| 1 | /* |
| 2 | * ring_buffer_backend.c |
| 3 | * |
| 4 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * |
| 6 | * This library is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU Lesser General Public |
| 8 | * License as published by the Free Software Foundation; only |
| 9 | * version 2.1 of the License. |
| 10 | * |
| 11 | * This library is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | * Lesser General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Lesser General Public |
| 17 | * License along with this library; if not, write to the Free Software |
| 18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | */ |
| 20 | |
| 21 | #define _GNU_SOURCE |
| 22 | #include <unistd.h> |
| 23 | #include <urcu/arch.h> |
| 24 | #include <limits.h> |
| 25 | |
| 26 | #include <lttng/ringbuffer-config.h> |
| 27 | #include "vatomic.h" |
| 28 | #include "backend.h" |
| 29 | #include "frontend.h" |
| 30 | #include "smp.h" |
| 31 | #include "shm.h" |
| 32 | |
| 33 | /** |
| 34 | * lib_ring_buffer_backend_allocate - allocate a channel buffer |
| 35 | * @config: ring buffer instance configuration |
| 36 | * @buf: the buffer struct |
| 37 | * @size: total size of the buffer |
| 38 | * @num_subbuf: number of subbuffers |
| 39 | * @extra_reader_sb: need extra subbuffer for reader |
| 40 | */ |
| 41 | static |
| 42 | int lib_ring_buffer_backend_allocate(const struct lttng_ust_lib_ring_buffer_config *config, |
| 43 | struct lttng_ust_lib_ring_buffer_backend *bufb, |
| 44 | size_t size, size_t num_subbuf, |
| 45 | int extra_reader_sb, |
| 46 | struct lttng_ust_shm_handle *handle, |
| 47 | struct shm_object *shmobj) |
| 48 | { |
| 49 | struct channel_backend *chanb; |
| 50 | unsigned long subbuf_size, mmap_offset = 0; |
| 51 | unsigned long num_subbuf_alloc; |
| 52 | unsigned long i; |
| 53 | long page_size; |
| 54 | |
| 55 | chanb = &shmp(handle, bufb->chan)->backend; |
| 56 | if (!chanb) |
| 57 | return -EINVAL; |
| 58 | |
| 59 | subbuf_size = chanb->subbuf_size; |
| 60 | num_subbuf_alloc = num_subbuf; |
| 61 | |
| 62 | if (extra_reader_sb) |
| 63 | num_subbuf_alloc++; |
| 64 | |
| 65 | page_size = sysconf(_SC_PAGE_SIZE); |
| 66 | if (page_size <= 0) { |
| 67 | goto page_size_error; |
| 68 | } |
| 69 | |
| 70 | align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp)); |
| 71 | set_shmp(bufb->array, zalloc_shm(shmobj, |
| 72 | sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc)); |
| 73 | if (caa_unlikely(!shmp(handle, bufb->array))) |
| 74 | goto array_error; |
| 75 | |
| 76 | /* |
| 77 | * This is the largest element (the buffer pages) which needs to |
| 78 | * be aligned on page size. |
| 79 | */ |
| 80 | align_shm(shmobj, page_size); |
| 81 | set_shmp(bufb->memory_map, zalloc_shm(shmobj, |
| 82 | subbuf_size * num_subbuf_alloc)); |
| 83 | if (caa_unlikely(!shmp(handle, bufb->memory_map))) |
| 84 | goto memory_map_error; |
| 85 | |
| 86 | /* Allocate backend pages array elements */ |
| 87 | for (i = 0; i < num_subbuf_alloc; i++) { |
| 88 | align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages)); |
| 89 | set_shmp(shmp_index(handle, bufb->array, i)->shmp, |
| 90 | zalloc_shm(shmobj, |
| 91 | sizeof(struct lttng_ust_lib_ring_buffer_backend_pages))); |
| 92 | if (!shmp(handle, shmp_index(handle, bufb->array, i)->shmp)) |
| 93 | goto free_array; |
| 94 | } |
| 95 | |
| 96 | /* Allocate write-side subbuffer table */ |
| 97 | align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer)); |
| 98 | set_shmp(bufb->buf_wsb, zalloc_shm(shmobj, |
| 99 | sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer) |
| 100 | * num_subbuf)); |
| 101 | if (caa_unlikely(!shmp(handle, bufb->buf_wsb))) |
| 102 | goto free_array; |
| 103 | |
| 104 | for (i = 0; i < num_subbuf; i++) { |
| 105 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *sb; |
| 106 | |
| 107 | sb = shmp_index(handle, bufb->buf_wsb, i); |
| 108 | if (!sb) |
| 109 | goto free_array; |
| 110 | sb->id = subbuffer_id(config, 0, 1, i); |
| 111 | } |
| 112 | |
| 113 | /* Assign read-side subbuffer table */ |
| 114 | if (extra_reader_sb) |
| 115 | bufb->buf_rsb.id = subbuffer_id(config, 0, 1, |
| 116 | num_subbuf_alloc - 1); |
| 117 | else |
| 118 | bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0); |
| 119 | |
| 120 | /* Assign pages to page index */ |
| 121 | for (i = 0; i < num_subbuf_alloc; i++) { |
| 122 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *sbp; |
| 123 | struct lttng_ust_lib_ring_buffer_backend_pages *pages; |
| 124 | struct shm_ref ref; |
| 125 | |
| 126 | ref.index = bufb->memory_map._ref.index; |
| 127 | ref.offset = bufb->memory_map._ref.offset; |
| 128 | ref.offset += i * subbuf_size; |
| 129 | |
| 130 | sbp = shmp_index(handle, bufb->array, i); |
| 131 | if (!sbp) |
| 132 | goto free_array; |
| 133 | pages = shmp(handle, sbp->shmp); |
| 134 | if (!pages) |
| 135 | goto free_array; |
| 136 | set_shmp(pages->p, ref); |
| 137 | if (config->output == RING_BUFFER_MMAP) { |
| 138 | pages->mmap_offset = mmap_offset; |
| 139 | mmap_offset += subbuf_size; |
| 140 | } |
| 141 | } |
| 142 | return 0; |
| 143 | |
| 144 | free_array: |
| 145 | /* bufb->array[i] will be freed by shm teardown */ |
| 146 | memory_map_error: |
| 147 | /* bufb->array will be freed by shm teardown */ |
| 148 | array_error: |
| 149 | page_size_error: |
| 150 | return -ENOMEM; |
| 151 | } |
| 152 | |
| 153 | int lib_ring_buffer_backend_create(struct lttng_ust_lib_ring_buffer_backend *bufb, |
| 154 | struct channel_backend *chanb, int cpu, |
| 155 | struct lttng_ust_shm_handle *handle, |
| 156 | struct shm_object *shmobj) |
| 157 | { |
| 158 | const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config; |
| 159 | |
| 160 | set_shmp(bufb->chan, handle->chan._ref); |
| 161 | bufb->cpu = cpu; |
| 162 | |
| 163 | return lib_ring_buffer_backend_allocate(config, bufb, chanb->buf_size, |
| 164 | chanb->num_subbuf, |
| 165 | chanb->extra_reader_sb, |
| 166 | handle, shmobj); |
| 167 | } |
| 168 | |
| 169 | void lib_ring_buffer_backend_reset(struct lttng_ust_lib_ring_buffer_backend *bufb, |
| 170 | struct lttng_ust_shm_handle *handle) |
| 171 | { |
| 172 | struct channel_backend *chanb; |
| 173 | const struct lttng_ust_lib_ring_buffer_config *config; |
| 174 | unsigned long num_subbuf_alloc; |
| 175 | unsigned int i; |
| 176 | |
| 177 | chanb = &shmp(handle, bufb->chan)->backend; |
| 178 | if (!chanb) |
| 179 | abort(); |
| 180 | config = &chanb->config; |
| 181 | |
| 182 | num_subbuf_alloc = chanb->num_subbuf; |
| 183 | if (chanb->extra_reader_sb) |
| 184 | num_subbuf_alloc++; |
| 185 | |
| 186 | for (i = 0; i < chanb->num_subbuf; i++) { |
| 187 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *sb; |
| 188 | |
| 189 | sb = shmp_index(handle, bufb->buf_wsb, i); |
| 190 | if (!sb) |
| 191 | abort(); |
| 192 | sb->id = subbuffer_id(config, 0, 1, i); |
| 193 | } |
| 194 | if (chanb->extra_reader_sb) |
| 195 | bufb->buf_rsb.id = subbuffer_id(config, 0, 1, |
| 196 | num_subbuf_alloc - 1); |
| 197 | else |
| 198 | bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0); |
| 199 | |
| 200 | for (i = 0; i < num_subbuf_alloc; i++) { |
| 201 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *sbp; |
| 202 | struct lttng_ust_lib_ring_buffer_backend_pages *pages; |
| 203 | |
| 204 | sbp = shmp_index(handle, bufb->array, i); |
| 205 | if (!sbp) |
| 206 | abort(); |
| 207 | pages = shmp(handle, sbp->shmp); |
| 208 | if (!pages) |
| 209 | abort(); |
| 210 | /* Don't reset mmap_offset */ |
| 211 | v_set(config, &pages->records_commit, 0); |
| 212 | v_set(config, &pages->records_unread, 0); |
| 213 | pages->data_size = 0; |
| 214 | /* Don't reset backend page and virt addresses */ |
| 215 | } |
| 216 | /* Don't reset num_pages_per_subbuf, cpu, allocated */ |
| 217 | v_set(config, &bufb->records_read, 0); |
| 218 | } |
| 219 | |
| 220 | /* |
| 221 | * The frontend is responsible for also calling ring_buffer_backend_reset for |
| 222 | * each buffer when calling channel_backend_reset. |
| 223 | */ |
| 224 | void channel_backend_reset(struct channel_backend *chanb) |
| 225 | { |
| 226 | struct channel *chan = caa_container_of(chanb, struct channel, backend); |
| 227 | const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config; |
| 228 | |
| 229 | /* |
| 230 | * Don't reset buf_size, subbuf_size, subbuf_size_order, |
| 231 | * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf, |
| 232 | * priv, notifiers, config, cpumask and name. |
| 233 | */ |
| 234 | chanb->start_tsc = config->cb.ring_buffer_clock_read(chan); |
| 235 | } |
| 236 | |
| 237 | /** |
| 238 | * channel_backend_init - initialize a channel backend |
| 239 | * @chanb: channel backend |
| 240 | * @name: channel name |
| 241 | * @config: client ring buffer configuration |
| 242 | * @parent: dentry of parent directory, %NULL for root directory |
| 243 | * @subbuf_size: size of sub-buffers (> page size, power of 2) |
| 244 | * @num_subbuf: number of sub-buffers (power of 2) |
| 245 | * @lttng_ust_shm_handle: shared memory handle |
| 246 | * @stream_fds: stream file descriptors. |
| 247 | * |
| 248 | * Returns channel pointer if successful, %NULL otherwise. |
| 249 | * |
| 250 | * Creates per-cpu channel buffers using the sizes and attributes |
| 251 | * specified. The created channel buffer files will be named |
| 252 | * name_0...name_N-1. File permissions will be %S_IRUSR. |
| 253 | * |
| 254 | * Called with CPU hotplug disabled. |
| 255 | */ |
| 256 | int channel_backend_init(struct channel_backend *chanb, |
| 257 | const char *name, |
| 258 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 259 | size_t subbuf_size, size_t num_subbuf, |
| 260 | struct lttng_ust_shm_handle *handle, |
| 261 | const int *stream_fds) |
| 262 | { |
| 263 | struct channel *chan = caa_container_of(chanb, struct channel, backend); |
| 264 | unsigned int i; |
| 265 | int ret; |
| 266 | size_t shmsize = 0, num_subbuf_alloc; |
| 267 | long page_size; |
| 268 | |
| 269 | if (!name) |
| 270 | return -EPERM; |
| 271 | |
| 272 | page_size = sysconf(_SC_PAGE_SIZE); |
| 273 | if (page_size <= 0) { |
| 274 | return -ENOMEM; |
| 275 | } |
| 276 | /* Check that the subbuffer size is larger than a page. */ |
| 277 | if (subbuf_size < page_size) |
| 278 | return -EINVAL; |
| 279 | |
| 280 | /* |
| 281 | * Make sure the number of subbuffers and subbuffer size are |
| 282 | * power of 2, and nonzero. |
| 283 | */ |
| 284 | if (!subbuf_size || (subbuf_size & (subbuf_size - 1))) |
| 285 | return -EINVAL; |
| 286 | if (!num_subbuf || (num_subbuf & (num_subbuf - 1))) |
| 287 | return -EINVAL; |
| 288 | /* |
| 289 | * Overwrite mode buffers require at least 2 subbuffers per |
| 290 | * buffer. |
| 291 | */ |
| 292 | if (config->mode == RING_BUFFER_OVERWRITE && num_subbuf < 2) |
| 293 | return -EINVAL; |
| 294 | |
| 295 | ret = subbuffer_id_check_index(config, num_subbuf); |
| 296 | if (ret) |
| 297 | return ret; |
| 298 | |
| 299 | chanb->buf_size = num_subbuf * subbuf_size; |
| 300 | chanb->subbuf_size = subbuf_size; |
| 301 | chanb->buf_size_order = get_count_order(chanb->buf_size); |
| 302 | chanb->subbuf_size_order = get_count_order(subbuf_size); |
| 303 | chanb->num_subbuf_order = get_count_order(num_subbuf); |
| 304 | chanb->extra_reader_sb = |
| 305 | (config->mode == RING_BUFFER_OVERWRITE) ? 1 : 0; |
| 306 | chanb->num_subbuf = num_subbuf; |
| 307 | strncpy(chanb->name, name, NAME_MAX); |
| 308 | chanb->name[NAME_MAX - 1] = '\0'; |
| 309 | memcpy(&chanb->config, config, sizeof(*config)); |
| 310 | |
| 311 | /* Per-cpu buffer size: control (prior to backend) */ |
| 312 | shmsize = offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer)); |
| 313 | shmsize += sizeof(struct lttng_ust_lib_ring_buffer); |
| 314 | |
| 315 | /* Per-cpu buffer size: backend */ |
| 316 | /* num_subbuf + 1 is the worse case */ |
| 317 | num_subbuf_alloc = num_subbuf + 1; |
| 318 | shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp)); |
| 319 | shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc; |
| 320 | shmsize += offset_align(shmsize, page_size); |
| 321 | shmsize += subbuf_size * num_subbuf_alloc; |
| 322 | shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages)); |
| 323 | shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages) * num_subbuf_alloc; |
| 324 | shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer)); |
| 325 | shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer) * num_subbuf; |
| 326 | /* Per-cpu buffer size: control (after backend) */ |
| 327 | shmsize += offset_align(shmsize, __alignof__(struct commit_counters_hot)); |
| 328 | shmsize += sizeof(struct commit_counters_hot) * num_subbuf; |
| 329 | shmsize += offset_align(shmsize, __alignof__(struct commit_counters_cold)); |
| 330 | shmsize += sizeof(struct commit_counters_cold) * num_subbuf; |
| 331 | |
| 332 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { |
| 333 | struct lttng_ust_lib_ring_buffer *buf; |
| 334 | /* |
| 335 | * We need to allocate for all possible cpus. |
| 336 | */ |
| 337 | for_each_possible_cpu(i) { |
| 338 | struct shm_object *shmobj; |
| 339 | |
| 340 | shmobj = shm_object_table_alloc(handle->table, shmsize, |
| 341 | SHM_OBJECT_SHM, stream_fds[i]); |
| 342 | if (!shmobj) |
| 343 | goto end; |
| 344 | align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer)); |
| 345 | set_shmp(chanb->buf[i].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer))); |
| 346 | buf = shmp(handle, chanb->buf[i].shmp); |
| 347 | if (!buf) |
| 348 | goto end; |
| 349 | set_shmp(buf->self, chanb->buf[i].shmp._ref); |
| 350 | ret = lib_ring_buffer_create(buf, chanb, i, |
| 351 | handle, shmobj); |
| 352 | if (ret) |
| 353 | goto free_bufs; /* cpu hotplug locked */ |
| 354 | } |
| 355 | } else { |
| 356 | struct shm_object *shmobj; |
| 357 | struct lttng_ust_lib_ring_buffer *buf; |
| 358 | |
| 359 | shmobj = shm_object_table_alloc(handle->table, shmsize, |
| 360 | SHM_OBJECT_SHM, stream_fds[0]); |
| 361 | if (!shmobj) |
| 362 | goto end; |
| 363 | align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer)); |
| 364 | set_shmp(chanb->buf[0].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer))); |
| 365 | buf = shmp(handle, chanb->buf[0].shmp); |
| 366 | if (!buf) |
| 367 | goto end; |
| 368 | set_shmp(buf->self, chanb->buf[0].shmp._ref); |
| 369 | ret = lib_ring_buffer_create(buf, chanb, -1, |
| 370 | handle, shmobj); |
| 371 | if (ret) |
| 372 | goto free_bufs; |
| 373 | } |
| 374 | chanb->start_tsc = config->cb.ring_buffer_clock_read(chan); |
| 375 | |
| 376 | return 0; |
| 377 | |
| 378 | free_bufs: |
| 379 | /* We only free the buffer data upon shm teardown */ |
| 380 | end: |
| 381 | return -ENOMEM; |
| 382 | } |
| 383 | |
| 384 | /** |
| 385 | * channel_backend_free - destroy the channel |
| 386 | * @chan: the channel |
| 387 | * |
| 388 | * Destroy all channel buffers and frees the channel. |
| 389 | */ |
| 390 | void channel_backend_free(struct channel_backend *chanb, |
| 391 | struct lttng_ust_shm_handle *handle) |
| 392 | { |
| 393 | /* SHM teardown takes care of everything */ |
| 394 | } |
| 395 | |
| 396 | /** |
| 397 | * lib_ring_buffer_read - read data from ring_buffer_buffer. |
| 398 | * @bufb : buffer backend |
| 399 | * @offset : offset within the buffer |
| 400 | * @dest : destination address |
| 401 | * @len : length to copy to destination |
| 402 | * |
| 403 | * Should be protected by get_subbuf/put_subbuf. |
| 404 | * Returns the length copied. |
| 405 | */ |
| 406 | size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset, |
| 407 | void *dest, size_t len, struct lttng_ust_shm_handle *handle) |
| 408 | { |
| 409 | struct channel_backend *chanb; |
| 410 | const struct lttng_ust_lib_ring_buffer_config *config; |
| 411 | ssize_t orig_len; |
| 412 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
| 413 | unsigned long sb_bindex, id; |
| 414 | void *src; |
| 415 | |
| 416 | chanb = &shmp(handle, bufb->chan)->backend; |
| 417 | if (!chanb) |
| 418 | return 0; |
| 419 | config = &chanb->config; |
| 420 | orig_len = len; |
| 421 | offset &= chanb->buf_size - 1; |
| 422 | |
| 423 | if (caa_unlikely(!len)) |
| 424 | return 0; |
| 425 | id = bufb->buf_rsb.id; |
| 426 | sb_bindex = subbuffer_id_get_index(config, id); |
| 427 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
| 428 | /* |
| 429 | * Underlying layer should never ask for reads across |
| 430 | * subbuffers. |
| 431 | */ |
| 432 | CHAN_WARN_ON(chanb, offset >= chanb->buf_size); |
| 433 | CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE |
| 434 | && subbuffer_id_is_noref(config, id)); |
| 435 | src = shmp_index(handle, shmp(handle, rpages->shmp)->p, |
| 436 | offset & (chanb->subbuf_size - 1)); |
| 437 | if (caa_unlikely(!src)) |
| 438 | return 0; |
| 439 | memcpy(dest, src, len); |
| 440 | return orig_len; |
| 441 | } |
| 442 | |
| 443 | /** |
| 444 | * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer. |
| 445 | * @bufb : buffer backend |
| 446 | * @offset : offset within the buffer |
| 447 | * @dest : destination address |
| 448 | * @len : destination's length |
| 449 | * |
| 450 | * Return string's length, or -EINVAL on error. |
| 451 | * Should be protected by get_subbuf/put_subbuf. |
| 452 | * Destination length should be at least 1 to hold '\0'. |
| 453 | */ |
| 454 | int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset, |
| 455 | void *dest, size_t len, struct lttng_ust_shm_handle *handle) |
| 456 | { |
| 457 | struct channel_backend *chanb; |
| 458 | const struct lttng_ust_lib_ring_buffer_config *config; |
| 459 | ssize_t string_len, orig_offset; |
| 460 | char *str; |
| 461 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
| 462 | unsigned long sb_bindex, id; |
| 463 | |
| 464 | chanb = &shmp(handle, bufb->chan)->backend; |
| 465 | if (!chanb) |
| 466 | return -EINVAL; |
| 467 | config = &chanb->config; |
| 468 | if (caa_unlikely(!len)) |
| 469 | return -EINVAL; |
| 470 | offset &= chanb->buf_size - 1; |
| 471 | orig_offset = offset; |
| 472 | id = bufb->buf_rsb.id; |
| 473 | sb_bindex = subbuffer_id_get_index(config, id); |
| 474 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
| 475 | /* |
| 476 | * Underlying layer should never ask for reads across |
| 477 | * subbuffers. |
| 478 | */ |
| 479 | CHAN_WARN_ON(chanb, offset >= chanb->buf_size); |
| 480 | CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE |
| 481 | && subbuffer_id_is_noref(config, id)); |
| 482 | str = shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)); |
| 483 | if (caa_unlikely(!str)) |
| 484 | return -EINVAL; |
| 485 | string_len = strnlen(str, len); |
| 486 | if (dest && len) { |
| 487 | memcpy(dest, str, string_len); |
| 488 | ((char *)dest)[0] = 0; |
| 489 | } |
| 490 | return offset - orig_offset; |
| 491 | } |
| 492 | |
| 493 | /** |
| 494 | * lib_ring_buffer_read_offset_address - get address of a buffer location |
| 495 | * @bufb : buffer backend |
| 496 | * @offset : offset within the buffer. |
| 497 | * |
| 498 | * Return the address where a given offset is located (for read). |
| 499 | * Should be used to get the current subbuffer header pointer. Given we know |
| 500 | * it's never on a page boundary, it's safe to read/write directly |
| 501 | * from/to this address, as long as the read/write is never bigger than |
| 502 | * a page size. |
| 503 | */ |
| 504 | void *lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
| 505 | size_t offset, |
| 506 | struct lttng_ust_shm_handle *handle) |
| 507 | { |
| 508 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
| 509 | struct channel_backend *chanb; |
| 510 | const struct lttng_ust_lib_ring_buffer_config *config; |
| 511 | unsigned long sb_bindex, id; |
| 512 | |
| 513 | chanb = &shmp(handle, bufb->chan)->backend; |
| 514 | if (!chanb) |
| 515 | return NULL; |
| 516 | config = &chanb->config; |
| 517 | offset &= chanb->buf_size - 1; |
| 518 | id = bufb->buf_rsb.id; |
| 519 | sb_bindex = subbuffer_id_get_index(config, id); |
| 520 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
| 521 | CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE |
| 522 | && subbuffer_id_is_noref(config, id)); |
| 523 | return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)); |
| 524 | } |
| 525 | |
| 526 | /** |
| 527 | * lib_ring_buffer_offset_address - get address of a location within the buffer |
| 528 | * @bufb : buffer backend |
| 529 | * @offset : offset within the buffer. |
| 530 | * |
| 531 | * Return the address where a given offset is located. |
| 532 | * Should be used to get the current subbuffer header pointer. Given we know |
| 533 | * it's always at the beginning of a page, it's safe to write directly to this |
| 534 | * address, as long as the write is never bigger than a page size. |
| 535 | */ |
| 536 | void *lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
| 537 | size_t offset, |
| 538 | struct lttng_ust_shm_handle *handle) |
| 539 | { |
| 540 | size_t sbidx; |
| 541 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
| 542 | struct channel_backend *chanb; |
| 543 | const struct lttng_ust_lib_ring_buffer_config *config; |
| 544 | unsigned long sb_bindex, id; |
| 545 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *sb; |
| 546 | |
| 547 | chanb = &shmp(handle, bufb->chan)->backend; |
| 548 | if (!chanb) |
| 549 | return NULL; |
| 550 | config = &chanb->config; |
| 551 | offset &= chanb->buf_size - 1; |
| 552 | sbidx = offset >> chanb->subbuf_size_order; |
| 553 | sb = shmp_index(handle, bufb->buf_wsb, sbidx); |
| 554 | if (!sb) |
| 555 | return NULL; |
| 556 | id = sb->id; |
| 557 | sb_bindex = subbuffer_id_get_index(config, id); |
| 558 | rpages = shmp_index(handle, bufb->array, sb_bindex); |
| 559 | CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE |
| 560 | && subbuffer_id_is_noref(config, id)); |
| 561 | return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)); |
| 562 | } |