Version 3 of the speculative execution improvements for s390. Changes to v2:
* Dropped the prctl to introduce the PR_ISOLATE_BP control and simply added two exported functions s390_isolate_bp and s390_isolate_bp_guest. There is currently no caller for these functions, for now an out-of-tree module can be used until an acceptable upstream solution for the user space interface is found. * Added an optimized version for the the array_index_mask_nospec function based on subtract with borrow for the spectre v1 defense. * Introduce "expoline", the s390 version of a retpoline. As s390 does not have a return instruction and the associate return stack we use an execute-type instruction on an indirect branch to get unpredicatable branches. This requires gcc support for -mindirect-branch=thunk / -mfunction-return=thunk. To be able to disable expolines there is another gcc option -mindirect-branch-table to keep a list of PC relative locations of calls to the execute thunks. With spectre_v2=off the call will be replaced with the original indirect branch and a nop. Martin Schwidefsky (6): s390: scrub registers on kernel entry and KVM exit s390: add optimized array_index_mask_nospec s390/alternative: use a copy of the facility bit mask s390: add options to change branch prediction behaviour for the kernel s390: run user space and KVM guests with modified branch prediction s390: introduce execute-trampolines for branches arch/s390/Kconfig | 45 ++++++ arch/s390/Makefile | 12 ++ arch/s390/include/asm/barrier.h | 24 ++++ arch/s390/include/asm/facility.h | 18 +++ arch/s390/include/asm/lowcore.h | 9 +- arch/s390/include/asm/nospec-branch.h | 18 +++ arch/s390/include/asm/processor.h | 4 + arch/s390/include/asm/thread_info.h | 4 + arch/s390/kernel/Makefile | 4 + arch/s390/kernel/alternative.c | 26 +++- arch/s390/kernel/early.c | 5 + arch/s390/kernel/entry.S | 249 ++++++++++++++++++++++++++++++---- arch/s390/kernel/ipl.c | 1 + arch/s390/kernel/module.c | 62 +++++++-- arch/s390/kernel/nospec-branch.c | 100 ++++++++++++++ arch/s390/kernel/processor.c | 18 +++ arch/s390/kernel/setup.c | 8 +- arch/s390/kernel/smp.c | 7 +- arch/s390/kernel/vmlinux.lds.S | 14 ++ drivers/s390/char/Makefile | 2 + 20 files changed, 591 insertions(+), 39 deletions(-) create mode 100644 arch/s390/include/asm/nospec-branch.h create mode 100644 arch/s390/kernel/nospec-branch.c -- 2.7.4
