cregit-Linux how code gets into the kernel

Release 4.7 include/linux/relay.h

Directory: include/linux
/*
 * 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/bug.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.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 timer_list timer; 	/* reader wake-up timer */
	
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 *buf[NR_CPUS]; /* 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 = chan->buf[smp_processor_id()]; 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); }

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/** * __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 = chan->buf[get_cpu()]; 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(); }

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/** * 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; struct rchan_buf *buf = chan->buf[smp_processor_id()]; if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { length = relay_switch_subbuf(buf, length); if (!length) return NULL; } reserved = buf->data + buf->offset; buf->offset += length; return reserved; }

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/** * 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; }

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

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mathieu desnoyersmathieu desnoyers273.56%112.50%
tom zanussitom zanussi60.79%112.50%
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Directory: include/linux
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