Exclusive page-frame ownership

> Importantly, it's a kernel-space address and, on some systems (x86 before 3.9 and all ARM), this memory range is executable by the kernel.

I think that the paper is somewhat outdated w.r.t. its comments regarding ARM.

For arm, since v3.18, as of commit 1e6b48116a95046e ("ARM: mm: allow non-text sections to be non-executable"), the linear map is not executable, modulo a small overlap with the kernel text mapping.

For arm64, since v3.19, commit da141706aea52c1a ("arm64: add better page protections to arm64"), the linear map is not executable, modulo a small overlap with the kernel text mapping. v4.5 commit 068a17a5805dfbca ("arm64: mm: create new fine-grained mappings at boot") gets rid of that overlap.