On 09/15/2016 06:49 AM, Mark Rutland wrote:
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 will be addressed by
subsequent patches.

In contrast to x86, we can't place some critical data such as
preempt_count in percpu variables, and we must store these in some
per-task location. This, compounded with the way headers are organised
conspires to require us to still define our own thread_info. I
understand that the longer term plan is to kill off thread_info
entirely, hence I'm sending this as an RFC so we can figure out if/how
we can achieve that.

These patches are based on Andy's x86/vmap_stack branch [1,2], and I've
pushed a copy to me arm64/ti-stack-split branch [3,4]. The result of
these patches boots happily on platforms within reach of my desk, but
has not seen much stressing so far.

FWIW, I used your ti-stack-split branch while running some kernel builds
and it seems to work well enough. You can take that as a Tested-by or I
can re-test with a non-RFC version.


[1] git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack
[3] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git 

Mark Rutland (8):
  thread_info: include <current.h> for THREAD_INFO_IN_TASK
  thread_info: allow custom in-task thread_info
  arm64: thread_info remove stale items
  arm64: asm-offsets: remove unused definitions
  arm64: assembler: introduce ldr_this_cpu
  arm64: traps: use task_struct instead of thread_info
  arm64: move sp_el0 and tpidr_el1 into cpu_suspend_ctx
  arm64: split thread_info from task stack

 arch/arm64/Kconfig                   |  2 ++
 arch/arm64/include/asm/Kbuild        |  1 -
 arch/arm64/include/asm/assembler.h   | 19 +++++++++++++++----
 arch/arm64/include/asm/current.h     | 22 ++++++++++++++++++++++
 arch/arm64/include/asm/smp.h         |  1 +
 arch/arm64/include/asm/suspend.h     |  2 +-
 arch/arm64/include/asm/thread_info.h | 21 ---------------------
 arch/arm64/kernel/asm-offsets.c      |  3 +--
 arch/arm64/kernel/entry.S            |  6 +++---
 arch/arm64/kernel/head.S             | 11 +++++------
 arch/arm64/kernel/process.c          | 31 ++++++++++++++++++++++++++-----
 arch/arm64/kernel/sleep.S            |  3 ---
 arch/arm64/kernel/smp.c              |  2 ++
 arch/arm64/kernel/stacktrace.c       |  5 +++++
 arch/arm64/kernel/suspend.c          |  6 ------
 arch/arm64/kernel/traps.c            | 12 ++++++------
 arch/arm64/mm/proc.S                 |  6 ++++++
 include/linux/thread_info.h          |  4 +++-
 init/Kconfig                         |  3 +++
 19 files changed, 101 insertions(+), 59 deletions(-)
 create mode 100644 arch/arm64/include/asm/current.h

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