What's the script language inside kernel Makefile?

Question

55 ifeq ("$(origin C)", "command line")
56   KBUILD_CHECKSRC = $(C)
57 endif
58 ifndef KBUILD_CHECKSRC
59   KBUILD_CHECKSRC = 0
60 endif

In normal bash,there's no keywords like ifndef...

Answer 1

(GNU)-Make has it's own syntax and the ifeq, ifndef, endif are comming from there. See the GNU Make Documentation.