/* * Public API and common code for kernel->userspace relay file support. * * See Documentation/filesystems/relay.rst for an overview. * * Copyright (C) 2002-2005 - Tom Zanussi ([email protected]), IBM Corp * Copyright (C) 1999-2005 - Karim Yaghmour ([email protected]) * * Moved to kernel/relay.c by Paul Mundt, 2006. * November 2006 - CPU hotplug support by Mathieu Desnoyers * ([email protected]) * * This file is released under the GPL. */ #include <linux/errno.h> #include <linux/stddef.h> #include <linux/slab.h> #include <linux/export.h> #include <linux/string.h> #include <linux/relay.h> #include <linux/vmalloc.h> #include <linux/mm.h> #include <linux/cpu.h> #include <linux/splice.h> /* list of open channels, for cpu hotplug */ static DEFINE_MUTEX(relay_channels_mutex); static LIST_HEAD(relay_channels); /* * fault() vm_op implementation for relay file mapping. */ static vm_fault_t relay_buf_fault(struct vm_fault *vmf) { … } /* * vm_ops for relay file mappings. */ static const struct vm_operations_struct relay_file_mmap_ops = …; /* * allocate an array of pointers of struct page */ static struct page **relay_alloc_page_array(unsigned int n_pages) { … } /* * free an array of pointers of struct page */ static void relay_free_page_array(struct page **array) { … } /** * relay_mmap_buf: - mmap channel buffer to process address space * @buf: relay channel buffer * @vma: vm_area_struct describing memory to be mapped * * Returns 0 if ok, negative on error * * Caller should already have grabbed mmap_lock. */ static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma) { … } /** * relay_alloc_buf - allocate a channel buffer * @buf: the buffer struct * @size: total size of the buffer * * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The * passed in size will get page aligned, if it isn't already. */ static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size) { … } /** * relay_create_buf - allocate and initialize a channel buffer * @chan: the relay channel * * Returns channel buffer if successful, %NULL otherwise. */ static struct rchan_buf *relay_create_buf(struct rchan *chan) { … } /** * relay_destroy_channel - free the channel struct * @kref: target kernel reference that contains the relay channel * * Should only be called from kref_put(). */ static void relay_destroy_channel(struct kref *kref) { … } /** * relay_destroy_buf - destroy an rchan_buf struct and associated buffer * @buf: the buffer struct */ static void relay_destroy_buf(struct rchan_buf *buf) { … } /** * relay_remove_buf - remove a channel buffer * @kref: target kernel reference that contains the relay buffer * * Removes the file from the filesystem, which also frees the * rchan_buf_struct and the channel buffer. Should only be called from * kref_put(). */ static void relay_remove_buf(struct kref *kref) { … } /** * relay_buf_empty - boolean, is the channel buffer empty? * @buf: channel buffer * * Returns 1 if the buffer is empty, 0 otherwise. */ static int relay_buf_empty(struct rchan_buf *buf) { … } /** * relay_buf_full - boolean, is the channel buffer full? * @buf: channel buffer * * Returns 1 if the buffer is full, 0 otherwise. */ int relay_buf_full(struct rchan_buf *buf) { … } EXPORT_SYMBOL_GPL(…); /* * High-level relay kernel API and associated functions. */ static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf, void *prev_subbuf, size_t prev_padding) { … } /** * wakeup_readers - wake up readers waiting on a channel * @work: contains the channel buffer * * This is the function used to defer reader waking */ static void wakeup_readers(struct irq_work *work) { … } /** * __relay_reset - reset a channel buffer * @buf: the channel buffer * @init: 1 if this is a first-time initialization * * See relay_reset() for description of effect. */ static void __relay_reset(struct rchan_buf *buf, unsigned int init) { … } /** * relay_reset - reset the channel * @chan: the channel * * This has the effect of erasing all data from all channel buffers * and restarting the channel in its initial state. The buffers * are not freed, so any mappings are still in effect. * * NOTE. Care should be taken that the channel isn't actually * being used by anything when this call is made. */ void relay_reset(struct rchan *chan) { … } EXPORT_SYMBOL_GPL(…); static inline void relay_set_buf_dentry(struct rchan_buf *buf, struct dentry *dentry) { … } static struct dentry *relay_create_buf_file(struct rchan *chan, struct rchan_buf *buf, unsigned int cpu) { … } /* * relay_open_buf - create a new relay channel buffer * * used by relay_open() and CPU hotplug. */ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu) { … } /** * relay_close_buf - close a channel buffer * @buf: channel buffer * * Marks the buffer finalized and restores the default callbacks. * The channel buffer and channel buffer data structure are then freed * automatically when the last reference is given up. */ static void relay_close_buf(struct rchan_buf *buf) { … } int relay_prepare_cpu(unsigned int cpu) { … } /** * relay_open - create a new relay channel * @base_filename: base name of files to create, %NULL for buffering only * @parent: dentry of parent directory, %NULL for root directory or buffer * @subbuf_size: size of sub-buffers * @n_subbufs: number of sub-buffers * @cb: client callback functions * @private_data: user-defined data * * Returns channel pointer if successful, %NULL otherwise. * * Creates a channel buffer for each cpu using the sizes and * attributes specified. The created channel buffer files * will be named base_filename0...base_filenameN-1. File * permissions will be %S_IRUSR. * * If opening a buffer (@parent = NULL) that you later wish to register * in a filesystem, call relay_late_setup_files() once the @parent dentry * is available. */ struct rchan *relay_open(const char *base_filename, struct dentry *parent, size_t subbuf_size, size_t n_subbufs, const struct rchan_callbacks *cb, void *private_data) { … } EXPORT_SYMBOL_GPL(…); struct rchan_percpu_buf_dispatcher { … }; /* Called in atomic context. */ static void __relay_set_buf_dentry(void *info) { … } /** * relay_late_setup_files - triggers file creation * @chan: channel to operate on * @base_filename: base name of files to create * @parent: dentry of parent directory, %NULL for root directory * * Returns 0 if successful, non-zero otherwise. * * Use to setup files for a previously buffer-only channel created * by relay_open() with a NULL parent dentry. * * For example, this is useful for perfomring early tracing in kernel, * before VFS is up and then exposing the early results once the dentry * is available. */ int relay_late_setup_files(struct rchan *chan, const char *base_filename, struct dentry *parent) { … } EXPORT_SYMBOL_GPL(…); /** * relay_switch_subbuf - switch to a new sub-buffer * @buf: channel buffer * @length: size of current event * * Returns either the length passed in or 0 if full. * * Performs sub-buffer-switch tasks such as invoking callbacks, * updating padding counts, waking up readers, etc. */ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) { … } EXPORT_SYMBOL_GPL(…); /** * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count * @chan: the channel * @cpu: the cpu associated with the channel buffer to update * @subbufs_consumed: number of sub-buffers to add to current buf's count * * Adds to the channel buffer's consumed sub-buffer count. * subbufs_consumed should be the number of sub-buffers newly consumed, * not the total consumed. * * NOTE. Kernel clients don't need to call this function if the channel * mode is 'overwrite'. */ void relay_subbufs_consumed(struct rchan *chan, unsigned int cpu, size_t subbufs_consumed) { … } EXPORT_SYMBOL_GPL(…); /** * relay_close - close the channel * @chan: the channel * * Closes all channel buffers and frees the channel. */ void relay_close(struct rchan *chan) { … } EXPORT_SYMBOL_GPL(…); /** * relay_flush - close the channel * @chan: the channel * * Flushes all channel buffers, i.e. forces buffer switch. */ void relay_flush(struct rchan *chan) { … } EXPORT_SYMBOL_GPL(…); /** * relay_file_open - open file op for relay files * @inode: the inode * @filp: the file * * Increments the channel buffer refcount. */ static int relay_file_open(struct inode *inode, struct file *filp) { … } /** * relay_file_mmap - mmap file op for relay files * @filp: the file * @vma: the vma describing what to map * * Calls upon relay_mmap_buf() to map the file into user space. */ static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma) { … } /** * relay_file_poll - poll file op for relay files * @filp: the file * @wait: poll table * * Poll implemention. */ static __poll_t relay_file_poll(struct file *filp, poll_table *wait) { … } /** * relay_file_release - release file op for relay files * @inode: the inode * @filp: the file * * Decrements the channel refcount, as the filesystem is * no longer using it. */ static int relay_file_release(struct inode *inode, struct file *filp) { … } /* * relay_file_read_consume - update the consumed count for the buffer */ static void relay_file_read_consume(struct rchan_buf *buf, size_t read_pos, size_t bytes_consumed) { … } /* * relay_file_read_avail - boolean, are there unconsumed bytes available? */ static int relay_file_read_avail(struct rchan_buf *buf) { … } /** * relay_file_read_subbuf_avail - return bytes available in sub-buffer * @read_pos: file read position * @buf: relay channel buffer */ static size_t relay_file_read_subbuf_avail(size_t read_pos, struct rchan_buf *buf) { … } /** * relay_file_read_start_pos - find the first available byte to read * @buf: relay channel buffer * * If the read_pos is in the middle of padding, return the * position of the first actually available byte, otherwise * return the original value. */ static size_t relay_file_read_start_pos(struct rchan_buf *buf) { … } /** * relay_file_read_end_pos - return the new read position * @read_pos: file read position * @buf: relay channel buffer * @count: number of bytes to be read */ static size_t relay_file_read_end_pos(struct rchan_buf *buf, size_t read_pos, size_t count) { … } static ssize_t relay_file_read(struct file *filp, char __user *buffer, size_t count, loff_t *ppos) { … } const struct file_operations relay_file_operations = …; EXPORT_SYMBOL_GPL(…);
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