kselftest/arm64: Fix enumeration of systems without 128 bit SME

The current signal handling tests for SME do not account for the fact that
unlike SVE all SME vector lengths are optional so we can't guarantee that
we will encounter the minimum possible VL, they will hang enumerating VLs
on such systems. Abort enumeration when we find the lowest VL.

Fixes: 4963aeb35a9e ("kselftest/arm64: signal: Add SME signal handling tests")
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230131-arm64-kselftest-sig-sme-no-128-v1-1-d47c13dc8e1e@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Include larger SVE and SME VLs in signal tests

Now that the core utilities for signal testing support handling data in
EXTRA_CONTEXT blocks we can test larger SVE and SME VLs which spill over
the limits in the base signal context. This is done by defining storage
for the context as a union with a ucontext_t and a buffer together with
some helpers for getting relevant sizes and offsets like we do for
fake_sigframe, this isn't the most lovely code ever but is fairly
straightforward to implement and much less invasive to the somewhat
unclear and indistinct layers of abstraction in the signal handling test
code.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829160703.874492-11-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Allow larger buffers in get_signal_context()

In order to allow testing of signal contexts that overflow the base signal
frame allow callers to pass the buffer size for the user context into
get_signal_context(). No functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829160703.874492-10-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Enumerate SME rather than SVE vector lengths for za_regs

The za_regs signal test was enumerating the SVE vector lengths rather than
the SME vector lengths through cut'n'paste error when determining what to
test. Enumerate the SME vector lengths instead.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829160703.874492-2-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Tighten up validation of ZA signal context

Currently we accept any size for the ZA signal context that the shared
code will accept which means we don't verify that any data is present.
Since we have enabled ZA we know that there must be data so strengthen
the check to only accept a signal frame with data, and while we're at it
since we enabled ZA but did not set any data we know that ZA must contain
zeros, confirm that.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829155728.854947-2-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: signal: Add SME signal handling tests

Add test cases for the SME signal handing ABI patterned off the SVE tests.
Due to the small size of the tests and the differences in ABI (especially
around needing to account for both streaming SVE and ZA) there is some code
duplication here.

We currently cover:
- Reporting of the vector length.
- Lack of support for changing vector length.
- Presence and size of register state for streaming SVE and ZA.

As with the SVE tests we do not yet have any validation of register
contents.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-36-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>