diff --git a/laos/Makefile b/laos/Makefile
index 542cdf4..a783c06 100644
--- a/laos/Makefile
+++ b/laos/Makefile
@@ -19,14 +19,15 @@ BIN			:= neula-os
 BINARY		:= $(BUILD_DIR)/$(BIN)
 
 TOP_SRC_DIR	:= src
-SOURCE_DIRS	:= $(shell ls $(TOP_SRC_DIR)/* -d)
+MODULES		:= kernel util
+SOURCE_DIRS	:= $(addprefix $(TOP_SRC_DIR)/,$(MODULES))
 MK_DIRS		:= $(addprefix MAKE/,$(SOURCE_DIRS))
 ALL_SRCS	:= $(shell find . -name '*.c')
 LD_CSRIPT	:= kernel.ld
 
 EXTRA_MACRO	:= # NDEBUG
 
-EXTRA_FLAGS =  -Wall -Werror -O -fno-omit-frame-pointer -ggdb -gdwarf-2
+EXTRA_FLAGS =  -Wall -Werror -O0 -fno-omit-frame-pointer -ggdb -gdwarf-2
 EXTRA_FLAGS += -MD
 EXTRA_FLAGS += -ffreestanding -fno-common -nostdlib
 EXTRA_FLAGS += -I.
@@ -57,4 +58,15 @@ build: $(MK_DIRS)
 	@$(OC) $(BINARY) -O binary $(BINARY).bin
 
 clean:
-	rm -rf $(BUILD_DIR)
\ No newline at end of file
+	rm -rf $(BUILD_DIR)
+
+
+# use native
+
+clean-usr:
+	rm -rf $(BUILD_DIR)/user
+
+usr:
+	@TOP_BUILD_DIR=$(ABS_BUILD) \
+	CPPFLAGS="$(CPPFLAGS)"		\
+	$(MAKE) native -C $(TOP_SRC_DIR)/user -j$(NPROC)
diff --git a/laos/include/asm.h b/laos/include/asm.h
index b188ff2..99b445f 100644
--- a/laos/include/asm.h
+++ b/laos/include/asm.h
@@ -3,6 +3,36 @@
 #ifndef ASM_H__
 #define ASM_H__
 
-#define CPUID   0x020
+// CSR infos
+#define CRMD        0x000 /* 当前模式信息 */
+#define PRMD        0x001 /* 例外前模式信息 */
+#define EUEN        0x002 /* 拓展部件使能 */
+#define ECFG        0x004 /* 例外配置 */
+#define ESTAT       0x005 /* 例外状态 */
+#define ERA         0x006 /* 例外返回地址 */
+#define BADV        0x007 /* 出错虚地址 */
+#define EENTRY      0x00c /* 例外地址入口 */
+#define TLBIDX      0x010 /* TLB 索引 */
+#define TLBEHI      0x011 /* TLB 表项高位 */
+#define TLBELO0     0x012 /* TLB 表项低位 0 */
+#define TLBELO1     0x013 /* TLB 表项低位 1 */
+#define ASID        0x018 /* 地址空间标识符 */
+#define PGDL        0x019 /* 低半地址空间全局目录基址 */
+#define PGDH        0x01a /* 高半地址空间全局目录基址 */
+#define PGD         0x01b /* 全局目录基址 */
+#define CPUID       0x020 /* 处理器编号 */
+#define SAVE0       0x030 /* 数据保存 0*/
+#define SAVE1       0x031 /* 数据保存 1*/
+#define SAVE2       0x032 /* 数据保存 2 */
+#define SAVE3       0x033 /* 数据保存 3 */
+#define TID         0x040 /* 定时器编号 */
+#define TCFG        0x041 /* 定时器配置 */
+#define TVAL        0x042 /* 定时器值 */
+#define TICLR       0x044 /* 定时中断清除 */
+#define LLBCTL      0x060 /* LLBit 控制 */
+#define TLBRENTRY   0x088 /* TLB 重填例外入口 */
+#define CTAG        0x098 /* 高速缓存标签 */
+#define DMW0        0x180 /* 直接映射配置窗口 0 */
+#define DMW1        0x181 /* 直接映射配置窗口 1 */
 
 #endif
\ No newline at end of file
diff --git a/laos/include/console.h b/laos/include/console.h
new file mode 100644
index 0000000..3d140fe
--- /dev/null
+++ b/laos/include/console.h
@@ -0,0 +1,6 @@
+#ifndef CONSOLE_H__
+#define CONSOLE_H__
+
+void consputc(int c);
+
+#endif
\ No newline at end of file
diff --git a/laos/include/defs.h b/laos/include/defs.h
index d87766b..5784ef3 100644
--- a/laos/include/defs.h
+++ b/laos/include/defs.h
@@ -1,6 +1,14 @@
 #ifndef DEFS_H__
 #define DEFS_H__
 
+#define NULL    ((void *)0)
+
 #define NCPU    1
+#define NPROC   64
+#define NOFILE  16
+
+
+#define SERIAL_TX_BUF_SIZE    32
+
 
 #endif
\ No newline at end of file
diff --git a/laos/include/fcntl.h b/laos/include/fcntl.h
new file mode 100644
index 0000000..df88ec1
--- /dev/null
+++ b/laos/include/fcntl.h
@@ -0,0 +1,10 @@
+#ifndef FCNTL_H__
+#define FCNTL_H__
+
+#define O_RDONLY  0x000
+#define O_WRONLY  0x001
+#define O_RDWR    0x002
+#define O_CREATE  0x200
+#define O_TRUNC   0x400
+
+#endif
\ No newline at end of file
diff --git a/laos/include/filesys.h b/laos/include/filesys.h
new file mode 100644
index 0000000..e69de29
diff --git a/laos/include/common.h b/laos/include/kernel.h
similarity index 63%
rename from laos/include/common.h
rename to laos/include/kernel.h
index 9749f1a..1ec981e 100644
--- a/laos/include/common.h
+++ b/laos/include/kernel.h
@@ -1,10 +1,11 @@
 #include "defs.h"
 
-#ifndef COMMON_H__
-#define COMMON_H__
+#ifndef KERNEL_H__
+#define KERNEL_H__
 
-void main();
-void start();
 void _entry() __attribute__ ((section (".entry")));
 
-#endif // COMMON_H__
\ No newline at end of file
+void start();
+void main();
+
+#endif
\ No newline at end of file
diff --git a/laos/include/kprintf.h b/laos/include/kprintf.h
new file mode 100644
index 0000000..aa46385
--- /dev/null
+++ b/laos/include/kprintf.h
@@ -0,0 +1,8 @@
+#ifndef KPRINTF_H__
+#define KPRINTF_H__
+
+
+void kprintf(char *fmt, ...);
+void panic(char *s);
+
+#endif
\ No newline at end of file
diff --git a/laos/include/la32r.h b/laos/include/la32r.h
index e69de29..5c06a6d 100644
--- a/laos/include/la32r.h
+++ b/laos/include/la32r.h
@@ -0,0 +1,104 @@
+#include "asm.h"
+#include "defs.h"
+#include "latype.h"
+#include "macro.h"
+
+#ifndef LA32R_H__
+#define LA32R_H__
+
+static inline uint r_crmd() {
+    uint recv;
+    asm volatile ("csrrd %0, " TOSTRING(CRMD) : "=r" (recv));
+    return recv;
+}
+
+static inline void w_crmd(uint wdata) {
+    asm volatile ("csrwr %0, " TOSTRING(CRMD) : "=r" (wdata));
+}
+
+static inline void w_eentry(uint wdata) {
+    asm volatile ("csrwr %0, " TOSTRING(EENTRY) : "=r" (wdata));
+}
+
+static inline uint r_cpuid() {
+    uint recv;
+    asm volatile ("csrrd %0, " TOSTRING(CPUID) : "=r" (recv));
+    return recv;
+}
+
+//
+// specified register io
+//
+
+static inline uint r_sp() {
+    uint recv;
+    asm volatile ("add.w %0, $sp, $zero" : "=r" (recv));
+    return recv;
+}
+
+static inline uint r_tp() {
+    uint recv;
+    asm volatile ("add.w %0, $tp, $zero" : "=r" (recv));
+    return recv;
+}
+
+static inline void w_tp(uint wdata) {
+    asm volatile("add.w $tp, %0, $zero" : : "r" (wdata));
+}
+
+static inline uint r_ra() {
+    uint recv;
+    asm volatile ("add.w %0, $ra, $zero" : "=r" (recv));
+    return recv;
+}
+
+//
+// mem misc
+//
+
+static inline void dbar() {
+  asm volatile("dbar 0");
+}
+
+static inline void ibar() {
+  asm volatile("ibar 0");
+}
+
+// need to be tested
+static inline void synchronize() {
+    dbar();
+    ibar();
+}
+
+
+//
+// tlb misc
+//
+
+//
+// cache misc
+//
+
+
+//
+// atomic
+//
+
+static inline uint llw(intptr_t addr) {
+    uint recv;
+    asm volatile ("ll.w %0, %1, 0": "=r" (recv) : "r" (addr));
+    return recv;
+}
+
+static inline uint scw(uint wdata, intptr_t addr) {
+    uint recv;
+    asm volatile (
+        "add.w %0, %1, $zero" "\n\t"
+        "sc.w %0, %2, 0"
+        : "=r" (recv)
+        : "r"  (wdata),
+          "r"  (addr));
+    return recv;
+}
+
+#endif
\ No newline at end of file
diff --git a/laos/include/latype.h b/laos/include/latype.h
new file mode 100644
index 0000000..c996a35
--- /dev/null
+++ b/laos/include/latype.h
@@ -0,0 +1,22 @@
+#ifndef LATYPE_H__
+#define LATYPE_H__
+
+typedef char            i8;
+typedef unsigned char   u8;
+typedef unsigned char   uchar;
+
+typedef short           i16;
+typedef unsigned short  u16;
+typedef unsigned short  ushort;
+
+typedef int             i32;
+typedef unsigned int    u32;
+typedef unsigned int    uint;
+
+typedef unsigned int    size_t;
+typedef unsigned int    intptr_t;
+
+typedef u32 pte_t;
+typedef u32 *pagetable_t;
+
+#endif
\ No newline at end of file
diff --git a/laos/include/macro.h b/laos/include/macro.h
new file mode 100644
index 0000000..aba4a9a
--- /dev/null
+++ b/laos/include/macro.h
@@ -0,0 +1,7 @@
+#ifndef MACRO_H__
+#define MACRO_H__
+
+#define TOSTRING_(x) #x
+#define TOSTRING(x) TOSTRING_(x)
+
+#endif
\ No newline at end of file
diff --git a/laos/include/memio.h b/laos/include/memio.h
new file mode 100644
index 0000000..543342c
--- /dev/null
+++ b/laos/include/memio.h
@@ -0,0 +1,11 @@
+#include "latype.h"
+
+
+#ifndef MEMIO_H__
+#define MEMIO_H__
+
+#define memb(addr) (*(u8  *)(addr))
+#define memh(addr) (*(u16 *)(addr))
+#define memw(addr) (*(u32 *)(addr))
+
+#endif
\ No newline at end of file
diff --git a/laos/include/memlayout.h b/laos/include/memlayout.h
new file mode 100644
index 0000000..214a31d
--- /dev/null
+++ b/laos/include/memlayout.h
@@ -0,0 +1,9 @@
+#ifndef MEMLAYOUT_H__
+#define MEMLAYOUT_H__
+
+#define DEV_BASE_ADDR   0xa0000000
+
+
+#define SERIAL_ADDR     (DEV_BASE_ADDR + 0x00000000)
+
+#endif
\ No newline at end of file
diff --git a/laos/include/proc.h b/laos/include/proc.h
new file mode 100644
index 0000000..b3f496f
--- /dev/null
+++ b/laos/include/proc.h
@@ -0,0 +1,117 @@
+#include "latype.h"
+#include "defs.h"
+#include "spinlock.h"
+
+#ifndef PROC_H__
+#define PROC_H__
+
+// Saved registers for kernel context switches.
+struct context {
+  u32 ra;
+  u32 sp;
+
+  // callee-saved
+  u32 s0;
+  u32 s1;
+  u32 s2;
+  u32 s3;
+  u32 s4;
+  u32 s5;
+  u32 s6;
+  u32 s7;
+  u32 s8;
+  u32 s9;
+};
+
+// Per-CPU state.
+struct cpu {
+  struct proc *proc;          // The process running on this cpu, or null.
+  struct context context;     // swtch() here to enter scheduler().
+  int noff;                   // Depth of push_off() nesting.
+  int intena;                 // Were interrupts enabled before push_off()?
+};
+
+extern struct cpu cpus[NCPU];
+
+
+// per-process data for the trap handling code in trampoline.S.
+// sits in a page by itself just under the trampoline page in the
+// user page table. not specially mapped in the kernel page table.
+// uservec in trampoline.S saves user registers in the trapframe,
+// then initializes registers from the trapframe's
+// kernel_sp, kernel_hartid, kernel_satp, and jumps to kernel_trap.
+// usertrapret() and userret in trampoline.S set up
+// the trapframe's kernel_*, restore user registers from the
+// trapframe, switch to the user page table, and enter user space.
+// the trapframe includes callee-saved user registers like s0-s11 because the
+// return-to-user path via usertrapret() doesn't return through
+// the entire kernel call stack.
+struct trapframe {
+  /*   0 */ u32 kernel_satp;   // kernel page table
+  /*   4 */ u32 kernel_sp;     // top of process's kernel stack
+  /*   8 */ u32 kernel_trap;   // usertrap()
+  /*  12 */ u32 eenrty;        // saved user program counter
+  /*  16 */ u32 kernel_hartid; // saved kernel tp
+  /*  20 */ u32 ra;
+  /*  24 */ u32 tp;
+  /*  28 */ u32 sp;
+  /*  32 */ u32 a0;
+  /*  36 */ u32 a1;
+  /*  40 */ u32 a2;
+  /*  44 */ u32 a3;
+  /*  48 */ u32 a4;
+  /*  52 */ u32 a5;
+  /*  56 */ u32 a6;
+  /*  60 */ u32 a7;
+  /*  64 */ u32 t0;
+  /*  68 */ u32 t1;
+  /*  72 */ u32 t2;
+  /*  76 */ u32 t3;
+  /*  80 */ u32 t4;
+  /*  84 */ u32 t5;
+  /*  88 */ u32 t6;
+  /*  92 */ u32 t7;
+  /*  96 */ u32 t8;
+  /* 100 */ u32 r21;
+  /* 104 */ u32 s9;
+  /* 108 */ u32 s0;
+  /* 112 */ u32 s1;
+  /* 116 */ u32 s2;
+  /* 120 */ u32 s3;
+  /* 124 */ u32 s4;
+  /* 128 */ u32 s5;
+  /* 132 */ u32 s6;
+  /* 136 */ u32 s7;
+  /* 140 */ u32 s8;
+};
+
+enum procstate { UNUSED, USED, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
+
+// Per-process state
+struct proc {
+  struct spinlock lock;
+
+  // p->lock must be held when using these:
+  enum procstate state;        // Process state
+  void *chan;                  // If non-zero, sleeping on chan
+  int killed;                  // If non-zero, have been killed
+  int xstate;                  // Exit status to be returned to parent's wait
+  int pid;                     // Process ID
+
+  // wait_lock must be held when using this:
+  struct proc *parent;         // Parent process
+
+  // these are private to the process, so p->lock need not be held.
+  u32 kstack;               // Virtual address of kernel stack
+  u32 sz;                   // Size of process memory (bytes)
+  pagetable_t pagetable;       // User page table
+  struct trapframe *trapframe; // data page for trampoline.S
+  struct context context;      // swtch() here to run process
+  struct file *ofile[NOFILE];  // Open files
+  struct inode *cwd;           // Current directory
+  char name[16];               // Process name (debugging)
+};
+
+struct cpu *mycpu();
+
+#endif
\ No newline at end of file
diff --git a/laos/include/spinlock.h b/laos/include/spinlock.h
new file mode 100644
index 0000000..193d19f
--- /dev/null
+++ b/laos/include/spinlock.h
@@ -0,0 +1,23 @@
+#include "latype.h"
+
+#ifndef SPINLOCK_H__
+#define SPINLOCK_H__
+
+struct spinlock {
+    uint locked;
+
+    // debugging
+    char *name;
+    struct cpu *cpu;
+};
+
+void initlock(struct spinlock *lck, char *name);
+
+void acquire(struct spinlock *lck);
+void release(struct spinlock *lck);
+
+int  holding(struct spinlock *lck);
+void push_off();
+void pop_off();
+
+#endif
\ No newline at end of file
diff --git a/laos/include/string.h b/laos/include/string.h
new file mode 100644
index 0000000..54a1dfd
--- /dev/null
+++ b/laos/include/string.h
@@ -0,0 +1,16 @@
+#include "latype.h"
+
+#ifndef STRING_H__
+#define STRING_H__
+
+void   *memset  (void *dst  , int c, uint n);
+int     memcmp  (const void *m1, const void *m2, uint n);
+void   *memmove (void *dst, const void *src, uint n);
+void   *memcpy  (void *dst, const void *src, uint n);
+
+int     strncmp (const char *p, const char *q, uint n);
+char   *strncpy (char *s, const char *t, int n);
+char   *strcpy_s(char *s, const char *t, int n);
+int     strlen  (const char *s);
+
+#endif
\ No newline at end of file
diff --git a/laos/include/unistd.h b/laos/include/unistd.h
new file mode 100644
index 0000000..effb9b2
--- /dev/null
+++ b/laos/include/unistd.h
@@ -0,0 +1,9 @@
+#ifndef UNISTD_H__
+#define UNISTD_H__
+
+/* Standard file descriptors.  */
+#define	STDIN_FILENO	0	/* Standard input.  */
+#define	STDOUT_FILENO	1	/* Standard output.  */
+#define	STDERR_FILENO	2	/* Standard error output.  */
+
+#endif
\ No newline at end of file
diff --git a/laos/src/dev/Makefile b/laos/src/dev/Makefile
new file mode 100644
index 0000000..c332099
--- /dev/null
+++ b/laos/src/dev/Makefile
@@ -0,0 +1,21 @@
+CURNAME		:= dev
+BUILD_DIR	:= $(TOP_BUILD_DIR)/$(CURNAME)
+
+CSRC		:= $(wildcard *.c)
+OBJS		:= $(patsubst %.c,%.o,$(CSRC))
+BUILD_OBJS	:= $(addprefix $(BUILD_DIR)/,$(OBJS))
+
+.PHONY: build all message
+
+all: message build
+
+$(BUILD_DIR):
+	@mkdir -p $(BUILD_DIR)
+
+$(BUILD_OBJS): $(BUILD_DIR)/%.o:%.c $(BUILD_DIR)
+	@$(CC) -c -o $@ $< $(CPPFLAGS) $(CFLAGS)
+
+build: $(BUILD_OBJS)
+
+message:
+	@echo "building $(CURNAME)"
\ No newline at end of file
diff --git a/laos/src/dev/serial.c b/laos/src/dev/serial.c
new file mode 100644
index 0000000..3e27f52
--- /dev/null
+++ b/laos/src/dev/serial.c
@@ -0,0 +1,31 @@
+#include "memlayout.h"
+#include "latype.h"
+#include "memio.h"
+#include "defs.h"
+
+struct spinlock serial_tx_lock;
+char serial_tx_buf[SERIAL_TX_BUF_SIZE];
+
+u32 serial_tx_w; // write next to serial_tx_buf[serial_tx_w % SERIAL_TX_BUF_SIZE]
+u32 serial_tx_r; // read next from serial_tx_buf[serial_tx_r % SERIAL_TX_BUF_SIZE]
+
+
+
+void serial_putc(int c) {
+    acquire(&serial_tx_lock);
+
+    // if(panicked){
+    //     for(;;)
+    //         ;
+    // }
+
+    while(serial_tx_w == serial_tx_r + SERIAL_TX_BUF_SIZE){
+        // buffer is full.
+        // wait for serialstart() to open up space in the buffer.
+        // sleep(&serial_tx_r, &serial_tx_lock);
+    }
+    serial_tx_buf[serial_tx_w % SERIAL_TX_BUF_SIZE] = c;
+    serial_tx_w += 1;
+    // serialstart();
+    release(&serial_tx_lock);
+}
\ No newline at end of file
diff --git a/laos/src/kernel/console.c b/laos/src/kernel/console.c
new file mode 100644
index 0000000..85aadc4
--- /dev/null
+++ b/laos/src/kernel/console.c
@@ -0,0 +1,28 @@
+#include "console.h"
+#include "memio.h"
+#include "memlayout.h"
+#include "spinlock.h"
+
+void consputc(int c) {
+    if (c == '\b') {
+        memb(SERIAL_ADDR) = '\b';
+        memb(SERIAL_ADDR) =  ' ';
+        memb(SERIAL_ADDR) = '\b';
+        return;
+    }
+
+    memb(SERIAL_ADDR) = c;
+}
+
+struct {
+  struct spinlock lock;
+  
+  // input
+#define INPUT_BUF_SIZE 128
+  char buf[INPUT_BUF_SIZE];
+  uint r;  // Read index
+  uint w;  // Write index
+  uint e;  // Edit index
+} cons;
+
+
diff --git a/laos/src/kernel/entry.S b/laos/src/kernel/entry.S
index 268c030..0b73253 100644
--- a/laos/src/kernel/entry.S
+++ b/laos/src/kernel/entry.S
@@ -8,13 +8,13 @@ _entry:
         # with a 4096-byte stack per CPU.
         # sp = stack0 + (hartid * 4096)
         la.global $sp, stack0
-        lu12i.w $a0, (1024*4 >> 12) & 0xfffff
-        addi.w $a0, $a0, 1024*4 & 0xfff
-        csrrd $a1, CPUID
-        addi.w $a1, $a1, 1
-        mul.w $a0, $a0, $a1
-        add.w $sp, $sp, $a0
+        lu12i.w   $a0, (1024*4 >> 12) & 0xfffff
+        addi.w    $a0, $a0, 1024*4 & 0xfff
+        csrrd     $a1, CPUID
+        addi.w    $a1, $a1, 1
+        mul.w     $a0, $a0, $a1
+        add.w     $sp, $sp, $a0
         # jump to start() in start.c
-        bl start
+        bl        start
 spin:
         b spin
\ No newline at end of file
diff --git a/laos/src/kernel/kprintf.c b/laos/src/kernel/kprintf.c
new file mode 100644
index 0000000..a78fad5
--- /dev/null
+++ b/laos/src/kernel/kprintf.c
@@ -0,0 +1,116 @@
+#include <stdarg.h>
+
+#include "latype.h"
+#include "console.h"
+#include "kprintf.h"
+#include "spinlock.h"
+
+volatile int panicked = 0;
+
+// lock to avoid interleaving concurrent printf's.
+static struct {
+  struct spinlock lock;
+  int locking;
+} pr;
+
+static char digits[] = "0123456789abcdef";
+
+static void print_int(int xx, int base, int sign) {
+    char buf[32];
+    int i;
+    uint x;
+    if (sign && (sign = xx < 0)) {
+        x = -xx;
+    } else {
+        x = xx;
+    }
+
+    i = 0;
+    do {
+        buf[i++] = digits[x % base];
+    } while ((x /= base) != 0);
+
+    if(sign) {
+        buf[i++] = '-';
+    }
+
+    while(--i >= 0)
+        consputc(buf[i]);
+}
+
+static void print_ptr(intptr_t x) {
+    consputc('0');
+    consputc('x');
+    for (int i = 0; i < (sizeof(intptr_t) * 2); i++, x <<= 4)
+        consputc(digits[x >> (sizeof(intptr_t) * 8 - 4)]);
+}
+
+void kprintf(char *fmt, ...) {
+    va_list ap;
+    int i, c, locking;
+    char *s;
+
+    locking = pr.locking;
+    if(locking)
+        acquire(&pr.lock);
+
+    if (fmt == 0)
+        panic("null fmt");
+
+    va_start(ap, fmt);
+    for (i = 0; (c = fmt[i] & 0xff) != 0; i++) {
+        if (c != '%') {
+            consputc(c);
+            continue;
+        }
+        c = fmt[++i] & 0xff;
+        if (c == 0) {
+            break;
+        }
+
+        switch (c) {
+        case 'd':
+            print_int(va_arg(ap, int), 10, 1);
+            break;
+        case 'x':
+            print_int(va_arg(ap, int), 16, 1);
+            break;
+        case 'p':
+            print_ptr(va_arg(ap, intptr_t));
+            break;
+        case 's':
+            if((s = va_arg(ap, char*)) == 0)
+                s = "(null)";
+            for(; *s; s++)
+                consputc(*s);
+            break;
+        case '%':
+            consputc('%');
+            break;
+        default:
+            // Print unknown % sequence to draw attention.
+            consputc('%');
+            consputc(c);
+            break;
+        }
+    }
+    va_end(ap);
+
+    if(locking)
+        release(&pr.lock);
+}
+
+void panic(char *s) {
+    pr.locking = 0;
+    kprintf("panic: ");
+    kprintf(s);
+    kprintf("\n");
+    panicked = 1; // freeze serial output from other CPUs
+    for(;;)
+        ;
+}
+
+void kprintf_init(void) {
+  initlock(&pr.lock, "pr");
+  pr.locking = 1;
+}
\ No newline at end of file
diff --git a/laos/src/kernel/main.c b/laos/src/kernel/main.c
index 52794b1..bfd4b9a 100644
--- a/laos/src/kernel/main.c
+++ b/laos/src/kernel/main.c
@@ -1,3 +1,25 @@
+#include "la32r.h"
+#include "spinlock.h"
+
+
+volatile static int started = 0;
+
 void main() {
+    struct spinlock lck[1];
+    initlock(lck, "main");
+    acquire(lck);
+    
+    if (r_cpuid() == 0) {
+
+
+        synchronize();
+        started = 1;
+    } else {
+        // 当前假定只有一个 hart
+        while (started == 0)
+            ;
+        synchronize();
+    }
+
 
 }
\ No newline at end of file
diff --git a/laos/src/kernel/proc.c b/laos/src/kernel/proc.c
new file mode 100644
index 0000000..be8cd1d
--- /dev/null
+++ b/laos/src/kernel/proc.c
@@ -0,0 +1,24 @@
+#include "proc.h"
+#include "la32r.h"
+#include "latype.h"
+
+struct cpu cpus[NCPU];
+
+struct proc proc[NPROC];
+
+struct proc *initproc;
+
+int nextpid = 1;
+struct spinlock pid_lock;
+
+// helps ensure that wakeups of wait()ing
+// parents are not lost. helps obey the
+// memory model when using p->parent.
+// must be acquired before any p->lock.
+struct spinlock wait_lock;
+
+struct cpu *mycpu() {
+    int id = r_cpuid();
+    struct cpu *c = &cpus[id];
+    return c;
+}
\ No newline at end of file
diff --git a/laos/src/kernel/spinlock.c b/laos/src/kernel/spinlock.c
new file mode 100644
index 0000000..c378221
--- /dev/null
+++ b/laos/src/kernel/spinlock.c
@@ -0,0 +1,54 @@
+#include "spinlock.h"
+#include "la32r.h"
+#include "defs.h"
+#include "kprintf.h"
+#include "proc.h"
+
+void initlock(struct spinlock *lck, char *name) {
+    lck->name = name;
+    lck->locked = 0;
+    lck->cpu = 0;
+}
+
+void acquire(struct spinlock *lck) {
+
+    if(holding(lck)) {
+        panic("acquire");
+    }
+
+
+    do {
+        // 如果已经上锁了，就等待
+        while (llw((intptr_t)&lck->locked) == 1)
+            ;
+    // 此时没有上锁，那就开始抢锁
+    // 没有抢成功就进入新的循环
+    } while (scw(1, (intptr_t)&lck->locked) != 1);
+
+    synchronize();
+    lck->cpu = mycpu();
+}
+
+void release(struct spinlock *lck) {
+    if (holding(lck) != 1) {
+        panic("release");
+    }
+
+    lck->cpu = NULL;
+
+    synchronize();
+
+    do {
+        // 标记上
+        llw((intptr_t)&lck->locked);
+
+    // 此时没有 hart 动，那就安全的释放
+    // 否则重新循环
+    } while (scw(0, (intptr_t)&lck->locked) != 1);
+}
+
+int holding(struct spinlock *lck) {
+  int r;
+  r = (lck->locked && lck->cpu == mycpu());
+  return r;
+}
\ No newline at end of file
diff --git a/laos/src/kernel/start.c b/laos/src/kernel/start.c
index 544d556..d699197 100644
--- a/laos/src/kernel/start.c
+++ b/laos/src/kernel/start.c
@@ -1,7 +1,20 @@
-#include "common.h"
+#include "kernel.h"
+#include "la32r.h"
 
 __attribute__ ((aligned (16))) char stack0[4096 * NCPU];
 
 void start() {
+    // 设置特权等级
+    volatile u32 crmd_info = r_crmd();
+    crmd_info = crmd_info & 0xfffffffc;
+    w_crmd(crmd_info);
 
+    // ERTN 返回地址
+    w_eentry((intptr_t)main);
+
+    // 设置 tp
+    int id = r_cpuid();
+    w_tp(id);
+
+    asm volatile("ertn");
 }
\ No newline at end of file
diff --git a/laos/src/lib/Makefile b/laos/src/lib/Makefile
new file mode 100644
index 0000000..2bd2ce9
--- /dev/null
+++ b/laos/src/lib/Makefile
@@ -0,0 +1,21 @@
+CURNAME		:= lib
+BUILD_DIR	:= $(TOP_BUILD_DIR)/$(CURNAME)
+
+CSRC		:= $(wildcard *.c)
+OBJS		:= $(patsubst %.c,%.o,$(CSRC))
+BUILD_OBJS	:= $(addprefix $(BUILD_DIR)/,$(OBJS))
+
+.PHONY: build all message
+
+all: message build
+
+$(BUILD_DIR):
+	@mkdir -p $(BUILD_DIR)
+
+$(BUILD_OBJS): $(BUILD_DIR)/%.o:%.c $(BUILD_DIR)
+	@$(CC) -c -o $@ $< $(CPPFLAGS) $(CFLAGS)
+
+build: $(BUILD_OBJS)
+
+message:
+	@echo "building $(CURNAME)"
\ No newline at end of file
diff --git a/laos/src/lib/path.c b/laos/src/lib/path.c
new file mode 100644
index 0000000..e69de29
diff --git a/laos/src/user/Makefile b/laos/src/user/Makefile
new file mode 100644
index 0000000..4ac8724
--- /dev/null
+++ b/laos/src/user/Makefile
@@ -0,0 +1,29 @@
+CURNAME		:= user
+BUILD_DIR	:= $(TOP_BUILD_DIR)/$(CURNAME)
+
+CSRC		:= $(wildcard *.c)
+OBJS		:= $(patsubst %.c,%.o,$(CSRC))
+BUILD_OBJS	:= $(addprefix $(BUILD_DIR)/,$(OBJS))
+BASENAMES	:= $(basename $(CSRC))
+BUILD_EXE	:= $(addprefix $(BUILD_DIR)/,$(BASENAMES))
+
+.PHONY: build all message
+
+all: message build
+
+$(BUILD_DIR):
+	@mkdir -p $(BUILD_DIR)
+
+$(BUILD_OBJS): $(BUILD_DIR)/%.o:%.c $(BUILD_DIR)
+	@$(CC) -c -o $@ $< $(CPPFLAGS) $(CFLAGS)
+
+$(BUILD_EXE): %:%.o
+	@$(CC) -o $@ $< $(CPPFLAGS) $(CFLAGS)
+
+build: $(BUILD_EXE)
+
+message:
+	@echo "building $(CURNAME)"
+
+native: $(BUILD_EXE)
+	@echo $(BASENAMES)
diff --git a/laos/src/user/echo.c b/laos/src/user/echo.c
new file mode 100644
index 0000000..974152b
--- /dev/null
+++ b/laos/src/user/echo.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char *argv[]) {
+    for (int i = 1; i < argc; i++) {
+        write(STDOUT_FILENO, argv[i], strlen(argv[i]));
+        if(i + 1 < argc){
+            write(STDOUT_FILENO, " ", 1);
+        } else {
+            write(STDOUT_FILENO, "\n", 1);
+        }
+    }
+    exit(0);
+}
\ No newline at end of file
diff --git a/laos/src/user/shell.c b/laos/src/user/shell.c
new file mode 100644
index 0000000..e69de29
diff --git a/laos/src/user/xargs.c b/laos/src/user/xargs.c
new file mode 100644
index 0000000..dec1b45
--- /dev/null
+++ b/laos/src/user/xargs.c
@@ -0,0 +1,49 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/wait.h>
+
+void remove_tail_newline(char *str, int len) {
+    if (len == 0) {
+        return;
+    }
+    if (str[len - 1] == '\n') {
+        str[len - 1] = '\0';
+    }
+}
+
+int main(int argc, char *argv[]) {
+    if (argc < 1) {
+        exit(EXIT_FAILURE);
+    }
+
+    char **args = malloc(argc * sizeof(char *));
+    memcpy(args, &argv[1], (argc - 1) * sizeof(char *));
+    argc -= 1;
+
+    const char *filename = argv[1];
+    char input[128];
+    read(STDIN_FILENO, input, 128);
+    remove_tail_newline(input, strlen(input));
+
+    char *tok = strtok(input, " ");
+    while (tok) {
+        if (*tok != '\n') {
+            args = realloc(args, (argc + 1) * sizeof(char *));
+            args[argc] = tok;
+            argc += 1;
+        }
+        tok = strtok(NULL, " ");
+    }
+
+    if (fork() == 0) {
+        execvp(filename, args);
+        exit(EXIT_FAILURE);
+    }
+
+    wait(NULL);
+    free(args);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/laos/src/util/memops.c b/laos/src/util/memops.c
deleted file mode 100644
index 9f55920..0000000
--- a/laos/src/util/memops.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <assert.h>
\ No newline at end of file
diff --git a/laos/src/util/string.c b/laos/src/util/string.c
new file mode 100644
index 0000000..c758f27
--- /dev/null
+++ b/laos/src/util/string.c
@@ -0,0 +1,93 @@
+#include "string.h"
+#include "latype.h"
+
+// mem ops could be more better
+// use loop unrolling
+
+void *memset(void *dst, int c, uint n) {
+    char *cdst = (char *) dst;
+    for (uint i = 0; i < n; ++i) {
+        cdst[i] = c;
+    }
+    return dst;
+}
+
+int memcmp(const void *m1, const void *m2, uint n) {
+    const uchar *s1, *s2;
+
+    s1 = m1;
+    s2 = m2;
+
+    while (n --> 0) {
+        if(*s1 != *s2)
+            return *s1 - *s2;
+        s1++;
+        s2++;
+    }
+
+    return 0;
+}
+
+void *memmove(void *dst, const void *src, uint n) {
+    const char *s;
+    char *d;
+
+    if(n == 0)
+        return dst;
+    
+    s = src;
+    d = dst;
+    if(s < d && s + n > d){
+        s += n;
+        d += n;
+        while(n-- > 0)
+            *--d = *--s;
+    } else
+        while(n-- > 0)
+            *d++ = *s++;
+
+    return dst;
+}
+
+void *memcpy(void *dst, const void *src, uint n) {
+    return memmove(dst, src, n);
+}
+
+int strncmp(const char *p, const char *q, uint n) {
+    while(n > 0 && *p && *p == *q)
+        n--, p++, q++;
+    if(n == 0)
+        return 0;
+    return (uchar)*p - (uchar)*q;
+}
+
+char *strncpy(char *s, const char *t, int n) {
+    char *os;
+
+    os = s;
+    while(n-- > 0 && (*s++ = *t++) != 0)
+        ;
+    while(n-- > 0)
+        *s++ = 0;
+    return os;
+}
+
+char *strcpy_s(char *s, const char *t, int n) {
+    char *os;
+
+    os = s;
+    if(n <= 0)
+        return os;
+    while(--n > 0 && (*s++ = *t++) != 0)
+        ;
+    *s = 0;
+    return os;
+}
+
+int strlen(const char *s) {
+    int n;
+
+    for(n = 0; s[n]; n++)
+        ;
+    return n;
+}
\ No newline at end of file