[PATCH] samples: pidfd: Fix compile error seen if __NR_pidfd_send_signal is undefined

[Guenter Roeck <linux@roeck-us.net>]

To make pidfd-metadata compile on all arches, irrespective of whether
or not syscall numbers are assigned, define the syscall number to -1
if it isn't to cause the kernel to return -ENOSYS.

Fixes: 43c6afee48d4 ("samples: show race-free pidfd metadata access")
Cc: Christian Brauner <christian@brauner.io>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 samples/pidfd/pidfd-metadata.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/samples/pidfd/pidfd-metadata.c b/samples/pidfd/pidfd-metadata.c
index 640f5f757c57..1e125ddde268 100644
--- a/samples/pidfd/pidfd-metadata.c
+++ b/samples/pidfd/pidfd-metadata.c
@@ -21,6 +21,10 @@
 #define CLONE_PIDFD 0x00001000
 #endif
 
+#ifndef __NR_pidfd_send_signal
+#define __NR_pidfd_send_signal	-1
+#endif
+
 static int do_child(void *args)
 {
 	printf("%d\n", getpid());
-- 
2.7.4