1 | /* |
2 | * Public API and common code for kernel->userspace relay file support. |
3 | * |
4 | * See Documentation/filesystems/relay.rst for an overview. |
5 | * |
6 | * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp |
7 | * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com) |
8 | * |
9 | * Moved to kernel/relay.c by Paul Mundt, 2006. |
10 | * November 2006 - CPU hotplug support by Mathieu Desnoyers |
11 | * (mathieu.desnoyers@polymtl.ca) |
12 | * |
13 | * This file is released under the GPL. |
14 | */ |
15 | #include <linux/errno.h> |
16 | #include <linux/stddef.h> |
17 | #include <linux/slab.h> |
18 | #include <linux/export.h> |
19 | #include <linux/string.h> |
20 | #include <linux/relay.h> |
21 | #include <linux/vmalloc.h> |
22 | #include <linux/mm.h> |
23 | #include <linux/cpu.h> |
24 | #include <linux/splice.h> |
25 | |
26 | /* list of open channels, for cpu hotplug */ |
27 | static DEFINE_MUTEX(relay_channels_mutex); |
28 | static LIST_HEAD(relay_channels); |
29 | |
30 | /* |
31 | * fault() vm_op implementation for relay file mapping. |
32 | */ |
33 | static vm_fault_t relay_buf_fault(struct vm_fault *vmf) |
34 | { |
35 | struct page *page; |
36 | struct rchan_buf *buf = vmf->vma->vm_private_data; |
37 | pgoff_t pgoff = vmf->pgoff; |
38 | |
39 | if (!buf) |
40 | return VM_FAULT_OOM; |
41 | |
42 | page = vmalloc_to_page(addr: buf->start + (pgoff << PAGE_SHIFT)); |
43 | if (!page) |
44 | return VM_FAULT_SIGBUS; |
45 | get_page(page); |
46 | vmf->page = page; |
47 | |
48 | return 0; |
49 | } |
50 | |
51 | /* |
52 | * vm_ops for relay file mappings. |
53 | */ |
54 | static const struct vm_operations_struct relay_file_mmap_ops = { |
55 | .fault = relay_buf_fault, |
56 | }; |
57 | |
58 | /* |
59 | * allocate an array of pointers of struct page |
60 | */ |
61 | static struct page **relay_alloc_page_array(unsigned int n_pages) |
62 | { |
63 | return kvcalloc(n: n_pages, size: sizeof(struct page *), GFP_KERNEL); |
64 | } |
65 | |
66 | /* |
67 | * free an array of pointers of struct page |
68 | */ |
69 | static void relay_free_page_array(struct page **array) |
70 | { |
71 | kvfree(addr: array); |
72 | } |
73 | |
74 | /** |
75 | * relay_mmap_buf: - mmap channel buffer to process address space |
76 | * @buf: relay channel buffer |
77 | * @vma: vm_area_struct describing memory to be mapped |
78 | * |
79 | * Returns 0 if ok, negative on error |
80 | * |
81 | * Caller should already have grabbed mmap_lock. |
82 | */ |
83 | static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma) |
84 | { |
85 | unsigned long length = vma->vm_end - vma->vm_start; |
86 | |
87 | if (!buf) |
88 | return -EBADF; |
89 | |
90 | if (length != (unsigned long)buf->chan->alloc_size) |
91 | return -EINVAL; |
92 | |
93 | vma->vm_ops = &relay_file_mmap_ops; |
94 | vm_flags_set(vma, VM_DONTEXPAND); |
95 | vma->vm_private_data = buf; |
96 | |
97 | return 0; |
98 | } |
99 | |
100 | /** |
101 | * relay_alloc_buf - allocate a channel buffer |
102 | * @buf: the buffer struct |
103 | * @size: total size of the buffer |
104 | * |
105 | * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The |
106 | * passed in size will get page aligned, if it isn't already. |
107 | */ |
108 | static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size) |
109 | { |
110 | void *mem; |
111 | unsigned int i, j, n_pages; |
112 | |
113 | *size = PAGE_ALIGN(*size); |
114 | n_pages = *size >> PAGE_SHIFT; |
115 | |
116 | buf->page_array = relay_alloc_page_array(n_pages); |
117 | if (!buf->page_array) |
118 | return NULL; |
119 | |
120 | for (i = 0; i < n_pages; i++) { |
121 | buf->page_array[i] = alloc_page(GFP_KERNEL); |
122 | if (unlikely(!buf->page_array[i])) |
123 | goto depopulate; |
124 | set_page_private(page: buf->page_array[i], private: (unsigned long)buf); |
125 | } |
126 | mem = vmap(pages: buf->page_array, count: n_pages, VM_MAP, PAGE_KERNEL); |
127 | if (!mem) |
128 | goto depopulate; |
129 | |
130 | memset(mem, 0, *size); |
131 | buf->page_count = n_pages; |
132 | return mem; |
133 | |
134 | depopulate: |
135 | for (j = 0; j < i; j++) |
136 | __free_page(buf->page_array[j]); |
137 | relay_free_page_array(array: buf->page_array); |
138 | return NULL; |
139 | } |
140 | |
141 | /** |
142 | * relay_create_buf - allocate and initialize a channel buffer |
143 | * @chan: the relay channel |
144 | * |
145 | * Returns channel buffer if successful, %NULL otherwise. |
146 | */ |
147 | static struct rchan_buf *relay_create_buf(struct rchan *chan) |
148 | { |
149 | struct rchan_buf *buf; |
150 | |
151 | if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t)) |
152 | return NULL; |
153 | |
154 | buf = kzalloc(size: sizeof(struct rchan_buf), GFP_KERNEL); |
155 | if (!buf) |
156 | return NULL; |
157 | buf->padding = kmalloc_array(n: chan->n_subbufs, size: sizeof(size_t), |
158 | GFP_KERNEL); |
159 | if (!buf->padding) |
160 | goto free_buf; |
161 | |
162 | buf->start = relay_alloc_buf(buf, size: &chan->alloc_size); |
163 | if (!buf->start) |
164 | goto free_buf; |
165 | |
166 | buf->chan = chan; |
167 | kref_get(kref: &buf->chan->kref); |
168 | return buf; |
169 | |
170 | free_buf: |
171 | kfree(objp: buf->padding); |
172 | kfree(objp: buf); |
173 | return NULL; |
174 | } |
175 | |
176 | /** |
177 | * relay_destroy_channel - free the channel struct |
178 | * @kref: target kernel reference that contains the relay channel |
179 | * |
180 | * Should only be called from kref_put(). |
181 | */ |
182 | static void relay_destroy_channel(struct kref *kref) |
183 | { |
184 | struct rchan *chan = container_of(kref, struct rchan, kref); |
185 | free_percpu(pdata: chan->buf); |
186 | kfree(objp: chan); |
187 | } |
188 | |
189 | /** |
190 | * relay_destroy_buf - destroy an rchan_buf struct and associated buffer |
191 | * @buf: the buffer struct |
192 | */ |
193 | static void relay_destroy_buf(struct rchan_buf *buf) |
194 | { |
195 | struct rchan *chan = buf->chan; |
196 | unsigned int i; |
197 | |
198 | if (likely(buf->start)) { |
199 | vunmap(addr: buf->start); |
200 | for (i = 0; i < buf->page_count; i++) |
201 | __free_page(buf->page_array[i]); |
202 | relay_free_page_array(array: buf->page_array); |
203 | } |
204 | *per_cpu_ptr(chan->buf, buf->cpu) = NULL; |
205 | kfree(objp: buf->padding); |
206 | kfree(objp: buf); |
207 | kref_put(kref: &chan->kref, release: relay_destroy_channel); |
208 | } |
209 | |
210 | /** |
211 | * relay_remove_buf - remove a channel buffer |
212 | * @kref: target kernel reference that contains the relay buffer |
213 | * |
214 | * Removes the file from the filesystem, which also frees the |
215 | * rchan_buf_struct and the channel buffer. Should only be called from |
216 | * kref_put(). |
217 | */ |
218 | static void relay_remove_buf(struct kref *kref) |
219 | { |
220 | struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref); |
221 | relay_destroy_buf(buf); |
222 | } |
223 | |
224 | /** |
225 | * relay_buf_empty - boolean, is the channel buffer empty? |
226 | * @buf: channel buffer |
227 | * |
228 | * Returns 1 if the buffer is empty, 0 otherwise. |
229 | */ |
230 | static int relay_buf_empty(struct rchan_buf *buf) |
231 | { |
232 | return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1; |
233 | } |
234 | |
235 | /** |
236 | * relay_buf_full - boolean, is the channel buffer full? |
237 | * @buf: channel buffer |
238 | * |
239 | * Returns 1 if the buffer is full, 0 otherwise. |
240 | */ |
241 | int relay_buf_full(struct rchan_buf *buf) |
242 | { |
243 | size_t ready = buf->subbufs_produced - buf->subbufs_consumed; |
244 | return (ready >= buf->chan->n_subbufs) ? 1 : 0; |
245 | } |
246 | EXPORT_SYMBOL_GPL(relay_buf_full); |
247 | |
248 | /* |
249 | * High-level relay kernel API and associated functions. |
250 | */ |
251 | |
252 | static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf, |
253 | void *prev_subbuf, size_t prev_padding) |
254 | { |
255 | if (!buf->chan->cb->subbuf_start) |
256 | return !relay_buf_full(buf); |
257 | |
258 | return buf->chan->cb->subbuf_start(buf, subbuf, |
259 | prev_subbuf, prev_padding); |
260 | } |
261 | |
262 | /** |
263 | * wakeup_readers - wake up readers waiting on a channel |
264 | * @work: contains the channel buffer |
265 | * |
266 | * This is the function used to defer reader waking |
267 | */ |
268 | static void wakeup_readers(struct irq_work *work) |
269 | { |
270 | struct rchan_buf *buf; |
271 | |
272 | buf = container_of(work, struct rchan_buf, wakeup_work); |
273 | wake_up_interruptible(&buf->read_wait); |
274 | } |
275 | |
276 | /** |
277 | * __relay_reset - reset a channel buffer |
278 | * @buf: the channel buffer |
279 | * @init: 1 if this is a first-time initialization |
280 | * |
281 | * See relay_reset() for description of effect. |
282 | */ |
283 | static void __relay_reset(struct rchan_buf *buf, unsigned int init) |
284 | { |
285 | size_t i; |
286 | |
287 | if (init) { |
288 | init_waitqueue_head(&buf->read_wait); |
289 | kref_init(kref: &buf->kref); |
290 | init_irq_work(work: &buf->wakeup_work, func: wakeup_readers); |
291 | } else { |
292 | irq_work_sync(work: &buf->wakeup_work); |
293 | } |
294 | |
295 | buf->subbufs_produced = 0; |
296 | buf->subbufs_consumed = 0; |
297 | buf->bytes_consumed = 0; |
298 | buf->finalized = 0; |
299 | buf->data = buf->start; |
300 | buf->offset = 0; |
301 | |
302 | for (i = 0; i < buf->chan->n_subbufs; i++) |
303 | buf->padding[i] = 0; |
304 | |
305 | relay_subbuf_start(buf, subbuf: buf->data, NULL, prev_padding: 0); |
306 | } |
307 | |
308 | /** |
309 | * relay_reset - reset the channel |
310 | * @chan: the channel |
311 | * |
312 | * This has the effect of erasing all data from all channel buffers |
313 | * and restarting the channel in its initial state. The buffers |
314 | * are not freed, so any mappings are still in effect. |
315 | * |
316 | * NOTE. Care should be taken that the channel isn't actually |
317 | * being used by anything when this call is made. |
318 | */ |
319 | void relay_reset(struct rchan *chan) |
320 | { |
321 | struct rchan_buf *buf; |
322 | unsigned int i; |
323 | |
324 | if (!chan) |
325 | return; |
326 | |
327 | if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) { |
328 | __relay_reset(buf, init: 0); |
329 | return; |
330 | } |
331 | |
332 | mutex_lock(&relay_channels_mutex); |
333 | for_each_possible_cpu(i) |
334 | if ((buf = *per_cpu_ptr(chan->buf, i))) |
335 | __relay_reset(buf, init: 0); |
336 | mutex_unlock(lock: &relay_channels_mutex); |
337 | } |
338 | EXPORT_SYMBOL_GPL(relay_reset); |
339 | |
340 | static inline void relay_set_buf_dentry(struct rchan_buf *buf, |
341 | struct dentry *dentry) |
342 | { |
343 | buf->dentry = dentry; |
344 | d_inode(dentry: buf->dentry)->i_size = buf->early_bytes; |
345 | } |
346 | |
347 | static struct dentry *relay_create_buf_file(struct rchan *chan, |
348 | struct rchan_buf *buf, |
349 | unsigned int cpu) |
350 | { |
351 | struct dentry *dentry; |
352 | char *tmpname; |
353 | |
354 | tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); |
355 | if (!tmpname) |
356 | return NULL; |
357 | snprintf(buf: tmpname, NAME_MAX, fmt: "%s%d" , chan->base_filename, cpu); |
358 | |
359 | /* Create file in fs */ |
360 | dentry = chan->cb->create_buf_file(tmpname, chan->parent, |
361 | S_IRUSR, buf, |
362 | &chan->is_global); |
363 | if (IS_ERR(ptr: dentry)) |
364 | dentry = NULL; |
365 | |
366 | kfree(objp: tmpname); |
367 | |
368 | return dentry; |
369 | } |
370 | |
371 | /* |
372 | * relay_open_buf - create a new relay channel buffer |
373 | * |
374 | * used by relay_open() and CPU hotplug. |
375 | */ |
376 | static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu) |
377 | { |
378 | struct rchan_buf *buf; |
379 | struct dentry *dentry; |
380 | |
381 | if (chan->is_global) |
382 | return *per_cpu_ptr(chan->buf, 0); |
383 | |
384 | buf = relay_create_buf(chan); |
385 | if (!buf) |
386 | return NULL; |
387 | |
388 | if (chan->has_base_filename) { |
389 | dentry = relay_create_buf_file(chan, buf, cpu); |
390 | if (!dentry) |
391 | goto free_buf; |
392 | relay_set_buf_dentry(buf, dentry); |
393 | } else { |
394 | /* Only retrieve global info, nothing more, nothing less */ |
395 | dentry = chan->cb->create_buf_file(NULL, NULL, |
396 | S_IRUSR, buf, |
397 | &chan->is_global); |
398 | if (IS_ERR_OR_NULL(ptr: dentry)) |
399 | goto free_buf; |
400 | } |
401 | |
402 | buf->cpu = cpu; |
403 | __relay_reset(buf, init: 1); |
404 | |
405 | if(chan->is_global) { |
406 | *per_cpu_ptr(chan->buf, 0) = buf; |
407 | buf->cpu = 0; |
408 | } |
409 | |
410 | return buf; |
411 | |
412 | free_buf: |
413 | relay_destroy_buf(buf); |
414 | return NULL; |
415 | } |
416 | |
417 | /** |
418 | * relay_close_buf - close a channel buffer |
419 | * @buf: channel buffer |
420 | * |
421 | * Marks the buffer finalized and restores the default callbacks. |
422 | * The channel buffer and channel buffer data structure are then freed |
423 | * automatically when the last reference is given up. |
424 | */ |
425 | static void relay_close_buf(struct rchan_buf *buf) |
426 | { |
427 | buf->finalized = 1; |
428 | irq_work_sync(work: &buf->wakeup_work); |
429 | buf->chan->cb->remove_buf_file(buf->dentry); |
430 | kref_put(kref: &buf->kref, release: relay_remove_buf); |
431 | } |
432 | |
433 | int relay_prepare_cpu(unsigned int cpu) |
434 | { |
435 | struct rchan *chan; |
436 | struct rchan_buf *buf; |
437 | |
438 | mutex_lock(&relay_channels_mutex); |
439 | list_for_each_entry(chan, &relay_channels, list) { |
440 | if (*per_cpu_ptr(chan->buf, cpu)) |
441 | continue; |
442 | buf = relay_open_buf(chan, cpu); |
443 | if (!buf) { |
444 | pr_err("relay: cpu %d buffer creation failed\n" , cpu); |
445 | mutex_unlock(lock: &relay_channels_mutex); |
446 | return -ENOMEM; |
447 | } |
448 | *per_cpu_ptr(chan->buf, cpu) = buf; |
449 | } |
450 | mutex_unlock(lock: &relay_channels_mutex); |
451 | return 0; |
452 | } |
453 | |
454 | /** |
455 | * relay_open - create a new relay channel |
456 | * @base_filename: base name of files to create, %NULL for buffering only |
457 | * @parent: dentry of parent directory, %NULL for root directory or buffer |
458 | * @subbuf_size: size of sub-buffers |
459 | * @n_subbufs: number of sub-buffers |
460 | * @cb: client callback functions |
461 | * @private_data: user-defined data |
462 | * |
463 | * Returns channel pointer if successful, %NULL otherwise. |
464 | * |
465 | * Creates a channel buffer for each cpu using the sizes and |
466 | * attributes specified. The created channel buffer files |
467 | * will be named base_filename0...base_filenameN-1. File |
468 | * permissions will be %S_IRUSR. |
469 | * |
470 | * If opening a buffer (@parent = NULL) that you later wish to register |
471 | * in a filesystem, call relay_late_setup_files() once the @parent dentry |
472 | * is available. |
473 | */ |
474 | struct rchan *relay_open(const char *base_filename, |
475 | struct dentry *parent, |
476 | size_t subbuf_size, |
477 | size_t n_subbufs, |
478 | const struct rchan_callbacks *cb, |
479 | void *private_data) |
480 | { |
481 | unsigned int i; |
482 | struct rchan *chan; |
483 | struct rchan_buf *buf; |
484 | |
485 | if (!(subbuf_size && n_subbufs)) |
486 | return NULL; |
487 | if (subbuf_size > UINT_MAX / n_subbufs) |
488 | return NULL; |
489 | if (!cb || !cb->create_buf_file || !cb->remove_buf_file) |
490 | return NULL; |
491 | |
492 | chan = kzalloc(size: sizeof(struct rchan), GFP_KERNEL); |
493 | if (!chan) |
494 | return NULL; |
495 | |
496 | chan->buf = alloc_percpu(struct rchan_buf *); |
497 | if (!chan->buf) { |
498 | kfree(objp: chan); |
499 | return NULL; |
500 | } |
501 | |
502 | chan->version = RELAYFS_CHANNEL_VERSION; |
503 | chan->n_subbufs = n_subbufs; |
504 | chan->subbuf_size = subbuf_size; |
505 | chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs); |
506 | chan->parent = parent; |
507 | chan->private_data = private_data; |
508 | if (base_filename) { |
509 | chan->has_base_filename = 1; |
510 | strscpy(p: chan->base_filename, q: base_filename, NAME_MAX); |
511 | } |
512 | chan->cb = cb; |
513 | kref_init(kref: &chan->kref); |
514 | |
515 | mutex_lock(&relay_channels_mutex); |
516 | for_each_online_cpu(i) { |
517 | buf = relay_open_buf(chan, cpu: i); |
518 | if (!buf) |
519 | goto free_bufs; |
520 | *per_cpu_ptr(chan->buf, i) = buf; |
521 | } |
522 | list_add(new: &chan->list, head: &relay_channels); |
523 | mutex_unlock(lock: &relay_channels_mutex); |
524 | |
525 | return chan; |
526 | |
527 | free_bufs: |
528 | for_each_possible_cpu(i) { |
529 | if ((buf = *per_cpu_ptr(chan->buf, i))) |
530 | relay_close_buf(buf); |
531 | } |
532 | |
533 | kref_put(kref: &chan->kref, release: relay_destroy_channel); |
534 | mutex_unlock(lock: &relay_channels_mutex); |
535 | return NULL; |
536 | } |
537 | EXPORT_SYMBOL_GPL(relay_open); |
538 | |
539 | struct rchan_percpu_buf_dispatcher { |
540 | struct rchan_buf *buf; |
541 | struct dentry *dentry; |
542 | }; |
543 | |
544 | /* Called in atomic context. */ |
545 | static void __relay_set_buf_dentry(void *info) |
546 | { |
547 | struct rchan_percpu_buf_dispatcher *p = info; |
548 | |
549 | relay_set_buf_dentry(buf: p->buf, dentry: p->dentry); |
550 | } |
551 | |
552 | /** |
553 | * relay_late_setup_files - triggers file creation |
554 | * @chan: channel to operate on |
555 | * @base_filename: base name of files to create |
556 | * @parent: dentry of parent directory, %NULL for root directory |
557 | * |
558 | * Returns 0 if successful, non-zero otherwise. |
559 | * |
560 | * Use to setup files for a previously buffer-only channel created |
561 | * by relay_open() with a NULL parent dentry. |
562 | * |
563 | * For example, this is useful for perfomring early tracing in kernel, |
564 | * before VFS is up and then exposing the early results once the dentry |
565 | * is available. |
566 | */ |
567 | int relay_late_setup_files(struct rchan *chan, |
568 | const char *base_filename, |
569 | struct dentry *parent) |
570 | { |
571 | int err = 0; |
572 | unsigned int i, curr_cpu; |
573 | unsigned long flags; |
574 | struct dentry *dentry; |
575 | struct rchan_buf *buf; |
576 | struct rchan_percpu_buf_dispatcher disp; |
577 | |
578 | if (!chan || !base_filename) |
579 | return -EINVAL; |
580 | |
581 | strscpy(p: chan->base_filename, q: base_filename, NAME_MAX); |
582 | |
583 | mutex_lock(&relay_channels_mutex); |
584 | /* Is chan already set up? */ |
585 | if (unlikely(chan->has_base_filename)) { |
586 | mutex_unlock(lock: &relay_channels_mutex); |
587 | return -EEXIST; |
588 | } |
589 | chan->has_base_filename = 1; |
590 | chan->parent = parent; |
591 | |
592 | if (chan->is_global) { |
593 | err = -EINVAL; |
594 | buf = *per_cpu_ptr(chan->buf, 0); |
595 | if (!WARN_ON_ONCE(!buf)) { |
596 | dentry = relay_create_buf_file(chan, buf, cpu: 0); |
597 | if (dentry && !WARN_ON_ONCE(!chan->is_global)) { |
598 | relay_set_buf_dentry(buf, dentry); |
599 | err = 0; |
600 | } |
601 | } |
602 | mutex_unlock(lock: &relay_channels_mutex); |
603 | return err; |
604 | } |
605 | |
606 | curr_cpu = get_cpu(); |
607 | /* |
608 | * The CPU hotplug notifier ran before us and created buffers with |
609 | * no files associated. So it's safe to call relay_setup_buf_file() |
610 | * on all currently online CPUs. |
611 | */ |
612 | for_each_online_cpu(i) { |
613 | buf = *per_cpu_ptr(chan->buf, i); |
614 | if (unlikely(!buf)) { |
615 | WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n" ); |
616 | err = -EINVAL; |
617 | break; |
618 | } |
619 | |
620 | dentry = relay_create_buf_file(chan, buf, cpu: i); |
621 | if (unlikely(!dentry)) { |
622 | err = -EINVAL; |
623 | break; |
624 | } |
625 | |
626 | if (curr_cpu == i) { |
627 | local_irq_save(flags); |
628 | relay_set_buf_dentry(buf, dentry); |
629 | local_irq_restore(flags); |
630 | } else { |
631 | disp.buf = buf; |
632 | disp.dentry = dentry; |
633 | smp_mb(); |
634 | /* relay_channels_mutex must be held, so wait. */ |
635 | err = smp_call_function_single(cpuid: i, |
636 | func: __relay_set_buf_dentry, |
637 | info: &disp, wait: 1); |
638 | } |
639 | if (unlikely(err)) |
640 | break; |
641 | } |
642 | put_cpu(); |
643 | mutex_unlock(lock: &relay_channels_mutex); |
644 | |
645 | return err; |
646 | } |
647 | EXPORT_SYMBOL_GPL(relay_late_setup_files); |
648 | |
649 | /** |
650 | * relay_switch_subbuf - switch to a new sub-buffer |
651 | * @buf: channel buffer |
652 | * @length: size of current event |
653 | * |
654 | * Returns either the length passed in or 0 if full. |
655 | * |
656 | * Performs sub-buffer-switch tasks such as invoking callbacks, |
657 | * updating padding counts, waking up readers, etc. |
658 | */ |
659 | size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) |
660 | { |
661 | void *old, *new; |
662 | size_t old_subbuf, new_subbuf; |
663 | |
664 | if (unlikely(length > buf->chan->subbuf_size)) |
665 | goto toobig; |
666 | |
667 | if (buf->offset != buf->chan->subbuf_size + 1) { |
668 | buf->prev_padding = buf->chan->subbuf_size - buf->offset; |
669 | old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; |
670 | buf->padding[old_subbuf] = buf->prev_padding; |
671 | buf->subbufs_produced++; |
672 | if (buf->dentry) |
673 | d_inode(dentry: buf->dentry)->i_size += |
674 | buf->chan->subbuf_size - |
675 | buf->padding[old_subbuf]; |
676 | else |
677 | buf->early_bytes += buf->chan->subbuf_size - |
678 | buf->padding[old_subbuf]; |
679 | smp_mb(); |
680 | if (waitqueue_active(wq_head: &buf->read_wait)) { |
681 | /* |
682 | * Calling wake_up_interruptible() from here |
683 | * will deadlock if we happen to be logging |
684 | * from the scheduler (trying to re-grab |
685 | * rq->lock), so defer it. |
686 | */ |
687 | irq_work_queue(work: &buf->wakeup_work); |
688 | } |
689 | } |
690 | |
691 | old = buf->data; |
692 | new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; |
693 | new = buf->start + new_subbuf * buf->chan->subbuf_size; |
694 | buf->offset = 0; |
695 | if (!relay_subbuf_start(buf, subbuf: new, prev_subbuf: old, prev_padding: buf->prev_padding)) { |
696 | buf->offset = buf->chan->subbuf_size + 1; |
697 | return 0; |
698 | } |
699 | buf->data = new; |
700 | buf->padding[new_subbuf] = 0; |
701 | |
702 | if (unlikely(length + buf->offset > buf->chan->subbuf_size)) |
703 | goto toobig; |
704 | |
705 | return length; |
706 | |
707 | toobig: |
708 | buf->chan->last_toobig = length; |
709 | return 0; |
710 | } |
711 | EXPORT_SYMBOL_GPL(relay_switch_subbuf); |
712 | |
713 | /** |
714 | * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count |
715 | * @chan: the channel |
716 | * @cpu: the cpu associated with the channel buffer to update |
717 | * @subbufs_consumed: number of sub-buffers to add to current buf's count |
718 | * |
719 | * Adds to the channel buffer's consumed sub-buffer count. |
720 | * subbufs_consumed should be the number of sub-buffers newly consumed, |
721 | * not the total consumed. |
722 | * |
723 | * NOTE. Kernel clients don't need to call this function if the channel |
724 | * mode is 'overwrite'. |
725 | */ |
726 | void relay_subbufs_consumed(struct rchan *chan, |
727 | unsigned int cpu, |
728 | size_t subbufs_consumed) |
729 | { |
730 | struct rchan_buf *buf; |
731 | |
732 | if (!chan || cpu >= NR_CPUS) |
733 | return; |
734 | |
735 | buf = *per_cpu_ptr(chan->buf, cpu); |
736 | if (!buf || subbufs_consumed > chan->n_subbufs) |
737 | return; |
738 | |
739 | if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed) |
740 | buf->subbufs_consumed = buf->subbufs_produced; |
741 | else |
742 | buf->subbufs_consumed += subbufs_consumed; |
743 | } |
744 | EXPORT_SYMBOL_GPL(relay_subbufs_consumed); |
745 | |
746 | /** |
747 | * relay_close - close the channel |
748 | * @chan: the channel |
749 | * |
750 | * Closes all channel buffers and frees the channel. |
751 | */ |
752 | void relay_close(struct rchan *chan) |
753 | { |
754 | struct rchan_buf *buf; |
755 | unsigned int i; |
756 | |
757 | if (!chan) |
758 | return; |
759 | |
760 | mutex_lock(&relay_channels_mutex); |
761 | if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) |
762 | relay_close_buf(buf); |
763 | else |
764 | for_each_possible_cpu(i) |
765 | if ((buf = *per_cpu_ptr(chan->buf, i))) |
766 | relay_close_buf(buf); |
767 | |
768 | if (chan->last_toobig) |
769 | printk(KERN_WARNING "relay: one or more items not logged " |
770 | "[item size (%zd) > sub-buffer size (%zd)]\n" , |
771 | chan->last_toobig, chan->subbuf_size); |
772 | |
773 | list_del(entry: &chan->list); |
774 | kref_put(kref: &chan->kref, release: relay_destroy_channel); |
775 | mutex_unlock(lock: &relay_channels_mutex); |
776 | } |
777 | EXPORT_SYMBOL_GPL(relay_close); |
778 | |
779 | /** |
780 | * relay_flush - close the channel |
781 | * @chan: the channel |
782 | * |
783 | * Flushes all channel buffers, i.e. forces buffer switch. |
784 | */ |
785 | void relay_flush(struct rchan *chan) |
786 | { |
787 | struct rchan_buf *buf; |
788 | unsigned int i; |
789 | |
790 | if (!chan) |
791 | return; |
792 | |
793 | if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) { |
794 | relay_switch_subbuf(buf, 0); |
795 | return; |
796 | } |
797 | |
798 | mutex_lock(&relay_channels_mutex); |
799 | for_each_possible_cpu(i) |
800 | if ((buf = *per_cpu_ptr(chan->buf, i))) |
801 | relay_switch_subbuf(buf, 0); |
802 | mutex_unlock(lock: &relay_channels_mutex); |
803 | } |
804 | EXPORT_SYMBOL_GPL(relay_flush); |
805 | |
806 | /** |
807 | * relay_file_open - open file op for relay files |
808 | * @inode: the inode |
809 | * @filp: the file |
810 | * |
811 | * Increments the channel buffer refcount. |
812 | */ |
813 | static int relay_file_open(struct inode *inode, struct file *filp) |
814 | { |
815 | struct rchan_buf *buf = inode->i_private; |
816 | kref_get(kref: &buf->kref); |
817 | filp->private_data = buf; |
818 | |
819 | return nonseekable_open(inode, filp); |
820 | } |
821 | |
822 | /** |
823 | * relay_file_mmap - mmap file op for relay files |
824 | * @filp: the file |
825 | * @vma: the vma describing what to map |
826 | * |
827 | * Calls upon relay_mmap_buf() to map the file into user space. |
828 | */ |
829 | static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma) |
830 | { |
831 | struct rchan_buf *buf = filp->private_data; |
832 | return relay_mmap_buf(buf, vma); |
833 | } |
834 | |
835 | /** |
836 | * relay_file_poll - poll file op for relay files |
837 | * @filp: the file |
838 | * @wait: poll table |
839 | * |
840 | * Poll implemention. |
841 | */ |
842 | static __poll_t relay_file_poll(struct file *filp, poll_table *wait) |
843 | { |
844 | __poll_t mask = 0; |
845 | struct rchan_buf *buf = filp->private_data; |
846 | |
847 | if (buf->finalized) |
848 | return EPOLLERR; |
849 | |
850 | if (filp->f_mode & FMODE_READ) { |
851 | poll_wait(filp, wait_address: &buf->read_wait, p: wait); |
852 | if (!relay_buf_empty(buf)) |
853 | mask |= EPOLLIN | EPOLLRDNORM; |
854 | } |
855 | |
856 | return mask; |
857 | } |
858 | |
859 | /** |
860 | * relay_file_release - release file op for relay files |
861 | * @inode: the inode |
862 | * @filp: the file |
863 | * |
864 | * Decrements the channel refcount, as the filesystem is |
865 | * no longer using it. |
866 | */ |
867 | static int relay_file_release(struct inode *inode, struct file *filp) |
868 | { |
869 | struct rchan_buf *buf = filp->private_data; |
870 | kref_put(kref: &buf->kref, release: relay_remove_buf); |
871 | |
872 | return 0; |
873 | } |
874 | |
875 | /* |
876 | * relay_file_read_consume - update the consumed count for the buffer |
877 | */ |
878 | static void relay_file_read_consume(struct rchan_buf *buf, |
879 | size_t read_pos, |
880 | size_t bytes_consumed) |
881 | { |
882 | size_t subbuf_size = buf->chan->subbuf_size; |
883 | size_t n_subbufs = buf->chan->n_subbufs; |
884 | size_t read_subbuf; |
885 | |
886 | if (buf->subbufs_produced == buf->subbufs_consumed && |
887 | buf->offset == buf->bytes_consumed) |
888 | return; |
889 | |
890 | if (buf->bytes_consumed + bytes_consumed > subbuf_size) { |
891 | relay_subbufs_consumed(buf->chan, buf->cpu, 1); |
892 | buf->bytes_consumed = 0; |
893 | } |
894 | |
895 | buf->bytes_consumed += bytes_consumed; |
896 | if (!read_pos) |
897 | read_subbuf = buf->subbufs_consumed % n_subbufs; |
898 | else |
899 | read_subbuf = read_pos / buf->chan->subbuf_size; |
900 | if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) { |
901 | if ((read_subbuf == buf->subbufs_produced % n_subbufs) && |
902 | (buf->offset == subbuf_size)) |
903 | return; |
904 | relay_subbufs_consumed(buf->chan, buf->cpu, 1); |
905 | buf->bytes_consumed = 0; |
906 | } |
907 | } |
908 | |
909 | /* |
910 | * relay_file_read_avail - boolean, are there unconsumed bytes available? |
911 | */ |
912 | static int relay_file_read_avail(struct rchan_buf *buf) |
913 | { |
914 | size_t subbuf_size = buf->chan->subbuf_size; |
915 | size_t n_subbufs = buf->chan->n_subbufs; |
916 | size_t produced = buf->subbufs_produced; |
917 | size_t consumed; |
918 | |
919 | relay_file_read_consume(buf, read_pos: 0, bytes_consumed: 0); |
920 | |
921 | consumed = buf->subbufs_consumed; |
922 | |
923 | if (unlikely(buf->offset > subbuf_size)) { |
924 | if (produced == consumed) |
925 | return 0; |
926 | return 1; |
927 | } |
928 | |
929 | if (unlikely(produced - consumed >= n_subbufs)) { |
930 | consumed = produced - n_subbufs + 1; |
931 | buf->subbufs_consumed = consumed; |
932 | buf->bytes_consumed = 0; |
933 | } |
934 | |
935 | produced = (produced % n_subbufs) * subbuf_size + buf->offset; |
936 | consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed; |
937 | |
938 | if (consumed > produced) |
939 | produced += n_subbufs * subbuf_size; |
940 | |
941 | if (consumed == produced) { |
942 | if (buf->offset == subbuf_size && |
943 | buf->subbufs_produced > buf->subbufs_consumed) |
944 | return 1; |
945 | return 0; |
946 | } |
947 | |
948 | return 1; |
949 | } |
950 | |
951 | /** |
952 | * relay_file_read_subbuf_avail - return bytes available in sub-buffer |
953 | * @read_pos: file read position |
954 | * @buf: relay channel buffer |
955 | */ |
956 | static size_t relay_file_read_subbuf_avail(size_t read_pos, |
957 | struct rchan_buf *buf) |
958 | { |
959 | size_t padding, avail = 0; |
960 | size_t read_subbuf, read_offset, write_subbuf, write_offset; |
961 | size_t subbuf_size = buf->chan->subbuf_size; |
962 | |
963 | write_subbuf = (buf->data - buf->start) / subbuf_size; |
964 | write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset; |
965 | read_subbuf = read_pos / subbuf_size; |
966 | read_offset = read_pos % subbuf_size; |
967 | padding = buf->padding[read_subbuf]; |
968 | |
969 | if (read_subbuf == write_subbuf) { |
970 | if (read_offset + padding < write_offset) |
971 | avail = write_offset - (read_offset + padding); |
972 | } else |
973 | avail = (subbuf_size - padding) - read_offset; |
974 | |
975 | return avail; |
976 | } |
977 | |
978 | /** |
979 | * relay_file_read_start_pos - find the first available byte to read |
980 | * @buf: relay channel buffer |
981 | * |
982 | * If the read_pos is in the middle of padding, return the |
983 | * position of the first actually available byte, otherwise |
984 | * return the original value. |
985 | */ |
986 | static size_t relay_file_read_start_pos(struct rchan_buf *buf) |
987 | { |
988 | size_t read_subbuf, padding, padding_start, padding_end; |
989 | size_t subbuf_size = buf->chan->subbuf_size; |
990 | size_t n_subbufs = buf->chan->n_subbufs; |
991 | size_t consumed = buf->subbufs_consumed % n_subbufs; |
992 | size_t read_pos = (consumed * subbuf_size + buf->bytes_consumed) |
993 | % (n_subbufs * subbuf_size); |
994 | |
995 | read_subbuf = read_pos / subbuf_size; |
996 | padding = buf->padding[read_subbuf]; |
997 | padding_start = (read_subbuf + 1) * subbuf_size - padding; |
998 | padding_end = (read_subbuf + 1) * subbuf_size; |
999 | if (read_pos >= padding_start && read_pos < padding_end) { |
1000 | read_subbuf = (read_subbuf + 1) % n_subbufs; |
1001 | read_pos = read_subbuf * subbuf_size; |
1002 | } |
1003 | |
1004 | return read_pos; |
1005 | } |
1006 | |
1007 | /** |
1008 | * relay_file_read_end_pos - return the new read position |
1009 | * @read_pos: file read position |
1010 | * @buf: relay channel buffer |
1011 | * @count: number of bytes to be read |
1012 | */ |
1013 | static size_t relay_file_read_end_pos(struct rchan_buf *buf, |
1014 | size_t read_pos, |
1015 | size_t count) |
1016 | { |
1017 | size_t read_subbuf, padding, end_pos; |
1018 | size_t subbuf_size = buf->chan->subbuf_size; |
1019 | size_t n_subbufs = buf->chan->n_subbufs; |
1020 | |
1021 | read_subbuf = read_pos / subbuf_size; |
1022 | padding = buf->padding[read_subbuf]; |
1023 | if (read_pos % subbuf_size + count + padding == subbuf_size) |
1024 | end_pos = (read_subbuf + 1) * subbuf_size; |
1025 | else |
1026 | end_pos = read_pos + count; |
1027 | if (end_pos >= subbuf_size * n_subbufs) |
1028 | end_pos = 0; |
1029 | |
1030 | return end_pos; |
1031 | } |
1032 | |
1033 | static ssize_t relay_file_read(struct file *filp, |
1034 | char __user *buffer, |
1035 | size_t count, |
1036 | loff_t *ppos) |
1037 | { |
1038 | struct rchan_buf *buf = filp->private_data; |
1039 | size_t read_start, avail; |
1040 | size_t written = 0; |
1041 | int ret; |
1042 | |
1043 | if (!count) |
1044 | return 0; |
1045 | |
1046 | inode_lock(inode: file_inode(f: filp)); |
1047 | do { |
1048 | void *from; |
1049 | |
1050 | if (!relay_file_read_avail(buf)) |
1051 | break; |
1052 | |
1053 | read_start = relay_file_read_start_pos(buf); |
1054 | avail = relay_file_read_subbuf_avail(read_pos: read_start, buf); |
1055 | if (!avail) |
1056 | break; |
1057 | |
1058 | avail = min(count, avail); |
1059 | from = buf->start + read_start; |
1060 | ret = avail; |
1061 | if (copy_to_user(to: buffer, from, n: avail)) |
1062 | break; |
1063 | |
1064 | buffer += ret; |
1065 | written += ret; |
1066 | count -= ret; |
1067 | |
1068 | relay_file_read_consume(buf, read_pos: read_start, bytes_consumed: ret); |
1069 | *ppos = relay_file_read_end_pos(buf, read_pos: read_start, count: ret); |
1070 | } while (count); |
1071 | inode_unlock(inode: file_inode(f: filp)); |
1072 | |
1073 | return written; |
1074 | } |
1075 | |
1076 | static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed) |
1077 | { |
1078 | rbuf->bytes_consumed += bytes_consumed; |
1079 | |
1080 | if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) { |
1081 | relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1); |
1082 | rbuf->bytes_consumed %= rbuf->chan->subbuf_size; |
1083 | } |
1084 | } |
1085 | |
1086 | static void relay_pipe_buf_release(struct pipe_inode_info *pipe, |
1087 | struct pipe_buffer *buf) |
1088 | { |
1089 | struct rchan_buf *rbuf; |
1090 | |
1091 | rbuf = (struct rchan_buf *)page_private(buf->page); |
1092 | relay_consume_bytes(rbuf, bytes_consumed: buf->private); |
1093 | } |
1094 | |
1095 | static const struct pipe_buf_operations relay_pipe_buf_ops = { |
1096 | .release = relay_pipe_buf_release, |
1097 | .try_steal = generic_pipe_buf_try_steal, |
1098 | .get = generic_pipe_buf_get, |
1099 | }; |
1100 | |
1101 | static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i) |
1102 | { |
1103 | } |
1104 | |
1105 | /* |
1106 | * subbuf_splice_actor - splice up to one subbuf's worth of data |
1107 | */ |
1108 | static ssize_t subbuf_splice_actor(struct file *in, |
1109 | loff_t *ppos, |
1110 | struct pipe_inode_info *pipe, |
1111 | size_t len, |
1112 | unsigned int flags, |
1113 | int *nonpad_ret) |
1114 | { |
1115 | unsigned int pidx, poff, total_len, subbuf_pages, nr_pages; |
1116 | struct rchan_buf *rbuf = in->private_data; |
1117 | unsigned int subbuf_size = rbuf->chan->subbuf_size; |
1118 | uint64_t pos = (uint64_t) *ppos; |
1119 | uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size; |
1120 | size_t read_start = (size_t) do_div(pos, alloc_size); |
1121 | size_t read_subbuf = read_start / subbuf_size; |
1122 | size_t padding = rbuf->padding[read_subbuf]; |
1123 | size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding; |
1124 | struct page *pages[PIPE_DEF_BUFFERS]; |
1125 | struct partial_page partial[PIPE_DEF_BUFFERS]; |
1126 | struct splice_pipe_desc spd = { |
1127 | .pages = pages, |
1128 | .nr_pages = 0, |
1129 | .nr_pages_max = PIPE_DEF_BUFFERS, |
1130 | .partial = partial, |
1131 | .ops = &relay_pipe_buf_ops, |
1132 | .spd_release = relay_page_release, |
1133 | }; |
1134 | ssize_t ret; |
1135 | |
1136 | if (rbuf->subbufs_produced == rbuf->subbufs_consumed) |
1137 | return 0; |
1138 | if (splice_grow_spd(pipe, &spd)) |
1139 | return -ENOMEM; |
1140 | |
1141 | /* |
1142 | * Adjust read len, if longer than what is available |
1143 | */ |
1144 | if (len > (subbuf_size - read_start % subbuf_size)) |
1145 | len = subbuf_size - read_start % subbuf_size; |
1146 | |
1147 | subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT; |
1148 | pidx = (read_start / PAGE_SIZE) % subbuf_pages; |
1149 | poff = read_start & ~PAGE_MASK; |
1150 | nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max); |
1151 | |
1152 | for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) { |
1153 | unsigned int this_len, this_end, private; |
1154 | unsigned int cur_pos = read_start + total_len; |
1155 | |
1156 | if (!len) |
1157 | break; |
1158 | |
1159 | this_len = min_t(unsigned long, len, PAGE_SIZE - poff); |
1160 | private = this_len; |
1161 | |
1162 | spd.pages[spd.nr_pages] = rbuf->page_array[pidx]; |
1163 | spd.partial[spd.nr_pages].offset = poff; |
1164 | |
1165 | this_end = cur_pos + this_len; |
1166 | if (this_end >= nonpad_end) { |
1167 | this_len = nonpad_end - cur_pos; |
1168 | private = this_len + padding; |
1169 | } |
1170 | spd.partial[spd.nr_pages].len = this_len; |
1171 | spd.partial[spd.nr_pages].private = private; |
1172 | |
1173 | len -= this_len; |
1174 | total_len += this_len; |
1175 | poff = 0; |
1176 | pidx = (pidx + 1) % subbuf_pages; |
1177 | |
1178 | if (this_end >= nonpad_end) { |
1179 | spd.nr_pages++; |
1180 | break; |
1181 | } |
1182 | } |
1183 | |
1184 | ret = 0; |
1185 | if (!spd.nr_pages) |
1186 | goto out; |
1187 | |
1188 | ret = *nonpad_ret = splice_to_pipe(pipe, &spd); |
1189 | if (ret < 0 || ret < total_len) |
1190 | goto out; |
1191 | |
1192 | if (read_start + ret == nonpad_end) |
1193 | ret += padding; |
1194 | |
1195 | out: |
1196 | splice_shrink_spd(&spd); |
1197 | return ret; |
1198 | } |
1199 | |
1200 | static ssize_t relay_file_splice_read(struct file *in, |
1201 | loff_t *ppos, |
1202 | struct pipe_inode_info *pipe, |
1203 | size_t len, |
1204 | unsigned int flags) |
1205 | { |
1206 | ssize_t spliced; |
1207 | int ret; |
1208 | int nonpad_ret = 0; |
1209 | |
1210 | ret = 0; |
1211 | spliced = 0; |
1212 | |
1213 | while (len && !spliced) { |
1214 | ret = subbuf_splice_actor(in, ppos, pipe, len, flags, nonpad_ret: &nonpad_ret); |
1215 | if (ret < 0) |
1216 | break; |
1217 | else if (!ret) { |
1218 | if (flags & SPLICE_F_NONBLOCK) |
1219 | ret = -EAGAIN; |
1220 | break; |
1221 | } |
1222 | |
1223 | *ppos += ret; |
1224 | if (ret > len) |
1225 | len = 0; |
1226 | else |
1227 | len -= ret; |
1228 | spliced += nonpad_ret; |
1229 | nonpad_ret = 0; |
1230 | } |
1231 | |
1232 | if (spliced) |
1233 | return spliced; |
1234 | |
1235 | return ret; |
1236 | } |
1237 | |
1238 | const struct file_operations relay_file_operations = { |
1239 | .open = relay_file_open, |
1240 | .poll = relay_file_poll, |
1241 | .mmap = relay_file_mmap, |
1242 | .read = relay_file_read, |
1243 | .llseek = no_llseek, |
1244 | .release = relay_file_release, |
1245 | .splice_read = relay_file_splice_read, |
1246 | }; |
1247 | EXPORT_SYMBOL_GPL(relay_file_operations); |
1248 | |