[lttng-modules.git] / lttng-context-callstack.c

/*
 * lttng-context-callstack.c
 *
 * LTTng callstack event context.
 *
 * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * The callstack context can be added to any kernel
 * event. It records either the kernel or the userspace callstack, up to a
 * max depth. The context is a CTF sequence, such that it uses only the space
 * required for the number of callstack entries.
 *
 * It allocates callstack buffers per-CPU up to 4 interrupt nesting. This
 * nesting limit is the same as defined in the ring buffer. It therefore uses a
 * fixed amount of memory, proportional to the number of CPUs:
 *
 *   size = cpus * nest * depth * sizeof(unsigned long)
 *
 * Which is about 800 bytes per-CPUs on 64-bit host and a depth of 25. The
 * allocation is done at the initialization to avoid memory allocation
 * overhead while tracing, using a shallow stack.
 *
 * The kernel callstack is recovered using save_stack_trace(), and the
 * userspace callstack uses save_stack_trace_user(). They rely on frame
 * pointers. These are usually available for the kernel, but the compiler
 * option -fomit-frame-pointer frequently used in popular Linux distributions
 * may cause the userspace callstack to be unreliable, and is a known
 * limitation of this approach. If frame pointers are not available, it
 * produces no error, but the callstack will be empty. We still provide the
 * feature, because it works well for runtime environments having frame
 * pointers. In the future, unwind support and/or last branch record may
 * provide a solution to this problem.
 *
 * The symbol name resolution is left to the trace reader.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/utsname.h>
#include <linux/stacktrace.h>
#include <linux/spinlock.h>
#include "lttng-events.h"
#include "wrapper/ringbuffer/backend.h"
#include "wrapper/ringbuffer/frontend.h"
#include "wrapper/vmalloc.h"
#include "lttng-tracer.h"

#define MAX_ENTRIES 25

struct lttng_cs_nesting {
	struct stack_trace stack_trace;
	unsigned long entries[MAX_ENTRIES];
};

struct lttng_cs {
	struct lttng_cs_nesting level[RING_BUFFER_MAX_NESTING];
};

struct field_data {
	struct lttng_cs __percpu *cs_percpu;
	int mode;
};

struct lttng_cs_type {
	const char *name;
	const char *save_func_name;
	void (*save_func)(struct stack_trace *trace);
};

enum lttng_cs_ctx_modes {
	CALLSTACK_KERNEL = 0,
	CALLSTACK_USER = 1,
};

static struct lttng_cs_type cs_types[] = {
	{
		.name		= "callstack_kernel",
		.save_func_name	= "save_stack_trace",
		.save_func	= NULL,
	},
	{
		.name		= "callstack_user",
		.save_func_name	= "save_stack_trace_user",
		.save_func	= NULL,
	},
};

static
int init_type(int mode)
{
	unsigned long func;

	if (cs_types[mode].save_func)
		return 0;
	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
	if (!func) {
		printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
				cs_types[mode].save_func_name);
		return -EINVAL;
	}
	cs_types[mode].save_func = (void *) func;
	return 0;
}

static
struct stack_trace *stack_trace_context(struct lttng_ctx_field *field,
					struct lib_ring_buffer_ctx *ctx)
{
	int nesting;
	struct lttng_cs *cs;
	struct field_data *fdata = field->priv;

	/*
	 * get_cpu() is not required, preemption is already
	 * disabled while event is written.
	 *
	 * max nesting is checked in lib_ring_buffer_get_cpu().
	 * Check it again as a safety net.
	 */
	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	if (nesting >= RING_BUFFER_MAX_NESTING) {
		return NULL;
	}
	return &cs->level[nesting].stack_trace;
}

/*
 * In order to reserve the correct size, the callstack is computed. The
 * resulting callstack is saved to be accessed in the record step.
 */
static
size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
				struct lib_ring_buffer_ctx *ctx,
				struct lttng_channel *chan)
{
	size_t size = 0;
	struct stack_trace *trace;
	struct field_data *fdata = field->priv;

	/* do not write data if no space is available */
	trace = stack_trace_context(field, ctx);
	if (!trace)
		return 0;

	/* reset stack trace, no need to clear memory */
	trace->nr_entries = 0;

	/* do the real work and reserve space */
	cs_types[fdata->mode].save_func(trace);
	/*
	 * Remove final ULONG_MAX delimiter. If we cannot find it, add
	 * our own marker to show that the stack is incomplete. This is
	 * more compact for a trace.
	 */
	if (trace->nr_entries > 0
			&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
		trace->nr_entries--;
	}
	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	size += sizeof(unsigned int);
	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	size += sizeof(unsigned long) * trace->nr_entries;
	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	if (trace->nr_entries == trace->max_entries)
		size += sizeof(unsigned long);
	return size;
}

static
void lttng_callstack_record(struct lttng_ctx_field *field,
			struct lib_ring_buffer_ctx *ctx,
			struct lttng_channel *chan)
{
	struct stack_trace *trace = stack_trace_context(field, ctx);
	unsigned int nr_seq_entries;

	if (!trace)
		return;
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
	nr_seq_entries = trace->nr_entries;
	if (trace->nr_entries == trace->max_entries)
		nr_seq_entries++;
	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	chan->ops->event_write(ctx, trace->entries,
			sizeof(unsigned long) * trace->nr_entries);
	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	if (trace->nr_entries == trace->max_entries) {
		unsigned long delim = ULONG_MAX;

		chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	}
}

static
void field_data_free(struct field_data *fdata)
{
	if (!fdata)
		return;
	free_percpu(fdata->cs_percpu);
	kfree(fdata);
}

static
struct field_data __percpu *field_data_create(int type)
{
	int cpu, i;
	struct lttng_cs __percpu *cs_set;
	struct field_data *fdata;

	fdata = kzalloc(sizeof(*fdata), GFP_KERNEL);
	if (!fdata)
		return NULL;
	cs_set = alloc_percpu(struct lttng_cs);
	if (!cs_set)
		goto error_alloc;

	fdata->cs_percpu = cs_set;
	for_each_possible_cpu(cpu) {
		struct lttng_cs *cs;

		cs = per_cpu_ptr(cs_set, cpu);
		for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
			struct lttng_cs_nesting *level;

			level = &cs->level[i];
			level->stack_trace.entries = level->entries;
			level->stack_trace.max_entries = MAX_ENTRIES;
		}
	}
	fdata->mode = type;
	return fdata;

error_alloc:
	field_data_free(fdata);
	return NULL;
}

static
void lttng_callstack_destroy(struct lttng_ctx_field *field)
{
	struct field_data *fdata = field->priv;

	field_data_free(fdata);
}

static
int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode)
{
	const char *ctx_name = cs_types[mode].name;
	struct lttng_ctx_field *field;
	struct field_data *fdata;
	int ret;

	ret = init_type(mode);
	if (ret)
		return ret;
	field = lttng_append_context(ctx);
	if (!field)
		return -ENOMEM;
	if (lttng_find_context(*ctx, ctx_name)) {
		ret = -EEXIST;
		goto error_find;
	}
	fdata = field_data_create(mode);
	if (!fdata) {
		ret = -ENOMEM;
		goto error_create;
	}

	field->event_field.name = ctx_name;
	field->event_field.type.atype = atype_sequence;
	field->event_field.type.u.sequence.elem_type.atype = atype_integer;
	field->event_field.type.u.sequence.elem_type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	field->event_field.type.u.sequence.elem_type.u.basic.integer.alignment = lttng_alignof(long) * CHAR_BIT;
	field->event_field.type.u.sequence.elem_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	field->event_field.type.u.sequence.elem_type.u.basic.integer.reverse_byte_order = 0;
	field->event_field.type.u.sequence.elem_type.u.basic.integer.base = 16;
	field->event_field.type.u.sequence.elem_type.u.basic.integer.encoding = lttng_encode_none;

	field->event_field.type.u.sequence.length_type.atype = atype_integer;
	field->event_field.type.u.sequence.length_type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT;
	field->event_field.type.u.sequence.length_type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
	field->event_field.type.u.sequence.length_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int);
	field->event_field.type.u.sequence.length_type.u.basic.integer.reverse_byte_order = 0;
	field->event_field.type.u.sequence.length_type.u.basic.integer.base = 10;
	field->event_field.type.u.sequence.length_type.u.basic.integer.encoding = lttng_encode_none;

	field->get_size_arg = lttng_callstack_get_size;
	field->record = lttng_callstack_record;
	field->priv = fdata;
	field->destroy = lttng_callstack_destroy;
	wrapper_vmalloc_sync_all();
	return 0;

error_create:
	field_data_free(fdata);
error_find:
	lttng_remove_context_field(ctx, field);
	return ret;
}

/**
 *	lttng_add_callstack_to_ctx - add callstack event context
 *
 *	@ctx: the lttng_ctx pointer to initialize
 *	@type: the context type
 *
 *	Supported callstack type supported:
 *	LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL
 *		Records the callstack of the kernel
 *	LTTNG_KERNEL_CONTEXT_CALLSTACK_USER
 *		Records the callstack of the userspace program (from the kernel)
 *
 * Return 0 for success, or error code.
 */
int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type)
{
	switch (type) {
	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
		return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
		return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
	default:
		return -EINVAL;
	}
}
EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);

MODULE_LICENSE("GPL and additional rights");
MODULE_AUTHOR("Francis Giraldeau");
MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support");
Commit	Line	Data
2fa2d39a FG	1	/*
	2	* lttng-context-callstack.c
	3	*
	4	* LTTng callstack event context.
	5	*
	6	* Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	* Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
	8	*
	9	* This library is free software; you can redistribute it and/or
	10	* modify it under the terms of the GNU Lesser General Public
	11	* License as published by the Free Software Foundation; only
	12	* version 2.1 of the License.
	13	*
	14	* This library is distributed in the hope that it will be useful,
	15	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	16	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	17	* Lesser General Public License for more details.
	18	*
	19	* You should have received a copy of the GNU Lesser General Public
	20	* License along with this library; if not, write to the Free Software
	21	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	22	*
	23	* The callstack context can be added to any kernel
	24	* event. It records either the kernel or the userspace callstack, up to a
	25	* max depth. The context is a CTF sequence, such that it uses only the space
	26	* required for the number of callstack entries.
	27	*
	28	* It allocates callstack buffers per-CPU up to 4 interrupt nesting. This
	29	* nesting limit is the same as defined in the ring buffer. It therefore uses a
	30	* fixed amount of memory, proportional to the number of CPUs:
	31	*
	32	* size = cpus * nest * depth * sizeof(unsigned long)
	33	*
	34	* Which is about 800 bytes per-CPUs on 64-bit host and a depth of 25. The
	35	* allocation is done at the initialization to avoid memory allocation
	36	* overhead while tracing, using a shallow stack.
	37	*
	38	* The kernel callstack is recovered using save_stack_trace(), and the
	39	* userspace callstack uses save_stack_trace_user(). They rely on frame
	40	* pointers. These are usually available for the kernel, but the compiler
	41	* option -fomit-frame-pointer frequently used in popular Linux distributions
	42	* may cause the userspace callstack to be unreliable, and is a known
	43	* limitation of this approach. If frame pointers are not available, it
	44	* produces no error, but the callstack will be empty. We still provide the
	45	* feature, because it works well for runtime environments having frame
	46	* pointers. In the future, unwind support and/or last branch record may
	47	* provide a solution to this problem.
	48	*
	49	* The symbol name resolution is left to the trace reader.
	50	*/
	51
	52	#include <linux/module.h>
	53	#include <linux/slab.h>
	54	#include <linux/sched.h>
	55	#include <linux/utsname.h>
	56	#include <linux/stacktrace.h>
	57	#include <linux/spinlock.h>
	58	#include "lttng-events.h"
	59	#include "wrapper/ringbuffer/backend.h"
	60	#include "wrapper/ringbuffer/frontend.h"
	61	#include "wrapper/vmalloc.h"
	62	#include "lttng-tracer.h"
	63
64cc198b MD	64	#define MAX_ENTRIES 25
	65
	66	struct lttng_cs_nesting {
	67	struct stack_trace stack_trace;
	68	unsigned long entries[MAX_ENTRIES];
	69	};
2fa2d39a FG	70
2fa2d39a FG	71	struct lttng_cs {
64cc198b	72	struct lttng_cs_nesting level[RING_BUFFER_MAX_NESTING];
2fa2d39a FG	73	};
	74
	75	struct field_data {
2fa2d39a	76	struct lttng_cs __percpu *cs_percpu;
64cc198b	77	int mode;
2fa2d39a FG	78	};
	79
	80	struct lttng_cs_type {
	81	const char *name;
	82	const char *save_func_name;
	83	void (save_func)(struct stack_trace trace);
	84	};
	85
	86	enum lttng_cs_ctx_modes {
	87	CALLSTACK_KERNEL = 0,
	88	CALLSTACK_USER = 1,
	89	};
	90
	91	static struct lttng_cs_type cs_types[] = {
	92	{
64cc198b MD	93	.name = "callstack_kernel",
	94	.save_func_name = "save_stack_trace",
	95	.save_func = NULL,
2fa2d39a FG	96	},
2fa2d39a FG	97	{
64cc198b MD	98	.name = "callstack_user",
	99	.save_func_name = "save_stack_trace_user",
	100	.save_func = NULL,
2fa2d39a FG	101	},
	102	};
	103
	104	static
	105	int init_type(int mode)
	106	{
	107	unsigned long func;
	108
	109	if (cs_types[mode].save_func)
	110	return 0;
	111	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
	112	if (!func) {
	113	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
	114	cs_types[mode].save_func_name);
	115	return -EINVAL;
	116	}
	117	cs_types[mode].save_func = (void *) func;
	118	return 0;
	119	}
	120
	121	static
	122	struct stack_trace stack_trace_context(struct lttng_ctx_field field,
	123	struct lib_ring_buffer_ctx *ctx)
	124	{
	125	int nesting;
	126	struct lttng_cs *cs;
3c1a57e8	127	struct field_data *fdata = field->priv;
2fa2d39a FG	128
	129	/*
	130	* get_cpu() is not required, preemption is already
	131	* disabled while event is written.
	132	*
	133	* max nesting is checked in lib_ring_buffer_get_cpu().
	134	* Check it again as a safety net.
	135	*/
	136	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	137	nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	138	if (nesting >= RING_BUFFER_MAX_NESTING) {
	139	return NULL;
	140	}
64cc198b	141	return &cs->level[nesting].stack_trace;
2fa2d39a FG	142	}
	143
	144	/*
	145	* In order to reserve the correct size, the callstack is computed. The
	146	* resulting callstack is saved to be accessed in the record step.
	147	*/
	148	static
	149	size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
	150	struct lib_ring_buffer_ctx *ctx,
	151	struct lttng_channel *chan)
	152	{
	153	size_t size = 0;
	154	struct stack_trace *trace;
3c1a57e8	155	struct field_data *fdata = field->priv;
2fa2d39a FG	156
	157	/* do not write data if no space is available */
	158	trace = stack_trace_context(field, ctx);
	159	if (!trace)
	160	return 0;
	161
	162	/* reset stack trace, no need to clear memory */
	163	trace->nr_entries = 0;
	164
	165	/* do the real work and reserve space */
	166	cs_types[fdata->mode].save_func(trace);
ea15538d MD	167	/*
	168	* Remove final ULONG_MAX delimiter. If we cannot find it, add
	169	* our own marker to show that the stack is incomplete. This is
	170	* more compact for a trace.
	171	*/
	172	if (trace->nr_entries > 0
	173	&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
	174	trace->nr_entries--;
	175	}
2fa2d39a FG	176	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	177	size += sizeof(unsigned int);
	178	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	179	size += sizeof(unsigned long) * trace->nr_entries;
ea15538d MD	180	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	181	if (trace->nr_entries == trace->max_entries)
	182	size += sizeof(unsigned long);
2fa2d39a FG	183	return size;
	184	}
	185
	186	static
	187	void lttng_callstack_record(struct lttng_ctx_field *field,
64cc198b MD	188	struct lib_ring_buffer_ctx *ctx,
64cc198b MD	189	struct lttng_channel *chan)
2fa2d39a FG	190	{
2fa2d39a FG	191	struct stack_trace *trace = stack_trace_context(field, ctx);
ea15538d	192	unsigned int nr_seq_entries;
2fa2d39a FG	193
	194	if (!trace)
	195	return;
	196	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
ea15538d MD	197	nr_seq_entries = trace->nr_entries;
	198	if (trace->nr_entries == trace->max_entries)
	199	nr_seq_entries++;
	200	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
2fa2d39a FG	201	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	202	chan->ops->event_write(ctx, trace->entries,
	203	sizeof(unsigned long) * trace->nr_entries);
ea15538d MD	204	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	205	if (trace->nr_entries == trace->max_entries) {
	206	unsigned long delim = ULONG_MAX;
	207
	208	chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	209	}
2fa2d39a FG	210	}
	211
	212	static
	213	void field_data_free(struct field_data *fdata)
	214	{
2fa2d39a FG	215	if (!fdata)
2fa2d39a FG	216	return;
2fa2d39a FG	217	free_percpu(fdata->cs_percpu);
	218	kfree(fdata);
	219	}
	220
	221	static
64cc198b	222	struct field_data __percpu *field_data_create(int type)
2fa2d39a FG	223	{
2fa2d39a FG	224	int cpu, i;
2fa2d39a	225	struct lttng_cs __percpu *cs_set;
64cc198b	226	struct field_data *fdata;
2fa2d39a	227
64cc198b	228	fdata = kzalloc(sizeof(*fdata), GFP_KERNEL);
2fa2d39a FG	229	if (!fdata)
	230	return NULL;
	231	cs_set = alloc_percpu(struct lttng_cs);
	232	if (!cs_set)
	233	goto error_alloc;
	234
	235	fdata->cs_percpu = cs_set;
	236	for_each_possible_cpu(cpu) {
64cc198b MD	237	struct lttng_cs *cs;
64cc198b MD	238
2fa2d39a FG	239	cs = per_cpu_ptr(cs_set, cpu);
2fa2d39a FG	240	for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
64cc198b MD	241	struct lttng_cs_nesting *level;
	242
	243	level = &cs->level[i];
	244	level->stack_trace.entries = level->entries;
	245	level->stack_trace.max_entries = MAX_ENTRIES;
2fa2d39a FG	246	}
	247	}
	248	fdata->mode = type;
	249	return fdata;
	250
	251	error_alloc:
	252	field_data_free(fdata);
	253	return NULL;
	254	}
	255
	256	static
	257	void lttng_callstack_destroy(struct lttng_ctx_field *field)
	258	{
3c1a57e8	259	struct field_data *fdata = field->priv;
2fa2d39a FG	260
	261	field_data_free(fdata);
	262	}
	263
	264	static
	265	int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode)
	266	{
	267	const char *ctx_name = cs_types[mode].name;
	268	struct lttng_ctx_field *field;
	269	struct field_data *fdata;
	270	int ret;
	271
	272	ret = init_type(mode);
	273	if (ret)
	274	return ret;
	275	field = lttng_append_context(ctx);
	276	if (!field)
	277	return -ENOMEM;
	278	if (lttng_find_context(*ctx, ctx_name)) {
2fa2d39a FG	279	ret = -EEXIST;
	280	goto error_find;
	281	}
64cc198b	282	fdata = field_data_create(mode);
2fa2d39a FG	283	if (!fdata) {
	284	ret = -ENOMEM;
	285	goto error_create;
	286	}
	287
	288	field->event_field.name = ctx_name;
	289	field->event_field.type.atype = atype_sequence;
	290	field->event_field.type.u.sequence.elem_type.atype = atype_integer;
	291	field->event_field.type.u.sequence.elem_type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	292	field->event_field.type.u.sequence.elem_type.u.basic.integer.alignment = lttng_alignof(long) * CHAR_BIT;
	293	field->event_field.type.u.sequence.elem_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	294	field->event_field.type.u.sequence.elem_type.u.basic.integer.reverse_byte_order = 0;
	295	field->event_field.type.u.sequence.elem_type.u.basic.integer.base = 16;
	296	field->event_field.type.u.sequence.elem_type.u.basic.integer.encoding = lttng_encode_none;
	297
	298	field->event_field.type.u.sequence.length_type.atype = atype_integer;
	299	field->event_field.type.u.sequence.length_type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT;
	300	field->event_field.type.u.sequence.length_type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
	301	field->event_field.type.u.sequence.length_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int);
	302	field->event_field.type.u.sequence.length_type.u.basic.integer.reverse_byte_order = 0;
	303	field->event_field.type.u.sequence.length_type.u.basic.integer.base = 10;
	304	field->event_field.type.u.sequence.length_type.u.basic.integer.encoding = lttng_encode_none;
	305
	306	field->get_size_arg = lttng_callstack_get_size;
	307	field->record = lttng_callstack_record;
3c1a57e8	308	field->priv = fdata;
2fa2d39a FG	309	field->destroy = lttng_callstack_destroy;
2fa2d39a FG	310	wrapper_vmalloc_sync_all();
2fa2d39a FG	311	return 0;
	312
	313	error_create:
	314	field_data_free(fdata);
	315	error_find:
	316	lttng_remove_context_field(ctx, field);
	317	return ret;
	318	}
	319
	320	/**
	321	* lttng_add_callstack_to_ctx - add callstack event context
	322	*
	323	* @ctx: the lttng_ctx pointer to initialize
	324	* @type: the context type
	325	*
	326	* Supported callstack type supported:
	327	* LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL
	328	* Records the callstack of the kernel
	329	* LTTNG_KERNEL_CONTEXT_CALLSTACK_USER
	330	* Records the callstack of the userspace program (from the kernel)
	331	*
	332	* Return 0 for success, or error code.
	333	*/
	334	int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type)
	335	{
	336	switch (type) {
	337	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
	338	return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
	339	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
	340	return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
	341	default:
	342	return -EINVAL;
	343	}
	344	}
	345	EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);
	346
	347	MODULE_LICENSE("GPL and additional rights");
	348	MODULE_AUTHOR("Francis Giraldeau");
	349	MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support");