[mirror_ubuntu-bionic-kernel.git] / include / linux / relay.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * linux/include/linux/relay.h
 *
 * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
 *
 * CONFIG_RELAY definitions and declarations
 */

#ifndef _LINUX_RELAY_H
#define _LINUX_RELAY_H

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/irq_work.h>
#include <linux/bug.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
#include <linux/percpu.h>

/*
 * Tracks changes to rchan/rchan_buf structs
 */
#define RELAYFS_CHANNEL_VERSION		7

/*
 * Per-cpu relay channel buffer
 */
struct rchan_buf
{
	void *start;			/* start of channel buffer */
	void *data;			/* start of current sub-buffer */
	size_t offset;			/* current offset into sub-buffer */
	size_t subbufs_produced;	/* count of sub-buffers produced */
	size_t subbufs_consumed;	/* count of sub-buffers consumed */
	struct rchan *chan;		/* associated channel */
	wait_queue_head_t read_wait;	/* reader wait queue */
	struct irq_work wakeup_work;	/* reader wakeup */
	struct dentry *dentry;		/* channel file dentry */
	struct kref kref;		/* channel buffer refcount */
	struct page **page_array;	/* array of current buffer pages */
	unsigned int page_count;	/* number of current buffer pages */
	unsigned int finalized;		/* buffer has been finalized */
	size_t *padding;		/* padding counts per sub-buffer */
	size_t prev_padding;		/* temporary variable */
	size_t bytes_consumed;		/* bytes consumed in cur read subbuf */
	size_t early_bytes;		/* bytes consumed before VFS inited */
	unsigned int cpu;		/* this buf's cpu */
} ____cacheline_aligned;

/*
 * Relay channel data structure
 */
struct rchan
{
	u32 version;			/* the version of this struct */
	size_t subbuf_size;		/* sub-buffer size */
	size_t n_subbufs;		/* number of sub-buffers per buffer */
	size_t alloc_size;		/* total buffer size allocated */
	struct rchan_callbacks *cb;	/* client callbacks */
	struct kref kref;		/* channel refcount */
	void *private_data;		/* for user-defined data */
	size_t last_toobig;		/* tried to log event > subbuf size */
	struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
	int is_global;			/* One global buffer ? */
	struct list_head list;		/* for channel list */
	struct dentry *parent;		/* parent dentry passed to open */
	int has_base_filename;		/* has a filename associated? */
	char base_filename[NAME_MAX];	/* saved base filename */
};

/*
 * Relay channel client callbacks
 */
struct rchan_callbacks
{
	/*
	 * subbuf_start - called on buffer-switch to a new sub-buffer
	 * @buf: the channel buffer containing the new sub-buffer
	 * @subbuf: the start of the new sub-buffer
	 * @prev_subbuf: the start of the previous sub-buffer
	 * @prev_padding: unused space at the end of previous sub-buffer
	 *
	 * The client should return 1 to continue logging, 0 to stop
	 * logging.
	 *
	 * NOTE: subbuf_start will also be invoked when the buffer is
	 *       created, so that the first sub-buffer can be initialized
	 *       if necessary.  In this case, prev_subbuf will be NULL.
	 *
	 * NOTE: the client can reserve bytes at the beginning of the new
	 *       sub-buffer by calling subbuf_start_reserve() in this callback.
	 */
	int (*subbuf_start) (struct rchan_buf *buf,
			     void *subbuf,
			     void *prev_subbuf,
			     size_t prev_padding);

	/*
	 * buf_mapped - relay buffer mmap notification
	 * @buf: the channel buffer
	 * @filp: relay file pointer
	 *
	 * Called when a relay file is successfully mmapped
	 */
        void (*buf_mapped)(struct rchan_buf *buf,
			   struct file *filp);

	/*
	 * buf_unmapped - relay buffer unmap notification
	 * @buf: the channel buffer
	 * @filp: relay file pointer
	 *
	 * Called when a relay file is successfully unmapped
	 */
        void (*buf_unmapped)(struct rchan_buf *buf,
			     struct file *filp);
	/*
	 * create_buf_file - create file to represent a relay channel buffer
	 * @filename: the name of the file to create
	 * @parent: the parent of the file to create
	 * @mode: the mode of the file to create
	 * @buf: the channel buffer
	 * @is_global: outparam - set non-zero if the buffer should be global
	 *
	 * Called during relay_open(), once for each per-cpu buffer,
	 * to allow the client to create a file to be used to
	 * represent the corresponding channel buffer.  If the file is
	 * created outside of relay, the parent must also exist in
	 * that filesystem.
	 *
	 * The callback should return the dentry of the file created
	 * to represent the relay buffer.
	 *
	 * Setting the is_global outparam to a non-zero value will
	 * cause relay_open() to create a single global buffer rather
	 * than the default set of per-cpu buffers.
	 *
	 * See Documentation/filesystems/relay.txt for more info.
	 */
	struct dentry *(*create_buf_file)(const char *filename,
					  struct dentry *parent,
					  umode_t mode,
					  struct rchan_buf *buf,
					  int *is_global);

	/*
	 * remove_buf_file - remove file representing a relay channel buffer
	 * @dentry: the dentry of the file to remove
	 *
	 * Called during relay_close(), once for each per-cpu buffer,
	 * to allow the client to remove a file used to represent a
	 * channel buffer.
	 *
	 * The callback should return 0 if successful, negative if not.
	 */
	int (*remove_buf_file)(struct dentry *dentry);
};

/*
 * CONFIG_RELAY kernel API, kernel/relay.c
 */

struct rchan *relay_open(const char *base_filename,
			 struct dentry *parent,
			 size_t subbuf_size,
			 size_t n_subbufs,
			 struct rchan_callbacks *cb,
			 void *private_data);
extern int relay_late_setup_files(struct rchan *chan,
				  const char *base_filename,
				  struct dentry *parent);
extern void relay_close(struct rchan *chan);
extern void relay_flush(struct rchan *chan);
extern void relay_subbufs_consumed(struct rchan *chan,
				   unsigned int cpu,
				   size_t consumed);
extern void relay_reset(struct rchan *chan);
extern int relay_buf_full(struct rchan_buf *buf);

extern size_t relay_switch_subbuf(struct rchan_buf *buf,
				  size_t length);

/**
 *	relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling interrupts.  Use this
 *	if you might be logging from interrupt context.  Try
 *	__relay_write() if you know you	won't be logging from
 *	interrupt context.
 */
static inline void relay_write(struct rchan *chan,
			       const void *data,
			       size_t length)
{
	unsigned long flags;
	struct rchan_buf *buf;

	local_irq_save(flags);
	buf = *this_cpu_ptr(chan->buf);
	if (unlikely(buf->offset + length > chan->subbuf_size))
		length = relay_switch_subbuf(buf, length);
	memcpy(buf->data + buf->offset, data, length);
	buf->offset += length;
	local_irq_restore(flags);
}

/**
 *	__relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling preemption.  Use
 *	relay_write() if you might be logging from interrupt
 *	context.
 */
static inline void __relay_write(struct rchan *chan,
				 const void *data,
				 size_t length)
{
	struct rchan_buf *buf;

	buf = *get_cpu_ptr(chan->buf);
	if (unlikely(buf->offset + length > buf->chan->subbuf_size))
		length = relay_switch_subbuf(buf, length);
	memcpy(buf->data + buf->offset, data, length);
	buf->offset += length;
	put_cpu_ptr(chan->buf);
}

/**
 *	relay_reserve - reserve slot in channel buffer
 *	@chan: relay channel
 *	@length: number of bytes to reserve
 *
 *	Returns pointer to reserved slot, NULL if full.
 *
 *	Reserves a slot in the current cpu's channel buffer.
 *	Does not protect the buffer at all - caller must provide
 *	appropriate synchronization.
 */
static inline void *relay_reserve(struct rchan *chan, size_t length)
{
	void *reserved = NULL;
	struct rchan_buf *buf = *get_cpu_ptr(chan->buf);

	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
		length = relay_switch_subbuf(buf, length);
		if (!length)
			goto end;
	}
	reserved = buf->data + buf->offset;
	buf->offset += length;

end:
	put_cpu_ptr(chan->buf);
	return reserved;
}

/**
 *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
 *	@buf: relay channel buffer
 *	@length: number of bytes to reserve
 *
 *	Helper function used to reserve bytes at the beginning of
 *	a sub-buffer in the subbuf_start() callback.
 */
static inline void subbuf_start_reserve(struct rchan_buf *buf,
					size_t length)
{
	BUG_ON(length >= buf->chan->subbuf_size - 1);
	buf->offset = length;
}

/*
 * exported relay file operations, kernel/relay.c
 */
extern const struct file_operations relay_file_operations;

#ifdef CONFIG_RELAY
int relay_prepare_cpu(unsigned int cpu);
#else
#define relay_prepare_cpu     NULL
#endif

#endif /* _LINUX_RELAY_H */
Commit	Line	Data
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>
b86ff981 JA	15	#include <linux/sched.h>
7c9cb383	16	#include <linux/timer.h>
b86ff981 JA	17	#include <linux/wait.h>
b86ff981 JA	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 */
48b3093f	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,
23c88752 MD	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;
017c59c0 AG	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:
017c59c0 AG	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 */
b86ff981 JA	300