[PATCH v16 16/23] selftests/vm/pkeys: Improve checks to determine pkey support

[Sandipan Das <sandipan@linux.ibm.com>]

From: Ram Pai <linuxram@us.ibm.com>

For the pkeys subsystem to work, both the CPU and the
kernel need to have support. So, additionally check if
the kernel supports pkeys apart from the CPU feature
checks.

cc: Dave Hansen <dave.hansen@intel.com>
cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
---
 tools/testing/selftests/vm/pkey-helpers.h    | 30 ++++++++++++++++++++
 tools/testing/selftests/vm/pkey-powerpc.h    |  3 +-
 tools/testing/selftests/vm/pkey-x86.h        |  2 +-
 tools/testing/selftests/vm/protection_keys.c |  7 +++--
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vm/pkey-helpers.h b/tools/testing/selftests/vm/pkey-helpers.h
index ec3f87d53b7d..ac9076136fc8 100644
--- a/tools/testing/selftests/vm/pkey-helpers.h
+++ b/tools/testing/selftests/vm/pkey-helpers.h
@@ -76,6 +76,8 @@ extern void abort_hooks(void);
 
 __attribute__((noinline)) int read_ptr(int *ptr);
 void expected_pkey_fault(int pkey);
+int sys_pkey_alloc(unsigned long flags, unsigned long init_val);
+int sys_pkey_free(unsigned long pkey);
 
 #if defined(__i386__) || defined(__x86_64__) /* arch */
 #include "pkey-x86.h"
@@ -186,4 +188,32 @@ static inline u32 *siginfo_get_pkey_ptr(siginfo_t *si)
 #endif
 }
 
+static inline int kernel_has_pkeys(void)
+{
+	/* try allocating a key and see if it succeeds */
+	int ret = sys_pkey_alloc(0, 0);
+	if (ret <= 0) {
+		return 0;
+	}
+	sys_pkey_free(ret);
+	return 1;
+}
+
+static inline int is_pkeys_supported(void)
+{
+	/* check if the cpu supports pkeys */
+	if (!cpu_has_pkeys()) {
+		dprintf1("SKIP: %s: no CPU support\n", __func__);
+		return 0;
+	}
+
+	/* check if the kernel supports pkeys */
+	if (!kernel_has_pkeys()) {
+		dprintf1("SKIP: %s: no kernel support\n", __func__);
+		return 0;
+	}
+
+	return 1;
+}
+
 #endif /* _PKEYS_HELPER_H */
diff --git a/tools/testing/selftests/vm/pkey-powerpc.h b/tools/testing/selftests/vm/pkey-powerpc.h
index eaced8c198a2..a5e5157c4f7e 100644
--- a/tools/testing/selftests/vm/pkey-powerpc.h
+++ b/tools/testing/selftests/vm/pkey-powerpc.h
@@ -63,8 +63,9 @@ static inline void __write_pkey_reg(u64 pkey_reg)
 			__func__, __read_pkey_reg(), pkey_reg);
 }
 
-static inline int cpu_has_pku(void)
+static inline int cpu_has_pkeys(void)
 {
+	/* No simple way to determine this */
 	return 1;
 }
 
diff --git a/tools/testing/selftests/vm/pkey-x86.h b/tools/testing/selftests/vm/pkey-x86.h
index 296151309a30..207e8c180f39 100644
--- a/tools/testing/selftests/vm/pkey-x86.h
+++ b/tools/testing/selftests/vm/pkey-x86.h
@@ -97,7 +97,7 @@ 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 int cpu_has_pkeys(void)
 {
 	unsigned int eax;
 	unsigned int ebx;
diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
index a91d11c6a0ec..4a0677e618ac 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c
@@ -1377,7 +1377,7 @@ void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey)
 	int size = PAGE_SIZE;
 	int sret;
 
-	if (cpu_has_pku()) {
+	if (cpu_has_pkeys()) {
 		dprintf1("SKIP: %s: no CPU support\n", __func__);
 		return;
 	}
@@ -1446,12 +1446,13 @@ void pkey_setup_shadow(void)
 int main(void)
 {
 	int nr_iterations = 22;
+	int pkeys_supported = is_pkeys_supported();
 
 	setup_handlers();
 
-	printf("has pku: %d\n", cpu_has_pku());
+	printf("has pkeys: %d\n", pkeys_supported);
 
-	if (!cpu_has_pku()) {
+	if (!pkeys_supported) {
 		int size = PAGE_SIZE;
 		int *ptr;
 
-- 
2.17.1