[PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels

[Dave Martin]

In kernels which support v6 and v7 platforms in a single binary
such as omap2plus_defconfig for example, undefined instruction
exceptions taken on Thumb instructions are not processed correctly,
because the kernel assumes at build-time that Thumb-2 won't be
supported in userspace.

This series implements a workaround, by allowing the __und_usr
handler to check the CPU architecture at runtime, in affected
kernels.

Changes since v1:
  * Because cpu_architecture() is no longer trivial, it has been
    moveed back out of line, into setup.c.

Changes since RFC:
  * Renamed the global variable to __cpu_architecture and provided
    cpu_architecture() as in inline function in <asm/system.h>.
    This brings back the old API, but more efficiently.
  * Dropped all the patches required to handle the reverted API
    change.
  * cpu_architecture is now declared __pure, which may lead to
    slightly more efficient code in some cases.
  * Added BUG_ON() to cpu_architecture() so that if
    __cpu_architecture is not set early enough, it gets noticed.

Thanks to Tixy and Nicolas Pitre for their helpful feedback which
helped slim down this series.

Dave Martin (3):
  ARM: Make cpu_architecture into a global variable
  ARM: entry: Remove unnecessary masking when decoding Thumb-2
    instructions
  ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels

 arch/arm/include/asm/system.h |    3 +-
 arch/arm/kernel/entry-armv.S  |   44 ++++++++++++++++++++++++++++++++++++----
 arch/arm/kernel/setup.c       |   20 +++++++++++++++++-
 3 files changed, 60 insertions(+), 7 deletions(-)

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1.7.4.1