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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 | ||
ddabe860 | 26 | __attribute__((visibility("hidden"))) |
4cfec15c | 27 | extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 28 | size_t offset, void *dest, size_t len, |
38fae1d3 | 29 | struct lttng_ust_shm_handle *handle); |
852c2936 | 30 | |
ddabe860 | 31 | __attribute__((visibility("hidden"))) |
4cfec15c | 32 | extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 33 | size_t offset, void *dest, size_t len, |
38fae1d3 | 34 | struct lttng_ust_shm_handle *handle); |
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 | */ | |
ddabe860 | 42 | __attribute__((visibility("hidden"))) |
852c2936 | 43 | extern void * |
4cfec15c | 44 | lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 45 | size_t offset, |
38fae1d3 | 46 | struct lttng_ust_shm_handle *handle); |
ddabe860 MJ |
47 | |
48 | __attribute__((visibility("hidden"))) | |
852c2936 | 49 | extern void * |
4cfec15c | 50 | lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb, |
1d498196 | 51 | size_t offset, |
38fae1d3 | 52 | struct lttng_ust_shm_handle *handle); |
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 | */ | |
00d0f8eb | 66 | static inline __attribute__((always_inline)) |
4cfec15c MD |
67 | void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config, |
68 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
852c2936 MD |
69 | const void *src, size_t len) |
70 | { | |
852c2936 | 71 | struct channel_backend *chanb = &ctx->chan->backend; |
aab8b172 | 72 | struct lttng_ust_shm_handle *handle = ctx->chan->handle; |
852c2936 | 73 | size_t offset = ctx->buf_offset; |
15500a1b MD |
74 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
75 | void *p; | |
852c2936 | 76 | |
0bf3c920 MD |
77 | if (caa_unlikely(!len)) |
78 | return; | |
a6352fd4 MD |
79 | /* |
80 | * Underlying layer should never ask for writes across | |
81 | * subbuffers. | |
82 | */ | |
a3492932 MD |
83 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
84 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
85 | if (caa_unlikely(!backend_pages)) { | |
86 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
87 | return; | |
88 | } | |
15500a1b MD |
89 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
90 | if (caa_unlikely(!p)) | |
91 | return; | |
92 | lib_ring_buffer_do_copy(config, p, src, len); | |
852c2936 MD |
93 | ctx->buf_offset += len; |
94 | } | |
95 | ||
a44c74d9 MD |
96 | /* |
97 | * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL | |
98 | * terminating character is found in @src. Returns the number of bytes | |
99 | * copied. Does *not* terminate @dest with NULL terminating character. | |
100 | */ | |
00d0f8eb | 101 | static inline __attribute__((always_inline)) |
a44c74d9 MD |
102 | size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
103 | char *dest, const char *src, size_t len) | |
104 | { | |
105 | size_t count; | |
106 | ||
107 | for (count = 0; count < len; count++) { | |
108 | char c; | |
109 | ||
110 | /* | |
111 | * Only read source character once, in case it is | |
112 | * modified concurrently. | |
113 | */ | |
114 | c = CMM_LOAD_SHARED(src[count]); | |
115 | if (!c) | |
116 | break; | |
117 | lib_ring_buffer_do_copy(config, &dest[count], &c, 1); | |
118 | } | |
119 | return count; | |
120 | } | |
121 | ||
122 | /** | |
123 | * lib_ring_buffer_strcpy - write string data to a buffer backend | |
124 | * @config : ring buffer instance configuration | |
125 | * @ctx: ring buffer context. (input arguments only) | |
126 | * @src : source pointer to copy from | |
127 | * @len : length of data to copy | |
128 | * @pad : character to use for padding | |
129 | * | |
130 | * This function copies @len - 1 bytes of string data from a source | |
131 | * pointer to a buffer backend, followed by a terminating '\0' | |
132 | * character, at the current context offset. This is more or less a | |
133 | * buffer backend-specific strncpy() operation. If a terminating '\0' | |
134 | * character is found in @src before @len - 1 characters are copied, pad | |
135 | * the buffer with @pad characters (e.g. '#'). | |
136 | */ | |
00d0f8eb | 137 | static inline __attribute__((always_inline)) |
a44c74d9 MD |
138 | void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config, |
139 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
b4c8bf2f | 140 | const char *src, size_t len, char pad) |
a44c74d9 | 141 | { |
a44c74d9 | 142 | struct channel_backend *chanb = &ctx->chan->backend; |
aab8b172 | 143 | struct lttng_ust_shm_handle *handle = ctx->chan->handle; |
a3492932 | 144 | size_t count; |
a44c74d9 | 145 | size_t offset = ctx->buf_offset; |
a3492932 MD |
146 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
147 | void *p; | |
a44c74d9 MD |
148 | |
149 | if (caa_unlikely(!len)) | |
150 | return; | |
a44c74d9 MD |
151 | /* |
152 | * Underlying layer should never ask for writes across | |
153 | * subbuffers. | |
154 | */ | |
a3492932 MD |
155 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); |
156 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
157 | if (caa_unlikely(!backend_pages)) { | |
158 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
159 | return; | |
160 | } | |
161 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
162 | if (caa_unlikely(!p)) | |
163 | return; | |
164 | ||
165 | count = lib_ring_buffer_do_strcpy(config, p, src, len - 1); | |
a44c74d9 MD |
166 | offset += count; |
167 | /* Padding */ | |
168 | if (caa_unlikely(count < len - 1)) { | |
169 | size_t pad_len = len - 1 - count; | |
170 | ||
a3492932 MD |
171 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
172 | if (caa_unlikely(!p)) | |
173 | return; | |
174 | lib_ring_buffer_do_memset(p, pad, pad_len); | |
a44c74d9 MD |
175 | offset += pad_len; |
176 | } | |
177 | /* Final '\0' */ | |
a3492932 MD |
178 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); |
179 | if (caa_unlikely(!p)) | |
180 | return; | |
181 | lib_ring_buffer_do_memset(p, '\0', 1); | |
a44c74d9 MD |
182 | ctx->buf_offset += len; |
183 | } | |
184 | ||
879f9b0a MD |
185 | /** |
186 | * lib_ring_buffer_pstrcpy - write to a buffer backend P-string | |
187 | * @config : ring buffer instance configuration | |
188 | * @ctx: ring buffer context. (input arguments only) | |
189 | * @src : source pointer to copy from | |
190 | * @len : length of data to copy | |
191 | * @pad : character to use for padding | |
192 | * | |
193 | * This function copies up to @len bytes of data from a source pointer | |
194 | * to a Pascal String into the buffer backend. If a terminating '\0' | |
195 | * character is found in @src before @len characters are copied, pad the | |
196 | * buffer with @pad characters (e.g. '\0'). | |
197 | * | |
198 | * The length of the pascal strings in the ring buffer is explicit: it | |
199 | * is either the array or sequence length. | |
200 | */ | |
201 | static inline __attribute__((always_inline)) | |
202 | void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config, | |
203 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
204 | const char *src, size_t len, char pad) | |
205 | { | |
206 | struct channel_backend *chanb = &ctx->chan->backend; | |
aab8b172 | 207 | struct lttng_ust_shm_handle *handle = ctx->chan->handle; |
879f9b0a MD |
208 | size_t count; |
209 | size_t offset = ctx->buf_offset; | |
210 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
211 | void *p; | |
212 | ||
213 | if (caa_unlikely(!len)) | |
214 | return; | |
215 | /* | |
216 | * Underlying layer should never ask for writes across | |
217 | * subbuffers. | |
218 | */ | |
219 | CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size); | |
220 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); | |
221 | if (caa_unlikely(!backend_pages)) { | |
222 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
223 | return; | |
224 | } | |
225 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
226 | if (caa_unlikely(!p)) | |
227 | return; | |
228 | ||
229 | count = lib_ring_buffer_do_strcpy(config, p, src, len); | |
230 | offset += count; | |
231 | /* Padding */ | |
232 | if (caa_unlikely(count < len)) { | |
233 | size_t pad_len = len - count; | |
234 | ||
235 | p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1)); | |
236 | if (caa_unlikely(!p)) | |
237 | return; | |
238 | lib_ring_buffer_do_memset(p, pad, pad_len); | |
239 | } | |
240 | ctx->buf_offset += len; | |
241 | } | |
242 | ||
852c2936 MD |
243 | /* |
244 | * This accessor counts the number of unread records in a buffer. | |
245 | * It only provides a consistent value if no reads not writes are performed | |
246 | * concurrently. | |
247 | */ | |
248 | static inline | |
249 | unsigned long lib_ring_buffer_get_records_unread( | |
4cfec15c MD |
250 | const struct lttng_ust_lib_ring_buffer_config *config, |
251 | struct lttng_ust_lib_ring_buffer *buf, | |
38fae1d3 | 252 | struct lttng_ust_shm_handle *handle) |
852c2936 | 253 | { |
4cfec15c | 254 | struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend; |
15500a1b | 255 | unsigned long records_unread = 0, sb_bindex; |
852c2936 | 256 | unsigned int i; |
5198080d | 257 | struct lttng_ust_lib_ring_buffer_channel *chan; |
852c2936 | 258 | |
15500a1b MD |
259 | chan = shmp(handle, bufb->chan); |
260 | if (!chan) | |
261 | return 0; | |
262 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
263 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; | |
264 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
265 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
266 | ||
267 | wsb = shmp_index(handle, bufb->buf_wsb, i); | |
268 | if (!wsb) | |
269 | return 0; | |
270 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
271 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
272 | if (!rpages) | |
273 | return 0; | |
274 | backend_pages = shmp(handle, rpages->shmp); | |
275 | if (!backend_pages) | |
276 | return 0; | |
277 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
278 | } |
279 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
15500a1b MD |
280 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; |
281 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
282 | ||
283 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
284 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
285 | if (!rpages) | |
286 | return 0; | |
287 | backend_pages = shmp(handle, rpages->shmp); | |
288 | if (!backend_pages) | |
289 | return 0; | |
290 | records_unread += v_read(config, &backend_pages->records_unread); | |
852c2936 MD |
291 | } |
292 | return records_unread; | |
293 | } | |
294 | ||
e92f3e28 | 295 | #endif /* _LTTNG_RING_BUFFER_BACKEND_H */ |