Define systrace_probe_func in subr_syscall.c where it's used, instead

of defining it in MD code. This eliminates porting to other architectures.

sys/amd64/amd64/trap.c

@@ -103,13 +103,6 @@ dtrace_trap_func_t	dtrace_trap_func;
 
 dtrace_doubletrap_func_t	dtrace_doubletrap_func;
 
-/*
- * This is a hook which is initialised by the systrace module
- * when it is loaded. This keeps the DTrace syscall provider
- * implementation opaque. 
- */
-systrace_probe_func_t	systrace_probe_func;
-
 /*
  * These hooks are necessary for the pid, usdt and fasttrap providers.
  */

sys/i386/i386/trap.c

@@ -112,13 +112,6 @@ dtrace_trap_func_t	dtrace_trap_func;
 
 dtrace_doubletrap_func_t	dtrace_doubletrap_func;
 
-/*
- * This is a hook which is initialised by the systrace module
- * when it is loaded. This keeps the DTrace syscall provider
- * implementation opaque. 
- */
-systrace_probe_func_t	systrace_probe_func;
-
 /*
  * These hooks are necessary for the pid, usdt and fasttrap providers.
  */

sys/kern/subr_syscall.c

@@ -52,6 +52,15 @@ __FBSDID("$FreeBSD$");
 #endif
 #include <security/audit/audit.h>
 
+#ifdef KDTRACE_HOOKS
+/*
+ * This is a hook which is initialised by the systrace module
+ * when it is loaded. This keeps the DTrace syscall provider
+ * implementation opaque.
+ */
+systrace_probe_func_t systrace_probe_func;
+#endif
+
 static inline int
 syscallenter(struct thread *td, struct syscall_args *sa)
 {