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1 : : /* SPDX-License-Identifier: GPL-2.0 */
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 : :
14 : : #include <linux/types.h>
15 : : #include <linux/sched.h>
16 : : #include <linux/timer.h>
17 : : #include <linux/wait.h>
18 : : #include <linux/list.h>
19 : : #include <linux/irq_work.h>
20 : : #include <linux/bug.h>
21 : : #include <linux/fs.h>
22 : : #include <linux/poll.h>
23 : : #include <linux/kref.h>
24 : : #include <linux/percpu.h>
25 : :
26 : : /*
27 : : * Tracks changes to rchan/rchan_buf structs
28 : : */
29 : : #define RELAYFS_CHANNEL_VERSION 7
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 */
43 : : struct irq_work wakeup_work; /* reader wakeup */
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 */
52 : : size_t early_bytes; /* bytes consumed before VFS inited */
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 */
69 : : struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
70 : : int is_global; /* One global buffer ? */
71 : : struct list_head list; /* for channel list */
72 : : struct dentry *parent; /* parent dentry passed to open */
73 : : int has_base_filename; /* has a filename associated? */
74 : : char base_filename[NAME_MAX]; /* saved base filename */
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 : : *
144 : : * See Documentation/filesystems/relay.txt for more info.
145 : : */
146 : : struct dentry *(*create_buf_file)(const char *filename,
147 : : struct dentry *parent,
148 : : umode_t mode,
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,
173 : : struct rchan_callbacks *cb,
174 : : void *private_data);
175 : : extern int relay_late_setup_files(struct rchan *chan,
176 : : const char *base_filename,
177 : : struct dentry *parent);
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);
210 : : buf = *this_cpu_ptr(chan->buf);
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 : :
236 : : buf = *get_cpu_ptr(chan->buf);
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;
241 : : put_cpu_ptr(chan->buf);
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 : 0 : static inline void *relay_reserve(struct rchan *chan, size_t length)
256 : : {
257 : : void *reserved = NULL;
258 : 0 : struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
259 : :
260 [ # # ]: 0 : if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
261 : 0 : length = relay_switch_subbuf(buf, length);
262 [ # # ]: 0 : if (!length)
263 : : goto end;
264 : : }
265 : 0 : reserved = buf->data + buf->offset;
266 : 0 : buf->offset += length;
267 : :
268 : : end:
269 : 0 : put_cpu_ptr(chan->buf);
270 : 0 : 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 : : */
291 : : extern const struct file_operations relay_file_operations;
292 : :
293 : : #ifdef CONFIG_RELAY
294 : : int relay_prepare_cpu(unsigned int cpu);
295 : : #else
296 : : #define relay_prepare_cpu NULL
297 : : #endif
298 : :
299 : : #endif /* _LINUX_RELAY_H */
300 : :
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