[PATCH v2 0/3] arm64/sve: Fix mutating register endianness on big-endian

Dave Martin Dave.Martin@arm.com
Wed Jun 12 16:00:00 GMT 2019

This is a respin of [1], swapping the first two patches so that (new)
patch 1 can go to stable stand-alone without depending on patch 2.

I've also smuggled in a new trivial patch 3, that just replaces a
couple of magic numbers for which there is now a suitable #define to
use, which have been bugging me for a while.

Original blurb:

By inspection while debugging something else, I noticed that the byte
order of FPSIMD V-register stores and SVE Z-register stores is not the
same when running on big-endian.

This is not properly taken into account when moving between the FPSIMD
and SVE register views inside the kernel, resulting in the bytes of a
V-register getting spontaneously reversed in some situations, from
userspace's point of view.  The signal frame and ptrace interface are
also affected.  The KVM ABI forbids mixing the two views and so should
not be affected.

See patch 2 for details.

Patch 1 does some trivial preparatory refactoring.

gdb may or may not be affected by this, depending on how it uses the
NT_PRFPREG and NT_ARM_SVE regsets.  I'll leave it to the developers to
assess that.

[1] [PATCH 0/2] arm64/sve: Fix mutating register endianness on big-endian

Dave Martin (3):
  arm64/sve: Fix missing SVE/FPSIMD endianness conversions
  arm64/sve: Factor out FPSIMD to SVE state conversion
  arm64/sve: Fix a couple of magic numbers for the Z-reg count

 Documentation/arm64/sve.txt              | 16 +++++++++++
 arch/arm64/include/uapi/asm/kvm.h        |  7 +++++
 arch/arm64/include/uapi/asm/ptrace.h     |  4 +++
 arch/arm64/include/uapi/asm/sigcontext.h | 14 +++++++++
 arch/arm64/kernel/fpsimd.c               | 49 ++++++++++++++++++++++++--------
 5 files changed, 78 insertions(+), 12 deletions(-)


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