1/*
2 * Copyright (c) 2006 Oracle.  All rights reserved.
3 *
4 * This software is available to you under a choice of one of two
5 * licenses.  You may choose to be licensed under the terms of the GNU
6 * General Public License (GPL) Version 2, available from the file
7 * COPYING in the main directory of this source tree, or the
8 * OpenIB.org BSD license below:
9 *
10 *     Redistribution and use in source and binary forms, with or
11 *     without modification, are permitted provided that the following
12 *     conditions are met:
13 *
14 *      - Redistributions of source code must retain the above
15 *        copyright notice, this list of conditions and the following
16 *        disclaimer.
17 *
18 *      - Redistributions in binary form must reproduce the above
19 *        copyright notice, this list of conditions and the following
20 *        disclaimer in the documentation and/or other materials
21 *        provided with the distribution.
22 *
23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30 * SOFTWARE.
31 *
32 */
33#include <linux/percpu.h>
34#include <linux/seq_file.h>
35#include <linux/slab.h>
36#include <linux/proc_fs.h>
37#include <linux/export.h>
38
39#include "rds.h"
40
41/*
42 * This file implements a getsockopt() call which copies a set of fixed
43 * sized structs into a user-specified buffer as a means of providing
44 * read-only information about RDS.
45 *
46 * For a given information source there are a given number of fixed sized
47 * structs at a given time.  The structs are only copied if the user-specified
48 * buffer is big enough.  The destination pages that make up the buffer
49 * are pinned for the duration of the copy.
50 *
51 * This gives us the following benefits:
52 *
53 * - simple implementation, no copy "position" across multiple calls
54 * - consistent snapshot of an info source
55 * - atomic copy works well with whatever locking info source has
56 * - one portable tool to get rds info across implementations
57 * - long-lived tool can get info without allocating
58 *
59 * at the following costs:
60 *
61 * - info source copy must be pinned, may be "large"
62 */
63
64struct rds_info_iterator {
65	struct page **pages;
66	void *addr;
67	unsigned long offset;
68};
69
70static DEFINE_SPINLOCK(rds_info_lock);
71static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
72
73void rds_info_register_func(int optname, rds_info_func func)
74{
75	int offset = optname - RDS_INFO_FIRST;
76
77	BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
78
79	spin_lock(&rds_info_lock);
80	BUG_ON(rds_info_funcs[offset]);
81	rds_info_funcs[offset] = func;
82	spin_unlock(&rds_info_lock);
83}
84EXPORT_SYMBOL_GPL(rds_info_register_func);
85
86void rds_info_deregister_func(int optname, rds_info_func func)
87{
88	int offset = optname - RDS_INFO_FIRST;
89
90	BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
91
92	spin_lock(&rds_info_lock);
93	BUG_ON(rds_info_funcs[offset] != func);
94	rds_info_funcs[offset] = NULL;
95	spin_unlock(&rds_info_lock);
96}
97EXPORT_SYMBOL_GPL(rds_info_deregister_func);
98
99/*
100 * Typically we hold an atomic kmap across multiple rds_info_copy() calls
101 * because the kmap is so expensive.  This must be called before using blocking
102 * operations while holding the mapping and as the iterator is torn down.
103 */
104void rds_info_iter_unmap(struct rds_info_iterator *iter)
105{
106	if (iter->addr) {
107		kunmap_atomic(iter->addr);
108		iter->addr = NULL;
109	}
110}
111
112/*
113 * get_user_pages() called flush_dcache_page() on the pages for us.
114 */
115void rds_info_copy(struct rds_info_iterator *iter, void *data,
116		   unsigned long bytes)
117{
118	unsigned long this;
119
120	while (bytes) {
121		if (!iter->addr)
122			iter->addr = kmap_atomic(*iter->pages);
123
124		this = min(bytes, PAGE_SIZE - iter->offset);
125
126		rdsdebug("page %p addr %p offset %lu this %lu data %p "
127			  "bytes %lu\n", *iter->pages, iter->addr,
128			  iter->offset, this, data, bytes);
129
130		memcpy(iter->addr + iter->offset, data, this);
131
132		data += this;
133		bytes -= this;
134		iter->offset += this;
135
136		if (iter->offset == PAGE_SIZE) {
137			kunmap_atomic(iter->addr);
138			iter->addr = NULL;
139			iter->offset = 0;
140			iter->pages++;
141		}
142	}
143}
144EXPORT_SYMBOL_GPL(rds_info_copy);
145
146/*
147 * @optval points to the userspace buffer that the information snapshot
148 * will be copied into.
149 *
150 * @optlen on input is the size of the buffer in userspace.  @optlen
151 * on output is the size of the requested snapshot in bytes.
152 *
153 * This function returns -errno if there is a failure, particularly -ENOSPC
154 * if the given userspace buffer was not large enough to fit the snapshot.
155 * On success it returns the positive number of bytes of each array element
156 * in the snapshot.
157 */
158int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
159			int __user *optlen)
160{
161	struct rds_info_iterator iter;
162	struct rds_info_lengths lens;
163	unsigned long nr_pages = 0;
164	unsigned long start;
165	rds_info_func func;
166	struct page **pages = NULL;
167	int ret;
168	int len;
169	int total;
170
171	if (get_user(len, optlen)) {
172		ret = -EFAULT;
173		goto out;
174	}
175
176	/* check for all kinds of wrapping and the like */
177	start = (unsigned long)optval;
178	if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) {
179		ret = -EINVAL;
180		goto out;
181	}
182
183	/* a 0 len call is just trying to probe its length */
184	if (len == 0)
185		goto call_func;
186
187	nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
188			>> PAGE_SHIFT;
189
190	pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL);
191	if (!pages) {
192		ret = -ENOMEM;
193		goto out;
194	}
195	ret = pin_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
196	if (ret != nr_pages) {
197		if (ret > 0)
198			nr_pages = ret;
199		else
200			nr_pages = 0;
201		ret = -EAGAIN; /* XXX ? */
202		goto out;
203	}
204
205	rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
206
207call_func:
208	func = rds_info_funcs[optname - RDS_INFO_FIRST];
209	if (!func) {
210		ret = -ENOPROTOOPT;
211		goto out;
212	}
213
214	iter.pages = pages;
215	iter.addr = NULL;
216	iter.offset = start & (PAGE_SIZE - 1);
217
218	func(sock, len, &iter, &lens);
219	BUG_ON(lens.each == 0);
220
221	total = lens.nr * lens.each;
222
223	rds_info_iter_unmap(&iter);
224
225	if (total > len) {
226		len = total;
227		ret = -ENOSPC;
228	} else {
229		len = total;
230		ret = lens.each;
231	}
232
233	if (put_user(len, optlen))
234		ret = -EFAULT;
235
236out:
237	if (pages)
238		unpin_user_pages(pages, nr_pages);
239	kfree(pages);
240
241	return ret;
242}
243