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	unsigned long i;
166	rds_info_func func;
167	struct page **pages = NULL;
168	int ret;
169	int len;
170	int total;
171
172	if (get_user(len, optlen)) {
173		ret = -EFAULT;
174		goto out;
175	}
176
177	/* check for all kinds of wrapping and the like */
178	start = (unsigned long)optval;
179	if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
180		ret = -EINVAL;
181		goto out;
182	}
183
184	/* a 0 len call is just trying to probe its length */
185	if (len == 0)
186		goto call_func;
187
188	nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
189			>> PAGE_SHIFT;
190
191	pages = kmalloc(nr_pages * sizeof(struct page *), GFP_KERNEL);
192	if (!pages) {
193		ret = -ENOMEM;
194		goto out;
195	}
196	ret = get_user_pages_fast(start, nr_pages, 1, pages);
197	if (ret != nr_pages) {
198		if (ret > 0)
199			nr_pages = ret;
200		else
201			nr_pages = 0;
202		ret = -EAGAIN; /* XXX ? */
203		goto out;
204	}
205
206	rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
207
208call_func:
209	func = rds_info_funcs[optname - RDS_INFO_FIRST];
210	if (!func) {
211		ret = -ENOPROTOOPT;
212		goto out;
213	}
214
215	iter.pages = pages;
216	iter.addr = NULL;
217	iter.offset = start & (PAGE_SIZE - 1);
218
219	func(sock, len, &iter, &lens);
220	BUG_ON(lens.each == 0);
221
222	total = lens.nr * lens.each;
223
224	rds_info_iter_unmap(&iter);
225
226	if (total > len) {
227		len = total;
228		ret = -ENOSPC;
229	} else {
230		len = total;
231		ret = lens.each;
232	}
233
234	if (put_user(len, optlen))
235		ret = -EFAULT;
236
237out:
238	for (i = 0; pages && i < nr_pages; i++)
239		put_page(pages[i]);
240	kfree(pages);
241
242	return ret;
243}