linux-kernel - [PATCH 8/9] x86, pkeys, selftests: add allow faults on unknown keys

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Message-Id: <20180427174540.91C386B5@viggo.jf.intel.com>
Date:   Fri, 27 Apr 2018 10:45:40 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        linuxram@...ibm.com, tglx@...utronix.de, dave.hansen@...el.com,
        mpe@...erman.id.au, mingo@...nel.org, akpm@...ux-foundation.org,
        shuah@...nel.org
Subject: [PATCH 8/9] x86, pkeys, selftests: add allow faults on unknown keys


From: Dave Hansen <dave.hansen@...ux.intel.com>

The exec-only pkey is allocated inside the kernel and userspace
is not told what it is.  So, allow PK faults to occur that have
an unknown key.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Ram Pai <linuxram@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Michael Ellermen <mpe@...erman.id.au>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Shuah Khan <shuah@...nel.org>
---

 b/tools/testing/selftests/x86/protection_keys.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff -puN tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-unknown-exec-only-key tools/testing/selftests/x86/protection_keys.c
--- a/tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-unknown-exec-only-key	2018-03-26 10:22:37.549170187 -0700
+++ b/tools/testing/selftests/x86/protection_keys.c	2018-03-26 10:22:37.553170187 -0700
@@ -922,13 +922,21 @@ void *malloc_pkey(long size, int prot, u
 }
 
 int last_pkru_faults;
+#define UNKNOWN_PKEY -2
 void expected_pk_fault(int pkey)
 {
 	dprintf2("%s(): last_pkru_faults: %d pkru_faults: %d\n",
 			__func__, last_pkru_faults, pkru_faults);
 	dprintf2("%s(%d): last_si_pkey: %d\n", __func__, pkey, last_si_pkey);
 	pkey_assert(last_pkru_faults + 1 == pkru_faults);
-	pkey_assert(last_si_pkey == pkey);
+
+       /*
+	* For exec-only memory, we do not know the pkey in
+	* advance, so skip this check.
+	*/
+	if (pkey != UNKNOWN_PKEY)
+		pkey_assert(last_si_pkey == pkey);
+
 	/*
 	 * The signal handler shold have cleared out PKRU to let the
 	 * test program continue.  We now have to restore it.
_