add KTRACE hooks into kevent... This will help people debug their kqueue

programs to find out exactly which events were registered and which were
returned...  This should be lower in kern_kevent, but that would require
special munging due to locks and the functions used to copyin/copyout
kevents...

If someone wants to teach ktrace how to output pretty kevents, I have a
kevent prety printer that can be used...

1 files changed, 38 insertions, 2 deletions

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index c3b37f5..8692808 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -28,6 +28,8 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_ktrace.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/kernel.h>
@@ -57,6 +59,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/syscallsubr.h>
 #include <sys/taskqueue.h>
 #include <sys/uio.h>
+#ifdef KTRACE
+#include <sys/ktrace.h>
+#endif
 
 #include <vm/uma.h>
 
@@ -560,6 +565,12 @@ kevent(struct thread *td, struct kevent_args *uap)
 					kevent_copyout,
 					kevent_copyin};
 	int error;
+#ifdef KTRACE
+	struct uio ktruio;
+	struct iovec ktriov;
+	struct uio *ktruioin = NULL;
+	struct uio *ktruioout = NULL;
+#endif
 
 	if (uap->timeout != NULL) {
 		error = copyin(uap->timeout, &ts, sizeof(ts));
@@ -569,8 +580,33 @@ kevent(struct thread *td, struct kevent_args *uap)
 	} else
 		tsp = NULL;
 
-	return (kern_kevent(td, uap->fd, uap->nchanges, uap->nevents,
-	    &k_ops, tsp));
+#ifdef KTRACE
+	if (KTRPOINT(td, KTR_GENIO)) {
+		ktriov.iov_base = uap->changelist;
+		ktriov.iov_len = uap->nchanges * sizeof(struct kevent);
+		ktruio = (struct uio){ .uio_iov = &ktriov, .uio_iovcnt = 1,
+		    .uio_segflg = UIO_USERSPACE, .uio_rw = UIO_READ,
+		    .uio_td = td };
+		ktruioin = cloneuio(&ktruio);
+		ktriov.iov_base = uap->eventlist;
+		ktriov.iov_len = uap->nevents * sizeof(struct kevent);
+		ktruioout = cloneuio(&ktruio);
+	}
+#endif
+
+	error = kern_kevent(td, uap->fd, uap->nchanges, uap->nevents,
+	    &k_ops, tsp);
+
+#ifdef KTRACE
+	if (ktruioin != NULL) {
+		ktruioin->uio_resid = uap->nchanges * sizeof(struct kevent);
+		ktrgenio(uap->fd, UIO_WRITE, ktruioin, 0);
+		ktruioout->uio_resid = td->td_retval[0] * sizeof(struct kevent);
+		ktrgenio(uap->fd, UIO_READ, ktruioout, error);
+	}
+#endif
+
+	return (error);
 }
 
 /*