前面加个TAB空格试一试.

多谢楼上的高手指点，但又出现了新的问题，请大虾指点

我在complie时没警告，但在make时出现了三个警告：

MyUart.s
IMPORT Main
AREA selfboot,CODE,READONLY
ENTRY
LDR R0, = 0X3FF0000
LDR R1, = 0XE7FFFF80
STR R1,[R0]
LDR SP, =0X3FE1000
BL Main
B .
END
ARM Linker中的Layout为：
Place at beginning of image:
Object/Symbol:MyUart.o
Section:seflboot

Warning: L6304W: Duplicate input file E:\armApp\MyUart\MyUart_Data\debugRel\ObjectCode\MyUart.o ignored
Warning: L6319W: Ignoring -first command. Cannot find section MyUart.o(selfboot.)
Warning: L6305W: Image does not have an entry point.(Not specified or not set due to multiple choice.)