selftests/powerpc: Fix exit status of pkey tests

Since main() does not return a value explicitly, the
return values from FAIL_IF() conditions are ignored
and the tests can still pass irrespective of failures.
This makes sure that we always explicitly return the
correct test exit status.

Fixes: 1addb6444791 ("selftests/powerpc: Add test for execute-disabled pkeys")
Fixes: c27f2fd1705a ("selftests/powerpc: Add test for pkey siginfo verification")
Reported-by: Eirik Fuller <efuller@redhat.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210118093145.10134-1-sandipan@linux.ibm.com

selftests/powerpc: Harden test for execute-disabled pkeys

Commit 192b6a7805989 ("powerpc/book3s64/pkeys: Fix
pkey_access_permitted() for execute disable pkey") fixed a
bug that caused repetitive faults for pkeys with no execute
rights alongside some combination of read and write rights.

This removes the last two cases of the test, which check
the behaviour of pkeys with read, write but no execute
rights and all the rights, in favour of checking all the
possible combinations of read, write and execute rights
to be able to detect bugs like the one mentioned above.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/db467500f8af47727bba6b35796e8974a78b71e5.1595821792.git.sandipan@linux.ibm.com

selftests/powerpc: Add pkey helpers for rights

This adds some new pkey-related helper to print
access rights of a pkey in the "rwx" format and
to generate different valid combinations of pkey
rights starting from a given combination.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6cc1c7d1f686618668a3e090f1d0c2a4cd9dea3f.1595821792.git.sandipan@linux.ibm.com

selftests/powerpc: Move pkey helpers to headers

This moves all the pkey-related helpers to a new header
file and also a helper to print error messages in signal
handlers to the existing utils header file.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/28e633fa9ec1a6500c12188e09ea1887b10a10c1.1595821792.git.sandipan@linux.ibm.com

selftests/powerpc: Add test for execute-disabled pkeys

Apart from read and write access, memory protection keys can
also be used for restricting execute permission of pages on
powerpc. This adds a test to verify if the feature works as
expected.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200604125610.649668-4-sandipan@linux.ibm.com