| 1 | /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only) |
| 2 | * |
| 3 | * ringbuffer/backend_internal.h |
| 4 | * |
| 5 | * Ring buffer backend (internal helpers). |
| 6 | * |
| 7 | * Copyright (C) 2008-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | */ |
| 9 | |
| 10 | #ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H |
| 11 | #define _LIB_RING_BUFFER_BACKEND_INTERNAL_H |
| 12 | |
| 13 | #include <wrapper/compiler.h> |
| 14 | #include <wrapper/inline_memcpy.h> |
| 15 | #include <ringbuffer/config.h> |
| 16 | #include <ringbuffer/backend_types.h> |
| 17 | #include <ringbuffer/frontend_types.h> |
| 18 | #include <linux/string.h> |
| 19 | #include <linux/uaccess.h> |
| 20 | |
| 21 | /* Ring buffer backend API presented to the frontend */ |
| 22 | |
| 23 | /* Ring buffer and channel backend create/free */ |
| 24 | |
| 25 | int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb, |
| 26 | struct channel_backend *chan, int cpu); |
| 27 | void channel_backend_unregister_notifiers(struct channel_backend *chanb); |
| 28 | void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb); |
| 29 | int channel_backend_init(struct channel_backend *chanb, |
| 30 | const char *name, |
| 31 | const struct lib_ring_buffer_config *config, |
| 32 | void *priv, size_t subbuf_size, |
| 33 | size_t num_subbuf); |
| 34 | void channel_backend_free(struct channel_backend *chanb); |
| 35 | |
| 36 | void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb); |
| 37 | void channel_backend_reset(struct channel_backend *chanb); |
| 38 | |
| 39 | int lib_ring_buffer_backend_init(void); |
| 40 | void lib_ring_buffer_backend_exit(void); |
| 41 | |
| 42 | extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb, |
| 43 | size_t offset, const void *src, size_t len, |
| 44 | size_t pagecpy); |
| 45 | extern void _lib_ring_buffer_memset(struct lib_ring_buffer_backend *bufb, |
| 46 | size_t offset, int c, size_t len, |
| 47 | size_t pagecpy); |
| 48 | extern void _lib_ring_buffer_strcpy(struct lib_ring_buffer_backend *bufb, |
| 49 | size_t offset, const char *src, size_t len, |
| 50 | size_t pagecpy, int pad); |
| 51 | extern void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb, |
| 52 | size_t offset, const void *src, |
| 53 | size_t len, size_t pagecpy); |
| 54 | extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lib_ring_buffer_backend *bufb, |
| 55 | size_t offset, const char __user *src, size_t len, |
| 56 | size_t pagecpy, int pad); |
| 57 | |
| 58 | /* |
| 59 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be |
| 60 | * exchanged atomically. |
| 61 | * |
| 62 | * Top half word, except lowest bit, belongs to "offset", which is used to keep |
| 63 | * to count the produced buffers. For overwrite mode, this provides the |
| 64 | * consumer with the capacity to read subbuffers in order, handling the |
| 65 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit |
| 66 | * systems) concurrently with a single execution of get_subbuf (between offset |
| 67 | * sampling and subbuffer ID exchange). |
| 68 | */ |
| 69 | |
| 70 | #define HALF_ULONG_BITS (BITS_PER_LONG >> 1) |
| 71 | |
| 72 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) |
| 73 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) |
| 74 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) |
| 75 | /* |
| 76 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. |
| 77 | */ |
| 78 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) |
| 79 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) |
| 80 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT |
| 81 | /* |
| 82 | * In overwrite mode: lowest half of word is used for index. |
| 83 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. |
| 84 | * In producer-consumer mode: whole word used for index. |
| 85 | */ |
| 86 | #define SB_ID_INDEX_SHIFT 0 |
| 87 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) |
| 88 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) |
| 89 | |
| 90 | /* |
| 91 | * Construct the subbuffer id from offset, index and noref. Use only the index |
| 92 | * for producer-consumer mode (offset and noref are only used in overwrite |
| 93 | * mode). |
| 94 | */ |
| 95 | static inline |
| 96 | unsigned long subbuffer_id(const struct lib_ring_buffer_config *config, |
| 97 | unsigned long offset, unsigned long noref, |
| 98 | unsigned long index) |
| 99 | { |
| 100 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 101 | return (offset << SB_ID_OFFSET_SHIFT) |
| 102 | | (noref << SB_ID_NOREF_SHIFT) |
| 103 | | index; |
| 104 | else |
| 105 | return index; |
| 106 | } |
| 107 | |
| 108 | /* |
| 109 | * Compare offset with the offset contained within id. Return 1 if the offset |
| 110 | * bits are identical, else 0. |
| 111 | */ |
| 112 | static inline |
| 113 | int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config, |
| 114 | unsigned long id, unsigned long offset) |
| 115 | { |
| 116 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); |
| 117 | } |
| 118 | |
| 119 | static inline |
| 120 | unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config, |
| 121 | unsigned long id) |
| 122 | { |
| 123 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 124 | return id & SB_ID_INDEX_MASK; |
| 125 | else |
| 126 | return id; |
| 127 | } |
| 128 | |
| 129 | static inline |
| 130 | unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config, |
| 131 | unsigned long id) |
| 132 | { |
| 133 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 134 | return !!(id & SB_ID_NOREF_MASK); |
| 135 | else |
| 136 | return 1; |
| 137 | } |
| 138 | |
| 139 | /* |
| 140 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile |
| 141 | * needed. |
| 142 | */ |
| 143 | static inline |
| 144 | void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config, |
| 145 | unsigned long *id) |
| 146 | { |
| 147 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 148 | *id |= SB_ID_NOREF_MASK; |
| 149 | } |
| 150 | |
| 151 | static inline |
| 152 | void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config, |
| 153 | unsigned long *id, unsigned long offset) |
| 154 | { |
| 155 | unsigned long tmp; |
| 156 | |
| 157 | if (config->mode == RING_BUFFER_OVERWRITE) { |
| 158 | tmp = *id; |
| 159 | tmp &= ~SB_ID_OFFSET_MASK; |
| 160 | tmp |= offset << SB_ID_OFFSET_SHIFT; |
| 161 | tmp |= SB_ID_NOREF_MASK; |
| 162 | /* Volatile store, read concurrently by readers. */ |
| 163 | WRITE_ONCE(*id, tmp); |
| 164 | } |
| 165 | } |
| 166 | |
| 167 | /* No volatile access, since already used locally */ |
| 168 | static inline |
| 169 | void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config, |
| 170 | unsigned long *id) |
| 171 | { |
| 172 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 173 | *id &= ~SB_ID_NOREF_MASK; |
| 174 | } |
| 175 | |
| 176 | /* |
| 177 | * For overwrite mode, cap the number of subbuffers per buffer to: |
| 178 | * 2^16 on 32-bit architectures |
| 179 | * 2^32 on 64-bit architectures |
| 180 | * This is required to fit in the index part of the ID. Return 0 on success, |
| 181 | * -EPERM on failure. |
| 182 | */ |
| 183 | static inline |
| 184 | int subbuffer_id_check_index(const struct lib_ring_buffer_config *config, |
| 185 | unsigned long num_subbuf) |
| 186 | { |
| 187 | if (config->mode == RING_BUFFER_OVERWRITE) |
| 188 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; |
| 189 | else |
| 190 | return 0; |
| 191 | } |
| 192 | |
| 193 | static inline |
| 194 | void lib_ring_buffer_backend_get_pages(const struct lib_ring_buffer_config *config, |
| 195 | struct lib_ring_buffer_ctx *ctx, |
| 196 | struct lib_ring_buffer_backend_pages **backend_pages) |
| 197 | { |
| 198 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; |
| 199 | struct channel_backend *chanb = &ctx->chan->backend; |
| 200 | size_t sbidx, offset = ctx->buf_offset; |
| 201 | unsigned long sb_bindex, id; |
| 202 | struct lib_ring_buffer_backend_pages *rpages; |
| 203 | |
| 204 | offset &= chanb->buf_size - 1; |
| 205 | sbidx = offset >> chanb->subbuf_size_order; |
| 206 | id = bufb->buf_wsb[sbidx].id; |
| 207 | sb_bindex = subbuffer_id_get_index(config, id); |
| 208 | rpages = bufb->array[sb_bindex]; |
| 209 | CHAN_WARN_ON(ctx->chan, |
| 210 | config->mode == RING_BUFFER_OVERWRITE |
| 211 | && subbuffer_id_is_noref(config, id)); |
| 212 | *backend_pages = rpages; |
| 213 | } |
| 214 | |
| 215 | /* Get backend pages from cache. */ |
| 216 | static inline |
| 217 | struct lib_ring_buffer_backend_pages * |
| 218 | lib_ring_buffer_get_backend_pages_from_ctx(const struct lib_ring_buffer_config *config, |
| 219 | struct lib_ring_buffer_ctx *ctx) |
| 220 | { |
| 221 | return ctx->backend_pages; |
| 222 | } |
| 223 | |
| 224 | /* |
| 225 | * The ring buffer can count events recorded and overwritten per buffer, |
| 226 | * but it is disabled by default due to its performance overhead. |
| 227 | */ |
| 228 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS |
| 229 | static inline |
| 230 | void subbuffer_count_record(const struct lib_ring_buffer_config *config, |
| 231 | struct lib_ring_buffer_backend *bufb, |
| 232 | unsigned long idx) |
| 233 | { |
| 234 | unsigned long sb_bindex; |
| 235 | |
| 236 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); |
| 237 | v_inc(config, &bufb->array[sb_bindex]->records_commit); |
| 238 | } |
| 239 | |
| 240 | /* |
| 241 | * Reader has exclusive subbuffer access for record consumption. No need to |
| 242 | * perform the decrement atomically. |
| 243 | */ |
| 244 | static inline |
| 245 | void subbuffer_consume_record(const struct lib_ring_buffer_config *config, |
| 246 | struct lib_ring_buffer_backend *bufb) |
| 247 | { |
| 248 | unsigned long sb_bindex; |
| 249 | |
| 250 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); |
| 251 | CHAN_WARN_ON(bufb->chan, |
| 252 | !v_read(config, &bufb->array[sb_bindex]->records_unread)); |
| 253 | /* Non-atomic decrement protected by exclusive subbuffer access */ |
| 254 | _v_dec(config, &bufb->array[sb_bindex]->records_unread); |
| 255 | v_inc(config, &bufb->records_read); |
| 256 | } |
| 257 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ |
| 258 | static inline |
| 259 | void subbuffer_count_record(const struct lib_ring_buffer_config *config, |
| 260 | struct lib_ring_buffer_backend *bufb, |
| 261 | unsigned long idx) |
| 262 | { |
| 263 | } |
| 264 | static inline |
| 265 | void subbuffer_consume_record(const struct lib_ring_buffer_config *config, |
| 266 | struct lib_ring_buffer_backend *bufb) |
| 267 | { |
| 268 | } |
| 269 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ |
| 270 | |
| 271 | static inline |
| 272 | unsigned long subbuffer_get_records_count( |
| 273 | const struct lib_ring_buffer_config *config, |
| 274 | struct lib_ring_buffer_backend *bufb, |
| 275 | unsigned long idx) |
| 276 | { |
| 277 | unsigned long sb_bindex; |
| 278 | |
| 279 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); |
| 280 | return v_read(config, &bufb->array[sb_bindex]->records_commit); |
| 281 | } |
| 282 | |
| 283 | /* |
| 284 | * Must be executed at subbuffer delivery when the writer has _exclusive_ |
| 285 | * subbuffer access. See lib_ring_buffer_check_deliver() for details. |
| 286 | * lib_ring_buffer_get_records_count() must be called to get the records |
| 287 | * count before this function, because it resets the records_commit |
| 288 | * count. |
| 289 | */ |
| 290 | static inline |
| 291 | unsigned long subbuffer_count_records_overrun( |
| 292 | const struct lib_ring_buffer_config *config, |
| 293 | struct lib_ring_buffer_backend *bufb, |
| 294 | unsigned long idx) |
| 295 | { |
| 296 | struct lib_ring_buffer_backend_pages *pages; |
| 297 | unsigned long overruns, sb_bindex; |
| 298 | |
| 299 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); |
| 300 | pages = bufb->array[sb_bindex]; |
| 301 | overruns = v_read(config, &pages->records_unread); |
| 302 | v_set(config, &pages->records_unread, |
| 303 | v_read(config, &pages->records_commit)); |
| 304 | v_set(config, &pages->records_commit, 0); |
| 305 | |
| 306 | return overruns; |
| 307 | } |
| 308 | |
| 309 | static inline |
| 310 | void subbuffer_set_data_size(const struct lib_ring_buffer_config *config, |
| 311 | struct lib_ring_buffer_backend *bufb, |
| 312 | unsigned long idx, |
| 313 | unsigned long data_size) |
| 314 | { |
| 315 | struct lib_ring_buffer_backend_pages *pages; |
| 316 | unsigned long sb_bindex; |
| 317 | |
| 318 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); |
| 319 | pages = bufb->array[sb_bindex]; |
| 320 | pages->data_size = data_size; |
| 321 | } |
| 322 | |
| 323 | static inline |
| 324 | unsigned long subbuffer_get_read_data_size( |
| 325 | const struct lib_ring_buffer_config *config, |
| 326 | struct lib_ring_buffer_backend *bufb) |
| 327 | { |
| 328 | struct lib_ring_buffer_backend_pages *pages; |
| 329 | unsigned long sb_bindex; |
| 330 | |
| 331 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); |
| 332 | pages = bufb->array[sb_bindex]; |
| 333 | return pages->data_size; |
| 334 | } |
| 335 | |
| 336 | static inline |
| 337 | unsigned long subbuffer_get_data_size( |
| 338 | const struct lib_ring_buffer_config *config, |
| 339 | struct lib_ring_buffer_backend *bufb, |
| 340 | unsigned long idx) |
| 341 | { |
| 342 | struct lib_ring_buffer_backend_pages *pages; |
| 343 | unsigned long sb_bindex; |
| 344 | |
| 345 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); |
| 346 | pages = bufb->array[sb_bindex]; |
| 347 | return pages->data_size; |
| 348 | } |
| 349 | |
| 350 | static inline |
| 351 | void subbuffer_inc_packet_count(const struct lib_ring_buffer_config *config, |
| 352 | struct lib_ring_buffer_backend *bufb, |
| 353 | unsigned long idx) |
| 354 | { |
| 355 | bufb->buf_cnt[idx].seq_cnt++; |
| 356 | } |
| 357 | |
| 358 | /** |
| 359 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by |
| 360 | * writer. |
| 361 | */ |
| 362 | static inline |
| 363 | void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config, |
| 364 | struct lib_ring_buffer_backend *bufb, |
| 365 | unsigned long idx) |
| 366 | { |
| 367 | unsigned long id, new_id; |
| 368 | |
| 369 | if (config->mode != RING_BUFFER_OVERWRITE) |
| 370 | return; |
| 371 | |
| 372 | /* |
| 373 | * Performing a volatile access to read the sb_pages, because we want to |
| 374 | * read a coherent version of the pointer and the associated noref flag. |
| 375 | */ |
| 376 | id = LTTNG_READ_ONCE(bufb->buf_wsb[idx].id); |
| 377 | for (;;) { |
| 378 | /* This check is called on the fast path for each record. */ |
| 379 | if (likely(!subbuffer_id_is_noref(config, id))) { |
| 380 | /* |
| 381 | * Store after load dependency ordering the writes to |
| 382 | * the subbuffer after load and test of the noref flag |
| 383 | * matches the memory barrier implied by the cmpxchg() |
| 384 | * in update_read_sb_index(). |
| 385 | */ |
| 386 | return; /* Already writing to this buffer */ |
| 387 | } |
| 388 | new_id = id; |
| 389 | subbuffer_id_clear_noref(config, &new_id); |
| 390 | new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id); |
| 391 | if (likely(new_id == id)) |
| 392 | break; |
| 393 | id = new_id; |
| 394 | } |
| 395 | } |
| 396 | |
| 397 | /** |
| 398 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, |
| 399 | * called by writer. |
| 400 | */ |
| 401 | static inline |
| 402 | void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config, |
| 403 | struct lib_ring_buffer_backend *bufb, |
| 404 | unsigned long idx, unsigned long offset) |
| 405 | { |
| 406 | if (config->mode != RING_BUFFER_OVERWRITE) |
| 407 | return; |
| 408 | |
| 409 | /* |
| 410 | * Because ring_buffer_set_noref() is only called by a single thread |
| 411 | * (the one which updated the cc_sb value), there are no concurrent |
| 412 | * updates to take care of: other writers have not updated cc_sb, so |
| 413 | * they cannot set the noref flag, and concurrent readers cannot modify |
| 414 | * the pointer because the noref flag is not set yet. |
| 415 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes |
| 416 | * to the subbuffer before this set noref operation. |
| 417 | * subbuffer_set_noref() uses a volatile store to deal with concurrent |
| 418 | * readers of the noref flag. |
| 419 | */ |
| 420 | CHAN_WARN_ON(bufb->chan, |
| 421 | subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id)); |
| 422 | /* |
| 423 | * Memory barrier that ensures counter stores are ordered before set |
| 424 | * noref and offset. |
| 425 | */ |
| 426 | smp_mb(); |
| 427 | subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset); |
| 428 | } |
| 429 | |
| 430 | /** |
| 431 | * update_read_sb_index - Read-side subbuffer index update. |
| 432 | */ |
| 433 | static inline |
| 434 | int update_read_sb_index(const struct lib_ring_buffer_config *config, |
| 435 | struct lib_ring_buffer_backend *bufb, |
| 436 | struct channel_backend *chanb, |
| 437 | unsigned long consumed_idx, |
| 438 | unsigned long consumed_count) |
| 439 | { |
| 440 | unsigned long old_id, new_id; |
| 441 | |
| 442 | if (config->mode == RING_BUFFER_OVERWRITE) { |
| 443 | /* |
| 444 | * Exchange the target writer subbuffer with our own unused |
| 445 | * subbuffer. No need to use READ_ONCE() here to read the |
| 446 | * old_wpage, because the value read will be confirmed by the |
| 447 | * following cmpxchg(). |
| 448 | */ |
| 449 | old_id = bufb->buf_wsb[consumed_idx].id; |
| 450 | if (unlikely(!subbuffer_id_is_noref(config, old_id))) |
| 451 | return -EAGAIN; |
| 452 | /* |
| 453 | * Make sure the offset count we are expecting matches the one |
| 454 | * indicated by the writer. |
| 455 | */ |
| 456 | if (unlikely(!subbuffer_id_compare_offset(config, old_id, |
| 457 | consumed_count))) |
| 458 | return -EAGAIN; |
| 459 | CHAN_WARN_ON(bufb->chan, |
| 460 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); |
| 461 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, |
| 462 | consumed_count); |
| 463 | new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id, |
| 464 | bufb->buf_rsb.id); |
| 465 | if (unlikely(old_id != new_id)) |
| 466 | return -EAGAIN; |
| 467 | bufb->buf_rsb.id = new_id; |
| 468 | } else { |
| 469 | /* No page exchange, use the writer page directly */ |
| 470 | bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id; |
| 471 | } |
| 472 | return 0; |
| 473 | } |
| 474 | |
| 475 | static inline __attribute__((always_inline)) |
| 476 | void lttng_inline_memcpy(void *dest, const void *src, |
| 477 | unsigned long len) |
| 478 | { |
| 479 | switch (len) { |
| 480 | case 1: |
| 481 | *(uint8_t *) dest = *(const uint8_t *) src; |
| 482 | break; |
| 483 | case 2: |
| 484 | *(uint16_t *) dest = *(const uint16_t *) src; |
| 485 | break; |
| 486 | case 4: |
| 487 | *(uint32_t *) dest = *(const uint32_t *) src; |
| 488 | break; |
| 489 | case 8: |
| 490 | *(uint64_t *) dest = *(const uint64_t *) src; |
| 491 | break; |
| 492 | default: |
| 493 | inline_memcpy(dest, src, len); |
| 494 | } |
| 495 | } |
| 496 | |
| 497 | /* |
| 498 | * Use the architecture-specific memcpy implementation for constant-sized |
| 499 | * inputs, but rely on an inline memcpy for length statically unknown. |
| 500 | * The function call to memcpy is just way too expensive for a fast path. |
| 501 | */ |
| 502 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ |
| 503 | do { \ |
| 504 | size_t __len = (len); \ |
| 505 | if (__builtin_constant_p(len)) \ |
| 506 | memcpy(dest, src, __len); \ |
| 507 | else \ |
| 508 | lttng_inline_memcpy(dest, src, __len); \ |
| 509 | } while (0) |
| 510 | |
| 511 | /* |
| 512 | * We use __copy_from_user_inatomic to copy userspace data since we already |
| 513 | * did the access_ok for the whole range. |
| 514 | * |
| 515 | * Return 0 if OK, nonzero on error. |
| 516 | */ |
| 517 | static inline |
| 518 | unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest, |
| 519 | const void __user *src, |
| 520 | unsigned long len) |
| 521 | { |
| 522 | return __copy_from_user_inatomic(dest, src, len); |
| 523 | } |
| 524 | |
| 525 | /* |
| 526 | * write len bytes to dest with c |
| 527 | */ |
| 528 | static inline |
| 529 | void lib_ring_buffer_do_memset(char *dest, int c, |
| 530 | unsigned long len) |
| 531 | { |
| 532 | unsigned long i; |
| 533 | |
| 534 | for (i = 0; i < len; i++) |
| 535 | dest[i] = c; |
| 536 | } |
| 537 | |
| 538 | #endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */ |