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

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * lttng-context-procname.c
 *
 * LTTng procname context.
 *
 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <lttng/events.h>
#include <lttng/events-internal.h>
#include <ringbuffer/frontend_types.h>
#include <wrapper/vmalloc.h>
#include <lttng/tracer.h>
#include <lttng/endian.h>

static
size_t procname_get_size(size_t offset)
{
	size_t size = 0;

	size += sizeof(current->comm);
	return size;
}

/*
 * Racy read of procname. We simply copy its whole array size.
 * Races with /proc/<task>/procname write only.
 * Otherwise having to take a mutex for each event is cumbersome and
 * could lead to crash in IRQ context and deadlock of the lockdep tracer.
 */
static
void procname_record(struct lttng_kernel_ctx_field *field,
		 struct lib_ring_buffer_ctx *ctx,
		 struct lttng_channel *chan)
{
	chan->ops->event_write(ctx, current->comm, sizeof(current->comm));
}

static
void procname_get_value(struct lttng_kernel_ctx_field *field,
		struct lttng_probe_ctx *lttng_probe_ctx,
		union lttng_ctx_value *value)
{
	value->str = current->comm;
}

static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
	lttng_kernel_static_event_field("procname",
		lttng_kernel_static_type_array_text(sizeof(current->comm)),
		false, false, false),
	procname_get_size,
	NULL,
	procname_record,
	procname_get_value,
	NULL, NULL);

int lttng_add_procname_to_ctx(struct lttng_kernel_ctx **ctx)
{
	int ret;

	if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
		return -EEXIST;
	ret = lttng_kernel_context_append(ctx, ctx_field);
	wrapper_vmalloc_sync_mappings();
	return ret;
}
EXPORT_SYMBOL_GPL(lttng_add_procname_to_ctx);
Commit	Line	Data
	1	/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
	2	*
	3	* lttng-context-procname.c
	4	*
	5	* LTTng procname context.
	6	*
	7	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	8	*/
	9
	10	#include <linux/module.h>
	11	#include <linux/slab.h>
	12	#include <linux/sched.h>
	13	#include <lttng/events.h>
	14	#include <lttng/events-internal.h>
	15	#include <ringbuffer/frontend_types.h>
	16	#include <wrapper/vmalloc.h>
	17	#include <lttng/tracer.h>
	18	#include <lttng/endian.h>
	19
	20	static
	21	size_t procname_get_size(size_t offset)
	22	{
	23	size_t size = 0;
	24
	25	size += sizeof(current->comm);
	26	return size;
	27	}
	28
	29	/*
	30	* Racy read of procname. We simply copy its whole array size.
	31	* Races with /proc/<task>/procname write only.
	32	* Otherwise having to take a mutex for each event is cumbersome and
	33	* could lead to crash in IRQ context and deadlock of the lockdep tracer.
	34	*/
	35	static
	36	void procname_record(struct lttng_kernel_ctx_field *field,
	37	struct lib_ring_buffer_ctx *ctx,
	38	struct lttng_channel *chan)
	39	{
	40	chan->ops->event_write(ctx, current->comm, sizeof(current->comm));
	41	}
	42
	43	static
	44	void procname_get_value(struct lttng_kernel_ctx_field *field,
	45	struct lttng_probe_ctx *lttng_probe_ctx,
	46	union lttng_ctx_value *value)
	47	{
	48	value->str = current->comm;
	49	}
	50
	51	static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
	52	lttng_kernel_static_event_field("procname",
	53	lttng_kernel_static_type_array_text(sizeof(current->comm)),
	54	false, false, false),
	55	procname_get_size,
	56	NULL,
	57	procname_record,
	58	procname_get_value,
	59	NULL, NULL);
	60
	61	int lttng_add_procname_to_ctx(struct lttng_kernel_ctx **ctx)
	62	{
	63	int ret;
	64
	65	if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
	66	return -EEXIST;
	67	ret = lttng_kernel_context_append(ctx, ctx_field);
	68	wrapper_vmalloc_sync_mappings();
	69	return ret;
	70	}
	71	EXPORT_SYMBOL_GPL(lttng_add_procname_to_ctx);