[PATCH v2 4/4] selftests/rseq: Add test for rseq+pkeys

[Dmitry Vyukov <dvyukov@google.com>]

Add a test that ensures that PKEY-protected struct rseq_cs
works and does not lead to process kills.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org

---
Changes in v2:
 - change test to install protected rseq_cs instead of rseq
---
 tools/testing/selftests/rseq/Makefile    |  2 +-
 tools/testing/selftests/rseq/pkey_test.c | 66 ++++++++++++++++++++++++
 tools/testing/selftests/rseq/rseq.h      |  1 +
 3 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index 5a3432fceb586..9111d25fea3af 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -16,7 +16,7 @@ OVERRIDE_TARGETS = 1
 
 TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_test param_test \
 		param_test_benchmark param_test_compare_twice param_test_mm_cid \
-		param_test_mm_cid_benchmark param_test_mm_cid_compare_twice
+		param_test_mm_cid_benchmark param_test_mm_cid_compare_twice pkey_test
 
 TEST_GEN_PROGS_EXTENDED = librseq.so
 
diff --git a/tools/testing/selftests/rseq/pkey_test.c b/tools/testing/selftests/rseq/pkey_test.c
new file mode 100644
index 0000000000000..0bca8fda9aa92
--- /dev/null
+++ b/tools/testing/selftests/rseq/pkey_test.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Ensure that rseq works when rseq data is protected with PKEYs.
+ */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "rseq.h"
+#include "rseq-abi.h"
+
+int main(int argc, char **argv)
+{
+	struct rseq_abi_cs *cs;
+	__u32 *sig;
+	unsigned long page_size;
+	int pkey, i;
+
+	pkey = pkey_alloc(0, 0);
+	if (pkey == -1) {
+		printf("[SKIP]\tKernel does not support PKEYs: %s\n",
+			strerror(errno));
+		return 0;
+	}
+
+	if (rseq_register_current_thread())
+		err(1, "rseq_register_current_thread failed");
+
+	page_size = getpagesize();
+	cs = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+		MAP_ANON | MAP_PRIVATE, -1, 0);
+	if (cs == MAP_FAILED)
+		err(1, "mmap failed");
+	/* Create valid rseq_cs. */
+	sig = (__u32 *)(cs + 1);
+	*sig = RSEQ_SIG;
+	cs->abort_ip = (__u64)(sig + 1);
+	if (pkey_mprotect(cs, page_size, PROT_READ | PROT_WRITE, pkey))
+		err(1, "pkey_mprotect failed");
+	if (pkey_set(pkey, PKEY_DISABLE_ACCESS))
+		err(1, "pkey_set failed");
+
+	/* Install pkey-protected rseq_cs. */
+	rseq_get_abi()->rseq_cs.ptr64 = (__u64)cs;
+
+	/*
+	 * If the kernel misbehaves, context switches in the following loop
+	 * will terminate the process with SIGSEGV.
+	 */
+	for (i = 0; i < 10; i++)
+		usleep(100);
+
+	/*
+	 * Ensure that the kernel has restored the previous value of pkeys
+	 * register after changing it.
+	 */
+	if (pkey_get(pkey) != PKEY_DISABLE_ACCESS)
+		errx(1, "pkey protection has changed");
+	return 0;
+}
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index ba424ce80a719..65da4a727c550 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -8,6 +8,7 @@
 #ifndef RSEQ_H
 #define RSEQ_H
 
+#include <assert.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <pthread.h>
-- 
2.48.1.601.g30ceb7b040-goog