When to hide kernel structures from userspace and when to not hide them?

Newer versions of our linux distributions had their includes revised: A lot of kernel structures that were previously exported to userspace now are not exported anymore. To take an example, definitions of page size (macro PAGE_SIZE), usually found on asm/page.h, that used to be available when one installed the kernel-headers (or equivalent) package. I see… Read More When to hide kernel structures from userspace and when to not hide them?