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

Dave Martin Dave.Martin@arm.com
Thu Jun 6 16:45:00 GMT 2019

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.

Dave Martin (2):
  arm64/sve: Factor out FPSIMD to SVE state conversion
  arm64/sve: Fix missing SVE/FPSIMD endianness conversions

 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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