[PATCH v4 3/4] selftests: pidfd: add pidfd.h UAPI wrapper

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Conflicts can arise between system fcntl.h and linux/fcntl.h, imported by
the linux/pidfd.h UAPI header.

Work around this by adding a wrapper for linux/pidfd.h to
tools/include/ which sets the linux/fcntl.h header guard ahead of
importing the pidfd.h header file.

Adjust the pidfd selftests Makefile to reference this include directory and
put it at a higher precidence than any make header installed headers to
ensure the wrapper is preferred.

This way we can directly import the UAPI header file without issue, use the
latest system header file without having to duplicate anything.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 tools/include/linux/pidfd.h            | 14 ++++++++++++++
 tools/testing/selftests/pidfd/Makefile |  3 +--
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 tools/include/linux/pidfd.h

diff --git a/tools/include/linux/pidfd.h b/tools/include/linux/pidfd.h
new file mode 100644
index 000000000000..113c8023072d
--- /dev/null
+++ b/tools/include/linux/pidfd.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _TOOLS_LINUX_PIDFD_H
+#define _TOOLS_LINUX_PIDFD_H
+
+/*
+ * Some systems have issues with the linux/fcntl.h import in linux/pidfd.h, so
+ * work around this by setting the header guard.
+ */
+#define _LINUX_FCNTL_H
+#include "../../../include/uapi/linux/pidfd.h"
+#undef _LINUX_FCNTL_H
+
+#endif /* _TOOLS_LINUX_PIDFD_H */
diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
index d731e3e76d5b..f5038c9dae14 100644
--- a/tools/testing/selftests/pidfd/Makefile
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -1,8 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
-CFLAGS += -g $(KHDR_INCLUDES) -pthread -Wall
+CFLAGS += -g -isystem $(top_srcdir)/tools/include $(KHDR_INCLUDES) -pthread -Wall
 
 TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test \
 	pidfd_poll_test pidfd_wait pidfd_getfd_test pidfd_setns_test
 
 include ../lib.mk
-
-- 
2.46.2