selftests/pidfd: add first supported_mask test

Verify that when PIDFD_INFO_SUPPORTED_MASK is requested, the kernel
returns the supported_mask field indicating which flags the kernel
supports.

Link: https://patch.msgid.link/20251028-work-coredump-signal-v1-10-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 a0eb6e81eaa26d1d44b94546397b1dd6dead4b29..b31a0597fbae65b7f02bf349f15c79efe50113fb 100644 (file)
--- a/tools/testing/selftests/pidfd/pidfd_info_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_info_test.c
@@ -690,4 +690,45 @@ TEST_F(pidfd_info, thread_group_exec_thread)
        EXPECT_EQ(close(pidfd_thread), 0);
 }
 
+/*
+ * Test: PIDFD_INFO_SUPPORTED_MASK field
+ *
+ * Verify that when PIDFD_INFO_SUPPORTED_MASK is requested, the kernel
+ * returns the supported_mask field indicating which flags the kernel supports.
+ */
+TEST(supported_mask_field)
+{
+       struct pidfd_info info = {
+               .mask = PIDFD_INFO_SUPPORTED_MASK,
+       };
+       int pidfd;
+       pid_t pid;
+
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0)
+               pause();
+
+       /* Request supported_mask field */
+       ASSERT_EQ(ioctl(pidfd, PIDFD_GET_INFO, &info), 0);
+
+       /* Verify PIDFD_INFO_SUPPORTED_MASK is set in the reply */
+       ASSERT_TRUE(!!(info.mask & PIDFD_INFO_SUPPORTED_MASK));
+
+       /* Verify supported_mask contains expected flags */
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_PID));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_CREDS));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_CGROUPID));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_EXIT));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_COREDUMP));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_SUPPORTED_MASK));
+       ASSERT_TRUE(!!(info.supported_mask & PIDFD_INFO_COREDUMP_SIGNAL));
+
+       /* Clean up */
+       sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0);
+       sys_waitid(P_PIDFD, pidfd, NULL, WEXITED);
+       close(pidfd);
+}
+
 TEST_HARNESS_MAIN