In the compilation of pidfs_setns_test.c , a warning as the following
will pop out.

pidfd_setns_test.c: In function ‘current_nsset_setup’:
pidfd_setns_test.c:173:54: warning: implicit declaration of function \
‘ioctl’ [-Wimplicit-function-declaration]
  173 |                 self->child_pidfd_derived_nsfds[i] = \
ioctl(self->pidfd, info->pidfd_ioctl, 0);

It's caused by wrong import of header file <linux/ioctl.h>, fix it to
<sys/ioctl.h>.

Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
---
 tools/testing/selftests/pidfd/pidfd_setns_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/pidfd/pidfd_setns_test.c b/tools/testing/selftests/pidfd/pidfd_setns_test.c
index 7c2a43491..3ed42f1eb 100644
--- a/tools/testing/selftests/pidfd/pidfd_setns_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_setns_test.c
@@ -16,7 +16,7 @@
 #include <unistd.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
-#include <linux/ioctl.h>
+#include <sys/ioctl.h>
 
 #include "pidfd.h"
 #include "../clone3/clone3_selftests.h"
-- 
2.43.0

Hello *,

On Wed,  5 Feb 2025 13:50:31 +0800, I Hsin Cheng <richard120310@gmail.com> wrote:

> In the compilation of pidfs_setns_test.c , a warning as the following
> will pop out.
> 
> pidfd_setns_test.c: In function ‘current_nsset_setup’:
> pidfd_setns_test.c:173:54: warning: implicit declaration of function \
> ‘ioctl’ [-Wimplicit-function-declaration]
>   173 |                 self->child_pidfd_derived_nsfds[i] = \
> ioctl(self->pidfd, info->pidfd_ioctl, 0);
> 
> It's caused by wrong import of header file <linux/ioctl.h>, fix it to
> <sys/ioctl.h>.
> 
> Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
> ---
>  tools/testing/selftests/pidfd/pidfd_setns_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/pidfd/pidfd_setns_test.c b/tools/testing/selftests/pidfd/pidfd_setns_test.c
> index 7c2a43491..3ed42f1eb 100644
> --- a/tools/testing/selftests/pidfd/pidfd_setns_test.c
> +++ b/tools/testing/selftests/pidfd/pidfd_setns_test.c
> @@ -16,7 +16,7 @@
>  #include <unistd.h>
>  #include <sys/socket.h>
>  #include <sys/stat.h>
> -#include <linux/ioctl.h>
> +#include <sys/ioctl.h>
>  
>  #include "pidfd.h"
>  #include "../clone3/clone3_selftests.h"

Predated patch already available, see

	https://lore.kernel.org/linux-kselftest/20250115105211.390370-2-ps.report@gmx.net/

Regards,
Peter