[U-Boot-Users] A question about _armboot_start

I am now studying uboot, and have some confusion about the Arm related boot code. In the specific board code file Start.S: _armboot_start is the address of the beginning of the start.o, and TEXT_BASE is the beginning address of boot code relocated in RAM, but when in the file lib_arm\board.c, there is a statement in the function start_armboot : gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t)); it seems that here _armboot_start is equal to TEXT_BASE???? but _armboot_start and TEXT_BASE both are constant, does it mean _armboot_start can be channged during relocating? how it happened?