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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 
 38 #include "rds.h"
 39 
 40 /*
 41  * This file implements a getsockopt() call which copies a set of fixed
 42  * sized structs into a user-specified buffer as a means of providing
 43  * read-only information about RDS.
 44  *
 45  * For a given information source there are a given number of fixed sized
 46  * structs at a given time.  The structs are only copied if the user-specified
 47  * buffer is big enough.  The destination pages that make up the buffer
 48  * are pinned for the duration of the copy.
 49  *
 50  * This gives us the following benefits:
 51  *
 52  * - simple implementation, no copy "position" across multiple calls
 53  * - consistent snapshot of an info source
 54  * - atomic copy works well with whatever locking info source has
 55  * - one portable tool to get rds info across implementations
 56  * - long-lived tool can get info without allocating
 57  *
 58  * at the following costs:
 59  *
 60  * - info source copy must be pinned, may be "large"
 61  */
 62 
 63 struct rds_info_iterator {
 64         struct page **pages;
 65         void *addr;
 66         unsigned long offset;
 67 };
 68 
 69 static DEFINE_SPINLOCK(rds_info_lock);
 70 static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
 71 
 72 void rds_info_register_func(int optname, rds_info_func func)
 73 {
 74         int offset = optname - RDS_INFO_FIRST;
 75 
 76         BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
 77 
 78         spin_lock(&rds_info_lock);
 79         BUG_ON(rds_info_funcs[offset]);
 80         rds_info_funcs[offset] = func;
 81         spin_unlock(&rds_info_lock);
 82 }
 83 EXPORT_SYMBOL_GPL(rds_info_register_func);
 84 
 85 void rds_info_deregister_func(int optname, rds_info_func func)
 86 {
 87         int offset = optname - RDS_INFO_FIRST;
 88 
 89         BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
 90 
 91         spin_lock(&rds_info_lock);
 92         BUG_ON(rds_info_funcs[offset] != func);
 93         rds_info_funcs[offset] = NULL;
 94         spin_unlock(&rds_info_lock);
 95 }
 96 EXPORT_SYMBOL_GPL(rds_info_deregister_func);
 97 
 98 /*
 99  * Typically we hold an atomic kmap across multiple rds_info_copy() calls
100  * because the kmap is so expensive.  This must be called before using blocking
101  * operations while holding the mapping and as the iterator is torn down.
102  */
103 void rds_info_iter_unmap(struct rds_info_iterator *iter)
104 {
105         if (iter->addr) {
106                 kunmap_atomic(iter->addr, KM_USER0);
107                 iter->addr = NULL;
108         }
109 }
110 
111 /*
112  * get_user_pages() called flush_dcache_page() on the pages for us.
113  */
114 void rds_info_copy(struct rds_info_iterator *iter, void *data,
115                    unsigned long bytes)
116 {
117         unsigned long this;
118 
119         while (bytes) {
120                 if (!iter->addr)
121                         iter->addr = kmap_atomic(*iter->pages, KM_USER0);
122 
123                 this = min(bytes, PAGE_SIZE - iter->offset);
124 
125                 rdsdebug("page %p addr %p offset %lu this %lu data %p "
126                           "bytes %lu\n", *iter->pages, iter->addr,
127                           iter->offset, this, data, bytes);
128 
129                 memcpy(iter->addr + iter->offset, data, this);
130 
131                 data += this;
132                 bytes -= this;
133                 iter->offset += this;
134 
135                 if (iter->offset == PAGE_SIZE) {
136                         kunmap_atomic(iter->addr, KM_USER0);
137                         iter->addr = NULL;
138                         iter->offset = 0;
139                         iter->pages++;
140                 }
141         }
142 }
143 EXPORT_SYMBOL_GPL(rds_info_copy);
144 
145 /*
146  * @optval points to the userspace buffer that the information snapshot
147  * will be copied into.
148  *
149  * @optlen on input is the size of the buffer in userspace.  @optlen
150  * on output is the size of the requested snapshot in bytes.
151  *
152  * This function returns -errno if there is a failure, particularly -ENOSPC
153  * if the given userspace buffer was not large enough to fit the snapshot.
154  * On success it returns the positive number of bytes of each array element
155  * in the snapshot.
156  */
157 int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
158                         int __user *optlen)
159 {
160         struct rds_info_iterator iter;
161         struct rds_info_lengths lens;
162         unsigned long nr_pages = 0;
163         unsigned long start;
164         unsigned long i;
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 + PAGE_SIZE - 1 < len || 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(nr_pages * sizeof(struct page *), GFP_KERNEL);
191         if (!pages) {
192                 ret = -ENOMEM;
193                 goto out;
194         }
195         ret = get_user_pages_fast(start, nr_pages, 1, 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 
207 call_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 
236 out:
237         for (i = 0; pages && i < nr_pages; i++)
238                 put_page(pages[i]);
239         kfree(pages);
240 
241         return ret;
242 }
243 

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