To address the "offset2lib" ASLR weakness[1], this separates ET_DYN ASLR from mmap ASLR, as already done on s390. The architectures that are already randomizing mmap (arm, arm64, mips, powerpc, s390, and x86), have their various forms of arch_mmap_rnd() made available via the new CONFIG_ARCH_HAS_ELF_RANDOMIZE. For these architectures, arch_randomize_brk() is collapsed as well. This is an alternative to the solutions in: https://lkml.org/lkml/2015/2/23/442 I've been able to test x86 and arm, and the buildbot (so far) seems happy with building the rest. Thanks! -Kees [1] http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html v4: - added Ack on powerpc (mpe) - fixed mmap_base argument convention to be the same on all archs - corrected paste-o in mips variable names (buildbot) - clarified ET_DYN vs mmap ASLR regions in 9/10 (mpe) v3: - split change on a per-arch basis for easier review - moved PF_RANDOMIZE check out of per-arch code (ingo) v2: - verbosified the commit logs, especially 4/5 (akpm)
