add null_call() system call

For kernel entry/exit tracing.

2 files changed, 9 insertions, 0 deletions

diff --git a/include/litmus.h b/include/litmus.h
index 7ee13dc..c578009 100644
--- a/include/litmus.h
+++ b/include/litmus.h
@@ -4,6 +4,8 @@
 #include <litmus/rt_param.h>
 #include <sys/types.h>
 
+#include "cycles.h" /* for null_call() */
+
 typedef int pid_t;       /* PID of a task */
 
 /* obtain the PID of a thread */
@@ -101,5 +103,7 @@ static inline int open_srp_sem(int fd, int name)
 }
 
 
+/* syscall overhead measuring */
+int null_call(cycles_t *timestamp);
 
 #endif
diff --git a/src/syscalls.c b/src/syscalls.c
index b2ab900..2c9a446 100644
--- a/src/syscalls.c
+++ b/src/syscalls.c
@@ -100,3 +100,8 @@ int release_ts(lt_t *delay)
 {
         return syscall(__NR_release_ts, delay);
 }
+
+int null_call(cycles_t *timestamp)
+{
+        return syscall(__NR_null_call, timestamp);
+}