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From:   Thiago Jung Bauermann <bauerman@linux.ibm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org, Ram Pai <linuxram@us.ibm.com>,
        Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Subject: Re: [PATCH 1/2] selftests/powerpc: Add ptrace tests for Protection Key registers
In-reply-to: <87tvr6mlbe.fsf@concordia.ellerman.id.au>
Date:   Thu, 24 May 2018 23:14:27 -0300
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Michael Ellerman <mpe@ellerman.id.au> writes:

> Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> writes:
>
>> This test exercises read and write access to the AMR, IAMR and UAMOR.
>>
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
>> ---
>>  tools/testing/selftests/powerpc/include/reg.h      |   1 +
>>  tools/testing/selftests/powerpc/ptrace/Makefile    |   5 +-
>>  tools/testing/selftests/powerpc/ptrace/child.h     | 130 ++++++++
>>  .../testing/selftests/powerpc/ptrace/ptrace-pkey.c | 326 +++++++++++++++++++++
>
> This is failing on machines without pkeys:
>
>   test: ptrace_pkey
>   tags: git_version:52e7d87
>   [FAIL] Test FAILED on line 117
>   [FAIL] Test FAILED on line 191
>   failure: ptrace_pkey
>
>
> I think the first fail is in the child here:
>
> int ptrace_read_regs(pid_t child, unsigned long type, unsigned long regs[],
> 		     int n)
> {
> 	struct iovec iov;
> 	long ret;
>
> 	FAIL_IF(start_trace(child));
>
> 	iov.iov_base = regs;
> 	iov.iov_len = n * sizeof(unsigned long);
>
> 	ret = ptrace(PTRACE_GETREGSET, child, type, &iov);
> 	FAIL_IF(ret != 0);
>
>
> Which makes sense.

Yes, that is indeed what is going on.

> The test needs to skip if pkeys are not available/enabled. Using the
> availability of the REGSET might actually be a nice way to detect that,
> because it's read-only.

 I forgot to consider the case of pkeys not available or not enabled,
 sorry about that.

I just sent a v2 which implements your suggestion above.

--
Thiago Jung Bauermann
IBM Linux Technology Center