增加x87FPU支持 (#212)

* remove `ret_from_syscall`
*修复ps2键盘驱动程序inode在进程fork的时候导致死锁的问题.
*更新: VFS每次拷贝文件描述符的时候,都会去调用inode的open函数

---------

Co-authored-by: longjin <longjin@RinGoTek.cn>

user/apps/about/about.c

@@ -36,9 +36,8 @@ void print_copyright()
 }
 
 int main()
-{
+{   
     print_ascii_logo();
-
     print_copyright();
 
     return 0;

user/apps/shell/cmd.c

@@ -486,6 +486,7 @@ int shell_cmd_exec(int argc, char **argv)
         char *file_path = get_target_filepath(argv[1], &path_len);
         // printf("before execv, path=%s, argc=%d\n", file_path, argc);
         execv(file_path, argv);
+        // printf("after execv, path=%s, argc=%d\n", file_path, argc);
         free(argv);
         free(file_path);
 
@@ -497,10 +498,8 @@ int shell_cmd_exec(int argc, char **argv)
         if (strcmp(argv[argc - 1], "&") != 0)
             waitpid(pid, &retval, 0);
         else
-        {
-            // 输出子进程的pid
-            printf("[1] %d\n", pid);
-        }
+            printf("[1] %d\n", pid); // 输出子进程的pid
+        
         free(argv);
     }
 }

user/apps/test_signal/main.c

@@ -18,11 +18,11 @@
  */
 
 #include <math.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <unistd.h>
-#include <signal.h>
 
 bool handle_ok = false;
 
@@ -39,6 +39,7 @@ int main()
     printf("registered.\n");
 
     clock_t last = clock();
+
     while (1)
     {
         if ((clock() - last) / CLOCKS_PER_SEC >= 1)