Sometimes, you’ll change things so much that make can’t figure out how to recompile the files correctly. make clean will remove all the object and kernel object files (ending in .o and .ko) and a few other things. make mrproper will do everything make clean does, plus remove your config file, the dependency files, and everything else that make config creates. Be sure to save your config file in another file before running make mrproper. Afterwards, copy the config file back to .config and start over, beginning at make menuconfig. A make mrproper will often fix strange kernel crashes that make no sense and strange compilation errors that make no sense.
make clean删除object和kernel object文件，还有其它一些文件。make mrproper是make clean的超集，它还会删除config文件，依赖文件，以及其它make config生成的文件。