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

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * 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>
 *
 * 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 4096 bytes per CPU on 64-bit host and a depth of 128.
 * 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 <ringbuffer/backend.h>
#include <ringbuffer/frontend.h>
#include <lttng/events.h>
#include <lttng/tracer.h>
#include <lttng/endian.h>
#include "wrapper/vmalloc.h"

#ifdef CONFIG_ARCH_STACKWALK
#include "lttng-context-callstack-stackwalk-impl.h"
#else
#include "lttng-context-callstack-legacy-impl.h"
#endif

#define NR_FIELDS	2

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(enum lttng_cs_ctx_modes mode)
{
	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;
	lttng_cs_set_init(cs_set);
	fdata->cs_percpu = cs_set;
	fdata->mode = mode;
	return fdata;

error_alloc:
	field_data_free(fdata);
	return NULL;
}

static
void lttng_callstack_sequence_destroy(struct lttng_kernel_ctx_field *field)
{
	struct field_data *fdata = field->priv;

	field_data_free(fdata);
}

static const struct lttng_kernel_event_field *event_fields_kernel[NR_FIELDS] = {
	lttng_kernel_static_event_field("_callstack_kernel_length",
		lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
		false, false, false),
	lttng_kernel_static_event_field("callstack_kernel",
		lttng_kernel_static_type_sequence("_callstack_kernel_length",
			lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
			0, none),
		false, false, false),
};

static const struct lttng_kernel_event_field *event_fields_user[NR_FIELDS] = {
	lttng_kernel_static_event_field("_callstack_user_length",
		lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
		false, false, false),
	lttng_kernel_static_event_field("callstack_user",
		lttng_kernel_static_type_sequence("_callstack_user_length",
			lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
			0, none),
		false, false, false),
};

const struct lttng_kernel_event_field **lttng_cs_event_fields(enum lttng_cs_ctx_modes mode)
{
	switch (mode) {
	case CALLSTACK_KERNEL:
		return event_fields_kernel;
	case CALLSTACK_USER:
		return event_fields_user;
	default:
		return NULL;
	}
}

static
int __lttng_add_callstack_generic(struct lttng_kernel_ctx **ctx,
		enum lttng_cs_ctx_modes mode)
{
	const struct lttng_kernel_event_field **event_fields;
	struct lttng_kernel_ctx_field ctx_field;
	struct field_data *fdata;
	int ret, i;

	ret = init_type(mode);
	if (ret)
		return ret;
	event_fields = lttng_cs_event_fields(mode);
	if (!event_fields) {
		return -EINVAL;
	}
	for (i = 0; i < NR_FIELDS; i++) {
		if (lttng_kernel_find_context(*ctx, event_fields[i]->name))
			return -EEXIST;
	}
	fdata = field_data_create(mode);
	if (!fdata) {
		ret = -ENOMEM;
		goto error_create;
	}
	memset(&ctx_field, 0, sizeof(ctx_field));
	ctx_field.event_field = event_fields[0];
	ctx_field.get_size_arg = lttng_callstack_length_get_size;
	ctx_field.record = lttng_callstack_length_record;
	ctx_field.priv = fdata;
	ret = lttng_kernel_context_append(ctx, &ctx_field);
	if (ret) {
		ret = -ENOMEM;
		goto error_append0;
	}

	memset(&ctx_field, 0, sizeof(ctx_field));
	ctx_field.event_field = event_fields[1];
	ctx_field.get_size_arg = lttng_callstack_sequence_get_size;
	ctx_field.record = lttng_callstack_sequence_record;
	ctx_field.destroy = lttng_callstack_sequence_destroy;
	ctx_field.priv = fdata;
	ret = lttng_kernel_context_append(ctx, &ctx_field);
	if (ret) {
		ret = -ENOMEM;
		goto error_append1;
	}
	return 0;

error_append1:
	lttng_kernel_context_remove_last(ctx);
error_append0:
	field_data_free(fdata);
error_create:
	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_kernel_ctx **ctx, int type)
{
	switch (type) {
	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
		return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
#ifdef CONFIG_X86
	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
		return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
#endif
	default:
		return -EINVAL;
	}
}
EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);
Commit	Line	Data
b7cdc182	1	/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
9f36eaed	2	*
2fa2d39a FG	3	* lttng-context-callstack.c
	4	*
	5	* LTTng callstack event context.
	6	*
	7	* Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	8	* Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
	9	*
0bb47c89 MD	10	* The callstack context can be added to any kernel event. It records
	11	* either the kernel or the userspace callstack, up to a max depth. The
	12	* context is a CTF sequence, such that it uses only the space required
	13	* for the number of callstack entries.
2fa2d39a	14	*
0bb47c89 MD	15	* It allocates callstack buffers per-CPU up to 4 interrupt nesting.
	16	* This nesting limit is the same as defined in the ring buffer. It
	17	* therefore uses a fixed amount of memory, proportional to the number
	18	* of CPUs:
2fa2d39a FG	19	*
	20	* size = cpus * nest * depth * sizeof(unsigned long)
	21	*
3685cc80	22	* Which is 4096 bytes per CPU on 64-bit host and a depth of 128.
0bb47c89 MD	23	* The allocation is done at the initialization to avoid memory
0bb47c89 MD	24	* allocation overhead while tracing, using a shallow stack.
2fa2d39a FG	25	*
	26	* The kernel callstack is recovered using save_stack_trace(), and the
	27	* userspace callstack uses save_stack_trace_user(). They rely on frame
0bb47c89 MD	28	* pointers. These are usually available for the kernel, but the
	29	* compiler option -fomit-frame-pointer frequently used in popular Linux
	30	* distributions may cause the userspace callstack to be unreliable, and
	31	* is a known limitation of this approach. If frame pointers are not
	32	* available, it produces no error, but the callstack will be empty. We
	33	* still provide the feature, because it works well for runtime
	34	* environments having frame pointers. In the future, unwind support
	35	* and/or last branch record may provide a solution to this problem.
2fa2d39a FG	36	*
	37	* The symbol name resolution is left to the trace reader.
	38	*/
	39
	40	#include <linux/module.h>
	41	#include <linux/slab.h>
	42	#include <linux/sched.h>
	43	#include <linux/utsname.h>
	44	#include <linux/stacktrace.h>
	45	#include <linux/spinlock.h>
24591303 MD	46	#include <ringbuffer/backend.h>
24591303 MD	47	#include <ringbuffer/frontend.h>
2df37e95 MD	48	#include <lttng/events.h>
	49	#include <lttng/tracer.h>
	50	#include <lttng/endian.h>
2fa2d39a	51	#include "wrapper/vmalloc.h"
2fa2d39a	52
b29c6286 MD	53	#ifdef CONFIG_ARCH_STACKWALK
	54	#include "lttng-context-callstack-stackwalk-impl.h"
	55	#else
b6ee48d2	56	#include "lttng-context-callstack-legacy-impl.h"
b29c6286	57	#endif
2fa2d39a	58
437d5aa5 MD	59	#define NR_FIELDS 2
437d5aa5 MD	60
2fa2d39a FG	61	static
	62	void field_data_free(struct field_data *fdata)
	63	{
2fa2d39a FG	64	if (!fdata)
2fa2d39a FG	65	return;
2fa2d39a FG	66	free_percpu(fdata->cs_percpu);
	67	kfree(fdata);
	68	}
	69
	70	static
0bb47c89	71	struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode)
2fa2d39a	72	{
2fa2d39a	73	struct lttng_cs __percpu *cs_set;
64cc198b	74	struct field_data *fdata;
2fa2d39a	75
64cc198b	76	fdata = kzalloc(sizeof(*fdata), GFP_KERNEL);
2fa2d39a FG	77	if (!fdata)
	78	return NULL;
	79	cs_set = alloc_percpu(struct lttng_cs);
	80	if (!cs_set)
	81	goto error_alloc;
b5a89a3f	82	lttng_cs_set_init(cs_set);
2fa2d39a	83	fdata->cs_percpu = cs_set;
0bb47c89	84	fdata->mode = mode;
2fa2d39a FG	85	return fdata;
	86
	87	error_alloc:
	88	field_data_free(fdata);
	89	return NULL;
	90	}
	91
	92	static
437d5aa5	93	void lttng_callstack_sequence_destroy(struct lttng_kernel_ctx_field *field)
2fa2d39a	94	{
3c1a57e8	95	struct field_data *fdata = field->priv;
2fa2d39a FG	96
	97	field_data_free(fdata);
	98	}
	99
437d5aa5 MD	100	static const struct lttng_kernel_event_field *event_fields_kernel[NR_FIELDS] = {
	101	lttng_kernel_static_event_field("_callstack_kernel_length",
	102	lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
	103	false, false, false),
	104	lttng_kernel_static_event_field("callstack_kernel",
	105	lttng_kernel_static_type_sequence("_callstack_kernel_length",
	106	lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
	107	0, none),
	108	false, false, false),
	109	};
	110
	111	static const struct lttng_kernel_event_field *event_fields_user[NR_FIELDS] = {
	112	lttng_kernel_static_event_field("_callstack_user_length",
	113	lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
	114	false, false, false),
	115	lttng_kernel_static_event_field("callstack_user",
	116	lttng_kernel_static_type_sequence("_callstack_user_length",
	117	lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
	118	0, none),
	119	false, false, false),
	120	};
	121
	122	const struct lttng_kernel_event_field **lttng_cs_event_fields(enum lttng_cs_ctx_modes mode)
	123	{
	124	switch (mode) {
	125	case CALLSTACK_KERNEL:
	126	return event_fields_kernel;
	127	case CALLSTACK_USER:
	128	return event_fields_user;
	129	default:
	130	return NULL;
	131	}
	132	}
ceabb767	133
2fa2d39a	134	static
437d5aa5	135	int __lttng_add_callstack_generic(struct lttng_kernel_ctx **ctx,
0bb47c89	136	enum lttng_cs_ctx_modes mode)
2fa2d39a	137	{
437d5aa5 MD	138	const struct lttng_kernel_event_field **event_fields;
437d5aa5 MD	139	struct lttng_kernel_ctx_field ctx_field;
2fa2d39a	140	struct field_data *fdata;
437d5aa5	141	int ret, i;
2fa2d39a FG	142
	143	ret = init_type(mode);
	144	if (ret)
	145	return ret;
437d5aa5 MD	146	event_fields = lttng_cs_event_fields(mode);
	147	if (!event_fields) {
	148	return -EINVAL;
ceabb767	149	}
437d5aa5 MD	150	for (i = 0; i < NR_FIELDS; i++) {
	151	if (lttng_kernel_find_context(*ctx, event_fields[i]->name))
	152	return -EEXIST;
2fa2d39a	153	}
64cc198b	154	fdata = field_data_create(mode);
2fa2d39a FG	155	if (!fdata) {
	156	ret = -ENOMEM;
	157	goto error_create;
	158	}
437d5aa5 MD	159	memset(&ctx_field, 0, sizeof(ctx_field));
	160	ctx_field.event_field = event_fields[0];
	161	ctx_field.get_size_arg = lttng_callstack_length_get_size;
	162	ctx_field.record = lttng_callstack_length_record;
	163	ctx_field.priv = fdata;
	164	ret = lttng_kernel_context_append(ctx, &ctx_field);
	165	if (ret) {
	166	ret = -ENOMEM;
	167	goto error_append0;
	168	}
2fa2d39a	169
437d5aa5 MD	170	memset(&ctx_field, 0, sizeof(ctx_field));
	171	ctx_field.event_field = event_fields[1];
	172	ctx_field.get_size_arg = lttng_callstack_sequence_get_size;
	173	ctx_field.record = lttng_callstack_sequence_record;
	174	ctx_field.destroy = lttng_callstack_sequence_destroy;
	175	ctx_field.priv = fdata;
	176	ret = lttng_kernel_context_append(ctx, &ctx_field);
	177	if (ret) {
	178	ret = -ENOMEM;
	179	goto error_append1;
	180	}
2fa2d39a FG	181	return 0;
2fa2d39a FG	182
437d5aa5 MD	183	error_append1:
	184	lttng_kernel_context_remove_last(ctx);
	185	error_append0:
	186	field_data_free(fdata);
2fa2d39a	187	error_create:
2fa2d39a FG	188	return ret;
	189	}
	190
	191	/**
	192	* lttng_add_callstack_to_ctx - add callstack event context
	193	*
	194	* @ctx: the lttng_ctx pointer to initialize
	195	* @type: the context type
	196	*
	197	* Supported callstack type supported:
	198	* LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL
	199	* Records the callstack of the kernel
	200	* LTTNG_KERNEL_CONTEXT_CALLSTACK_USER
	201	* Records the callstack of the userspace program (from the kernel)
	202	*
	203	* Return 0 for success, or error code.
	204	*/
437d5aa5	205	int lttng_add_callstack_to_ctx(struct lttng_kernel_ctx **ctx, int type)
2fa2d39a FG	206	{
	207	switch (type) {
	208	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
	209	return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
b874d3f3	210	#ifdef CONFIG_X86
2fa2d39a FG	211	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
2fa2d39a FG	212	return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
b874d3f3	213	#endif
2fa2d39a FG	214	default:
	215	return -EINVAL;
	216	}
	217	}
	218	EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);