We very intermittently see failures in the single_thread_different_keys
PAC test. As noted in the comment in the test the PAC field can be quite
narrow so there is a chance of collisions even with different keys with a
chance of 5% for 7 bit keys, and the potential for narrower keys. The test
tries to avoid this by running repeatedly, but only tries 10 times which
even with a 5% chance of collisions isn't enough.
Increase the number of times we attempt to look for collisions by a factor
of 100, this also affects other tests which are following a similar pattern
with running the test repeatedly and either don't care like with
pac_instruction_not_nop or potentially have the same issue like
exec_sign_all.
The PAC tests are very fast, running in a second or two even in emulation,
so the 100x increased cost is mildly irritating but not a huge issue. The
bulk of the overhead is in the exec_sign_all test which does a fork() and
exec() per iteration.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241111-arm64-pac-test-collisions-v1-2-171875f37e44@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
PAuth signs and verifies return addresses on the stack. It does so by
inserting a Pointer Authentication code (PAC) into some of the unused top
bits of an address. This is achieved by adding paciasp/autiasp instructions
at the beginning and end of a function.
This feature is partially backwards compatible with earlier versions of the
ARM architecture. To coerce the compiler into emitting fully backwards
compatible code the main file is compiled to target an earlier ARM version.
This allows the tests to check for the feature and print meaningful error
messages instead of crashing.
Add a test to verify that corrupting the return address results in a
SIGSEGV on return.
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200918104715.182310-2-boian4o1@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
