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From: Dave Hansen <dave.hansen@intel.com>
To: Ram Pai <linuxram@us.ibm.com>,
	shuahkh@osg.samsung.com, linux-kselftest@vger.kernel.org
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
	linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org,
	mingo@redhat.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
	fweimer@redhat.com, msuchanek@suse.de,
	aneesh.kumar@linux.vnet.ibm.com
Subject: Re: [PATCH v13 10/24] selftests/vm: clear the bits in shadow reg when a pkey is freed.
Date: Wed, 20 Jun 2018 07:49:31 -0700	[thread overview]
Message-ID: <41034628-c643-7a4b-006d-9606201ded6e@intel.com> (raw)
In-Reply-To: <1528937115-10132-11-git-send-email-linuxram@us.ibm.com>

On 06/13/2018 05:45 PM, Ram Pai wrote:
> When a key is freed, the  key  is  no  more  effective.
> Clear the bits corresponding to the pkey in the shadow
> register. Otherwise  it  will carry some spurious bits
> which can trigger false-positive asserts.
...--- a/tools/testing/selftests/vm/protection_keys.c
> +++ b/tools/testing/selftests/vm/protection_keys.c
> @@ -556,6 +556,9 @@ int alloc_pkey(void)
>  int sys_pkey_free(unsigned long pkey)
>  {
>  	int ret = syscall(SYS_pkey_free, pkey);
> +
> +	if (!ret)
> +		shadow_pkey_reg &= clear_pkey_flags(pkey, PKEY_DISABLE_ACCESS);
>  	dprintf1("%s(pkey=%ld) syscall ret: %d\n", __func__, pkey, ret);
>  	return ret;
>  }

This would be great code for an actual application.  But, I'm not
immediately convinced we want sane, kind behavior in our selftest.  x86
doesn't clear the hardware register at pkey_free, so wouldn't this cause
the shadow and the hardware register to diverge?

  reply	other threads:[~2018-06-20 14:49 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-14  0:44 [PATCH v13 00/24] selftests, powerpc, x86 : Memory Protection Keys Ram Pai
2018-06-14  0:44 ` [PATCH v13 01/24] selftests/x86: Move protecton key selftest to arch neutral directory Ram Pai
2018-06-14  0:44 ` [PATCH v13 02/24] selftests/vm: rename all references to pkru to a generic name Ram Pai
2018-06-14  0:44 ` [PATCH v13 03/24] selftests/vm: move generic definitions to header file Ram Pai
2018-06-14  0:44 ` [PATCH v13 04/24] selftests/vm: move arch-specific definitions to arch-specific header Ram Pai
2018-06-14  0:44 ` [PATCH v13 05/24] selftests/vm: Make gcc check arguments of sigsafe_printf() Ram Pai
2018-06-14  0:44 ` [PATCH v13 06/24] selftests/vm: typecast the pkey register Ram Pai
2018-06-14  0:44 ` [PATCH v13 07/24] selftests/vm: generic function to handle shadow key register Ram Pai
2018-06-14  0:44 ` [PATCH v13 08/24] selftests/vm: fix the wrong assert in pkey_disable_set() Ram Pai
2018-06-20 14:47   ` Dave Hansen
2018-07-17 15:58     ` Ram Pai
2018-07-17 17:53       ` Dave Hansen
2018-06-14  0:45 ` [PATCH v13 09/24] selftests/vm: fixed bugs in pkey_disable_clear() Ram Pai
2018-06-14  0:45 ` [PATCH v13 10/24] selftests/vm: clear the bits in shadow reg when a pkey is freed Ram Pai
2018-06-20 14:49   ` Dave Hansen [this message]
2018-07-17 16:00     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 11/24] selftests/vm: fix alloc_random_pkey() to make it really random Ram Pai
2018-06-14  0:45 ` [PATCH v13 12/24] selftests/vm: introduce two arch independent abstraction Ram Pai
2018-06-14  0:45 ` [PATCH v13 13/24] selftests/vm: pkey register should match shadow pkey Ram Pai
2018-06-20 14:53   ` Dave Hansen
2018-07-17 16:02     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 14/24] selftests/vm: generic cleanup Ram Pai
2018-06-20 14:57   ` Dave Hansen
2018-06-14  0:45 ` [PATCH v13 15/24] selftests/vm: powerpc implementation for generic abstraction Ram Pai
2018-06-20 15:06   ` Dave Hansen
2018-06-14  0:45 ` [PATCH v13 16/24] selftests/vm: clear the bits in shadow reg when a pkey is freed Ram Pai
2018-06-20 15:07   ` Dave Hansen
2018-07-17 16:03     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 17/24] selftests/vm: powerpc implementation to check support for pkey Ram Pai
2018-06-20 15:09   ` Dave Hansen
2018-07-17 16:05     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 18/24] selftests/vm: fix an assertion in test_pkey_alloc_exhaust() Ram Pai
2018-06-20 15:11   ` Dave Hansen
2018-07-17 16:08     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 19/24] selftests/vm: associate key on a mapped page and detect access violation Ram Pai
2018-06-20 15:16   ` Dave Hansen
2018-07-17 16:13     ` Ram Pai
2018-07-17 17:56       ` Dave Hansen
2018-07-17 19:10         ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 20/24] selftests/vm: associate key on a mapped page and detect write violation Ram Pai
2018-06-14  0:45 ` [PATCH v13 21/24] selftests/vm: detect write violation on a mapped access-denied-key page Ram Pai
2018-06-14  0:45 ` [PATCH v13 22/24] selftests/vm: testcases must restore pkey-permissions Ram Pai
2018-06-20 15:20   ` Dave Hansen
2018-07-17 16:09     ` Ram Pai
2018-06-14  0:45 ` [PATCH v13 23/24] selftests/vm: sub-page allocator Ram Pai
2018-06-14  0:45 ` [PATCH v13 24/24] selftests/vm: test correct behavior of pkey-0 Ram Pai
2018-06-20 15:22   ` Dave Hansen
2018-06-14 20:19 ` [PATCH v13 00/24] selftests, powerpc, x86 : Memory Protection Keys Florian Weimer
2018-06-15  0:58   ` Ram Pai

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