When SME support was merged support for TPIDR2 in signal frames was omitted, meaning that it was not possible for signal handers to inspect or modify it. This will present an issue for programs using signals to implement lightweight threads so let's provide access to TPIDR2 in signal handlers.

Implement a new record type for TPIDR2 using the same format as we use for ESR and add coverage to make sure that this appears in the signal context as expected. Due to TPIDR2 being reserved for libc we only validate that the value is unchanged, meaning we're likely to just be validating the default value of 0 on current systems. I have tested with a modified version that sets an explicit value.

v3: - Rebase onto v6.2-rc1. v2: - Rebase onto v6.1-rc3. - Change the signal frame magic to 0x54504902 (TPI).

To: Catalin Marinas catalin.marinas@arm.com To: Will Deacon will@kernel.org To: Shuah Khan shuah@kernel.org Cc: Szabolcs Nagy szabolcs.nagy@arm.com Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kselftest@vger.kernel.org Signed-off-by: Mark Brown broonie@kernel.org

--- Mark Brown (4): arm64/sme: Document ABI for TPIDR2 signal information arm64/signal: Include TPIDR2 in the signal context kselftest/arm64: Add TPIDR2 to the set of known signal context records kselftest/arm64: Add test case for TPIDR2 signal frame records

Documentation/arm64/sme.rst | 3 + arch/arm64/include/uapi/asm/sigcontext.h | 8 ++ arch/arm64/kernel/signal.c | 59 ++++++++++++++ tools/testing/selftests/arm64/signal/.gitignore | 1 + .../selftests/arm64/signal/testcases/testcases.c | 4 + .../arm64/signal/testcases/tpidr2_siginfo.c | 90 ++++++++++++++++++++++ 6 files changed, 165 insertions(+) --- base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2 change-id: 20221208-arm64-tpidr2-sig-8fbb93725d8e

Best regards,