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

[Dmitry Vyukov]

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

Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 tools/testing/selftests/rseq/Makefile    |  2 +-
 tools/testing/selftests/rseq/pkey_test.c | 61 ++++++++++++++++++++++++
 2 files changed, 62 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..ba5c1f6e99ab5
--- /dev/null
+++ b/tools/testing/selftests/rseq/pkey_test.c
@@ -0,0 +1,61 @@
+// 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 <sys/syscall.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+	void *rseq;
+	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;
+	}
+
+	/*
+	 * Prevent glibc from registering own struct rseq.
+	 * We need to know the rseq address to protect it, but also we need
+	 * it to be placed on own page that does not contain other data
+	 * (e.g. errno).
+	 */
+	if (!getenv("RSEQ_TEST_REEXECED")) {
+		setenv("RSEQ_TEST_REEXECED", "1", 1);
+		setenv("GLIBC_TUNABLES", "glibc.pthread.rseq=0", 1);
+		if (execvpe(argv[0], argv, environ))
+			err(1, "execvpe failed");
+	}
+
+	page_size = getpagesize();
+	rseq = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+		MAP_ANON | MAP_PRIVATE, -1, 0);
+	if (rseq == MAP_FAILED)
+		err(1, "mmap failed");
+	if (pkey_mprotect(rseq, page_size, PROT_READ | PROT_WRITE, pkey))
+		err(1, "pkey_mprotect failed");
+	if (syscall(__NR_rseq, rseq, 32, 0, 0))
+		err(1, "rseq failed");
+	if (pkey_set(pkey, PKEY_DISABLE_ACCESS))
+		err(1, "pkey_set failed");
+
+	/*
+	 * If the kernel misbehaves, context switches in the following loop
+	 * will kill the process with SIGSEGV.
+	 */
+	for (i = 0; i < 10; i++)
+		usleep(100);
+	return 0;
+}
-- 
2.48.1.601.g30ceb7b040-goog