Re: [PATCH] selftests: powerpc: Add test for execute-disabled pkeys

From: Michael Ellerman <mpe@ellerman.id.au>
To: Sandipan Das <sandipan@linux.ibm.com>
Cc: linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-mm@kvack.org, linuxram@us.ibm.com,
	aneesh.kumar@linux.ibm.com, bauerman@linux.ibm.com,
	fweimer@redhat.com, ruscur@russell.cc
Subject: Re: [PATCH] selftests: powerpc: Add test for execute-disabled pkeys
Date: Wed, 27 May 2020 10:17:22 +1000	[thread overview]
Message-ID: <87tv02dyel.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <6b73bf3f-0d10-6e8c-acd9-27de53573dec@linux.ibm.com>

Sandipan Das <sandipan@linux.ibm.com> writes:
> Hi Michael,
>
> On 26/05/20 6:05 pm, Michael Ellerman wrote:
>> [...]
>>> +
>>> +/* Override definitions as they might be inconsistent */
>>> +#undef PKEY_DISABLE_ACCESS
>>> +#define PKEY_DISABLE_ACCESS	0x3
>> 
>> Why would they be inconsistent?
>> 
>
> The definition in sys/mman.h still uses the value specific to
> Intel's implementation i.e. 1, when this should have been 3
> for powerpc. I have seen this on Ubuntu 18.04 and 20.04.

Hmm OK, that's a bug but oh well nothing we can do about it.

>> I think a reasonable solution is to use the absence of SEGV_PKUERR to
>> basically turn the whole test into a nop at build time, eg:
...
>
> Or can I use this from the pkey tests under selftests/vm?
>
> static inline u32 *siginfo_get_pkey_ptr(siginfo_t *si)
> {
> #ifdef si_pkey
> 	return &si->si_pkey;
> #else
> 	return (u32 *)(((u8 *)si) + si_pkey_offset);
> #endif
> }
>
> Where si_pkey_offset is 0x20 for powerpc.

Yeah that's fine if it works. Please send a v2 with that change.

cheers