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852c2936 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
852c2936 | 3 | * |
e92f3e28 MD |
4 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
5 | * | |
c0c0989a | 6 | * Ring buffer backend (API). |
852c2936 MD |
7 | * |
8 | * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by | |
9 | * the reader in flight recorder mode. | |
10 | */ | |
11 | ||
c0c0989a MJ |
12 | #ifndef _LTTNG_RING_BUFFER_BACKEND_H |
13 | #define _LTTNG_RING_BUFFER_BACKEND_H | |
14 | ||
b4051ad8 | 15 | #include <stddef.h> |
14641deb MD |
16 | #include <unistd.h> |
17 | ||
852c2936 | 18 | /* Internal helpers */ |
4931a13e MD |
19 | #include "backend_internal.h" |
20 | #include "frontend_internal.h" | |
852c2936 MD |
21 | |
22 | /* Ring buffer backend API */ | |
23 | ||
24 | /* Ring buffer backend access (read/write) */ | |
25 | ||
4cfec15c | 26 | extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 27 | size_t offset, void *dest, size_t len, |
1d18d519 MJ |
28 | struct lttng_ust_shm_handle *handle) |
29 | __attribute__((visibility("hidden"))); | |
852c2936 | 30 | |
4cfec15c | 31 | extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 32 | size_t offset, void *dest, size_t len, |
1d18d519 MJ |
33 | struct lttng_ust_shm_handle *handle) |
34 | __attribute__((visibility("hidden"))); | |
852c2936 | 35 | |
852c2936 MD |
36 | /* |
37 | * Return the address where a given offset is located. | |
38 | * Should be used to get the current subbuffer header pointer. Given we know | |
39 | * it's never on a page boundary, it's safe to write directly to this address, | |
40 | * as long as the write is never bigger than a page size. | |
41 | */ | |
42 | extern void * | |
4cfec15c | 43 | lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 44 | size_t offset, |
1d18d519 MJ |
45 | struct lttng_ust_shm_handle *handle) |
46 | __attribute__((visibility("hidden"))); | |
ddabe860 | 47 | |
852c2936 | 48 | extern void * |
4cfec15c | 49 | lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 50 | size_t offset, |
1d18d519 MJ |
51 | struct lttng_ust_shm_handle *handle) |
52 | __attribute__((visibility("hidden"))); | |
852c2936 MD |
53 | |
54 | /** | |
55 | * lib_ring_buffer_write - write data to a buffer backend | |
56 | * @config : ring buffer instance configuration | |
57 | * @ctx: ring buffer context. (input arguments only) | |
58 | * @src : source pointer to copy from | |
59 | * @len : length of data to copy | |
60 | * | |
61 | * This function copies "len" bytes of data from a source pointer to a buffer | |
62 | * backend, at the current context offset. This is more or less a buffer | |
63 | * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write) | |
64 | * if copy is crossing a page boundary. | |
65 | */ | |
5f6daaef MJ |
66 | static inline |
67 | void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config, | |
68 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
69 | const void *src, size_t len) | |
70 | __attribute__((always_inline)); | |
71 | static inline | |
4cfec15c MD |
72 | void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config, |
73 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
852c2936 MD |
74 | const void *src, size_t len) |
75 | { | |
8936b6c0 MD |
76 | struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv; |
77 | struct channel_backend *chanb = &ctx_private->chan->backend; | |
78 | struct lttng_ust_shm_handle *handle = ctx_private->chan->handle; | |
79 | size_t offset = ctx_private->buf_offset; | |
15500a1b MD |
80 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
81 | void *p; | |
852c2936 | 82 | |
0bf3c920 MD |
83 | if (caa_unlikely(!len)) |
84 | return; | |
a6352fd4 MD |
85 | /* |
86 | * Underlying layer should never ask for writes across | |
87 | * subbuffers. | |
88 | */ | |
a3492932 MD |
89 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
90 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
91 | if (caa_unlikely(!backend_pages)) { | |
92 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
93 | return; | |
94 | } | |
15500a1b MD |
95 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
96 | if (caa_unlikely(!p)) | |
97 | return; | |
98 | lib_ring_buffer_do_copy(config, p, src, len); | |
8936b6c0 | 99 | ctx_private->buf_offset += len; |
852c2936 MD |
100 | } |
101 | ||
a44c74d9 MD |
102 | /* |
103 | * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL | |
104 | * terminating character is found in @src. Returns the number of bytes | |
105 | * copied. Does *not* terminate @dest with NULL terminating character. | |
106 | */ | |
5f6daaef MJ |
107 | static inline |
108 | size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
109 | char *dest, const char *src, size_t len) | |
110 | __attribute__((always_inline)); | |
111 | static inline | |
a44c74d9 MD |
112 | size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
113 | char *dest, const char *src, size_t len) | |
114 | { | |
115 | size_t count; | |
116 | ||
117 | for (count = 0; count < len; count++) { | |
118 | char c; | |
119 | ||
120 | /* | |
121 | * Only read source character once, in case it is | |
122 | * modified concurrently. | |
123 | */ | |
124 | c = CMM_LOAD_SHARED(src[count]); | |
125 | if (!c) | |
126 | break; | |
127 | lib_ring_buffer_do_copy(config, &dest[count], &c, 1); | |
128 | } | |
129 | return count; | |
130 | } | |
131 | ||
132 | /** | |
133 | * lib_ring_buffer_strcpy - write string data to a buffer backend | |
134 | * @config : ring buffer instance configuration | |
135 | * @ctx: ring buffer context. (input arguments only) | |
136 | * @src : source pointer to copy from | |
137 | * @len : length of data to copy | |
138 | * @pad : character to use for padding | |
139 | * | |
140 | * This function copies @len - 1 bytes of string data from a source | |
141 | * pointer to a buffer backend, followed by a terminating '\0' | |
142 | * character, at the current context offset. This is more or less a | |
143 | * buffer backend-specific strncpy() operation. If a terminating '\0' | |
144 | * character is found in @src before @len - 1 characters are copied, pad | |
145 | * the buffer with @pad characters (e.g. '#'). | |
146 | */ | |
5f6daaef MJ |
147 | static inline |
148 | void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
149 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
150 | const char *src, size_t len, char pad) | |
151 | __attribute__((always_inline)); | |
152 | static inline | |
a44c74d9 MD |
153 | void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
154 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
b4c8bf2f | 155 | const char *src, size_t len, char pad) |
a44c74d9 | 156 | { |
8936b6c0 MD |
157 | struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv; |
158 | struct channel_backend *chanb = &ctx_private->chan->backend; | |
159 | struct lttng_ust_shm_handle *handle = ctx_private->chan->handle; | |
a3492932 | 160 | size_t count; |
8936b6c0 | 161 | size_t offset = ctx_private->buf_offset; |
a3492932 MD |
162 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
163 | void *p; | |
a44c74d9 MD |
164 | |
165 | if (caa_unlikely(!len)) | |
166 | return; | |
a44c74d9 MD |
167 | /* |
168 | * Underlying layer should never ask for writes across | |
169 | * subbuffers. | |
170 | */ | |
a3492932 MD |
171 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
172 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
173 | if (caa_unlikely(!backend_pages)) { | |
174 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
175 | return; | |
176 | } | |
177 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
178 | if (caa_unlikely(!p)) | |
179 | return; | |
180 | ||
181 | count = lib_ring_buffer_do_strcpy(config, p, src, len - 1); | |
a44c74d9 MD |
182 | offset += count; |
183 | /* Padding */ | |
184 | if (caa_unlikely(count < len - 1)) { | |
185 | size_t pad_len = len - 1 - count; | |
186 | ||
a3492932 MD |
187 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
188 | if (caa_unlikely(!p)) | |
189 | return; | |
190 | lib_ring_buffer_do_memset(p, pad, pad_len); | |
a44c74d9 MD |
191 | offset += pad_len; |
192 | } | |
193 | /* Final '\0' */ | |
a3492932 MD |
194 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
195 | if (caa_unlikely(!p)) | |
196 | return; | |
197 | lib_ring_buffer_do_memset(p, '\0', 1); | |
8936b6c0 | 198 | ctx_private->buf_offset += len; |
a44c74d9 MD |
199 | } |
200 | ||
879f9b0a MD |
201 | /** |
202 | * lib_ring_buffer_pstrcpy - write to a buffer backend P-string | |
203 | * @config : ring buffer instance configuration | |
204 | * @ctx: ring buffer context. (input arguments only) | |
205 | * @src : source pointer to copy from | |
206 | * @len : length of data to copy | |
207 | * @pad : character to use for padding | |
208 | * | |
209 | * This function copies up to @len bytes of data from a source pointer | |
210 | * to a Pascal String into the buffer backend. If a terminating '\0' | |
211 | * character is found in @src before @len characters are copied, pad the | |
212 | * buffer with @pad characters (e.g. '\0'). | |
213 | * | |
214 | * The length of the pascal strings in the ring buffer is explicit: it | |
215 | * is either the array or sequence length. | |
216 | */ | |
5f6daaef MJ |
217 | static inline |
218 | void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
219 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
220 | const char *src, size_t len, char pad) | |
221 | __attribute__((always_inline)); | |
222 | static inline | |
879f9b0a MD |
223 | void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
224 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
225 | const char *src, size_t len, char pad) | |
226 | { | |
8936b6c0 MD |
227 | struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv; |
228 | struct channel_backend *chanb = &ctx_private->chan->backend; | |
229 | struct lttng_ust_shm_handle *handle = ctx_private->chan->handle; | |
879f9b0a | 230 | size_t count; |
8936b6c0 | 231 | size_t offset = ctx_private->buf_offset; |
879f9b0a MD |
232 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
233 | void *p; | |
234 | ||
235 | if (caa_unlikely(!len)) | |
236 | return; | |
237 | /* | |
238 | * Underlying layer should never ask for writes across | |
239 | * subbuffers. | |
240 | */ | |
241 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); | |
242 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
243 | if (caa_unlikely(!backend_pages)) { | |
244 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
245 | return; | |
246 | } | |
247 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
248 | if (caa_unlikely(!p)) | |
249 | return; | |
250 | ||
251 | count = lib_ring_buffer_do_strcpy(config, p, src, len); | |
252 | offset += count; | |
253 | /* Padding */ | |
254 | if (caa_unlikely(count < len)) { | |
255 | size_t pad_len = len - count; | |
256 | ||
257 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
258 | if (caa_unlikely(!p)) | |
259 | return; | |
260 | lib_ring_buffer_do_memset(p, pad, pad_len); | |
261 | } | |
8936b6c0 | 262 | ctx_private->buf_offset += len; |
879f9b0a MD |
263 | } |
264 | ||
852c2936 MD |
265 | /* |
266 | * This accessor counts the number of unread records in a buffer. | |
267 | * It only provides a consistent value if no reads not writes are performed | |
268 | * concurrently. | |
269 | */ | |
270 | static inline | |
271 | unsigned long lib_ring_buffer_get_records_unread( | |
4cfec15c MD |
272 | const struct lttng_ust_lib_ring_buffer_config *config, |
273 | struct lttng_ust_lib_ring_buffer *buf, | |
38fae1d3 | 274 | struct lttng_ust_shm_handle *handle) |
852c2936 | 275 | { |
4cfec15c | 276 | struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend; |
15500a1b | 277 | unsigned long records_unread = 0, sb_bindex; |
852c2936 | 278 | unsigned int i; |
5198080d | 279 | struct lttng_ust_lib_ring_buffer_channel *chan; |
852c2936 | 280 | |
15500a1b MD |
281 | chan = shmp(handle, bufb->chan); |
282 | if (!chan) | |
283 | return 0; | |
284 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
285 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; | |
286 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
287 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
288 | ||
289 | wsb = shmp_index(handle, bufb->buf_wsb, i); | |
290 | if (!wsb) | |
291 | return 0; | |
292 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
293 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
294 | if (!rpages) | |
295 | return 0; | |
296 | backend_pages = shmp(handle, rpages->shmp); | |
297 | if (!backend_pages) | |
298 | return 0; | |
299 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
300 | } |
301 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
15500a1b MD |
302 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
303 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
304 | ||
305 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
306 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
307 | if (!rpages) | |
308 | return 0; | |
309 | backend_pages = shmp(handle, rpages->shmp); | |
310 | if (!backend_pages) | |
311 | return 0; | |
312 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
313 | } |
314 | return records_unread; | |
315 | } | |
316 | ||
e92f3e28 | 317 | #endif /* _LTTNG_RING_BUFFER_BACKEND_H */ |