feat:添加symlink系统调用 (#984)

* 添加symlink系统调用

* 修改FATInode的dname的获取逻辑

* 修改fat对Dname的处理，分离dname和inode缓存的key

---------

Co-authored-by: sparkzky <sparkhhhhhhhhh@outlook.com>
Co-authored-by: longjin <longjin@DragonOS.org>

kernel/src/syscall/mod.rs

@@ -346,6 +346,20 @@ impl Syscall {
                 Self::unlinkat(dirfd, path, flags)
             }
 
+            #[cfg(target_arch = "x86_64")]
+            SYS_SYMLINK => {
+                let oldname = args[0] as *const u8;
+                let newname = args[1] as *const u8;
+                Self::symlink(oldname, newname)
+            }
+
+            SYS_SYMLINKAT => {
+                let oldname = args[0] as *const u8;
+                let newdfd = args[1] as i32;
+                let newname = args[2] as *const u8;
+                Self::symlinkat(oldname, newdfd, newname)
+            }
+
             #[cfg(target_arch = "x86_64")]
             SYS_RMDIR => {
                 let path = args[0] as *const u8;