syscall lab need to finish

user/trace.c

@@ -0,0 +1,29 @@
+#include "kernel/param.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+int
+main(int argc, char *argv[])
+{
+  int i;
+  //存储待跟踪程序的名称和参数
+  char *nargv[MAXARG];
+
+  //保证trace的参数不少于三个，并且跟踪的系统调用号在0-99之间
+  if(argc < 3 || (argv[1][0] < '0' || argv[1][0] > '9')){
+    fprintf(2, "Usage: %s mask command\n", argv[0]);
+    exit(1);
+  }
+  //调用trace系统调用，传入待跟踪系统调用号
+  if (trace(atoi(argv[1])) < 0) {
+    fprintf(2, "%s: trace failed\n", argv[0]);
+    exit(1);
+  }
+  //保存待跟踪程序的名称和参数
+  for(i = 2; i < argc && i < MAXARG; i++){
+    nargv[i-2] = argv[i];
+  }
+  //运行待跟踪的程序
+  exec(nargv[0], nargv);
+  exit(0);
+}