[PATCH] selftests:arm64: Test PR_SVE_VL_INHERIT after a double fork

[Dorine Tipo <dorine.a.tipo@gmail.com>]

Add a new test, double_fork_test() to check the inheritance of the SVE
vector length after a double fork.
The `EXPECTED_TESTS` macro has been updated to account for this additional
test.
This patch addresses task 7 on the TODO list.

Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
---
 tools/testing/selftests/arm64/fp/za-fork.c | 95 +++++++++++++++++++++-
 1 file changed, 94 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/arm64/fp/za-fork.c b/tools/testing/selftests/arm64/fp/za-fork.c
index 587b94648222..35229e570dcf 100644
--- a/tools/testing/selftests/arm64/fp/za-fork.c
+++ b/tools/testing/selftests/arm64/fp/za-fork.c
@@ -11,7 +11,7 @@

 #include "kselftest.h"

-#define EXPECTED_TESTS 1
+#define EXPECTED_TESTS 2

 int fork_test(void);
 int verify_fork(void);
@@ -69,6 +69,97 @@ int fork_test_c(void)
	}
 }

+int double_fork_test(void)
+{
+	pid_t newpid, grandchild_pid, waiting;
+	int ret, child_status, parent_result;
+
+	ret = prctl(PR_SVE_SET_VL, vl | PR_SVE_VL_INHERIT);
+	if (ret < 0)
+		ksft_exit_fail_msg("Failed to set SVE VL %d\n", vl);
+
+	newpid = fork();
+	if (newpid == 0) {
+		/* In child */
+		if (!verify_fork()) {
+			ksft_print_msg("ZA state invalid in child\n");
+			exit(0);
+		}
+
+		grandchild_pid = fork();
+		if (grandchild_pid == 0) {
+			/* in grandchild */
+			if (!verfy_fork()) {
+				ksft_print_msg("ZA state invalid in grandchild\n");
+				exit(0);
+			}
+
+			ret = prctl(PR_SVE_GET_VL);
+			if (ret & PR_SVE_VL_INHERIT) {
+				ksft_print_msg("prctl() reports _INHERIT\n");
+				return;
+			}
+			 ksft_print_msg("prctl() does not report _INHERIT\n");
+
+		} else if (grandchild_pid < 0) {
+			ksft_print_msg("fork() failed in first child: %d\n", grandchild_pid);
+			return 0;
+		}
+
+		/*  Wait for the grandchild process to exit */
+		waiting = waitpid(grandchild_pid, &child_status, 0);
+		if (waiting < 0) {
+			if (errno == EINTR)
+				continue;
+			ksft_print_msg("waitpid() failed: %d\n", errno);
+			return 0;
+		}
+		if (waiting != grandchild_pid) {
+			ksft_print_msg("waitpid() returned wrong PID\n");
+			return 0;
+		}
+
+		if (!WIFEXITED(child_status)) {
+			ksft_print_msg("grandchild did not exit\n");
+			return 0;
+		}
+
+		exit(1);
+		}
+	}
+	if (newpid < 0) {
+		ksft_print_msg("fork() failed: %d\n", newpid);
+
+		return 0;
+	}
+
+	parent_result = verify_fork();
+	if (!parent_result)
+		ksft_print_msg("ZA state invalid in parent\n");
+
+	for (;;) {
+		waiting = waitpid(newpid, &child_status, 0);
+
+		if (waiting < 0) {
+			if (errno == EINTR)
+				continue;
+			ksft_print_msg("waitpid() failed: %d\n", errno);
+			return 0;
+		}
+		if (waiting != newpid) {
+			ksft_print_msg("waitpid() returned wrong PID\n");
+			return 0;
+		}
+
+		if (!WIFEXITED(child_status)) {
+			ksft_print_msg("child did not exit\n");
+			return 0;
+		}
+
+		return WEXITSTATUS(child_status) && parent_result;
+	}
+}
+
 int main(int argc, char **argv)
 {
 	int ret, i;
@@ -86,11 +177,13 @@ int main(int argc, char **argv)
 	ret = open("/proc/sys/abi/sme_default_vector_length", O_RDONLY, 0);
 	if (ret >= 0) {
 		ksft_test_result(fork_test(), "fork_test\n");
+		ksft_test_result(double_fork_test(), "double_fork_test\n");

 	} else {
 		ksft_print_msg("SME not supported\n");
 		for (i = 0; i < EXPECTED_TESTS; i++) {
 			ksft_test_result_skip("fork_test\n");
+			ksft_test_result_skip("double_fork_test\n");
 		}
 	}

--
2.25.1