Introduce uiomove_fromphys(). This is a variant of uiomove() that takes

a collection of physical pages as the source.  On amd64 it is implemented
using the direct virtual-to-physical map.

sys/amd64/amd64/uio_machdep.c

@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2004 Alan L. Cox <alc@cs.rice.edu>
+ * Copyright (c) 1982, 1986, 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ * (c) UNIX System Laboratories, Inc.
+ * All or some portions of this file are derived from material licensed
+ * to the University of California by American Telephone and Telegraph
+ * Co. or Unix System Laboratories, Inc. and are reproduced herein with
+ * the permission of UNIX System Laboratories, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)kern_subr.c	8.3 (Berkeley) 1/21/94
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/proc.h>
+#include <sys/systm.h>
+#include <sys/uio.h>
+
+#include <vm/vm.h>
+#include <vm/vm_page.h>
+
+#include <machine/vmparam.h>
+
+/*
+ * Implement uiomove(9) from physical memory using the direct map to
+ * avoid the creation and destruction of emphemeral mappings.
+ */
+int
+uiomove_fromphys(vm_page_t ma[], vm_offset_t offset, int n, struct uio *uio)
+{
+	struct thread *td = curthread;
+	struct iovec *iov;
+	void *cp;
+	vm_offset_t page_offset;
+	size_t cnt;
+	int error = 0;
+	int save = 0;
+
+	KASSERT(uio->uio_rw == UIO_READ || uio->uio_rw == UIO_WRITE,
+	    ("uiomove_fromphys: mode"));
+	KASSERT(uio->uio_segflg != UIO_USERSPACE || uio->uio_td == curthread,
+	    ("uiomove_fromphys proc"));
+	if (td != NULL) {
+		mtx_lock_spin(&sched_lock);
+		save = td->td_flags & TDF_DEADLKTREAT;
+		td->td_flags |= TDF_DEADLKTREAT;
+		mtx_unlock_spin(&sched_lock);
+	}
+	while (n > 0 && uio->uio_resid) {
+		iov = uio->uio_iov;
+		cnt = iov->iov_len;
+		if (cnt == 0) {
+			uio->uio_iov++;
+			uio->uio_iovcnt--;
+			continue;
+		}
+		if (cnt > n)
+			cnt = n;
+		page_offset = offset & PAGE_MASK;
+		cnt = min(cnt, PAGE_SIZE - page_offset);
+		cp = (char *)PHYS_TO_DMAP(ma[offset >> PAGE_SHIFT]->phys_addr) +
+		    page_offset;
+		switch (uio->uio_segflg) {
+		case UIO_USERSPACE:
+			if (ticks - PCPU_GET(switchticks) >= hogticks)
+				uio_yield();
+			if (uio->uio_rw == UIO_READ)
+				error = copyout(cp, iov->iov_base, cnt);
+			else
+				error = copyin(iov->iov_base, cp, cnt);
+			if (error)
+				goto out;
+			break;
+		case UIO_SYSSPACE:
+			if (uio->uio_rw == UIO_READ)
+				bcopy(cp, iov->iov_base, cnt);
+			else
+				bcopy(iov->iov_base, cp, cnt);
+			break;
+		case UIO_NOCOPY:
+			break;
+		}
+		iov->iov_base = (char *)iov->iov_base + cnt;
+		iov->iov_len -= cnt;
+		uio->uio_resid -= cnt;
+		uio->uio_offset += cnt;
+		offset += cnt;
+		n -= cnt;
+	}
+out:
+	if (td != NULL && save == 0) {
+		mtx_lock_spin(&sched_lock);
+		td->td_flags &= ~TDF_DEADLKTREAT;
+		mtx_unlock_spin(&sched_lock);
+	}
+	return (error);
+}

sys/conf/files.amd64

@@ -75,6 +75,7 @@ amd64/amd64/support.S		standard
 amd64/amd64/sys_machdep.c	standard
 amd64/amd64/trap.c		standard
 amd64/amd64/tsc.c		standard
+amd64/amd64/uio_machdep.c	standard
 amd64/amd64/uma_machdep.c	standard
 amd64/amd64/vm_machdep.c	standard
 amd64/isa/atpic.c		optional	atpic isa

sys/sys/uio.h

@@ -84,6 +84,7 @@ struct uio {
 #define UIO_SMALLIOV	8		/* 8 on stack, else malloc */
 
 struct vm_object;
+struct vm_page;
 
 int	copyinfrom(const void * __restrict src, void * __restrict dst,
 	    size_t len, int seg);
@@ -93,6 +94,8 @@ 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,
+	    struct uio *uio);
 int	uiomoveco(void *cp, int n, struct uio *uio, struct vm_object *obj,
 	    int disposable);