drivers/staging/lttng/ltt-ring-buffer-client.h - kernel/msm-4.9 - Gitiles

 /*
  * ltt-ring-buffer-client.h
  *
  * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
  * LTTng lib ring buffer client template.
  *
  * Dual LGPL v2.1/GPL v2 license.
  */

 #include <linux/module.h>
 #include <linux/types.h>
 #include "lib/bitfield.h"
 #include "wrapper/vmalloc.h"	/* for wrapper_vmalloc_sync_all() */
 #include "wrapper/trace-clock.h"
 #include "ltt-events.h"
 #include "ltt-tracer.h"
 #include "wrapper/ringbuffer/frontend_types.h"

 /*
  * Keep the natural field alignment for _each field_ within this structure if
  * you ever add/remove a field from this header. Packed attribute is not used
  * because gcc generates poor code on at least powerpc and mips. Don't ever
  * let gcc add padding between the structure elements.
  *
  * The guarantee we have with timestamps is that all the events in a
  * packet are included (inclusive) within the begin/end timestamps of
  * the packet. Another guarantee we have is that the "timestamp begin",
  * as well as the event timestamps, are monotonically increasing (never
  * decrease) when moving forward in a stream (physically). But this
  * guarantee does not apply to "timestamp end", because it is sampled at
  * commit time, which is not ordered with respect to space reservation.
  */

 struct packet_header {
 	/* Trace packet header */
 	uint32_t magic;			/*
 					 * Trace magic number.
 					 * contains endianness information.
 					 */
 	uint8_t uuid[16];
 	uint32_t stream_id;

 	struct {
 		/* Stream packet context */
 		uint64_t timestamp_begin;	/* Cycle count at subbuffer start */
 		uint64_t timestamp_end;		/* Cycle count at subbuffer end */
 		uint32_t events_discarded;	/*
 						 * Events lost in this subbuffer since
 						 * the beginning of the trace.
 						 * (may overflow)
 						 */
 		uint32_t content_size;		/* Size of data in subbuffer */
 		uint32_t packet_size;		/* Subbuffer size (include padding) */
 		uint32_t cpu_id;		/* CPU id associated with stream */
 		uint8_t header_end;		/* End of header */
 	} ctx;
 };


 static inline notrace u64 lib_ring_buffer_clock_read(struct channel *chan)
 {
 	return trace_clock_read64();
 }

 static inline
 size_t ctx_get_size(size_t offset, struct lttng_ctx *ctx)
 {
 	int i;
 	size_t orig_offset = offset;

 	if (likely(!ctx))
 		return 0;
 	for (i = 0; i < ctx->nr_fields; i++)
 		offset += ctx->fields[i].get_size(offset);
 	return offset - orig_offset;
 }

 static inline
 void ctx_record(struct lib_ring_buffer_ctx *bufctx,
 		struct ltt_channel *chan,
 		struct lttng_ctx *ctx)
 {
 	int i;

 	if (likely(!ctx))
 		return;
 	for (i = 0; i < ctx->nr_fields; i++)
 		ctx->fields[i].record(&ctx->fields[i], bufctx, chan);
 }

 /*
  * record_header_size - Calculate the header size and padding necessary.
  * @config: ring buffer instance configuration
  * @chan: channel
  * @offset: offset in the write buffer
  * @pre_header_padding: padding to add before the header (output)
  * @ctx: reservation context
  *
  * Returns the event header size (including padding).
  *
  * The payload must itself determine its own alignment from the biggest type it
  * contains.
  */
 static __inline__
 unsigned char record_header_size(const struct lib_ring_buffer_config *config,
 				 struct channel *chan, size_t offset,
 				 size_t *pre_header_padding,
 				 struct lib_ring_buffer_ctx *ctx)
 {
 	struct ltt_channel *ltt_chan = channel_get_private(chan);
 	struct ltt_event *event = ctx->priv;
 	size_t orig_offset = offset;
 	size_t padding;

 	switch (ltt_chan->header_type) {
 	case 1:	/* compact */
 		padding = lib_ring_buffer_align(offset, ltt_alignof(uint32_t));
 		offset += padding;
 		if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) {
 			offset += sizeof(uint32_t);	/* id and timestamp */
 		} else {
 			/* Minimum space taken by 5-bit id */
 			offset += sizeof(uint8_t);
 			/* Align extended struct on largest member */
 			offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
 			offset += sizeof(uint32_t);	/* id */
 			offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
 			offset += sizeof(uint64_t);	/* timestamp */
 		}
 		break;
 	case 2:	/* large */
 		padding = lib_ring_buffer_align(offset, ltt_alignof(uint16_t));
 		offset += padding;
 		offset += sizeof(uint16_t);
 		if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) {
 			offset += lib_ring_buffer_align(offset, ltt_alignof(uint32_t));
 			offset += sizeof(uint32_t);	/* timestamp */
 		} else {
 			/* Align extended struct on largest member */
 			offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
 			offset += sizeof(uint32_t);	/* id */
 			offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
 			offset += sizeof(uint64_t);	/* timestamp */
 		}
 		break;
 	default:
 		padding = 0;
 		WARN_ON_ONCE(1);
 	}
 	offset += ctx_get_size(offset, event->ctx);
 	offset += ctx_get_size(offset, ltt_chan->ctx);

 	*pre_header_padding = padding;
 	return offset - orig_offset;
 }

 #include "wrapper/ringbuffer/api.h"

 static
 void ltt_write_event_header_slow(const struct lib_ring_buffer_config *config,
 				 struct lib_ring_buffer_ctx *ctx,
 				 uint32_t event_id);

 /*
  * ltt_write_event_header
  *
  * Writes the event header to the offset (already aligned on 32-bits).
  *
  * @config: ring buffer instance configuration
  * @ctx: reservation context
  * @event_id: event ID
  */
 static __inline__
 void ltt_write_event_header(const struct lib_ring_buffer_config *config,
 			    struct lib_ring_buffer_ctx *ctx,
 			    uint32_t event_id)
 {
 	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
 	struct ltt_event *event = ctx->priv;

 	if (unlikely(ctx->rflags))
 		goto slow_path;

 	switch (ltt_chan->header_type) {
 	case 1:	/* compact */
 	{
 		uint32_t id_time = 0;

 		bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id);
 		bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc);
 		lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 		break;
 	}
 	case 2:	/* large */
 	{
 		uint32_t timestamp = (uint32_t) ctx->tsc;
 		uint16_t id = event_id;

 		lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 		lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint32_t));
 		lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 		break;
 	}
 	default:
 		WARN_ON_ONCE(1);
 	}

 	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
 	ctx_record(ctx, ltt_chan, event->ctx);
 	lib_ring_buffer_align_ctx(ctx, ctx->largest_align);

 	return;

 slow_path:
 	ltt_write_event_header_slow(config, ctx, event_id);
 }

 static
 void ltt_write_event_header_slow(const struct lib_ring_buffer_config *config,
 				 struct lib_ring_buffer_ctx *ctx,
 				 uint32_t event_id)
 {
 	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
 	struct ltt_event *event = ctx->priv;

 	switch (ltt_chan->header_type) {
 	case 1:	/* compact */
 		if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) {
 			uint32_t id_time = 0;

 			bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id);
 			bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc);
 			lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 		} else {
 			uint8_t id = 0;
 			uint64_t timestamp = ctx->tsc;

 			bt_bitfield_write(&id, uint8_t, 0, 5, 31);
 			lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 			/* Align extended struct on largest member */
 			lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
 			lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 			lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
 			lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 		}
 		break;
 	case 2:	/* large */
 	{
 		if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) {
 			uint32_t timestamp = (uint32_t) ctx->tsc;
 			uint16_t id = event_id;

 			lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 			lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint32_t));
 			lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 		} else {
 			uint16_t id = 65535;
 			uint64_t timestamp = ctx->tsc;

 			lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 			/* Align extended struct on largest member */
 			lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
 			lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 			lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
 			lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 		}
 		break;
 	}
 	default:
 		WARN_ON_ONCE(1);
 	}
 	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
 	ctx_record(ctx, ltt_chan, event->ctx);
 	lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
 }

 static const struct lib_ring_buffer_config client_config;

 static u64 client_ring_buffer_clock_read(struct channel *chan)
 {
 	return lib_ring_buffer_clock_read(chan);
 }

 static
 size_t client_record_header_size(const struct lib_ring_buffer_config *config,
 				 struct channel *chan, size_t offset,
 				 size_t *pre_header_padding,
 				 struct lib_ring_buffer_ctx *ctx)
 {
 	return record_header_size(config, chan, offset,
 				  pre_header_padding, ctx);
 }

 /**
  * client_packet_header_size - called on buffer-switch to a new sub-buffer
  *
  * Return header size without padding after the structure. Don't use packed
  * structure because gcc generates inefficient code on some architectures
  * (powerpc, mips..)
  */
 static size_t client_packet_header_size(void)
 {
 	return offsetof(struct packet_header, ctx.header_end);
 }

 static void client_buffer_begin(struct lib_ring_buffer *buf, u64 tsc,
 				unsigned int subbuf_idx)
 {
 	struct channel *chan = buf->backend.chan;
 	struct packet_header *header =
 		(struct packet_header *)
 			lib_ring_buffer_offset_address(&buf->backend,
 				subbuf_idx * chan->backend.subbuf_size);
 	struct ltt_channel *ltt_chan = channel_get_private(chan);
 	struct ltt_session *session = ltt_chan->session;

 	header->magic = CTF_MAGIC_NUMBER;
 	memcpy(header->uuid, session->uuid.b, sizeof(session->uuid));
 	header->stream_id = ltt_chan->id;
 	header->ctx.timestamp_begin = tsc;
 	header->ctx.timestamp_end = 0;
 	header->ctx.events_discarded = 0;
 	header->ctx.content_size = 0xFFFFFFFF; /* for debugging */
 	header->ctx.packet_size = 0xFFFFFFFF;
 	header->ctx.cpu_id = buf->backend.cpu;
 }

 /*
  * offset is assumed to never be 0 here : never deliver a completely empty
  * subbuffer. data_size is between 1 and subbuf_size.
  */
 static void client_buffer_end(struct lib_ring_buffer *buf, u64 tsc,
 			      unsigned int subbuf_idx, unsigned long data_size)
 {
 	struct channel *chan = buf->backend.chan;
 	struct packet_header *header =
 		(struct packet_header *)
 			lib_ring_buffer_offset_address(&buf->backend,
 				subbuf_idx * chan->backend.subbuf_size);
 	unsigned long records_lost = 0;

 	header->ctx.timestamp_end = tsc;
 	header->ctx.content_size = data_size * CHAR_BIT; 	/* in bits */
 	header->ctx.packet_size = PAGE_ALIGN(data_size) * CHAR_BIT; /* in bits */
 	records_lost += lib_ring_buffer_get_records_lost_full(&client_config, buf);
 	records_lost += lib_ring_buffer_get_records_lost_wrap(&client_config, buf);
 	records_lost += lib_ring_buffer_get_records_lost_big(&client_config, buf);
 	header->ctx.events_discarded = records_lost;
 }

 static int client_buffer_create(struct lib_ring_buffer *buf, void *priv,
 				int cpu, const char *name)
 {
 	return 0;
 }

 static void client_buffer_finalize(struct lib_ring_buffer *buf, void *priv, int cpu)
 {
 }

 static const struct lib_ring_buffer_config client_config = {
 	.cb.ring_buffer_clock_read = client_ring_buffer_clock_read,
 	.cb.record_header_size = client_record_header_size,
 	.cb.subbuffer_header_size = client_packet_header_size,
 	.cb.buffer_begin = client_buffer_begin,
 	.cb.buffer_end = client_buffer_end,
 	.cb.buffer_create = client_buffer_create,
 	.cb.buffer_finalize = client_buffer_finalize,

 	.tsc_bits = 32,
 	.alloc = RING_BUFFER_ALLOC_PER_CPU,
 	.sync = RING_BUFFER_SYNC_PER_CPU,
 	.mode = RING_BUFFER_MODE_TEMPLATE,
 	.backend = RING_BUFFER_PAGE,
 	.output = RING_BUFFER_OUTPUT_TEMPLATE,
 	.oops = RING_BUFFER_OOPS_CONSISTENCY,
 	.ipi = RING_BUFFER_IPI_BARRIER,
 	.wakeup = RING_BUFFER_WAKEUP_BY_TIMER,
 };

 static
 struct channel *_channel_create(const char *name,
 				struct ltt_channel *ltt_chan, void *buf_addr,
 				size_t subbuf_size, size_t num_subbuf,
 				unsigned int switch_timer_interval,
 				unsigned int read_timer_interval)
 {
 	return channel_create(&client_config, name, ltt_chan, buf_addr,
 			      subbuf_size, num_subbuf, switch_timer_interval,
 			      read_timer_interval);
 }

 static
 void ltt_channel_destroy(struct channel *chan)
 {
 	channel_destroy(chan);
 }

 static
 struct lib_ring_buffer *ltt_buffer_read_open(struct channel *chan)
 {
 	struct lib_ring_buffer *buf;
 	int cpu;

 	for_each_channel_cpu(cpu, chan) {
 		buf = channel_get_ring_buffer(&client_config, chan, cpu);
 		if (!lib_ring_buffer_open_read(buf))
 			return buf;
 	}
 	return NULL;
 }

 static
 int ltt_buffer_has_read_closed_stream(struct channel *chan)
 {
 	struct lib_ring_buffer *buf;
 	int cpu;

 	for_each_channel_cpu(cpu, chan) {
 		buf = channel_get_ring_buffer(&client_config, chan, cpu);
 		if (!atomic_long_read(&buf->active_readers))
 			return 1;
 	}
 	return 0;
 }

 static
 void ltt_buffer_read_close(struct lib_ring_buffer *buf)
 {
 	lib_ring_buffer_release_read(buf);
 }

 static
 int ltt_event_reserve(struct lib_ring_buffer_ctx *ctx,
 		      uint32_t event_id)
 {
 	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
 	int ret, cpu;

 	cpu = lib_ring_buffer_get_cpu(&client_config);
 	if (cpu < 0)
 		return -EPERM;
 	ctx->cpu = cpu;

 	switch (ltt_chan->header_type) {
 	case 1:	/* compact */
 		if (event_id > 30)
 			ctx->rflags |= LTT_RFLAG_EXTENDED;
 		break;
 	case 2:	/* large */
 		if (event_id > 65534)
 			ctx->rflags |= LTT_RFLAG_EXTENDED;
 		break;
 	default:
 		WARN_ON_ONCE(1);
 	}

 	ret = lib_ring_buffer_reserve(&client_config, ctx);
 	if (ret)
 		goto put;
 	ltt_write_event_header(&client_config, ctx, event_id);
 	return 0;
 put:
 	lib_ring_buffer_put_cpu(&client_config);
 	return ret;
 }

 static
 void ltt_event_commit(struct lib_ring_buffer_ctx *ctx)
 {
 	lib_ring_buffer_commit(&client_config, ctx);
 	lib_ring_buffer_put_cpu(&client_config);
 }

 static
 void ltt_event_write(struct lib_ring_buffer_ctx *ctx, const void *src,
 		     size_t len)
 {
 	lib_ring_buffer_write(&client_config, ctx, src, len);
 }

 static
 void ltt_event_write_from_user(struct lib_ring_buffer_ctx *ctx,
 			       const void __user *src, size_t len)
 {
 	lib_ring_buffer_copy_from_user(&client_config, ctx, src, len);
 }

 static
 void ltt_event_memset(struct lib_ring_buffer_ctx *ctx,
 		int c, size_t len)
 {
 	lib_ring_buffer_memset(&client_config, ctx, c, len);
 }

 static
 wait_queue_head_t *ltt_get_writer_buf_wait_queue(struct channel *chan, int cpu)
 {
 	struct lib_ring_buffer *buf = channel_get_ring_buffer(&client_config,
 					chan, cpu);
 	return &buf->write_wait;
 }

 static
 wait_queue_head_t *ltt_get_hp_wait_queue(struct channel *chan)
 {
 	return &chan->hp_wait;
 }

 static
 int ltt_is_finalized(struct channel *chan)
 {
 	return lib_ring_buffer_channel_is_finalized(chan);
 }

 static
 int ltt_is_disabled(struct channel *chan)
 {
 	return lib_ring_buffer_channel_is_disabled(chan);
 }

 static struct ltt_transport ltt_relay_transport = {
 	.name = "relay-" RING_BUFFER_MODE_TEMPLATE_STRING,
 	.owner = THIS_MODULE,
 	.ops = {
 		.channel_create = _channel_create,
 		.channel_destroy = ltt_channel_destroy,
 		.buffer_read_open = ltt_buffer_read_open,
 		.buffer_has_read_closed_stream =
 			ltt_buffer_has_read_closed_stream,
 		.buffer_read_close = ltt_buffer_read_close,
 		.event_reserve = ltt_event_reserve,
 		.event_commit = ltt_event_commit,
 		.event_write = ltt_event_write,
 		.event_write_from_user = ltt_event_write_from_user,
 		.event_memset = ltt_event_memset,
 		.packet_avail_size = NULL,	/* Would be racy anyway */
 		.get_writer_buf_wait_queue = ltt_get_writer_buf_wait_queue,
 		.get_hp_wait_queue = ltt_get_hp_wait_queue,
 		.is_finalized = ltt_is_finalized,
 		.is_disabled = ltt_is_disabled,
 	},
 };

 static int __init ltt_ring_buffer_client_init(void)
 {
 	/*
 	 * This vmalloc sync all also takes care of the lib ring buffer
 	 * vmalloc'd module pages when it is built as a module into LTTng.
 	 */
 	wrapper_vmalloc_sync_all();
 	ltt_transport_register(&ltt_relay_transport);
 	return 0;
 }

 module_init(ltt_ring_buffer_client_init);

 static void __exit ltt_ring_buffer_client_exit(void)
 {
 	ltt_transport_unregister(&ltt_relay_transport);
 }

 module_exit(ltt_ring_buffer_client_exit);

 MODULE_LICENSE("GPL and additional rights");
 MODULE_AUTHOR("Mathieu Desnoyers");
 MODULE_DESCRIPTION("LTTng ring buffer " RING_BUFFER_MODE_TEMPLATE_STRING
 		   " client");
	/*
	* ltt-ring-buffer-client.h
	*
	* Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	*
	* LTTng lib ring buffer client template.
	*
	* Dual LGPL v2.1/GPL v2 license.
	*/

	#include <linux/module.h>
	#include <linux/types.h>
	#include "lib/bitfield.h"
	#include "wrapper/vmalloc.h" /* for wrapper_vmalloc_sync_all() */
	#include "wrapper/trace-clock.h"
	#include "ltt-events.h"
	#include "ltt-tracer.h"
	#include "wrapper/ringbuffer/frontend_types.h"

	/*
	* Keep the natural field alignment for _each field_ within this structure if
	* you ever add/remove a field from this header. Packed attribute is not used
	* because gcc generates poor code on at least powerpc and mips. Don't ever
	* let gcc add padding between the structure elements.
	*
	* The guarantee we have with timestamps is that all the events in a
	* packet are included (inclusive) within the begin/end timestamps of
	* the packet. Another guarantee we have is that the "timestamp begin",
	* as well as the event timestamps, are monotonically increasing (never
	* decrease) when moving forward in a stream (physically). But this
	* guarantee does not apply to "timestamp end", because it is sampled at
	* commit time, which is not ordered with respect to space reservation.
	*/

	struct packet_header {
	/* Trace packet header */
	uint32_t magic; /*
	* Trace magic number.
	* contains endianness information.
	*/
	uint8_t uuid[16];
	uint32_t stream_id;

	struct {
	/* Stream packet context */
	uint64_t timestamp_begin; /* Cycle count at subbuffer start */
	uint64_t timestamp_end; /* Cycle count at subbuffer end */
	uint32_t events_discarded; /*
	* Events lost in this subbuffer since
	* the beginning of the trace.
	* (may overflow)
	*/
	uint32_t content_size; /* Size of data in subbuffer */
	uint32_t packet_size; /* Subbuffer size (include padding) */
	uint32_t cpu_id; /* CPU id associated with stream */
	uint8_t header_end; /* End of header */
	} ctx;
	};


	static inline notrace u64 lib_ring_buffer_clock_read(struct channel *chan)
	{
	return trace_clock_read64();
	}

	static inline
	size_t ctx_get_size(size_t offset, struct lttng_ctx *ctx)
	{
	int i;
	size_t orig_offset = offset;

	if (likely(!ctx))
	return 0;
	for (i = 0; i < ctx->nr_fields; i++)
	offset += ctx->fields[i].get_size(offset);
	return offset - orig_offset;
	}

	static inline
	void ctx_record(struct lib_ring_buffer_ctx *bufctx,
	struct ltt_channel *chan,
	struct lttng_ctx *ctx)
	{
	int i;

	if (likely(!ctx))
	return;
	for (i = 0; i < ctx->nr_fields; i++)
	ctx->fields[i].record(&ctx->fields[i], bufctx, chan);
	}

	/*
	* record_header_size - Calculate the header size and padding necessary.
	* @config: ring buffer instance configuration
	* @chan: channel
	* @offset: offset in the write buffer
	* @pre_header_padding: padding to add before the header (output)
	* @ctx: reservation context
	*
	* Returns the event header size (including padding).
	*
	* The payload must itself determine its own alignment from the biggest type it
	* contains.
	*/
	static __inline__
	unsigned char record_header_size(const struct lib_ring_buffer_config *config,
	struct channel *chan, size_t offset,
	size_t *pre_header_padding,
	struct lib_ring_buffer_ctx *ctx)
	{
	struct ltt_channel *ltt_chan = channel_get_private(chan);
	struct ltt_event *event = ctx->priv;
	size_t orig_offset = offset;
	size_t padding;

	switch (ltt_chan->header_type) {
	case 1: /* compact */
	padding = lib_ring_buffer_align(offset, ltt_alignof(uint32_t));
	offset += padding;
	if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC \| LTT_RFLAG_EXTENDED))) {
	offset += sizeof(uint32_t); /* id and timestamp */
	} else {
	/* Minimum space taken by 5-bit id */
	offset += sizeof(uint8_t);
	/* Align extended struct on largest member */
	offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
	offset += sizeof(uint32_t); /* id */
	offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
	offset += sizeof(uint64_t); /* timestamp */
	}
	break;
	case 2: /* large */
	padding = lib_ring_buffer_align(offset, ltt_alignof(uint16_t));
	offset += padding;
	offset += sizeof(uint16_t);
	if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC \| LTT_RFLAG_EXTENDED))) {
	offset += lib_ring_buffer_align(offset, ltt_alignof(uint32_t));
	offset += sizeof(uint32_t); /* timestamp */
	} else {
	/* Align extended struct on largest member */
	offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
	offset += sizeof(uint32_t); /* id */
	offset += lib_ring_buffer_align(offset, ltt_alignof(uint64_t));
	offset += sizeof(uint64_t); /* timestamp */
	}
	break;
	default:
	padding = 0;
	WARN_ON_ONCE(1);
	}
	offset += ctx_get_size(offset, event->ctx);
	offset += ctx_get_size(offset, ltt_chan->ctx);

	*pre_header_padding = padding;
	return offset - orig_offset;
	}

	#include "wrapper/ringbuffer/api.h"

	static
	void ltt_write_event_header_slow(const struct lib_ring_buffer_config *config,
	struct lib_ring_buffer_ctx *ctx,
	uint32_t event_id);

	/*
	* ltt_write_event_header
	*
	* Writes the event header to the offset (already aligned on 32-bits).
	*
	* @config: ring buffer instance configuration
	* @ctx: reservation context
	* @event_id: event ID
	*/
	static __inline__
	void ltt_write_event_header(const struct lib_ring_buffer_config *config,
	struct lib_ring_buffer_ctx *ctx,
	uint32_t event_id)
	{
	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
	struct ltt_event *event = ctx->priv;

	if (unlikely(ctx->rflags))
	goto slow_path;

	switch (ltt_chan->header_type) {
	case 1: /* compact */
	{
	uint32_t id_time = 0;

	bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id);
	bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc);
	lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
	break;
	}
	case 2: /* large */
	{
	uint32_t timestamp = (uint32_t) ctx->tsc;
	uint16_t id = event_id;

	lib_ring_buffer_write(config, ctx, &id, sizeof(id));
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint32_t));
	lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
	break;
	}
	default:
	WARN_ON_ONCE(1);
	}

	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
	ctx_record(ctx, ltt_chan, event->ctx);
	lib_ring_buffer_align_ctx(ctx, ctx->largest_align);

	return;

	slow_path:
	ltt_write_event_header_slow(config, ctx, event_id);
	}

	static
	void ltt_write_event_header_slow(const struct lib_ring_buffer_config *config,
	struct lib_ring_buffer_ctx *ctx,
	uint32_t event_id)
	{
	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
	struct ltt_event *event = ctx->priv;

	switch (ltt_chan->header_type) {
	case 1: /* compact */
	if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC \| LTT_RFLAG_EXTENDED))) {
	uint32_t id_time = 0;

	bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id);
	bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc);
	lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
	} else {
	uint8_t id = 0;
	uint64_t timestamp = ctx->tsc;

	bt_bitfield_write(&id, uint8_t, 0, 5, 31);
	lib_ring_buffer_write(config, ctx, &id, sizeof(id));
	/* Align extended struct on largest member */
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
	lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
	lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
	}
	break;
	case 2: /* large */
	{
	if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC \| LTT_RFLAG_EXTENDED))) {
	uint32_t timestamp = (uint32_t) ctx->tsc;
	uint16_t id = event_id;

	lib_ring_buffer_write(config, ctx, &id, sizeof(id));
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint32_t));
	lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
	} else {
	uint16_t id = 65535;
	uint64_t timestamp = ctx->tsc;

	lib_ring_buffer_write(config, ctx, &id, sizeof(id));
	/* Align extended struct on largest member */
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
	lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
	lib_ring_buffer_align_ctx(ctx, ltt_alignof(uint64_t));
	lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
	}
	break;
	}
	default:
	WARN_ON_ONCE(1);
	}
	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
	ctx_record(ctx, ltt_chan, event->ctx);
	lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
	}

	static const struct lib_ring_buffer_config client_config;

	static u64 client_ring_buffer_clock_read(struct channel *chan)
	{
	return lib_ring_buffer_clock_read(chan);
	}

	static
	size_t client_record_header_size(const struct lib_ring_buffer_config *config,
	struct channel *chan, size_t offset,
	size_t *pre_header_padding,
	struct lib_ring_buffer_ctx *ctx)
	{
	return record_header_size(config, chan, offset,
	pre_header_padding, ctx);
	}

	/**
	* client_packet_header_size - called on buffer-switch to a new sub-buffer
	*
	* Return header size without padding after the structure. Don't use packed
	* structure because gcc generates inefficient code on some architectures
	* (powerpc, mips..)
	*/
	static size_t client_packet_header_size(void)
	{
	return offsetof(struct packet_header, ctx.header_end);
	}

	static void client_buffer_begin(struct lib_ring_buffer *buf, u64 tsc,
	unsigned int subbuf_idx)
	{
	struct channel *chan = buf->backend.chan;
	struct packet_header *header =
	(struct packet_header *)
	lib_ring_buffer_offset_address(&buf->backend,
	subbuf_idx * chan->backend.subbuf_size);
	struct ltt_channel *ltt_chan = channel_get_private(chan);
	struct ltt_session *session = ltt_chan->session;

	header->magic = CTF_MAGIC_NUMBER;
	memcpy(header->uuid, session->uuid.b, sizeof(session->uuid));
	header->stream_id = ltt_chan->id;
	header->ctx.timestamp_begin = tsc;
	header->ctx.timestamp_end = 0;
	header->ctx.events_discarded = 0;
	header->ctx.content_size = 0xFFFFFFFF; /* for debugging */
	header->ctx.packet_size = 0xFFFFFFFF;
	header->ctx.cpu_id = buf->backend.cpu;
	}

	/*
	* offset is assumed to never be 0 here : never deliver a completely empty
	* subbuffer. data_size is between 1 and subbuf_size.
	*/
	static void client_buffer_end(struct lib_ring_buffer *buf, u64 tsc,
	unsigned int subbuf_idx, unsigned long data_size)
	{
	struct channel *chan = buf->backend.chan;
	struct packet_header *header =
	(struct packet_header *)
	lib_ring_buffer_offset_address(&buf->backend,
	subbuf_idx * chan->backend.subbuf_size);
	unsigned long records_lost = 0;

	header->ctx.timestamp_end = tsc;
	header->ctx.content_size = data_size * CHAR_BIT; /* in bits */
	header->ctx.packet_size = PAGE_ALIGN(data_size) * CHAR_BIT; /* in bits */
	records_lost += lib_ring_buffer_get_records_lost_full(&client_config, buf);
	records_lost += lib_ring_buffer_get_records_lost_wrap(&client_config, buf);
	records_lost += lib_ring_buffer_get_records_lost_big(&client_config, buf);
	header->ctx.events_discarded = records_lost;
	}

	static int client_buffer_create(struct lib_ring_buffer buf, void priv,
	int cpu, const char *name)
	{
	return 0;
	}

	static void client_buffer_finalize(struct lib_ring_buffer buf, void priv, int cpu)
	{
	}

	static const struct lib_ring_buffer_config client_config = {
	.cb.ring_buffer_clock_read = client_ring_buffer_clock_read,
	.cb.record_header_size = client_record_header_size,
	.cb.subbuffer_header_size = client_packet_header_size,
	.cb.buffer_begin = client_buffer_begin,
	.cb.buffer_end = client_buffer_end,
	.cb.buffer_create = client_buffer_create,
	.cb.buffer_finalize = client_buffer_finalize,

	.tsc_bits = 32,
	.alloc = RING_BUFFER_ALLOC_PER_CPU,
	.sync = RING_BUFFER_SYNC_PER_CPU,
	.mode = RING_BUFFER_MODE_TEMPLATE,
	.backend = RING_BUFFER_PAGE,
	.output = RING_BUFFER_OUTPUT_TEMPLATE,
	.oops = RING_BUFFER_OOPS_CONSISTENCY,
	.ipi = RING_BUFFER_IPI_BARRIER,
	.wakeup = RING_BUFFER_WAKEUP_BY_TIMER,
	};

	static
	struct channel _channel_create(const char name,
	struct ltt_channel ltt_chan, void buf_addr,
	size_t subbuf_size, size_t num_subbuf,
	unsigned int switch_timer_interval,
	unsigned int read_timer_interval)
	{
	return channel_create(&client_config, name, ltt_chan, buf_addr,
	subbuf_size, num_subbuf, switch_timer_interval,
	read_timer_interval);
	}

	static
	void ltt_channel_destroy(struct channel *chan)
	{
	channel_destroy(chan);
	}

	static
	struct lib_ring_buffer ltt_buffer_read_open(struct channel chan)
	{
	struct lib_ring_buffer *buf;
	int cpu;

	for_each_channel_cpu(cpu, chan) {
	buf = channel_get_ring_buffer(&client_config, chan, cpu);
	if (!lib_ring_buffer_open_read(buf))
	return buf;
	}
	return NULL;
	}

	static
	int ltt_buffer_has_read_closed_stream(struct channel *chan)
	{
	struct lib_ring_buffer *buf;
	int cpu;

	for_each_channel_cpu(cpu, chan) {
	buf = channel_get_ring_buffer(&client_config, chan, cpu);
	if (!atomic_long_read(&buf->active_readers))
	return 1;
	}
	return 0;
	}

	static
	void ltt_buffer_read_close(struct lib_ring_buffer *buf)
	{
	lib_ring_buffer_release_read(buf);
	}

	static
	int ltt_event_reserve(struct lib_ring_buffer_ctx *ctx,
	uint32_t event_id)
	{
	struct ltt_channel *ltt_chan = channel_get_private(ctx->chan);
	int ret, cpu;

	cpu = lib_ring_buffer_get_cpu(&client_config);
	if (cpu < 0)
	return -EPERM;
	ctx->cpu = cpu;

	switch (ltt_chan->header_type) {
	case 1: /* compact */
	if (event_id > 30)
	ctx->rflags \|= LTT_RFLAG_EXTENDED;
	break;
	case 2: /* large */
	if (event_id > 65534)
	ctx->rflags \|= LTT_RFLAG_EXTENDED;
	break;
	default:
	WARN_ON_ONCE(1);
	}

	ret = lib_ring_buffer_reserve(&client_config, ctx);
	if (ret)
	goto put;
	ltt_write_event_header(&client_config, ctx, event_id);
	return 0;
	put:
	lib_ring_buffer_put_cpu(&client_config);
	return ret;
	}

	static
	void ltt_event_commit(struct lib_ring_buffer_ctx *ctx)
	{
	lib_ring_buffer_commit(&client_config, ctx);
	lib_ring_buffer_put_cpu(&client_config);
	}

	static
	void ltt_event_write(struct lib_ring_buffer_ctx ctx, const void src,
	size_t len)
	{
	lib_ring_buffer_write(&client_config, ctx, src, len);
	}

	static
	void ltt_event_write_from_user(struct lib_ring_buffer_ctx *ctx,
	const void __user *src, size_t len)
	{
	lib_ring_buffer_copy_from_user(&client_config, ctx, src, len);
	}

	static
	void ltt_event_memset(struct lib_ring_buffer_ctx *ctx,
	int c, size_t len)
	{
	lib_ring_buffer_memset(&client_config, ctx, c, len);
	}

	static
	wait_queue_head_t ltt_get_writer_buf_wait_queue(struct channel chan, int cpu)
	{
	struct lib_ring_buffer *buf = channel_get_ring_buffer(&client_config,
	chan, cpu);
	return &buf->write_wait;
	}

	static
	wait_queue_head_t ltt_get_hp_wait_queue(struct channel chan)
	{
	return &chan->hp_wait;
	}

	static
	int ltt_is_finalized(struct channel *chan)
	{
	return lib_ring_buffer_channel_is_finalized(chan);
	}

	static
	int ltt_is_disabled(struct channel *chan)
	{
	return lib_ring_buffer_channel_is_disabled(chan);
	}

	static struct ltt_transport ltt_relay_transport = {
	.name = "relay-" RING_BUFFER_MODE_TEMPLATE_STRING,
	.owner = THIS_MODULE,
	.ops = {
	.channel_create = _channel_create,
	.channel_destroy = ltt_channel_destroy,
	.buffer_read_open = ltt_buffer_read_open,
	.buffer_has_read_closed_stream =
	ltt_buffer_has_read_closed_stream,
	.buffer_read_close = ltt_buffer_read_close,
	.event_reserve = ltt_event_reserve,
	.event_commit = ltt_event_commit,
	.event_write = ltt_event_write,
	.event_write_from_user = ltt_event_write_from_user,
	.event_memset = ltt_event_memset,
	.packet_avail_size = NULL, /* Would be racy anyway */
	.get_writer_buf_wait_queue = ltt_get_writer_buf_wait_queue,
	.get_hp_wait_queue = ltt_get_hp_wait_queue,
	.is_finalized = ltt_is_finalized,
	.is_disabled = ltt_is_disabled,
	},
	};

	static int __init ltt_ring_buffer_client_init(void)
	{
	/*
	* This vmalloc sync all also takes care of the lib ring buffer
	* vmalloc'd module pages when it is built as a module into LTTng.
	*/
	wrapper_vmalloc_sync_all();
	ltt_transport_register(&ltt_relay_transport);
	return 0;
	}

	module_init(ltt_ring_buffer_client_init);

	static void __exit ltt_ring_buffer_client_exit(void)
	{
	ltt_transport_unregister(&ltt_relay_transport);
	}

	module_exit(ltt_ring_buffer_client_exit);

	MODULE_LICENSE("GPL and additional rights");
	MODULE_AUTHOR("Mathieu Desnoyers");
	MODULE_DESCRIPTION("LTTng ring buffer " RING_BUFFER_MODE_TEMPLATE_STRING
	" client");