| /* 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 */ |
| const 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. |
| * |
| * This callback is optional. |
| * |
| * 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); |
| |
| /* |
| * 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. |
| * |
| * This callback is mandatory. |
| * |
| * See Documentation/filesystems/relay.rst 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. |
| * |
| * This callback is mandatory. |
| */ |
| 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, |
| const 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 */ |
| |