/local-include/csr.h b/nemu/src/isa/riscv32/local-include/csr.h
new file mode 100644
index 0000000..9dfca1c
--- /dev/null
+++ b/nemu/src/isa/riscv32/local-include/csr.h
@@ -0,0 +1,29 @@
+#ifndef __NEMU_CSR_H__
+#define __NEMU_CSR_H__
+#include <isa-def.h>
+#include <types.h>
+
+#define MSTATUS 0x300
+#define MISA 0x301
+#define MIE 0x304
+#define MTVEC 0x305
+#define MEPC 0x341
+#define MCAUSE 0x342
+
+enum { CauseEnvironmentCallFromMMode = 11 };
+
+typedef uint16_t csr_addr_t;
+
+void init_csr(csr_t csr);
+
+/* macro for setting and clearing csr bits */
+#define set_csr_bits(csr, reg, mask)                                           \
+  write_csr(csr, reg, read_csr(csr, reg) | (mask))
+
+#define clear_csr_bits(csr, reg, mask)                                         \
+  write_csr(csr, reg, read_csr(csr, reg) & ~(mask))
+
+void write_csr(csr_t csr, csr_addr_t csrnum, word_t value);
+word_t read_csr(csr_t csr, csr_addr_t csrnum);
+
+#endif // __NEMU_CSR_H__
diff --git a/nemu/src/isa/riscv32/reg.c b/nemu/src/isa/riscv32/reg.c
index fe96b86..b76282c 100644
--- a/nemu/src/isa/riscv32/reg.c
+++ b/nemu/src/isa/riscv32/reg.c
@@ -14,6 +14,7 @@
 ***************************************************************************************/
 
 #include "local-include/reg.h"
+#include "csr.h"
 #include "macro.h"
 #include <errno.h>
 #include <gdbstub.h>
@@ -51,11 +52,13 @@ word_t isa_reg_str2val(const char *s, bool *success) {
 }
 
 int isa_read_reg(void *args, int regno, size_t *reg_value) {
-  if (regno > 32) {
+  if (regno > 33) {
     return EFAULT;
   }
 
-  if (regno == 32) {
+  if (regno == 33) {
+    *reg_value = cpu.csr[MTVEC];
+  } else if (regno == 32) {
     *reg_value = cpu.pc;
   } else {
     *reg_value = cpu.gpr[regno];
@@ -64,11 +67,13 @@ int isa_read_reg(void *args, int regno, size_t *reg_value) {
 }
 
 int isa_write_reg(void *args, int regno, size_t data) {
-  if (regno > 32) {
+  if (regno > 33) {
     return EFAULT;
   }
 
-  if (regno == 32) {
+  if (regno == 33) {
+    cpu.csr[MTVEC] = data;
+  } else if (regno == 32) {
     cpu.pc = data;
   } else {
     cpu.gpr[regno] = data;
@@ -76,6 +81,6 @@ int isa_write_reg(void *args, int regno, size_t data) {
   return 0;
 }
 
-__EXPORT arch_info_t isa_arch_info = {.reg_num = 32,
+__EXPORT arch_info_t isa_arch_info = {.reg_num = 33,
                                       .reg_byte = MUXDEF(CONFIG_RV64, 8, 4),
                                       .target_desc = TARGET_RV32};
diff --git a/nemu/src/isa/riscv32/system/intr.c b/nemu/src/isa/riscv32/system/intr.c
index 3619b59..4fc8c35 100644
--- a/nemu/src/isa/riscv32/system/intr.c
+++ b/nemu/src/isa/riscv32/system/intr.c
@@ -13,16 +13,14 @@
 * See the Mulan PSL v2 for more details.
 ***************************************************************************************/
 
+#include <csr.h>
 #include <isa.h>
 
 word_t isa_raise_intr(word_t NO, vaddr_t epc) {
-  /* TODO: Trigger an interrupt/exception with ``NO''.
-   * Then return the address of the interrupt/exception vector.
-   */
+  write_csr(cpu.csr, MEPC, epc);
+  write_csr(cpu.csr, MCAUSE, NO);
 
-  return 0;
+  return read_csr(cpu.csr, MTVEC);
 }
 
-word_t isa_query_intr() {
-  return INTR_EMPTY;
-}
+word_t isa_query_intr() { return INTR_EMPTY; }
diff --git a/nemu/src/monitor/gdbstub.cc b/nemu/src/monitor/gdbstub.cc
index 5905ef4..5963b72 100644
--- a/nemu/src/monitor/gdbstub.cc
+++ b/nemu/src/monitor/gdbstub.cc
@@ -59,6 +59,11 @@ static void nemu_is_stopped(gdb_action_t *act, breakpoint_t *stopped_at) {
     }
     break;
 
+  case NEMU_GDB_INTERRUPT:
+    act->reason = gdb_action_t::ACT_BREAKPOINT;
+    act->data = cpu.pc;
+    break;
+
   default:
     act->reason = gdb_action_t::ACT_SHUTDOWN;
     act->data = nemu_state.halt_ret;
@@ -103,7 +108,7 @@ __EXPORT bool nemu_del_bp(void *args, size_t addr, bp_type_t type) {
 }
 
 __EXPORT void nemu_on_interrupt(void *args) {
-  // fputs("Not implemented", stderr);
+  nemu_state.state = NEMU_GDB_INTERRUPT;
 }
 
 __EXPORT int nemu_read_reg(void *args, int regno, size_t *data) {
@@ -121,7 +126,8 @@ static struct target_ops nemu_gdbstub_ops = {.cont = nemu_cont,
                                              .write_mem = nemu_write_mem,
                                              .set_bp = nemu_set_bp,
                                              .del_bp = nemu_del_bp,
-                                             .on_interrupt = NULL};
+                                             .on_interrupt = nemu_on_interrupt,
+                                             .monitor = NULL};
 static DbgState *pdbg;
 static gdbstub_t gdbstub_priv;
 const char SOCKET_ADDR[] = "/tmp/gdbstub-nemu.sock";
@@ -152,7 +158,7 @@ __EXPORT void nemu_init(void *args) {
 
 int gdbstub_loop() {
   if (!gdbstub_init(&gdbstub_priv, &nemu_gdbstub_ops,
-                    (arch_info_t)isa_arch_info, SOCKET_ADDR)) {
+                    (arch_info_t)isa_arch_info, NULL, SOCKET_ADDR)) {
     return EINVAL;
   }
   printf("Waiting for gdb connection at %s", SOCKET_ADDR);