[PATCH v17 17/24] 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 2f4b1eb3a680..59ccdff18214 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 319673bbab0b..7d7c3ffafdd9 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 a0c59d4f7af2..6421b846aa16 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 5fcbbc525364..95f173049f43 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c
@@ -1378,7 +1378,7 @@ 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;
 	}
@@ -1447,12 +1447,13 @@ 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