4 files changed, 15 insertions, 3 deletions

diff --git a/sys/cddl/dev/systrace/systrace.c b/sys/cddl/dev/systrace/systrace.c
index 02b089b425269..2ef74cb15e0ad 100644
--- a/sys/cddl/dev/systrace/systrace.c
+++ b/sys/cddl/dev/systrace/systrace.c
@@ -135,6 +135,8 @@ extern const char *freebsd32_syscallnames[];
 #error 1 << SYSTRACE_SHIFT must exceed number of system calls
 #endif
 
+static int systrace_enabled_count;
+
 static void	systrace_load(void *);
 static void	systrace_unload(void *);
 
@@ -315,6 +317,9 @@ systrace_enable(void *arg, dtrace_id_t id, void *parg)
 		SYSENT[sysnum].sy_entry = id;
 	else
 		SYSENT[sysnum].sy_return = id;
+	systrace_enabled_count++;
+	if (systrace_enabled_count == 1)
+		systrace_enabled = true;
 }
 
 static void
@@ -324,6 +329,9 @@ systrace_disable(void *arg, dtrace_id_t id, void *parg)
 
 	SYSENT[sysnum].sy_entry = 0;
 	SYSENT[sysnum].sy_return = 0;
+	systrace_enabled_count--;
+	if (systrace_enabled_count == 0)
+		systrace_enabled = false;
 }
 
 static void
diff --git a/sys/kern/kern_dtrace.c b/sys/kern/kern_dtrace.c
index 7b13a52b3f3b5..cbe6bdf15fd8d 100644
--- a/sys/kern/kern_dtrace.c
+++ b/sys/kern/kern_dtrace.c
@@ -56,7 +56,8 @@ dtrace_doubletrap_func_t	dtrace_doubletrap_func;
 dtrace_pid_probe_ptr_t		dtrace_pid_probe_ptr;
 dtrace_return_probe_ptr_t	dtrace_return_probe_ptr;
 
-systrace_probe_func_t __read_frequently	systrace_probe_func;
+bool __read_frequently		systrace_enabled;
+systrace_probe_func_t 		systrace_probe_func;
 
 /* Return the DTrace process data size compiled in the kernel hooks. */
 size_t
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index bca47edaf6134..6c70ddc9f789a 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -126,7 +126,8 @@ syscallenter(struct thread *td)
 
 #ifdef KDTRACE_HOOKS
 		/* Give the syscall:::entry DTrace probe a chance to fire. */
-		if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
+		if (__predict_false(systrace_enabled &&
+		    sa->callp->sy_entry != 0))
 			(*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
 #endif
 
@@ -140,7 +141,8 @@ syscallenter(struct thread *td)
 
 #ifdef KDTRACE_HOOKS
 		/* Give the syscall:::return DTrace probe a chance to fire. */
-		if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
+		if (__predict_false(systrace_enabled &&
+		    sa->callp->sy_return != 0))
 			(*systrace_probe_func)(sa, SYSTRACE_RETURN,
 			    error ? -1 : td->td_retval[0]);
 #endif
diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h
index c811a4a7f3bd4..9d85728e1593a 100644
--- a/sys/sys/sysent.h
+++ b/sys/sys/sysent.h
@@ -53,6 +53,7 @@ typedef	void	(*systrace_probe_func_t)(struct syscall_args *,
 		    enum systrace_probe_t, int);
 typedef	void	(*systrace_args_func_t)(int, void *, uint64_t *, int *);
 
+extern bool			systrace_enabled;
 extern systrace_probe_func_t	systrace_probe_func;
 
 struct sysent {			/* system call table */