[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 /* BUG: saving more than 30 entries causes trace corruption */

struct lttng_cs {
	struct stack_trace items[RING_BUFFER_MAX_NESTING];
};

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

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->items[nesting];
}

/*
 * 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)
{
	int cpu, i;
	struct lttng_cs *cs;

	if (!fdata)
		return;
	for_each_possible_cpu(cpu) {
		cs = per_cpu_ptr(fdata->cs_percpu, cpu);
		for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
			kfree(cs->items[i].entries);
		}
	}
	free_percpu(fdata->cs_percpu);
	kfree(fdata);
}

static
struct field_data __percpu *field_data_create(unsigned int entries, int type)
{
	int cpu, i;
	struct stack_trace *item;
	struct lttng_cs *cs;
	struct lttng_cs __percpu *cs_set;
	struct field_data* fdata;

	fdata = kzalloc(sizeof(unsigned long) * entries, 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) {
		cs = per_cpu_ptr(cs_set, cpu);
		for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
			item = &cs->items[i];
			item->entries = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL);
			if (!item->entries) {
				goto error_alloc;
			}
			item->max_entries = 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(MAX_ENTRIES, 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
	64	#define MAX_ENTRIES 25 /* BUG: saving more than 30 entries causes trace corruption */
65
66	struct lttng_cs {
67	struct stack_trace items[RING_BUFFER_MAX_NESTING];
68	};
69
70	struct field_data {
71	int mode;
72	struct lttng_cs __percpu *cs_percpu;
73	};
74
75	struct lttng_cs_type {
76	const char *name;
77	const char *save_func_name;
78	void (save_func)(struct stack_trace trace);
79	};
80
81	enum lttng_cs_ctx_modes {
82	CALLSTACK_KERNEL = 0,
83	CALLSTACK_USER = 1,
84	};
85
86	static struct lttng_cs_type cs_types[] = {
87	{
88	.name = "callstack_kernel",
89	.save_func_name = "save_stack_trace",
90	.save_func = NULL,
91	},
92	{
93	.name = "callstack_user",
94	.save_func_name = "save_stack_trace_user",
95	.save_func = NULL,
96	},
97	};
98
99	static
100	int init_type(int mode)
101	{
102	unsigned long func;
103
104	if (cs_types[mode].save_func)
105	return 0;
106	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
107	if (!func) {
108	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
109	cs_types[mode].save_func_name);
110	return -EINVAL;
111	}
112	cs_types[mode].save_func = (void *) func;
113	return 0;
114	}
115
116	static
117	struct stack_trace stack_trace_context(struct lttng_ctx_field field,
118	struct lib_ring_buffer_ctx *ctx)
119	{
120	int nesting;
121	struct lttng_cs *cs;
3c1a57e8	122	struct field_data *fdata = field->priv;
2fa2d39a FG	123
	124	/*
	125	* get_cpu() is not required, preemption is already
	126	* disabled while event is written.
	127	*
	128	* max nesting is checked in lib_ring_buffer_get_cpu().
	129	* Check it again as a safety net.
	130	*/
	131	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	132	nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	133	if (nesting >= RING_BUFFER_MAX_NESTING) {
	134	return NULL;
	135	}
	136	return &cs->items[nesting];
	137	}
	138
	139	/*
	140	* In order to reserve the correct size, the callstack is computed. The
	141	* resulting callstack is saved to be accessed in the record step.
	142	*/
	143	static
	144	size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
	145	struct lib_ring_buffer_ctx *ctx,
	146	struct lttng_channel *chan)
	147	{
	148	size_t size = 0;
	149	struct stack_trace *trace;
3c1a57e8	150	struct field_data *fdata = field->priv;
2fa2d39a FG	151
	152	/* do not write data if no space is available */
	153	trace = stack_trace_context(field, ctx);
	154	if (!trace)
	155	return 0;
	156
	157	/* reset stack trace, no need to clear memory */
	158	trace->nr_entries = 0;
	159
	160	/* do the real work and reserve space */
	161	cs_types[fdata->mode].save_func(trace);
ea15538d MD	162	/*
	163	* Remove final ULONG_MAX delimiter. If we cannot find it, add
	164	* our own marker to show that the stack is incomplete. This is
	165	* more compact for a trace.
	166	*/
	167	if (trace->nr_entries > 0
	168	&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
	169	trace->nr_entries--;
	170	}
2fa2d39a FG	171	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	172	size += sizeof(unsigned int);
	173	size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	174	size += sizeof(unsigned long) * trace->nr_entries;
ea15538d MD	175	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	176	if (trace->nr_entries == trace->max_entries)
	177	size += sizeof(unsigned long);
2fa2d39a FG	178	return size;
	179	}
	180
	181	static
	182	void lttng_callstack_record(struct lttng_ctx_field *field,
	183	struct lib_ring_buffer_ctx *ctx,
	184	struct lttng_channel *chan)
	185	{
	186	struct stack_trace *trace = stack_trace_context(field, ctx);
ea15538d	187	unsigned int nr_seq_entries;
2fa2d39a FG	188
	189	if (!trace)
	190	return;
	191	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
ea15538d MD	192	nr_seq_entries = trace->nr_entries;
	193	if (trace->nr_entries == trace->max_entries)
	194	nr_seq_entries++;
	195	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
2fa2d39a FG	196	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	197	chan->ops->event_write(ctx, trace->entries,
	198	sizeof(unsigned long) * trace->nr_entries);
ea15538d MD	199	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	200	if (trace->nr_entries == trace->max_entries) {
	201	unsigned long delim = ULONG_MAX;
	202
	203	chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	204	}
2fa2d39a FG	205	}
	206
	207	static
	208	void field_data_free(struct field_data *fdata)
	209	{
	210	int cpu, i;
	211	struct lttng_cs *cs;
	212
	213	if (!fdata)
	214	return;
	215	for_each_possible_cpu(cpu) {
	216	cs = per_cpu_ptr(fdata->cs_percpu, cpu);
	217	for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
	218	kfree(cs->items[i].entries);
	219	}
	220	}
	221	free_percpu(fdata->cs_percpu);
	222	kfree(fdata);
	223	}
	224
	225	static
	226	struct field_data __percpu *field_data_create(unsigned int entries, int type)
	227	{
	228	int cpu, i;
	229	struct stack_trace *item;
	230	struct lttng_cs *cs;
	231	struct lttng_cs __percpu *cs_set;
	232	struct field_data* fdata;
	233
	234	fdata = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL);
	235	if (!fdata)
	236	return NULL;
	237	cs_set = alloc_percpu(struct lttng_cs);
	238	if (!cs_set)
	239	goto error_alloc;
	240
	241	fdata->cs_percpu = cs_set;
	242	for_each_possible_cpu(cpu) {
	243	cs = per_cpu_ptr(cs_set, cpu);
	244	for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
	245	item = &cs->items[i];
	246	item->entries = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL);
	247	if (!item->entries) {
	248	goto error_alloc;
	249	}
	250	item->max_entries = entries;
	251	}
	252	}
	253	fdata->mode = type;
	254	return fdata;
	255
	256	error_alloc:
	257	field_data_free(fdata);
	258	return NULL;
	259	}
	260
	261	static
	262	void lttng_callstack_destroy(struct lttng_ctx_field *field)
	263	{
3c1a57e8	264	struct field_data *fdata = field->priv;
2fa2d39a FG	265
	266	field_data_free(fdata);
	267	}
	268
	269	static
	270	int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode)
	271	{
	272	const char *ctx_name = cs_types[mode].name;
	273	struct lttng_ctx_field *field;
	274	struct field_data *fdata;
	275	int ret;
	276
	277	ret = init_type(mode);
	278	if (ret)
	279	return ret;
	280	field = lttng_append_context(ctx);
	281	if (!field)
	282	return -ENOMEM;
	283	if (lttng_find_context(*ctx, ctx_name)) {
2fa2d39a FG	284	ret = -EEXIST;
	285	goto error_find;
	286	}
	287	fdata = field_data_create(MAX_ENTRIES, mode);
	288	if (!fdata) {
	289	ret = -ENOMEM;
	290	goto error_create;
	291	}
	292
	293	field->event_field.name = ctx_name;
	294	field->event_field.type.atype = atype_sequence;
	295	field->event_field.type.u.sequence.elem_type.atype = atype_integer;
	296	field->event_field.type.u.sequence.elem_type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	297	field->event_field.type.u.sequence.elem_type.u.basic.integer.alignment = lttng_alignof(long) * CHAR_BIT;
	298	field->event_field.type.u.sequence.elem_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	299	field->event_field.type.u.sequence.elem_type.u.basic.integer.reverse_byte_order = 0;
	300	field->event_field.type.u.sequence.elem_type.u.basic.integer.base = 16;
	301	field->event_field.type.u.sequence.elem_type.u.basic.integer.encoding = lttng_encode_none;
	302
	303	field->event_field.type.u.sequence.length_type.atype = atype_integer;
	304	field->event_field.type.u.sequence.length_type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT;
	305	field->event_field.type.u.sequence.length_type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
	306	field->event_field.type.u.sequence.length_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int);
	307	field->event_field.type.u.sequence.length_type.u.basic.integer.reverse_byte_order = 0;
	308	field->event_field.type.u.sequence.length_type.u.basic.integer.base = 10;
	309	field->event_field.type.u.sequence.length_type.u.basic.integer.encoding = lttng_encode_none;
	310
	311	field->get_size_arg = lttng_callstack_get_size;
	312	field->record = lttng_callstack_record;
3c1a57e8	313	field->priv = fdata;
2fa2d39a FG	314	field->destroy = lttng_callstack_destroy;
2fa2d39a FG	315	wrapper_vmalloc_sync_all();
2fa2d39a FG	316	return 0;
	317
	318	error_create:
	319	field_data_free(fdata);
	320	error_find:
	321	lttng_remove_context_field(ctx, field);
	322	return ret;
	323	}
	324
	325	/**
	326	* lttng_add_callstack_to_ctx - add callstack event context
	327	*
	328	* @ctx: the lttng_ctx pointer to initialize
	329	* @type: the context type
	330	*
	331	* Supported callstack type supported:
	332	* LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL
	333	* Records the callstack of the kernel
	334	* LTTNG_KERNEL_CONTEXT_CALLSTACK_USER
	335	* Records the callstack of the userspace program (from the kernel)
	336	*
	337	* Return 0 for success, or error code.
	338	*/
	339	int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type)
	340	{
	341	switch (type) {
	342	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
	343	return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
	344	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
	345	return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
	346	default:
	347	return -EINVAL;
	348	}
	349	}
	350	EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);
	351
	352	MODULE_LICENSE("GPL and additional rights");
	353	MODULE_AUTHOR("Francis Giraldeau");
	354	MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support");