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TOMOYO Linux Cross Reference
Linux/net/rds/info.c

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  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 
 64 struct rds_info_iterator {
 65         struct page **pages;
 66         void *addr;
 67         unsigned long offset;
 68 };
 69 
 70 static DEFINE_SPINLOCK(rds_info_lock);
 71 static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
 72 
 73 void 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 }
 84 EXPORT_SYMBOL_GPL(rds_info_register_func);
 85 
 86 void 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 }
 97 EXPORT_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  */
104 void 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  */
115 void 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 }
144 EXPORT_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  */
158 int 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 > INT_MAX - PAGE_SIZE + 1 || 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 
208 call_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 
237 out:
238         for (i = 0; pages && i < nr_pages; i++)
239                 put_page(pages[i]);
240         kfree(pages);
241 
242         return ret;
243 }
244 

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