diff --git a/libcpu/sim/posix/cpu_port.c b/libcpu/sim/posix/cpu_port.c
new file mode 100755
index 0000000000000000000000000000000000000000..919abc5209e34ce448c847274bc36cea2a418d0d
--- /dev/null
+++ b/libcpu/sim/posix/cpu_port.c
@@ -0,0 +1,447 @@
+#include <rtthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+#include <unistd.h>
+#include <semaphore.h>
+#include <time.h>
+#include <sys/time.h>
+
+//#define TRACE       printf
+#define TRACE(...)
+#define _DEBUG
+
+typedef struct _thread
+{
+    pthread_t pthread;
+    void (*task)(void *);
+    void *para;
+    void (*exit)(void);
+    sem_t sem;
+    rt_thread_t rtthread;
+    void *data;
+} thread_t;
+
+#define THREAD_T(thread)  ((thread_t *)thread)
+
+#define MSG_SUSPEND  SIGUSR1    /* 10 */
+/* #define MSG_RESUME   SIGUSR2 */
+#define MSG_TICK     SIGALRM    /* 14 */
+#define TIMER_TYPE   ITIMER_REAL
+#define MAX_INTERRUPT_NUM ((unsigned int)sizeof(unsigned int) * 8)
+
+
+/* #define INT_ENABLE   0
+ * #define INT_DISABLE  1
+ */
+/* flag in interrupt handling */
+rt_uint32_t rt_interrupt_from_thread, rt_interrupt_to_thread;
+rt_uint32_t rt_thread_switch_interrupt_flag;
+
+/* interrupt event mutex */
+static pthread_mutex_t *ptr_int_mutex;
+static pthread_cond_t cond_int_hit; /* interrupt occured! */
+static volatile unsigned int  cpu_pending_interrupts;
+static int (* cpu_isr_table[MAX_INTERRUPT_NUM])(void) = {0};
+
+static pthread_t mainthread_pid;
+
+/* function definition */
+static void start_sys_timer(void);
+static int tick_interrupt_isr(void);
+static void mthread_signal_tick(int sig);
+static int mainthread_scheduler(void);
+
+int signal_install(int sig, void (*func)(int))
+{
+    struct sigaction act;
+
+    /* set the signal handler */
+    act.sa_handler = func ;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = 0;
+    sigaction(sig, &act, 0);
+}
+
+int signal_mask(void)
+{
+    sigset_t  sigmask, oldmask;
+
+    /* set signal mask */
+    sigemptyset(&sigmask);
+    sigaddset(&sigmask, SIGALRM);
+    pthread_sigmask(SIG_BLOCK, &sigmask, &oldmask);
+}
+static void thread_switch_handler(int sig)
+{
+    pthread_t pid = pthread_self();
+    thread_t *thread_from;
+    thread_t *thread_to;
+    rt_thread_t tid;
+
+    if (sig != MSG_SUSPEND)
+    {
+        printf("get an unexpected signal <%d>, exit\n", sig);
+        exit(EXIT_FAILURE);
+    }
+
+    thread_from = (thread_t *) rt_interrupt_from_thread;
+    thread_to = (thread_t *) rt_interrupt_to_thread;
+
+    /* FIXME 注意！此时 rt_thread_self的值是to线程的值！ */
+    tid = rt_thread_self();
+    RT_ASSERT(thread_from->pthread == pid);
+    RT_ASSERT((thread_t *)(tid->sp) == thread_to);
+
+    TRACE("signal: SIGSUSPEND suspend <%s>\n", thread_from->rtthread->name);
+    sem_wait(&thread_from->sem);
+    TRACE("signal: SIGSUSPEND resume  <%s>\n", thread_from->rtthread->name);
+}
+
+static void *thread_run(void *parameter)
+{
+    rt_thread_t tid;
+    thread_t *thread;
+    thread = THREAD_T(parameter);
+    int res;
+
+    /* FIXME set signal mask, mask the timer! */
+    signal_mask();
+
+    TRACE("pid <%08x> stop on sem...\n", (unsigned int)(thread->pthread));
+    sem_wait(&thread->sem);
+
+    tid = rt_thread_self();
+    TRACE("pid <%08x> tid <%s> starts...\n", (unsigned int)(thread->pthread),
+          tid->name);
+    thread->rtthread = tid;
+    thread->task(thread->para);
+    TRACE("pid <%08x> tid <%s> exit...\n", (unsigned int)(thread->pthread),
+          tid->name);
+    //FIXME
+    thread->exit();
+    //sem_destroy(&thread->sem); //<--------------
+
+    pthread_exit(NULL);
+}
+static int thread_create(
+    thread_t *thread, void *task, void *parameter, void *pexit)
+{
+    int res;
+    pthread_attr_t attr;
+
+    thread->task = task;
+    thread->para = parameter;
+    thread->exit = pexit;
+
+    if (sem_init(&thread->sem, 0, 0) != 0)
+    {
+        printf("init thread->sem failed, exit \n");
+        exit(EXIT_FAILURE);
+    }
+    /* No need to join the threads. */
+    pthread_attr_init(&attr);
+    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+
+    /* create a posix thread */
+    res = pthread_create(&thread->pthread, &attr, &thread_run, (void *)thread);
+    if (res)
+    {
+        printf("pthread create faild, <%d>\n", res);
+        exit(EXIT_FAILURE);
+    }
+
+    return 0;
+}
+
+/* resume the thread */
+static int thread_resume(thread_t *thread)
+{
+    sem_post(& thread->sem);
+}
+
+
+rt_uint8_t *rt_hw_stack_init(
+    void *pEntry,
+    void *pParam,
+    rt_uint8_t *pStackAddr,
+    void *pExit)
+{
+    thread_t *thread;
+
+    thread = (thread_t *)(pStackAddr - sizeof(thread_t));
+
+    /* set the filed to zero */
+    memset(thread, 0x00, sizeof(thread_t));
+
+    thread_create(thread, pEntry, pParam, pExit);
+    //TRACE("thread %x created\n", (unsigned int)thread_table[t].pthread);
+
+    return (rt_uint8_t *) thread;
+}
+
+
+/* interrupt contex switch hit, value 1 or 0 */
+static long int_cs_hit;
+
+rt_base_t rt_hw_interrupt_disable(void)
+{
+    if (ptr_int_mutex != NULL)
+    {
+//        pthread_mutex_lock(ptr_int_mutex); //FIXME
+    }
+
+    /*TODO: It may need to mask the signal */
+    return 0;
+}
+
+void rt_hw_interrupt_enable(rt_base_t level)
+{
+    level = level;
+
+    if (ptr_int_mutex != NULL)
+    {
+//       pthread_mutex_unlock(ptr_int_mutex); //FIXME
+    }
+    /*TODO: It may need to unmask the signal */
+}
+
+void rt_hw_context_switch_interrupt(rt_uint32_t from,
+                                    rt_uint32_t to)
+{
+    rt_hw_context_switch(from, to);
+}
+
+void rt_hw_context_switch(rt_uint32_t from,
+                          rt_uint32_t to)
+{
+    struct rt_thread * tid;
+    pthread_t pid;
+    thread_t *thread_from;
+    thread_t *thread_to;
+
+    RT_ASSERT(from != to);
+
+#if 0
+    if (rt_thread_switch_interrupt_flag != 1)
+    {
+        rt_thread_switch_interrupt_flag = 1;
+
+        // set rt_interrupt_from_thread
+        rt_interrupt_from_thread = *((rt_uint32_t *)from);
+    }
+#endif
+    rt_interrupt_from_thread = *((rt_uint32_t *)from);
+    rt_interrupt_to_thread = *((rt_uint32_t *)to);
+
+    thread_from = (thread_t *) rt_interrupt_from_thread;
+    thread_to = (thread_t *) rt_interrupt_to_thread;
+
+    /* FIXME note: now, rt_current_thread is the thread_to! scheduler.c:272 */
+    tid = rt_thread_self();
+    pid = pthread_self();
+
+    /* 注意，只有两种可可能，一种是线程函数中调用此函数，一种是在中断中调用
+     * 而在中断调用是在主线程的信号处理函数中实现（目前只有tick中断）。
+     * 即, 只有如下两种可能:
+     * 1)普通RTT线程间接调用，如rt_thread_delay函数
+     * 2)或者主线程信号处理函数,如rt_tick_increase中调用
+     */
+    if (pid != mainthread_pid)
+    {
+        TRACE("conswitch: P in pid<%x> ,suspend <%s>, resume <%s>!\n",
+              (unsigned int)pid,
+              thread_from->rtthread->name,
+              thread_to->rtthread->name);
+        /* from线程就是当前rtt线程 */
+
+        /* 确定一下，这两个值一定是相等的！ */
+        RT_ASSERT(thread_from->pthread == pid);
+
+        /* 唤醒to线程 */
+        sem_post(& thread_to->sem);
+
+        /* 挂起from线程, 既然from线程就是当前线程，所以应该直接
+         * 挂起在这里
+         */
+        sem_wait(& thread_from->sem);
+    }
+    else
+    {
+        /* FIXME: 注意这段代码是在system tick 函数中执行的，
+         * 即此时位于主线程的SIGALRM信号处理函数中 */
+        TRACE("conswitch: S in pid<%x>  ,suspend <%s>, resume <%s>!\n",
+              (unsigned int)pid,
+              thread_from->rtthread->name,
+              thread_to->rtthread->name);
+
+        /* 挂起from线程 */
+        pthread_kill(thread_from->pthread, MSG_SUSPEND);
+
+        /* 唤醒to线程 */
+        sem_post(& thread_to->sem);
+    }
+}
+
+void rt_hw_context_switch_to(rt_uint32_t to)
+{
+    //set to thread
+    rt_interrupt_to_thread = *((rt_uint32_t *)(to));
+
+    //clear from thread
+    rt_interrupt_from_thread = 0;
+
+    //set interrupt to 1
+    rt_thread_switch_interrupt_flag = 0; //<------
+
+    //start the main thread scheduler
+    mainthread_scheduler();
+
+    //never reach here!
+    return;
+}
+
+static int mainthread_scheduler(void)
+{
+    int i, res;
+    thread_t *thread_from;
+    thread_t *thread_to;
+    pthread_mutex_t mutex;
+    pthread_mutexattr_t mutexattr;
+    unsigned int contex_switch_mask;
+
+    /* save the main thread id */
+    mainthread_pid = pthread_self();
+    TRACE("pid <%08x> mainthread\n", (unsigned int)(mainthread_pid));
+
+    /* register interrupts which is simulated for yield and systick */
+    //register_interrupt(CPU_INTERRUPT_YIELD, yield_interrupt_isr);
+    //register_interrupt(CPU_INTERRUPT_TICK, tick_interrupt_isr);
+
+    /* install signal handler of system tick */
+    signal_install(SIGALRM, mthread_signal_tick);
+    /* install signal handler used to suspend itself */
+    signal_install(MSG_SUSPEND, thread_switch_handler);
+
+    /* create a mutex and condition val, used to indicate interrupts occrue */
+    ptr_int_mutex = &mutex;
+    pthread_mutexattr_init(&mutexattr);
+    pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_RECURSIVE);
+    pthread_mutex_init(ptr_int_mutex, &mutexattr);
+    pthread_cond_init(&cond_int_hit, NULL);
+
+    /* start timer */
+    start_sys_timer();
+
+    /* FIXME: note that, cond var could not released earlier than pthread_con_wait */
+    /* trigger_interrupt(CPU_INTERRUPT_YIELD); */
+    thread_to = (thread_t *) rt_interrupt_to_thread;
+    thread_resume(thread_to);
+
+    for (;;)
+    {
+#if 0
+        pthread_mutex_lock(ptr_int_mutex);
+        /*Lock mutex and wait for signal.  Note that the pthread_cond_wait
+         *routine will automatically and atomically unlock mutex while it waits.
+         */
+        TRACE("mthread: wait cond val!\n");
+        pthread_cond_wait(&cond_int_hit, ptr_int_mutex);
+        TRACE("mthread: got cond val!\n");
+
+        pthread_mutex_unlock(ptr_int_mutex);
+#endif
+        //printf("main thread...\n");
+        sleep(1);
+    }
+
+    return 0;
+}
+
+/*
+ * Setup the systick timer to generate the tick interrupts at the required
+ * frequency.
+ */
+static void start_sys_timer(void)
+{
+    struct itimerval itimer, oitimer;
+    int us;
+
+    RT_ASSERT(RT_TICK_PER_SECOND <= 1000000 || RT_TICK_PER_SECOND >= 1);
+
+    us = 1000000 / RT_TICK_PER_SECOND - 1;
+
+    TRACE("start system tick!\n");
+    /* Initialise the structure with the current timer information. */
+    if (0 != getitimer(TIMER_TYPE, &itimer))
+    {
+        TRACE("get timer failed.\n");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Set the interval between timer events. */
+    itimer.it_interval.tv_sec = 0;
+    itimer.it_interval.tv_usec = us;
+    /* Set the current count-down. */
+    itimer.it_value.tv_sec = 0;
+    itimer.it_value.tv_usec = us;
+
+    /* Set-up the timer interrupt. */
+    if (0 != setitimer(TIMER_TYPE, &itimer, &oitimer))
+    {
+        TRACE("set timer failed.\n");
+        exit(EXIT_FAILURE);
+    }
+}
+
+static void mthread_signal_tick(int sig)
+{
+    pthread_t pid = pthread_self();
+
+    if (sig == SIGALRM)
+    {
+        TRACE("pid <%x> signal: SIGALRM enter!\n", (unsigned int)pid);
+        tick_interrupt_isr();
+        TRACE("pid <%x> signal: SIGALRM leave!\n", (unsigned int)pid);
+    }
+    else
+    {
+        TRACE("got an unexpected signal <%d>\n", sig);
+        exit(EXIT_FAILURE);
+    }
+}
+
+/* isr return value: 1, should not be masked, if 0, can be masked */
+static int tick_interrupt_isr(void)
+{
+    TRACE("isr: systick enter!\n");
+    /* enter interrupt */
+    rt_interrupt_enter();
+
+    rt_tick_increase();
+
+    /* leave interrupt */
+    rt_interrupt_leave();
+
+    TRACE("isr: systick leave!\n");
+    return 0;
+}
+
+#if 0
+
+static void trigger_interrupt(int index)
+{
+    if ((index < MAX_INTERRUPT_NUM) && ptr_int_mutex != NULL)
+    {
+        pthread_mutex_lock(ptr_int_mutex);
+        cpu_pending_interrupts |= (1 << index);
+
+        /* signal the condition val */
+        pthread_cond_signal(&cond_int_hit);
+
+        pthread_mutex_unlock(ptr_int_mutex);
+    }
+}
+#endif
+