arm64: move thread_info off of the task stack

Hi all,

Building atop of Andy's work on x86 and generic code, these patches move arm64's thread_info off of the stack and into task_struct. This protects thread_info from corruption in the face of stack overflow, and serves as a step towards fully robust stack overflow handling, which will be addressed by subsequent patches.

The patches are based atop of a couple or preparatory patches (also needed for s390) which I've placed in my kernel.org repo, tagged as core-ti-stack-split. I expect this to be a stable base for both arm64 and s390.

This series, atop of that, is in the arm64/ti-stack-split branch [2].

Since RFC [3]:
* Rely on prior patches to make thread_info arch-specific
* Make smp_processor_id() use a per-cpu variable
* Split out current_stack_pointer
* Make SMP actually work

Since v1 [4]:
* Fix irq stack entry from EL1
* Fix single step entry from EL0
* Add Laura's Tested-by
* Make comments more helpful
* Make asm-offsets use task_struct, and s/TI_*/TSK_TI_*/
* Add patch to unexport walk_stackframe

[1] https://git.kernel.org/cgit/linux/kernel/git/mark/linux.git/log/?h=core-ti-stack-split
[2] https://git.kernel.org/cgit/linux/kernel/git/mark/linux.git/log/?h=arm64/ti-stack-split
[3] https://lkml.kernel.org/r/1473947349-14521-1-git-send-email-mark.rutland at arm.com
[4] https://lkml.kernel.org/r/1476904234-9511-1-git-send-email-mark.rutland at arm.com

Thanks,
Mark.

Mark Rutland (11):
arm64: thread_info remove stale items
arm64: asm-offsets: remove unused definitions
arm64: factor out current_stack_pointer
arm64: traps: simplify die() and __die()
arm64: unexport walk_stackframe
arm64: prep stack walkers for THREAD_INFO_IN_TASK
arm64: move sp_el0 and tpidr_el1 into cpu_suspend_ctx
arm64: smp: prepare for smp_processor_id() rework
arm64: make cpu number a percpu variable
arm64: assembler: introduce ldr_this_cpu
arm64: split thread_info from task stack

 arch/arm64/Kconfig                     |  1 +
 arch/arm64/include/asm/Kbuild          |  1 -
 arch/arm64/include/asm/assembler.h     | 19 +++++++++++----
 arch/arm64/include/asm/current.h       | 22 +++++++++++++++++
 arch/arm64/include/asm/percpu.h        |  2 ++
 arch/arm64/include/asm/perf_event.h    |  2 ++
 arch/arm64/include/asm/smp.h           | 12 +++++++++-
 arch/arm64/include/asm/stack_pointer.h |  9 +++++++
 arch/arm64/include/asm/suspend.h       |  2 +-
 arch/arm64/include/asm/thread_info.h   | 32 +------------------------
 arch/arm64/kernel/asm-offsets.c        | 10 ++++----
 arch/arm64/kernel/entry.S              | 43 +++++++++++++++++-----------------
 arch/arm64/kernel/head.S               | 11 +++++----
 arch/arm64/kernel/process.c            | 36 +++++++++++++++++++++++-----
 arch/arm64/kernel/return_address.c     |  1 +
 arch/arm64/kernel/sleep.S              |  3 ---
 arch/arm64/kernel/smp.c                | 14 ++++++++---
 arch/arm64/kernel/stacktrace.c         |  7 +++++-
 arch/arm64/kernel/suspend.c            |  6 -----
 arch/arm64/kernel/traps.c              | 19 +++++++++------
 arch/arm64/mm/proc.S                   |  6 +++++
 21 files changed, 162 insertions(+), 96 deletions(-)
 create mode 100644 arch/arm64/include/asm/current.h
 create mode 100644 arch/arm64/include/asm/stack_pointer.h

2.7.4