uipc_cow.c revision 219028 
1/*--
2 * Copyright (c) 1997, Duke University
3 * All rights reserved.
4 *
5 * Author:
6 *         Andrew Gallatin <gallatin@cs.duke.edu>
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. The name of Duke University may not be used to endorse or promote
17 *    products derived from this software without specific prior written
18 *    permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY DUKE UNIVERSITY ``AS IS'' AND ANY
21 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
23 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DUKE UNIVERSITY BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITSOR BUSINESS
27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
28 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
29 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
30 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33/*
34 * This is a set of routines for enabling and disabling copy on write
35 * protection for data written into sockets.
36 */
37
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: head/sys/kern/uipc_cow.c 219028 2011-02-25 10:11:01Z netchild $");
40
41#include <sys/param.h>
42#include <sys/systm.h>
43#include <sys/sysctl.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/lock.h>
47#include <sys/mutex.h>
48#include <sys/mbuf.h>
49#include <sys/sf_buf.h>
50#include <sys/socketvar.h>
51#include <sys/uio.h>
52
53#include <vm/vm.h>
54#include <vm/vm_extern.h>
55#include <vm/vm_param.h>
56#include <vm/pmap.h>
57#include <vm/vm_map.h>
58#include <vm/vm_page.h>
59#include <vm/vm_object.h>
60
61FEATURE(zero_copy_sockets, "Zero copy sockets support");
62
63struct netsend_cow_stats {
64	int attempted;
65	int fail_not_mapped;
66	int fail_sf_buf;
67	int success;
68	int iodone;
69};
70
71static struct netsend_cow_stats socow_stats;
72
73static void socow_iodone(void *addr, void *args);
74
75static void
76socow_iodone(void *addr, void *args)
77{
78	struct sf_buf *sf;
79	vm_page_t pp;
80
81	sf = args;
82	pp = sf_buf_page(sf);
83	sf_buf_free(sf);
84	/* remove COW mapping  */
85	vm_page_lock(pp);
86	vm_page_cowclear(pp);
87	vm_page_unwire(pp, 0);
88	/*
89	 * Check for the object going away on us. This can
90	 * happen since we don't hold a reference to it.
91	 * If so, we're responsible for freeing the page.
92	 */
93	if (pp->wire_count == 0 && pp->object == NULL)
94		vm_page_free(pp);
95	vm_page_unlock(pp);
96	socow_stats.iodone++;
97}
98
99int
100socow_setup(struct mbuf *m0, struct uio *uio)
101{
102	struct sf_buf *sf;
103	vm_page_t pp;
104	struct iovec *iov;
105	struct vmspace *vmspace;
106	struct vm_map *map;
107	vm_offset_t offset, uva;
108	vm_size_t len;
109
110	socow_stats.attempted++;
111	vmspace = curproc->p_vmspace;
112	map = &vmspace->vm_map;
113	uva = (vm_offset_t) uio->uio_iov->iov_base;
114	offset = uva & PAGE_MASK;
115	len = PAGE_SIZE - offset;
116
117	/*
118	 * Verify that access to the given address is allowed from user-space.
119	 */
120	if (vm_fault_quick_hold_pages(map, uva, len, VM_PROT_READ, &pp, 1) <
121	    0) {
122		socow_stats.fail_not_mapped++;
123		return(0);
124	}
125
126	/*
127	 * set up COW
128	 */
129	vm_page_lock(pp);
130	if (vm_page_cowsetup(pp) != 0) {
131		vm_page_unhold(pp);
132		vm_page_unlock(pp);
133		return (0);
134	}
135
136	/*
137	 * wire the page for I/O
138	 */
139	vm_page_wire(pp);
140	vm_page_unhold(pp);
141	vm_page_unlock(pp);
142	/*
143	 * Allocate an sf buf
144	 */
145	sf = sf_buf_alloc(pp, SFB_CATCH);
146	if (sf == NULL) {
147		vm_page_lock(pp);
148		vm_page_cowclear(pp);
149		vm_page_unwire(pp, 0);
150		/*
151		 * Check for the object going away on us. This can
152		 * happen since we don't hold a reference to it.
153		 * If so, we're responsible for freeing the page.
154		 */
155		if (pp->wire_count == 0 && pp->object == NULL)
156			vm_page_free(pp);
157		vm_page_unlock(pp);
158		socow_stats.fail_sf_buf++;
159		return(0);
160	}
161	/*
162	 * attach to mbuf
163	 */
164	MEXTADD(m0, sf_buf_kva(sf), PAGE_SIZE, socow_iodone,
165	    (void*)sf_buf_kva(sf), sf, M_RDONLY, EXT_SFBUF);
166	m0->m_len = len;
167	m0->m_data = (caddr_t)sf_buf_kva(sf) + offset;
168	socow_stats.success++;
169
170	iov = uio->uio_iov;
171	iov->iov_base = (char *)iov->iov_base + m0->m_len;
172	iov->iov_len -= m0->m_len;
173	uio->uio_resid -= m0->m_len;
174	uio->uio_offset += m0->m_len;
175	if (iov->iov_len == 0) {
176		uio->uio_iov++;
177		uio->uio_iovcnt--;
178	}
179
180	return(m0->m_len);
181}
182