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From:   Ram Pai <linuxram@us.ibm.com>
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Subject: [PATCH v12 15/22] selftests/vm: powerpc implementation to check support for pkey
Date:   Wed, 21 Feb 2018 17:55:34 -0800
Message-Id: <1519264541-7621-16-git-send-email-linuxram@us.ibm.com>
In-Reply-To: <1519264541-7621-1-git-send-email-linuxram@us.ibm.com>
References: <1519264541-7621-1-git-send-email-linuxram@us.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
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pkey subsystem is supported if the hardware and kernel has support.
We determine that by checking if allocation of a key succeeds or not.

cc: Dave Hansen <dave.hansen@intel.com>
cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
 tools/testing/selftests/vm/pkey-helpers.h    |   22 ++++++++++++++++------
 tools/testing/selftests/vm/protection_keys.c |    9 +++++----
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/vm/pkey-helpers.h b/tools/testing/selftests/vm/pkey-helpers.h
index c47aead..88ef58f 100644
--- a/tools/testing/selftests/vm/pkey-helpers.h
+++ b/tools/testing/selftests/vm/pkey-helpers.h
@@ -258,7 +258,7 @@ static inline void __cpuid(unsigned int *eax, unsigned int *ebx,
 #define X86_FEATURE_PKU        (1<<3) /* Protection Keys for Userspace */
 #define X86_FEATURE_OSPKE      (1<<4) /* OS Protection Keys Enable */
 
-static inline int cpu_has_pku(void)
+static inline bool is_pkey_supported(void)
 {
 	unsigned int eax;
 	unsigned int ebx;
@@ -271,13 +271,13 @@ static inline int cpu_has_pku(void)
 
 	if (!(ecx & X86_FEATURE_PKU)) {
 		dprintf2("cpu does not have PKU\n");
-		return 0;
+		return false;
 	}
 	if (!(ecx & X86_FEATURE_OSPKE)) {
 		dprintf2("cpu does not have OSPKE\n");
-		return 0;
+		return false;
 	}
-	return 1;
+	return true;
 }
 
 #define XSTATE_PKEY_BIT	(9)
@@ -323,9 +323,19 @@ static inline void __page_o_noops(void)
 #elif __powerpc64__ /* arch */
 
 #define PAGE_SIZE (0x1UL << 16)
-static inline int cpu_has_pku(void)
+static inline bool is_pkey_supported(void)
 {
-	return 1;
+	/*
+	 * No simple way to determine this.
+	 * lets try allocating a key and see if it succeeds.
+	 */
+	int ret = sys_pkey_alloc(0, 0);
+
+	if (ret > 0) {
+		sys_pkey_free(ret);
+		return true;
+	}
+	return false;
 }
 
 /* 8-bytes of instruction * 16384bytes = 1 page */
diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
index e82bd88..58da5a0 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c
@@ -1299,8 +1299,8 @@ void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey)
 	int size = PAGE_SIZE;
 	int sret;
 
-	if (cpu_has_pku()) {
-		dprintf1("SKIP: %s: no CPU support\n", __func__);
+	if (is_pkey_supported()) {
+		dprintf1("SKIP: %s: no CPU/kernel support\n", __func__);
 		return;
 	}
 
@@ -1362,12 +1362,13 @@ void run_tests_once(void)
 int main(void)
 {
 	int nr_iterations = 22;
+	int pkey_supported = is_pkey_supported();
 
 	setup_handlers();
 
-	printf("has pkey: %d\n", cpu_has_pku());
+	printf("has pkey: %s\n", pkey_supported ? "Yes" : "No");
 
-	if (!cpu_has_pku()) {
+	if (!pkey_supported) {
 		int size = PAGE_SIZE;
 		int *ptr;
 
-- 
1.7.1