diff --git a/sys/compat/linux/linux_socket.c b/sys/compat/linux/linux_socket.c
index 465c5737d177..c73a57a87fd7 100644
--- a/sys/compat/linux/linux_socket.c
+++ b/sys/compat/linux/linux_socket.c
@@ -993,35 +993,22 @@ linux_sendmsg(struct thread *td, struct linux_sendmsg_args *args)
 {
 	struct linux_sendmsg_args linux_args;
 	struct msghdr msg;
-	struct iovec aiov[UIO_SMALLIOV], *iov;
+	struct iovec *iov;
 	int error;
 
-	if ((error = copyin(args, &linux_args, sizeof(linux_args))))
+	error = copyin(args, &linux_args, sizeof(linux_args));
+	if (error)
 		return (error);
-
 	error = copyin(linux_args.msg, &msg, sizeof(msg));
 	if (error)
 		return (error);
-	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
-		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV)
-			return (EMSGSIZE);
-		MALLOC(iov, struct iovec *,
-			sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
-			M_WAITOK);
-	} else {
-		iov = aiov;
-	}
-	if (msg.msg_iovlen &&
-	    (error = copyin(msg.msg_iov, iov,
-	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)))))
-		goto done;
+	error = copyiniov(msg.msg_iov, msg.msg_iovlen, &iov, EMSGSIZE);
+	if (error)
+		return (error);
 	msg.msg_iov = iov;
 	msg.msg_flags = 0;
-
 	error = linux_sendit(td, linux_args.s, &msg, linux_args.flags);
-done:
-	if (iov != aiov)
-		FREE(iov, M_IOV);
+	free(iov, M_IOV);
 	return (error);
 }
 
diff --git a/sys/compat/svr4/svr4_stream.c b/sys/compat/svr4/svr4_stream.c
index 853a2722aa8c..d91c185c33a8 100644
--- a/sys/compat/svr4/svr4_stream.c
+++ b/sys/compat/svr4/svr4_stream.c
@@ -163,8 +163,7 @@ svr4_sendit(td, s, mp, flags)
 	int len, error;
 	struct socket *so;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
+	struct uio *ktruio = NULL;
 #endif
 
 	if ((error = fgetsock(td, s, &so, NULL)) != 0)
@@ -212,13 +211,8 @@ svr4_sendit(td, s, mp, flags)
 		control = 0;
 	}
 #ifdef KTRACE
-	if (KTRPOINT(td, KTR_GENIO)) {
-		int iovlen = auio.uio_iovcnt * sizeof (struct iovec);
-
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy((caddr_t)auio.uio_iov, (caddr_t)ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(&auio);
 #endif
 	len = auio.uio_resid;
 	error = so->so_proto->pr_usrreqs->pru_sosend(so, to, &auio, 0, control,
@@ -236,13 +230,9 @@ svr4_sendit(td, s, mp, flags)
 	if (error == 0)
 		td->td_retval[0] = len - auio.uio_resid;
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = td->td_retval[0];
-			ktrgenio(s, UIO_WRITE, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = td->td_retval[0];
+		ktrgenio(s, UIO_WRITE, ktruio, error);
 	}
 #endif
 bad:
@@ -269,8 +259,7 @@ svr4_recvit(td, s, mp, namelenp)
 	struct socket *so;
 	struct sockaddr *fromsa = 0;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
+	struct uio *ktruio = NULL;
 #endif
 
 	if ((error = fgetsock(td, s, &so, NULL)) != 0)
@@ -299,13 +288,8 @@ svr4_recvit(td, s, mp, namelenp)
 		}
 	}
 #ifdef KTRACE
-	if (KTRPOINT(td, KTR_GENIO)) {
-		int iovlen = auio.uio_iovcnt * sizeof (struct iovec);
-
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy((caddr_t)auio.uio_iov, (caddr_t)ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO)) 
+		ktruio = cloneuio(&auio);
 #endif
 	len = auio.uio_resid;
 	error = so->so_proto->pr_usrreqs->pru_soreceive(so, &fromsa, &auio,
@@ -317,13 +301,9 @@ svr4_recvit(td, s, mp, namelenp)
 			error = 0;
 	}
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = len - auio.uio_resid;
-			ktrgenio(s, UIO_READ, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = len - auio.uio_resid;
+		ktrgenio(s, UIO_READ, ktruio, error);
 	}
 #endif
 	if (error)
diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 8a2b0a512f09..694634a91023 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -413,13 +413,17 @@ ktrgenio(fd, rw, uio, error)
 	int datalen;
 	char *buf;
 
-	if (error)
+	if (error) {
+		free(uio, M_IOV);
 		return;
+	}
 	uio->uio_offset = 0;
 	uio->uio_rw = UIO_WRITE;
 	datalen = imin(uio->uio_resid, ktr_geniosize);
 	buf = malloc(datalen, M_KTRACE, M_WAITOK);
-	if (uiomove(buf, datalen, uio)) {
+	error = uiomove(buf, datalen, uio);
+	free(uio, M_IOV);
+	if (error) {
 		free(buf, M_KTRACE);
 		return;
 	}
diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index 7ccccddf6739..8d5c6f07d9e7 100644
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -474,40 +474,69 @@ copyinstrfrom(const void * __restrict src, void * __restrict dst, size_t len,
 }
 
 int
-uiofromiov(struct iovec *iovp, u_int iovcnt, struct uio *uio)
+copyiniov(struct iovec *iovp, u_int iovcnt, struct iovec **iov, int error)
+{
+	u_int iovlen;
+
+	*iov = NULL;
+	if (iovcnt > UIO_MAXIOV)
+		return (error);
+	iovlen = iovcnt * sizeof (struct iovec);
+	*iov = malloc(iovlen, M_IOV, M_WAITOK);
+	error = copyin(iovp, *iov, iovlen);
+	if (error) {
+		free(*iov, M_IOV);
+		*iov = NULL;
+	}
+	return (error);
+}
+
+int
+copyinuio(struct iovec *iovp, u_int iovcnt, struct uio **uiop)
 {
 	struct iovec *iov;
+	struct uio *uio;
 	u_int iovlen;
 	int error, i;
 
-	/* note: can't use iovlen until iovcnt is validated */
+	*uiop = NULL;
+	if (iovcnt > UIO_MAXIOV)
+		return (EINVAL);
 	iovlen = iovcnt * sizeof (struct iovec);
-	if (iovcnt > UIO_MAXIOV) {
-		error = EINVAL;
-		goto done;
+	uio = malloc(iovlen + sizeof *uio, M_IOV, M_WAITOK);
+	iov = (struct iovec *)(uio + 1);
+	error = copyin(iovp, iov, iovlen);
+	if (error) {
+		free(uio, M_IOV);
+		return (error);
 	}
-	MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
 	uio->uio_iov = iov;
 	uio->uio_iovcnt = iovcnt;
 	uio->uio_segflg = UIO_USERSPACE;
 	uio->uio_offset = -1;
-	if ((error = copyin(iovp, iov, iovlen)))
-		goto done;
 	uio->uio_resid = 0;
 	for (i = 0; i < iovcnt; i++) {
 		if (iov->iov_len > INT_MAX - uio->uio_resid) {
-			error = EINVAL;
-			goto done;
+			free(uio, M_IOV);
+			return (EINVAL);
 		}
 		uio->uio_resid += iov->iov_len;
 		iov++;
 	}
-
-done:
-	if (error && uio->uio_iov) {
-		FREE(uio->uio_iov, M_IOV);
-		uio->uio_iov = NULL;
-	}
-	return (error);
-
+	*uiop = uio;
+	return (0);
+}
+
+struct uio *
+cloneuio(struct uio *uiop)
+{
+	struct uio *uio;
+	int iovlen;
+
+	iovlen = uiop->uio_iovcnt * sizeof (struct iovec);
+	uio = malloc(iovlen + sizeof *uio, M_IOV, M_WAITOK);
+	*uio = *uiop;
+	uio->uio_iov = (struct iovec *)(uio + 1);
+	bcopy(uiop->uio_iov, uio->uio_iov, iovlen);
+	return (uio);
 }
diff --git a/sys/kern/subr_prf.c b/sys/kern/subr_prf.c
index 9f4bedd75eab..3650ca1ff45b 100644
--- a/sys/kern/subr_prf.c
+++ b/sys/kern/subr_prf.c
@@ -243,9 +243,7 @@ log(int level, const char *fmt, ...)
 void
 log_console(struct uio *uio)
 {
-	int c, i, error, iovlen, nl;
-	struct uio muio;
-	struct iovec *miov = NULL;
+	int c, i, error, nl;
 	char *consbuffer;
 	int pri;
 
@@ -253,13 +251,8 @@ log_console(struct uio *uio)
 		return;
 
 	pri = LOG_INFO | LOG_CONSOLE;
-	muio = *uio;
-	iovlen = uio->uio_iovcnt * sizeof (struct iovec);
-	MALLOC(miov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-	MALLOC(consbuffer, char *, CONSCHUNK, M_TEMP, M_WAITOK);
-	bcopy(muio.uio_iov, miov, iovlen);
-	muio.uio_iov = miov;
-	uio = &muio;
+	uio = cloneuio(uio);
+	consbuffer = malloc(CONSCHUNK, M_TEMP, M_WAITOK);
 
 	nl = 0;
 	while (uio->uio_resid > 0) {
@@ -278,8 +271,8 @@ log_console(struct uio *uio)
 	if (!nl)
 		msglogchar('\n', pri);
 	msgbuftrigger = 1;
-	FREE(miov, M_TEMP);
-	FREE(consbuffer, M_TEMP);
+	free(uio, M_IOV);
+	free(consbuffer, M_TEMP);
 	return;
 }
 
diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
index ab48888f76ad..13b5125847c4 100644
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -164,9 +164,7 @@ dofileread(td, fp, fd, buf, nbyte, offset, flags)
 	struct iovec aiov;
 	long cnt, error = 0;
 #ifdef KTRACE
-	struct iovec ktriov;
-	struct uio ktruio;
-	int didktr = 0;
+	struct uio *ktruio = NULL;
 #endif
 
 	aiov.iov_base = buf;
@@ -181,14 +179,8 @@ dofileread(td, fp, fd, buf, nbyte, offset, flags)
 	auio.uio_segflg = UIO_USERSPACE;
 	auio.uio_td = td;
 #ifdef KTRACE
-	/*
-	 * if tracing, save a copy of iovec
-	 */
-	if (KTRPOINT(td, KTR_GENIO)) {
-		ktriov = aiov;
-		ktruio = auio;
-		didktr = 1;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(&auio);
 #endif
 	cnt = nbyte;
 
@@ -199,10 +191,9 @@ dofileread(td, fp, fd, buf, nbyte, offset, flags)
 	}
 	cnt -= auio.uio_resid;
 #ifdef KTRACE
-	if (didktr && error == 0) {
-		ktruio.uio_iov = &ktriov;
-		ktruio.uio_resid = cnt;
-		ktrgenio(fd, UIO_READ, &ktruio, error);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = cnt;
+		ktrgenio(fd, UIO_READ, ktruio, error);
 	}
 #endif
 	td->td_retval[0] = cnt;
@@ -223,86 +214,46 @@ struct readv_args {
  * MPSAFE
  */
 int
-readv(td, uap)
-	struct thread *td;
-	struct readv_args *uap;
+readv(struct thread *td, struct readv_args *uap)
 {
 	struct file *fp;
-	struct uio auio;
-	struct iovec *iov;
-	struct iovec *needfree;
-	struct iovec aiov[UIO_SMALLIOV];
-	long i, cnt;
+	struct uio *auio = NULL;
+	long cnt;
 	int error;
-	u_int iovlen;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
+	struct uio *ktruio = NULL;
 #endif
 
-	if ((error = fget_read(td, uap->fd, &fp)) != 0)
+	error = fget_read(td, uap->fd, &fp);
+	if (error)
+		return (error);
+	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
+	if (error) {
+		fdrop(fp, td);
 		return (error);
-	needfree = NULL;
-	/* note: can't use iovlen until iovcnt is validated */
-	iovlen = uap->iovcnt * sizeof (struct iovec);
-	if (uap->iovcnt > UIO_SMALLIOV) {
-		if (uap->iovcnt > UIO_MAXIOV) {
-			error = EINVAL;
-			goto done;
-		}
-		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
-		needfree = iov;
-	} else
-		iov = aiov;
-	auio.uio_iov = iov;
-	auio.uio_iovcnt = uap->iovcnt;
-	auio.uio_rw = UIO_READ;
-	auio.uio_segflg = UIO_USERSPACE;
-	auio.uio_td = td;
-	auio.uio_offset = -1;
-	if ((error = copyin(uap->iovp, iov, iovlen)))
-		goto done;
-	auio.uio_resid = 0;
-	for (i = 0; i < uap->iovcnt; i++) {
-		if (iov->iov_len > INT_MAX - auio.uio_resid) {
-			error = EINVAL;
-			goto done;
-		}
-		auio.uio_resid += iov->iov_len;
-		iov++;
 	}
+	auio->uio_rw = UIO_READ;
+	auio->uio_td = td;
 #ifdef KTRACE
-	/*
-	 * if tracing, save a copy of iovec
-	 */
-	if (KTRPOINT(td, KTR_GENIO))  {
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy(auio.uio_iov, ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO)) 
+		ktruio = cloneuio(auio);
 #endif
-	cnt = auio.uio_resid;
-	if ((error = fo_read(fp, &auio, td->td_ucred, 0, td))) {
-		if (auio.uio_resid != cnt && (error == ERESTART ||
+	cnt = auio->uio_resid;
+	if ((error = fo_read(fp, auio, td->td_ucred, 0, td))) {
+		if (auio->uio_resid != cnt && (error == ERESTART ||
 		    error == EINTR || error == EWOULDBLOCK))
 			error = 0;
 	}
-	cnt -= auio.uio_resid;
+	cnt -= auio->uio_resid;
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = cnt;
-			ktrgenio(uap->fd, UIO_READ, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = cnt;
+		ktrgenio(uap->fd, UIO_READ, ktruio, error);
 	}
 #endif
 	td->td_retval[0] = cnt;
-done:
+	free(auio, M_IOV);
 	fdrop(fp, td);
-	if (needfree)
-		FREE(needfree, M_IOV);
 	return (error);
 }
 
@@ -389,9 +340,7 @@ dofilewrite(td, fp, fd, buf, nbyte, offset, flags)
 	struct iovec aiov;
 	long cnt, error = 0;
 #ifdef KTRACE
-	struct iovec ktriov;
-	struct uio ktruio;
-	int didktr = 0;
+	struct uio *ktruio = NULL;
 #endif
 
 	aiov.iov_base = (void *)(uintptr_t)buf;
@@ -406,14 +355,8 @@ dofilewrite(td, fp, fd, buf, nbyte, offset, flags)
 	auio.uio_segflg = UIO_USERSPACE;
 	auio.uio_td = td;
 #ifdef KTRACE
-	/*
-	 * if tracing, save a copy of iovec and uio
-	 */
-	if (KTRPOINT(td, KTR_GENIO)) {
-		ktriov = aiov;
-		ktruio = auio;
-		didktr = 1;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(&auio);
 #endif
 	cnt = nbyte;
 	if (fp->f_type == DTYPE_VNODE)
@@ -431,10 +374,9 @@ dofilewrite(td, fp, fd, buf, nbyte, offset, flags)
 	}
 	cnt -= auio.uio_resid;
 #ifdef KTRACE
-	if (didktr && error == 0) {
-		ktruio.uio_iov = &ktriov;
-		ktruio.uio_resid = cnt;
-		ktrgenio(fd, UIO_WRITE, &ktruio, error);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = cnt;
+		ktrgenio(fd, UIO_WRITE, ktruio, error);
 	}
 #endif
 	td->td_retval[0] = cnt;
@@ -455,68 +397,35 @@ struct writev_args {
  * MPSAFE
  */
 int
-writev(td, uap)
-	struct thread *td;
-	register struct writev_args *uap;
+writev(struct thread *td, struct writev_args *uap)
 {
 	struct file *fp;
-	struct uio auio;
-	register struct iovec *iov;
-	struct iovec *needfree;
-	struct iovec aiov[UIO_SMALLIOV];
-	long i, cnt, error = 0;
-	u_int iovlen;
+	struct uio *auio = NULL;
+	long cnt;
+	int error;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
+	struct uio *ktruio = NULL;
 #endif
 
-	if ((error = fget_write(td, uap->fd, &fp)) != 0)
+	error = fget_write(td, uap->fd, &fp);
+	if (error)
 		return (EBADF);
-	needfree = NULL;
-	/* note: can't use iovlen until iovcnt is validated */
-	iovlen = uap->iovcnt * sizeof (struct iovec);
-	if (uap->iovcnt > UIO_SMALLIOV) {
-		if (uap->iovcnt > UIO_MAXIOV) {
-			error = EINVAL;
-			goto done;
-		}
-		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
-		needfree = iov;
-	} else
-		iov = aiov;
-	auio.uio_iov = iov;
-	auio.uio_iovcnt = uap->iovcnt;
-	auio.uio_rw = UIO_WRITE;
-	auio.uio_segflg = UIO_USERSPACE;
-	auio.uio_td = td;
-	auio.uio_offset = -1;
-	if ((error = copyin(uap->iovp, iov, iovlen)))
-		goto done;
-	auio.uio_resid = 0;
-	for (i = 0; i < uap->iovcnt; i++) {
-		if (iov->iov_len > INT_MAX - auio.uio_resid) {
-			error = EINVAL;
-			goto done;
-		}
-		auio.uio_resid += iov->iov_len;
-		iov++;
+	error = copyinuio(uap->iovp, uap->iovcnt, &auio);
+	if (error) {
+		fdrop(fp, td);
+		return (error);
 	}
+	auio->uio_rw = UIO_WRITE;
+	auio->uio_td = td;
 #ifdef KTRACE
-	/*
-	 * if tracing, save a copy of iovec and uio
-	 */
-	if (KTRPOINT(td, KTR_GENIO))  {
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy(auio.uio_iov, ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(auio);
 #endif
-	cnt = auio.uio_resid;
+	cnt = auio->uio_resid;
 	if (fp->f_type == DTYPE_VNODE)
 		bwillwrite();
-	if ((error = fo_write(fp, &auio, td->td_ucred, 0, td))) {
-		if (auio.uio_resid != cnt && (error == ERESTART ||
+	if ((error = fo_write(fp, auio, td->td_ucred, 0, td))) {
+		if (auio->uio_resid != cnt && (error == ERESTART ||
 		    error == EINTR || error == EWOULDBLOCK))
 			error = 0;
 		if (error == EPIPE) {
@@ -525,22 +434,16 @@ writev(td, uap)
 			PROC_UNLOCK(td->td_proc);
 		}
 	}
-	cnt -= auio.uio_resid;
+	cnt -= auio->uio_resid;
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = cnt;
-			ktrgenio(uap->fd, UIO_WRITE, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = cnt;
+		ktrgenio(uap->fd, UIO_WRITE, ktruio, error);
 	}
 #endif
 	td->td_retval[0] = cnt;
-done:
 	fdrop(fp, td);
-	if (needfree)
-		FREE(needfree, M_IOV);
+	free(auio, M_IOV);
 	return (error);
 }
 
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 27440d4d9ea2..eeff60dd7e8b 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -701,9 +701,7 @@ kern_sendit(td, s, mp, flags, control)
 	int i;
 	int len, error;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
-	int iovlen;
+	struct uio *ktruio = NULL;
 #endif
 
 	NET_LOCK_GIANT();
@@ -733,12 +731,8 @@ kern_sendit(td, s, mp, flags, control)
 		}
 	}
 #ifdef KTRACE
-	if (KTRPOINT(td, KTR_GENIO)) {
-		iovlen = auio.uio_iovcnt * sizeof (struct iovec);
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy(auio.uio_iov, ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(&auio);
 #endif
 	len = auio.uio_resid;
 	error = so->so_proto->pr_usrreqs->pru_sosend(so, mp->msg_name, &auio,
@@ -757,13 +751,9 @@ kern_sendit(td, s, mp, flags, control)
 	if (error == 0)
 		td->td_retval[0] = len - auio.uio_resid;
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = td->td_retval[0];
-			ktrgenio(s, UIO_WRITE, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = td->td_retval[0];
+		ktrgenio(s, UIO_WRITE, ktruio, error);
 	}
 #endif
 bad:
@@ -842,41 +832,26 @@ osend(td, uap)
 int
 osendmsg(td, uap)
 	struct thread *td;
-	register struct osendmsg_args /* {
+	struct osendmsg_args /* {
 		int	s;
 		caddr_t	msg;
 		int	flags;
 	} */ *uap;
 {
 	struct msghdr msg;
-	struct iovec aiov[UIO_SMALLIOV], *iov;
+	struct iovec *iov;
 	int error;
 
 	error = copyin(uap->msg, &msg, sizeof (struct omsghdr));
 	if (error)
-		goto done2;
-	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
-		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV) {
-			error = EMSGSIZE;
-			goto done2;
-		}
-		MALLOC(iov, struct iovec *,
-		      sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
-		      M_WAITOK);
-	} else {
-		iov = aiov;
-	}
-	error = copyin(msg.msg_iov, iov,
-	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)));
+		return (error);
+	error = copyiniov(msg.msg_iov, msg.msg_iovlen, &iov, EMSGSIZE);
 	if (error)
-		goto done;
-	msg.msg_flags = MSG_COMPAT;
+		return (error);
 	msg.msg_iov = iov;
+	msg.msg_flags = MSG_COMPAT;
 	error = sendit(td, uap->s, &msg, uap->flags);
-done:
-	if (iov != aiov)
-		FREE(iov, M_IOV);
-done2:
+	free(iov, M_IOV);
 	return (error);
 }
 #endif
@@ -887,56 +862,41 @@ osendmsg(td, uap)
 int
 sendmsg(td, uap)
 	struct thread *td;
-	register struct sendmsg_args /* {
+	struct sendmsg_args /* {
 		int	s;
 		caddr_t	msg;
 		int	flags;
 	} */ *uap;
 {
 	struct msghdr msg;
-	struct iovec aiov[UIO_SMALLIOV], *iov;
+	struct iovec *iov;
 	int error;
 
 	error = copyin(uap->msg, &msg, sizeof (msg));
 	if (error)
-		goto done2;
-	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
-		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV) {
-			error = EMSGSIZE;
-			goto done2;
-		}
-		MALLOC(iov, struct iovec *,
-		       sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
-		       M_WAITOK);
-	} else {
-		iov = aiov;
-	}
-	if (msg.msg_iovlen &&
-	    (error = copyin(msg.msg_iov, iov,
-	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)))))
-		goto done;
+		return (error);
+	error = copyiniov(msg.msg_iov, msg.msg_iovlen, &iov, EMSGSIZE);
+	if (error)
+		return (error);
 	msg.msg_iov = iov;
 #ifdef COMPAT_OLDSOCK
 	msg.msg_flags = 0;
 #endif
 	error = sendit(td, uap->s, &msg, uap->flags);
-done:
-	if (iov != aiov)
-		FREE(iov, M_IOV);
-done2:
+	free(iov, M_IOV);
 	return (error);
 }
 
 static int
 recvit(td, s, mp, namelenp)
-	register struct thread *td;
+	struct thread *td;
 	int s;
-	register struct msghdr *mp;
+	struct msghdr *mp;
 	void *namelenp;
 {
 	struct uio auio;
-	register struct iovec *iov;
-	register int i;
+	struct iovec *iov;
+	int i;
 	socklen_t len;
 	int error;
 	struct mbuf *m, *control = 0;
@@ -944,9 +904,7 @@ recvit(td, s, mp, namelenp)
 	struct socket *so;
 	struct sockaddr *fromsa = 0;
 #ifdef KTRACE
-	struct iovec *ktriov = NULL;
-	struct uio ktruio;
-	int iovlen;
+	struct uio *ktruio = NULL;
 #endif
 
 	NET_LOCK_GIANT();
@@ -982,12 +940,8 @@ recvit(td, s, mp, namelenp)
 		}
 	}
 #ifdef KTRACE
-	if (KTRPOINT(td, KTR_GENIO)) {
-		iovlen = auio.uio_iovcnt * sizeof (struct iovec);
-		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
-		bcopy(auio.uio_iov, ktriov, iovlen);
-		ktruio = auio;
-	}
+	if (KTRPOINT(td, KTR_GENIO))
+		ktruio = cloneuio(&auio);
 #endif
 	len = auio.uio_resid;
 	error = so->so_proto->pr_usrreqs->pru_soreceive(so, &fromsa, &auio,
@@ -999,13 +953,9 @@ recvit(td, s, mp, namelenp)
 			error = 0;
 	}
 #ifdef KTRACE
-	if (ktriov != NULL) {
-		if (error == 0) {
-			ktruio.uio_iov = ktriov;
-			ktruio.uio_resid = (int)len - auio.uio_resid;
-			ktrgenio(s, UIO_READ, &ktruio, error);
-		}
-		FREE(ktriov, M_TEMP);
+	if (ktruio != NULL) {
+		ktruio->uio_resid = (int)len - auio.uio_resid;
+		ktrgenio(s, UIO_READ, ktruio, error);
 	}
 #endif
 	if (error)
@@ -1189,46 +1139,29 @@ orecv(td, uap)
 int
 orecvmsg(td, uap)
 	struct thread *td;
-	register struct orecvmsg_args /* {
+	struct orecvmsg_args /* {
 		int	s;
 		struct	omsghdr *msg;
 		int	flags;
 	} */ *uap;
 {
 	struct msghdr msg;
-	struct iovec aiov[UIO_SMALLIOV], *iov;
+	struct iovec *iov;
 	int error;
 
 	error = copyin(uap->msg, &msg, sizeof (struct omsghdr));
 	if (error)
 		return (error);
-
-	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
-		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV) {
-			error = EMSGSIZE;
-			goto done2;
-		}
-		MALLOC(iov, struct iovec *,
-		      sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
-		      M_WAITOK);
-	} else {
-		iov = aiov;
-	}
-	msg.msg_flags = uap->flags | MSG_COMPAT;
-	error = copyin(msg.msg_iov, iov,
-	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)));
+	error = copyiniov(msg.msg_iov, msg.msg_iovlen, &iov, EMSGSIZE);
 	if (error)
-		goto done;
+		return (error);
+	msg.msg_flags = uap->flags | MSG_COMPAT;
 	msg.msg_iov = iov;
 	error = recvit(td, uap->s, &msg, &uap->msg->msg_namelen);
-
 	if (msg.msg_controllen && error == 0)
 		error = copyout(&msg.msg_controllen,
 		    &uap->msg->msg_accrightslen, sizeof (int));
-done:
-	if (iov != aiov)
-		FREE(iov, M_IOV);
-done2:
+	free(iov, M_IOV);
 	return (error);
 }
 #endif
@@ -1239,50 +1172,34 @@ orecvmsg(td, uap)
 int
 recvmsg(td, uap)
 	struct thread *td;
-	register struct recvmsg_args /* {
+	struct recvmsg_args /* {
 		int	s;
 		struct	msghdr *msg;
 		int	flags;
 	} */ *uap;
 {
 	struct msghdr msg;
-	struct iovec aiov[UIO_SMALLIOV], *uiov, *iov;
-	register int error;
+	struct iovec *uiov, *iov;
+	int error;
 
 	error = copyin(uap->msg, &msg, sizeof (msg));
 	if (error)
-		goto done2;
-	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
-		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV) {
-			error = EMSGSIZE;
-			goto done2;
-		}
-		MALLOC(iov, struct iovec *,
-		       sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
-		       M_WAITOK);
-	} else {
-		iov = aiov;
-	}
-#ifdef COMPAT_OLDSOCK
-	msg.msg_flags = uap->flags &~ MSG_COMPAT;
-#else
+		return (error);
+	error = copyiniov(msg.msg_iov, msg.msg_iovlen, &iov, EMSGSIZE);
+	if (error)
+		return (error);
 	msg.msg_flags = uap->flags;
+#ifdef COMPAT_OLDSOCK
+	msg.msg_flags &= ~MSG_COMPAT;
 #endif
 	uiov = msg.msg_iov;
 	msg.msg_iov = iov;
-	error = copyin(uiov, iov,
-	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)));
-	if (error)
-		goto done;
 	error = recvit(td, uap->s, &msg, NULL);
-	if (!error) {
+	if (error == 0) {
 		msg.msg_iov = uiov;
 		error = copyout(&msg, uap->msg, sizeof(msg));
 	}
-done:
-	if (iov != aiov)
-		FREE(iov, M_IOV);
-done2:
+	free(iov, M_IOV);
 	return (error);
 }
 
@@ -1727,10 +1644,9 @@ do_sendfile(struct thread *td, struct sendfile_args *uap, int compat)
 	struct vm_page *pg;
 	struct writev_args nuap;
 	struct sf_hdtr hdtr;
-	struct uio hdr_uio;
+	struct uio *hdr_uio = NULL;
 	off_t off, xfsize, hdtr_size, sbytes = 0;
 	int error, headersize = 0, headersent = 0;
-	struct iovec *hdr_iov = NULL;
 
 	mtx_lock(&Giant);
 
@@ -1783,16 +1699,13 @@ do_sendfile(struct thread *td, struct sendfile_args *uap, int compat)
 		 * Send any headers.
 		 */
 		if (hdtr.headers != NULL) {
-			hdr_uio.uio_td = td;
-			hdr_uio.uio_rw = UIO_WRITE;
-			error = uiofromiov(hdtr.headers, hdtr.hdr_cnt,
-				&hdr_uio);
+			error = copyinuio(hdtr.headers, hdtr.hdr_cnt, &hdr_uio);
 			if (error)
 				goto done;
-			/* Cache hdr_iov, m_uiotombuf may change it. */
-			hdr_iov = hdr_uio.uio_iov;
-			if (hdr_uio.uio_resid > 0) {
-				m_header = m_uiotombuf(&hdr_uio, M_DONTWAIT, 0);
+			hdr_uio->uio_td = td;
+			hdr_uio->uio_rw = UIO_WRITE;
+			if (hdr_uio->uio_resid > 0) {
+				m_header = m_uiotombuf(hdr_uio, M_DONTWAIT, 0);
 				if (m_header == NULL)
 					goto done;
 				headersize = m_header->m_pkthdr.len;
@@ -2110,8 +2023,8 @@ do_sendfile(struct thread *td, struct sendfile_args *uap, int compat)
 		vrele(vp);
 	if (so)
 		fputsock(so);
-	if (hdr_iov)
-		FREE(hdr_iov, M_IOV);
+	if (hdr_uio != NULL)
+		free(hdr_uio, M_IOV);
 	if (m_header)
 		m_freem(m_header);
 
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 22048f41b5fb..5252b3bc7cb3 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -376,46 +376,32 @@ nmount(td, uap)
 		int flags;
 	} */ *uap;
 {
-	struct uio auio;
-	struct iovec *iov, *needfree;
-	struct iovec aiov[UIO_SMALLIOV];
+	struct uio *auio;
+	struct iovec *iov;
 	unsigned int i;
 	int error;
-	u_int iovlen, iovcnt;
+	u_int iovcnt;
 
 	iovcnt = uap->iovcnt;
-	iovlen = iovcnt * sizeof (struct iovec);
 	/*
 	 * Check that we have an even number of iovec's
 	 * and that we have at least two options.
 	 */
-	if ((iovcnt & 1) || (iovcnt < 4) || (iovcnt > UIO_MAXIOV))
+	if ((iovcnt & 1) || (iovcnt < 4))
 		return (EINVAL);
-
-	if (iovcnt > UIO_SMALLIOV) {
-		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
-		needfree = iov;
-	} else {
-		iov = aiov;
-		needfree = NULL;
-	}
-	auio.uio_iov = iov;
-	auio.uio_iovcnt = iovcnt;
-	auio.uio_segflg = UIO_USERSPACE;
-	if ((error = copyin(uap->iovp, iov, iovlen)))
-		goto finish;
-
+	error = copyinuio(uap->iovp, iovcnt, &auio);
+	if (error)
+		return (error);
+	iov = auio->uio_iov;
 	for (i = 0; i < iovcnt; i++) {
 		if (iov->iov_len > MMAXOPTIONLEN) {
-			error = EINVAL;
-			goto finish;
+			free(auio, M_IOV);
+			return (EINVAL);
 		}
 		iov++;
 	}
-	error = vfs_nmount(td, uap->flags, &auio);
-finish:
-	if (needfree != NULL)
-		free(needfree, M_TEMP);
+	error = vfs_nmount(td, uap->flags, auio);
+	free(auio, M_IOV);
 	return (error);
 }
 
diff --git a/sys/sys/uio.h b/sys/sys/uio.h
index 600fcff2dc1f..f89c9c4c9d64 100644
--- a/sys/sys/uio.h
+++ b/sys/sys/uio.h
@@ -77,17 +77,19 @@ struct uio {
  * IOV_MAX.
  */
 #define UIO_MAXIOV	1024		/* max 1K of iov's */
-#define UIO_SMALLIOV	8		/* 8 on stack, else malloc */
 
 struct vm_object;
 struct vm_page;
 
+struct uio *cloneuio(struct uio *uiop);
 int	copyinfrom(const void * __restrict src, void * __restrict dst,
 	    size_t len, int seg);
+int	copyiniov(struct iovec *iovp, u_int iovcnt, struct iovec **iov,
+	    int error);
 int	copyinstrfrom(const void * __restrict src, void * __restrict dst,
 	    size_t len, size_t * __restrict copied, int seg);
+int	copyinuio(struct iovec *iovp, u_int iovcnt, struct uio **uiop);
 void	uio_yield(void);
-int	uiofromiov(struct iovec *iovp, u_int iovcnt, struct uio *auio);
 int	uiomove(void *cp, int n, struct uio *uio);
 int	uiomove_frombuf(void *buf, int buflen, struct uio *uio);
 int	uiomove_fromphys(struct vm_page *ma[], vm_offset_t offset, int n,