ILOG2_4MB
kern_base = (prom_boot_mapping_phys_low >> ILOG2_4MB) << ILOG2_4MB;
num_kernel_image_mappings = DIV_ROUND_UP(real_end - KERNBASE, 1 << ILOG2_4MB);
phys_page = (prom_boot_mapping_phys_low >> ILOG2_4MB) << ILOG2_4MB;