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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
b86ff981 JA |
2 | /* |
3 | * linux/include/linux/relay.h | |
4 | * | |
5 | * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp | |
6 | * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com) | |
7 | * | |
8 | * CONFIG_RELAY definitions and declarations | |
9 | */ | |
10 | ||
11 | #ifndef _LINUX_RELAY_H | |
12 | #define _LINUX_RELAY_H | |
13 | ||
b86ff981 JA |
14 | #include <linux/types.h> |
15 | #include <linux/sched.h> | |
7c9cb383 | 16 | #include <linux/timer.h> |
b86ff981 JA |
17 | #include <linux/wait.h> |
18 | #include <linux/list.h> | |
26b5679e | 19 | #include <linux/irq_work.h> |
187f1882 | 20 | #include <linux/bug.h> |
b86ff981 JA |
21 | #include <linux/fs.h> |
22 | #include <linux/poll.h> | |
23 | #include <linux/kref.h> | |
017c59c0 | 24 | #include <linux/percpu.h> |
b86ff981 | 25 | |
b86ff981 JA |
26 | /* |
27 | * Tracks changes to rchan/rchan_buf structs | |
28 | */ | |
23c88752 | 29 | #define RELAYFS_CHANNEL_VERSION 7 |
b86ff981 JA |
30 | |
31 | /* | |
32 | * Per-cpu relay channel buffer | |
33 | */ | |
34 | struct rchan_buf | |
35 | { | |
36 | void *start; /* start of channel buffer */ | |
37 | void *data; /* start of current sub-buffer */ | |
38 | size_t offset; /* current offset into sub-buffer */ | |
39 | size_t subbufs_produced; /* count of sub-buffers produced */ | |
40 | size_t subbufs_consumed; /* count of sub-buffers consumed */ | |
41 | struct rchan *chan; /* associated channel */ | |
42 | wait_queue_head_t read_wait; /* reader wait queue */ | |
26b5679e | 43 | struct irq_work wakeup_work; /* reader wakeup */ |
b86ff981 JA |
44 | struct dentry *dentry; /* channel file dentry */ |
45 | struct kref kref; /* channel buffer refcount */ | |
46 | struct page **page_array; /* array of current buffer pages */ | |
47 | unsigned int page_count; /* number of current buffer pages */ | |
48 | unsigned int finalized; /* buffer has been finalized */ | |
49 | size_t *padding; /* padding counts per sub-buffer */ | |
50 | size_t prev_padding; /* temporary variable */ | |
51 | size_t bytes_consumed; /* bytes consumed in cur read subbuf */ | |
20d8b67c | 52 | size_t early_bytes; /* bytes consumed before VFS inited */ |
b86ff981 JA |
53 | unsigned int cpu; /* this buf's cpu */ |
54 | } ____cacheline_aligned; | |
55 | ||
56 | /* | |
57 | * Relay channel data structure | |
58 | */ | |
59 | struct rchan | |
60 | { | |
61 | u32 version; /* the version of this struct */ | |
62 | size_t subbuf_size; /* sub-buffer size */ | |
63 | size_t n_subbufs; /* number of sub-buffers per buffer */ | |
64 | size_t alloc_size; /* total buffer size allocated */ | |
65 | struct rchan_callbacks *cb; /* client callbacks */ | |
66 | struct kref kref; /* channel refcount */ | |
67 | void *private_data; /* for user-defined data */ | |
68 | size_t last_toobig; /* tried to log event > subbuf size */ | |
017c59c0 | 69 | struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */ |
23c88752 MD |
70 | int is_global; /* One global buffer ? */ |
71 | struct list_head list; /* for channel list */ | |
72 | struct dentry *parent; /* parent dentry passed to open */ | |
20d8b67c | 73 | int has_base_filename; /* has a filename associated? */ |
23c88752 | 74 | char base_filename[NAME_MAX]; /* saved base filename */ |
b86ff981 JA |
75 | }; |
76 | ||
77 | /* | |
78 | * Relay channel client callbacks | |
79 | */ | |
80 | struct rchan_callbacks | |
81 | { | |
82 | /* | |
83 | * subbuf_start - called on buffer-switch to a new sub-buffer | |
84 | * @buf: the channel buffer containing the new sub-buffer | |
85 | * @subbuf: the start of the new sub-buffer | |
86 | * @prev_subbuf: the start of the previous sub-buffer | |
87 | * @prev_padding: unused space at the end of previous sub-buffer | |
88 | * | |
89 | * The client should return 1 to continue logging, 0 to stop | |
90 | * logging. | |
91 | * | |
92 | * NOTE: subbuf_start will also be invoked when the buffer is | |
93 | * created, so that the first sub-buffer can be initialized | |
94 | * if necessary. In this case, prev_subbuf will be NULL. | |
95 | * | |
96 | * NOTE: the client can reserve bytes at the beginning of the new | |
97 | * sub-buffer by calling subbuf_start_reserve() in this callback. | |
98 | */ | |
99 | int (*subbuf_start) (struct rchan_buf *buf, | |
100 | void *subbuf, | |
101 | void *prev_subbuf, | |
102 | size_t prev_padding); | |
103 | ||
104 | /* | |
105 | * buf_mapped - relay buffer mmap notification | |
106 | * @buf: the channel buffer | |
107 | * @filp: relay file pointer | |
108 | * | |
109 | * Called when a relay file is successfully mmapped | |
110 | */ | |
111 | void (*buf_mapped)(struct rchan_buf *buf, | |
112 | struct file *filp); | |
113 | ||
114 | /* | |
115 | * buf_unmapped - relay buffer unmap notification | |
116 | * @buf: the channel buffer | |
117 | * @filp: relay file pointer | |
118 | * | |
119 | * Called when a relay file is successfully unmapped | |
120 | */ | |
121 | void (*buf_unmapped)(struct rchan_buf *buf, | |
122 | struct file *filp); | |
123 | /* | |
124 | * create_buf_file - create file to represent a relay channel buffer | |
125 | * @filename: the name of the file to create | |
126 | * @parent: the parent of the file to create | |
127 | * @mode: the mode of the file to create | |
128 | * @buf: the channel buffer | |
129 | * @is_global: outparam - set non-zero if the buffer should be global | |
130 | * | |
131 | * Called during relay_open(), once for each per-cpu buffer, | |
132 | * to allow the client to create a file to be used to | |
133 | * represent the corresponding channel buffer. If the file is | |
134 | * created outside of relay, the parent must also exist in | |
135 | * that filesystem. | |
136 | * | |
137 | * The callback should return the dentry of the file created | |
138 | * to represent the relay buffer. | |
139 | * | |
140 | * Setting the is_global outparam to a non-zero value will | |
141 | * cause relay_open() to create a single global buffer rather | |
142 | * than the default set of per-cpu buffers. | |
143 | * | |
55dff495 | 144 | * See Documentation/filesystems/relay.txt for more info. |
b86ff981 JA |
145 | */ |
146 | struct dentry *(*create_buf_file)(const char *filename, | |
147 | struct dentry *parent, | |
f4ae40a6 | 148 | umode_t mode, |
b86ff981 JA |
149 | struct rchan_buf *buf, |
150 | int *is_global); | |
151 | ||
152 | /* | |
153 | * remove_buf_file - remove file representing a relay channel buffer | |
154 | * @dentry: the dentry of the file to remove | |
155 | * | |
156 | * Called during relay_close(), once for each per-cpu buffer, | |
157 | * to allow the client to remove a file used to represent a | |
158 | * channel buffer. | |
159 | * | |
160 | * The callback should return 0 if successful, negative if not. | |
161 | */ | |
162 | int (*remove_buf_file)(struct dentry *dentry); | |
163 | }; | |
164 | ||
165 | /* | |
166 | * CONFIG_RELAY kernel API, kernel/relay.c | |
167 | */ | |
168 | ||
169 | struct rchan *relay_open(const char *base_filename, | |
170 | struct dentry *parent, | |
171 | size_t subbuf_size, | |
172 | size_t n_subbufs, | |
23c88752 MD |
173 | struct rchan_callbacks *cb, |
174 | void *private_data); | |
20d8b67c EGM |
175 | extern int relay_late_setup_files(struct rchan *chan, |
176 | const char *base_filename, | |
177 | struct dentry *parent); | |
b86ff981 JA |
178 | extern void relay_close(struct rchan *chan); |
179 | extern void relay_flush(struct rchan *chan); | |
180 | extern void relay_subbufs_consumed(struct rchan *chan, | |
181 | unsigned int cpu, | |
182 | size_t consumed); | |
183 | extern void relay_reset(struct rchan *chan); | |
184 | extern int relay_buf_full(struct rchan_buf *buf); | |
185 | ||
186 | extern size_t relay_switch_subbuf(struct rchan_buf *buf, | |
187 | size_t length); | |
188 | ||
189 | /** | |
190 | * relay_write - write data into the channel | |
191 | * @chan: relay channel | |
192 | * @data: data to be written | |
193 | * @length: number of bytes to write | |
194 | * | |
195 | * Writes data into the current cpu's channel buffer. | |
196 | * | |
197 | * Protects the buffer by disabling interrupts. Use this | |
198 | * if you might be logging from interrupt context. Try | |
199 | * __relay_write() if you know you won't be logging from | |
200 | * interrupt context. | |
201 | */ | |
202 | static inline void relay_write(struct rchan *chan, | |
203 | const void *data, | |
204 | size_t length) | |
205 | { | |
206 | unsigned long flags; | |
207 | struct rchan_buf *buf; | |
208 | ||
209 | local_irq_save(flags); | |
017c59c0 | 210 | buf = *this_cpu_ptr(chan->buf); |
b86ff981 JA |
211 | if (unlikely(buf->offset + length > chan->subbuf_size)) |
212 | length = relay_switch_subbuf(buf, length); | |
213 | memcpy(buf->data + buf->offset, data, length); | |
214 | buf->offset += length; | |
215 | local_irq_restore(flags); | |
216 | } | |
217 | ||
218 | /** | |
219 | * __relay_write - write data into the channel | |
220 | * @chan: relay channel | |
221 | * @data: data to be written | |
222 | * @length: number of bytes to write | |
223 | * | |
224 | * Writes data into the current cpu's channel buffer. | |
225 | * | |
226 | * Protects the buffer by disabling preemption. Use | |
227 | * relay_write() if you might be logging from interrupt | |
228 | * context. | |
229 | */ | |
230 | static inline void __relay_write(struct rchan *chan, | |
231 | const void *data, | |
232 | size_t length) | |
233 | { | |
234 | struct rchan_buf *buf; | |
235 | ||
017c59c0 | 236 | buf = *get_cpu_ptr(chan->buf); |
b86ff981 JA |
237 | if (unlikely(buf->offset + length > buf->chan->subbuf_size)) |
238 | length = relay_switch_subbuf(buf, length); | |
239 | memcpy(buf->data + buf->offset, data, length); | |
240 | buf->offset += length; | |
017c59c0 | 241 | put_cpu_ptr(chan->buf); |
b86ff981 JA |
242 | } |
243 | ||
244 | /** | |
245 | * relay_reserve - reserve slot in channel buffer | |
246 | * @chan: relay channel | |
247 | * @length: number of bytes to reserve | |
248 | * | |
249 | * Returns pointer to reserved slot, NULL if full. | |
250 | * | |
251 | * Reserves a slot in the current cpu's channel buffer. | |
252 | * Does not protect the buffer at all - caller must provide | |
253 | * appropriate synchronization. | |
254 | */ | |
255 | static inline void *relay_reserve(struct rchan *chan, size_t length) | |
256 | { | |
017c59c0 AG |
257 | void *reserved = NULL; |
258 | struct rchan_buf *buf = *get_cpu_ptr(chan->buf); | |
b86ff981 JA |
259 | |
260 | if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { | |
261 | length = relay_switch_subbuf(buf, length); | |
262 | if (!length) | |
017c59c0 | 263 | goto end; |
b86ff981 JA |
264 | } |
265 | reserved = buf->data + buf->offset; | |
266 | buf->offset += length; | |
267 | ||
017c59c0 AG |
268 | end: |
269 | put_cpu_ptr(chan->buf); | |
b86ff981 JA |
270 | return reserved; |
271 | } | |
272 | ||
273 | /** | |
274 | * subbuf_start_reserve - reserve bytes at the start of a sub-buffer | |
275 | * @buf: relay channel buffer | |
276 | * @length: number of bytes to reserve | |
277 | * | |
278 | * Helper function used to reserve bytes at the beginning of | |
279 | * a sub-buffer in the subbuf_start() callback. | |
280 | */ | |
281 | static inline void subbuf_start_reserve(struct rchan_buf *buf, | |
282 | size_t length) | |
283 | { | |
284 | BUG_ON(length >= buf->chan->subbuf_size - 1); | |
285 | buf->offset = length; | |
286 | } | |
287 | ||
288 | /* | |
289 | * exported relay file operations, kernel/relay.c | |
290 | */ | |
15ad7cdc | 291 | extern const struct file_operations relay_file_operations; |
b86ff981 | 292 | |
e6d4989a RW |
293 | #ifdef CONFIG_RELAY |
294 | int relay_prepare_cpu(unsigned int cpu); | |
295 | #else | |
296 | #define relay_prepare_cpu NULL | |
297 | #endif | |
298 | ||
b86ff981 JA |
299 | #endif /* _LINUX_RELAY_H */ |
300 |