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/srcu.h> 36 #include <linux/slab.h> 37 #include <linux/proc_fs.h> 38 #include <linux/export.h> 39 #include <linux/uio.h> 40 41 #include "rds.h" 42 43 /* 44 * This file implements a getsockopt() call which copies a set of fixed 45 * sized structs into a user-specified buffer as a means of providing 46 * read-only information about RDS. 47 * 48 * For a given information source there are a given number of fixed sized 49 * structs at a given time. The structs are only copied if the user-specified 50 * buffer is big enough. The destination pages that make up the buffer 51 * are pinned for the duration of the copy. 52 * 53 * This gives us the following benefits: 54 * 55 * - simple implementation, no copy "position" across multiple calls 56 * - consistent snapshot of an info source 57 * - atomic copy works well with whatever locking info source has 58 * - one portable tool to get rds info across implementations 59 * - long-lived tool can get info without allocating 60 * 61 * at the following costs: 62 * 63 * - info source copy must be pinned, may be "large" 64 */ 65 66 struct rds_info_iterator { 67 struct page **pages; 68 void *addr; 69 unsigned long offset; 70 }; 71 72 DEFINE_STATIC_SRCU(rds_info_srcu); 73 static DEFINE_SPINLOCK(rds_info_lock); 74 static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1]; 75 76 void rds_info_register_func(int optname, rds_info_func func) 77 { 78 int offset = optname - RDS_INFO_FIRST; 79 80 BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); 81 82 spin_lock(&rds_info_lock); 83 if (WARN_ON_ONCE(rds_info_funcs[offset])) { 84 spin_unlock(&rds_info_lock); 85 return; 86 } 87 WRITE_ONCE(rds_info_funcs[offset], func); 88 spin_unlock(&rds_info_lock); 89 } 90 EXPORT_SYMBOL_GPL(rds_info_register_func); 91 92 void rds_info_deregister_func(int optname, rds_info_func func) 93 { 94 int offset = optname - RDS_INFO_FIRST; 95 96 BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); 97 98 spin_lock(&rds_info_lock); 99 if (WARN_ON_ONCE(rds_info_funcs[offset] != func)) { 100 spin_unlock(&rds_info_lock); 101 return; 102 } 103 WRITE_ONCE(rds_info_funcs[offset], NULL); 104 spin_unlock(&rds_info_lock); 105 synchronize_srcu(&rds_info_srcu); 106 } 107 EXPORT_SYMBOL_GPL(rds_info_deregister_func); 108 109 /* 110 * Typically we hold an atomic kmap across multiple rds_info_copy() calls 111 * because the kmap is so expensive. This must be called before using blocking 112 * operations while holding the mapping and as the iterator is torn down. 113 */ 114 void rds_info_iter_unmap(struct rds_info_iterator *iter) 115 { 116 if (iter->addr) { 117 kunmap_atomic(iter->addr); 118 iter->addr = NULL; 119 } 120 } 121 122 /* 123 * get_user_pages() called flush_dcache_page() on the pages for us. 124 */ 125 void rds_info_copy(struct rds_info_iterator *iter, void *data, 126 unsigned long bytes) 127 { 128 unsigned long this; 129 130 while (bytes) { 131 if (!iter->addr) 132 iter->addr = kmap_atomic(*iter->pages); 133 134 this = min(bytes, PAGE_SIZE - iter->offset); 135 136 rdsdebug("page %p addr %p offset %lu this %lu data %p " 137 "bytes %lu\n", *iter->pages, iter->addr, 138 iter->offset, this, data, bytes); 139 140 memcpy(iter->addr + iter->offset, data, this); 141 142 data += this; 143 bytes -= this; 144 iter->offset += this; 145 146 if (iter->offset == PAGE_SIZE) { 147 kunmap_atomic(iter->addr); 148 iter->addr = NULL; 149 iter->offset = 0; 150 iter->pages++; 151 } 152 } 153 } 154 EXPORT_SYMBOL_GPL(rds_info_copy); 155 156 /* 157 * @opt->iter_out describes the buffer that the information snapshot will be 158 * copied into, and @opt->optlen is the size of that buffer on input. On 159 * output @opt->optlen is set to the size of the requested snapshot in bytes. 160 * 161 * This function returns -errno if there is a failure, particularly -ENOSPC 162 * if the given buffer was not large enough to fit the snapshot. On success 163 * it returns the positive number of bytes of each array element in the 164 * snapshot. 165 */ 166 int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt) 167 { 168 struct rds_info_iterator iter; 169 struct rds_info_lengths lens; 170 unsigned long nr_pages = 0; 171 rds_info_func func; 172 struct page **pages = NULL; 173 size_t offset0 = 0; 174 int srcu_idx; 175 int npages = 0; 176 int ret; 177 int len; 178 int total; 179 180 len = opt->optlen; 181 182 /* check for all kinds of wrapping and the like */ 183 if (len < 0 || len > INT_MAX - PAGE_SIZE + 1) { 184 ret = -EINVAL; 185 goto out; 186 } 187 188 /* The info producers write into the pages with kmap_atomic() while 189 * holding a spinlock, so they need a genuine page-backed user buffer. 190 */ 191 if (!user_backed_iter(&opt->iter_out)) { 192 ret = -EOPNOTSUPP; 193 goto out; 194 } 195 196 /* a 0 len call is just trying to probe its length */ 197 if (len == 0) 198 goto call_func; 199 200 /* 201 * Preallocate the page array and pass it in so that 202 * iov_iter_extract_pages() fills it in place rather than allocating 203 * one for us. Handing it a non-NULL array keeps ownership of the 204 * array with us on every return path, instead of depending on the 205 * iterator code to allocate and hand it back. 206 */ 207 npages = iov_iter_npages(&opt->iter_out, INT_MAX); 208 pages = kvmalloc_array(npages, sizeof(*pages), GFP_KERNEL); 209 if (!pages) { 210 ret = -ENOMEM; 211 goto out; 212 } 213 214 ret = iov_iter_extract_pages(&opt->iter_out, &pages, len, npages, 215 0, &offset0); 216 if (ret < 0) 217 goto out; 218 nr_pages = DIV_ROUND_UP(offset0 + ret, PAGE_SIZE); 219 if (ret != len) { 220 ret = -EAGAIN; /* XXX ? */ 221 goto out; 222 } 223 224 rdsdebug("len %d nr_pages %lu\n", len, nr_pages); 225 226 call_func: 227 srcu_idx = srcu_read_lock(&rds_info_srcu); 228 func = READ_ONCE(rds_info_funcs[optname - RDS_INFO_FIRST]); 229 if (!func) { 230 srcu_read_unlock(&rds_info_srcu, srcu_idx); 231 ret = -ENOPROTOOPT; 232 goto out; 233 } 234 235 iter.pages = pages; 236 iter.addr = NULL; 237 iter.offset = offset0; 238 239 func(sock, len, &iter, &lens); 240 srcu_read_unlock(&rds_info_srcu, srcu_idx); 241 BUG_ON(lens.each == 0); 242 243 total = lens.nr * lens.each; 244 245 rds_info_iter_unmap(&iter); 246 247 if (total > len) { 248 len = total; 249 ret = -ENOSPC; 250 } else { 251 len = total; 252 ret = lens.each; 253 } 254 255 opt->optlen = len; 256 257 out: 258 /* 259 * iov_iter_extract_pages() pins only user-backed (ubuf) iters; 260 * iov_iter_extract_will_pin() reports whether an unpin is owed here. 261 */ 262 if (pages && iov_iter_extract_will_pin(&opt->iter_out)) 263 unpin_user_pages_dirty_lock(pages, nr_pages, true); 264 kvfree(pages); 265 266 return ret; 267 } 268