diff --git a/code/os/11-syscall/entry.S b/code/os/11-syscall/entry.S
index 4759321..1fd9a7c 100644
--- a/code/os/11-syscall/entry.S
+++ b/code/os/11-syscall/entry.S
@@ -1,6 +1,12 @@
+#ifdef CONFIG_RV64
+#define LOAD		ld
+#define STORE		sd
+#define SIZE_REG	8
+#else
 #define LOAD		lw
 #define STORE		sw
 #define SIZE_REG	4
+#endif
 
 # Save all General-Purpose(GP) registers to context.
 # struct context *base = &ctx_task;
diff --git a/code/os/11-syscall/mem.S b/code/os/11-syscall/mem.S
index 5dede60..3d3341d 100644
--- a/code/os/11-syscall/mem.S
+++ b/code/os/11-syscall/mem.S
@@ -1,4 +1,8 @@
+#ifdef CONFIG_RV64
+#define SIZE_PTR .dword
+#else
 #define SIZE_PTR .word
+#endif
 
 .section .rodata
 .global HEAP_START
diff --git a/code/os/11-syscall/riscv.h b/code/os/11-syscall/riscv.h
index 051749a..01d82e8 100644
--- a/code/os/11-syscall/riscv.h
+++ b/code/os/11-syscall/riscv.h
@@ -93,8 +93,13 @@ static inline void w_mie(reg_t x)
 }
 
 /* Machine-mode Cause Masks */
+#ifdef CONFIG_RV64
+#define MCAUSE_MASK_INTERRUPT	(reg_t)0x8000000000000000
+#define MCAUSE_MASK_ECODE	(reg_t)0x7FFFFFFFFFFFFFFF
+#else
 #define MCAUSE_MASK_INTERRUPT	(reg_t)0x80000000
 #define MCAUSE_MASK_ECODE	(reg_t)0x7FFFFFFF
+#endif
 
 static inline reg_t r_mcause()
 {
diff --git a/code/os/11-syscall/types.h b/code/os/11-syscall/types.h
index f2497fe..0162166 100644
--- a/code/os/11-syscall/types.h
+++ b/code/os/11-syscall/types.h
@@ -9,7 +9,12 @@ typedef unsigned long long uint64_t;
 /*
  * Register Width
  */
+#ifdef CONFIG_RV64
+typedef uint64_t reg_t;
+typedef uint64_t ptr_t;
+#else
 typedef uint32_t reg_t;
 typedef uint32_t ptr_t;
+#endif
 
 #endif /* __TYPES_H__ */
diff --git a/code/os/common.mk b/code/os/common.mk
index 11feb45..c81ecc3 100644
--- a/code/os/common.mk
+++ b/code/os/common.mk
@@ -2,15 +2,25 @@
 # This file will be included by the Makefile of each project.
 
 # Custom Macro Definition (Common part)
+ARCH = RV64
 
 include ../defines.mk
 DEFS +=
 
 CROSS_COMPILE = riscv64-unknown-elf-
 CFLAGS += -nostdlib -fno-builtin -g -Wall
+ifeq (${ARCH}, RV64)
+CFLAGS += -march=rv64g -mabi=lp64 -mcmodel=medany
+else
 CFLAGS += -march=rv32g -mabi=ilp32
+endif
 
+ifeq (${ARCH}, RV64)
+QEMU = qemu-system-riscv64
+else
 QEMU = qemu-system-riscv32
+endif
+
 QFLAGS = -nographic -smp 1 -machine virt -bios none
 
 GDB = gdb-multiarch
diff --git a/code/os/defines.mk b/code/os/defines.mk
index ca9b040..016b3bc 100644
--- a/code/os/defines.mk
+++ b/code/os/defines.mk
@@ -2,6 +2,13 @@
 # Support customization in the Makefile files for each project separately.
 # And also support customization in common.mk
 
+ifeq (${ARCH}, RV64)
+DEFS += -DCONFIG_RV64
+else
+# RV32 or default is 32bit
+DEFS += -DCONFIG_RV32
+endif
+
 ifeq (${SYSCALL}, y)
 DEFS += -DCONFIG_SYSCALL
 endif