链接器脚本编写语法问题

OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS{
. = 0x50008000;

. = ALIGN(4);
.text:
{
start.o(.text)
*(.text)
}

. = ALIGN(4);
.data:
{
*(.data)
}

. = ALIGN(4);
bss_start = . ;
.bss:
{
*(.bss)
}
bss_end = . ;
}