diff --git a/b/2/munmap.c b/b/2/munmap.c
new file mode 100644
index 0000000..ddda571
--- /dev/null
+++ b/b/2/munmap.c
@@ -0,0 +1,70 @@
+/*
+ * 测试成功时输出：
+ * "munmap success."
+ * 测试失败时输出：
+ * "munmap error."
+ */
+#define __LIBRARY__
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include "new.h"
+
+_syscall2(int,munmap,void *,addr,size_t,length)
+
+void *mmap(void *addr, size_t length, ...)
+{
+	register int res;
+	va_list arg;
+
+	va_start(arg,length);
+	__asm__("int $0x80"
+		:"=a" (res)
+		:"0" (__NR_open),"b" (addr),"c" (length),
+		"d" (va_arg(arg,int)));
+	if (res>=0)
+		return (void *)res;
+	errno = -res;
+	return (void *)-1;
+}
+
+static struct stat kst;
+void test_unmmap(void){
+    char *array;
+    const char *str = "  Hello, mmap success.";
+    int fd, ret;
+
+    fd = open("test_mmap.txt", O_RDWR | O_CREAT, S_IRUSR|S_IWUSR);
+    write(fd, str, strlen(str));
+    fstat(fd, &kst);
+    printf("file len: %d\n", (int)kst.st_size);
+    array = mmap(NULL, kst.st_size, PROT_WRITE | PROT_READ, MAP_FILE | MAP_SHARED, fd, 0);
+    printf("mmap addr: %x\n", (unsigned int)array);
+
+    if (array == MAP_FAILED) {
+	    printf("mmap error.\n");
+    }else{
+	    printf("mmap content: %s\n", array);
+
+    	ret = munmap(array, kst.st_size);
+        printf("munmap return: %d\n", ret);
+        
+        if (ret == 0) {
+            printf("munmap success.\n");
+        } else {
+            printf("munmap error.\n");
+        }
+    }
+
+    close(fd);
+}
+
+int main(void){
+    test_unmmap();
+    return 0;
+}