[PATCH 0/5] arm: Early IRQ enabling in the Undef user handler

[catalin.marinas@arm.com (Catalin Marinas)]

The __und_usr handler accesses the user space to read the opcode of the
faulting instruction. This is currently done with interrupts disabled
but it could potentially cause a data abort of the page table was
modified from another CPU. The data abort with interrupts disabled
triggers a might_sleep() warning in do_page_fault() or, worse, deadlock
on the pte lock when TLB ops broadcasting is enabled (ARM11MPCore or A15
together with workaround for erratum 798181).

To enable interrupts earlier, the preemption needs to be disabled in the
crunch and iwmmxt handlers. The series needs testing on such hardware.

(an alternative simpler patch would be to enable the interrupts only
around the user access instructions in __und_usr and disable them
afterwards, so I would rather do it as in this series).

Catalin Marinas (5):
  arm: Move asm macro get_thread_info to asm/assembler.h
  arm: Add {inc,dec}_preempt_count asm macros
  arm: Disable preemption in iwmmxt_task_enable()
  arm: Disable preemption in crunch_task_enable()
  arm: Enable IRQs before attempting to read user space in __und_usr

 arch/arm/include/asm/assembler.h   | 42 ++++++++++++++++++++++++++++++++++++++
 arch/arm/kernel/entry-armv.S       | 11 ++++++----
 arch/arm/kernel/entry-header.S     | 11 ----------
 arch/arm/kernel/iwmmxt.S           | 15 ++++++++++----
 arch/arm/mach-ep93xx/crunch-bits.S | 13 +++++++++---
 arch/arm/vfp/entry.S               | 28 ++++++++-----------------
 arch/arm/vfp/vfphw.S               | 19 ++++++-----------
 7 files changed, 84 insertions(+), 55 deletions(-)