selftests/pidfd: add second supported_mask test

Verify that supported_mask is returned even when other fields are
requested.

Link: https://patch.msgid.link/20251028-work-coredump-signal-v1-11-ca449b7b7aa0@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/pidfd/pidfd_info_test.c b/tools/testing/selftests/pidfd/pidfd_info_test.c
index b31a0597fbae65b7f02bf349f15c79efe50113fb..cb5430a2fd7545e2a6b3d3d50ead84e3cb823fa4 100644 (file)
--- a/tools/testing/selftests/pidfd/pidfd_info_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_info_test.c
@@ -731,4 +731,36 @@ TEST(supported_mask_field)
        close(pidfd);
 }
 
+/*
+ * Test: PIDFD_INFO_SUPPORTED_MASK always available
+ *
+ * Verify that supported_mask is returned even when other fields are requested.
+ */
+TEST(supported_mask_with_other_fields)
+{
+       struct pidfd_info info = {
+               .mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_SUPPORTED_MASK,
+       };
+       int pidfd;
+       pid_t pid;
+
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0)
+               pause();
+
+       ASSERT_EQ(ioctl(pidfd, PIDFD_GET_INFO, &info), 0);
+
+       /* Both fields should be present */
+       ASSERT_TRUE(!!(info.mask & PIDFD_INFO_CGROUPID));
+       ASSERT_TRUE(!!(info.mask & PIDFD_INFO_SUPPORTED_MASK));
+       ASSERT_NE(info.supported_mask, 0);
+
+       /* Clean up */
+       sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0);
+       sys_waitid(P_PIDFD, pidfd, NULL, WEXITED);
+       close(pidfd);
+}
+
 TEST_HARNESS_MAIN