Kconfig (#432)

* 内核编译配置

* 将kernel.config的解析代码搬入crate

* 将设置feature函数放入CargoHandler中

docs/index.rst

@@ -30,6 +30,7 @@
    kernel/ktest/index
    kernel/cpu_arch/index
    kernel/libs/index
+   kernel/configuration/index
 
 
 .. toctree::

docs/kernel/configuration/config.md

@@ -0,0 +1,105 @@
+# 内核编译配置说明
+
+## 原理
+
+  在内核目录下，用kernel.config来设置内核编译配置信息，以类似解析toml文件的方式去解析该文件，然后接着去解析各模块下的d.config以获取feature的启用情况
+
+## 示例
+
+**kernel.config**
+
+```toml
+[[module.include]]
+name = "init"
+path = "src/init/"
+enable = "y"
+description = ""
+
+[[module.include]]
+name = "mm"
+path = "src/mm/"
+enable = "y"
+description = ""
+```
+
+
+- **[[module.include]]:** 将模块加入到include列表中
+- **name:** 模块名
+- **path:** 模块路径，存放着d.config
+- **enable:**
+  - **y:** 启用，解析模块下的d.config
+  - **n:** 不启用，不解析
+- **description:** 模块的描述信息
+
+
+**src/mm/d.config**
+
+```toml
+[module]
+name = "mm"
+description = ""
+
+[[module.include]]
+name = "allocator"
+path = "src/mm/allocator/"
+enable = "y"
+description = ""
+
+[[module.features]]
+name = "mm_debug"
+enable = "y"
+description = ""
+```
+
+
+- **\[module\]:** 当前模块
+  - **name:** 当前模块名称
+  - **description:** 模块的描述信息
+- **[[module.include]]:** 当前模块下所包含的模块，与kernel.config下的相同
+- **[[module.features]]:** 当前模块下的feature
+  - **name:** feature名
+  - **enable:** 是否开启
+    - **y:** 开启
+    - **n:** 不开启
+  - **description:** feature的描述信息
+
+
+*以下是其它模块下的d.config：*
+
+**src/mm/allocator/d.config**
+
+```toml
+[module]
+name = "allocator"
+description = ""
+
+[[module.features]]
+name = "allocator_debug"
+enable = "y"
+description = ""
+```
+
+**src/init/d.config**
+
+```toml
+[module]
+name = "init"
+description = ""
+
+[[module.features]]
+name = "init_debug"
+enable = "y"
+description = ""
+```
+
+
+上面所有已开启模块的d.config中的feature，会最终生成到内核目录下的D.config文件，即D.config是最终内核编译的配置，如下：
+
+
+**D.config**
+
+```
+init_debug = y
+allocator_debug = y
+mm_debug = y
+```

docs/kernel/configuration/index.rst

@@ -0,0 +1,9 @@
+内核编译配置
+====================================
+    
+   
+.. toctree::
+   :maxdepth: 1
+   :caption: 目录
+
+   config