/*

 * lttng-context-procname.c

 *

 * LTTng UST procname context.

 *

 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.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

 */

#include <lttng/ust-events.h>

#include <lttng/ust-tracer.h>

#include <lttng/ringbuffer-config.h>

#include <urcu/tls-compat.h>

#include <assert.h>

#include "compat.h"

/*

 * We cache the result to ensure we don't trigger a system call for

 * each event.

 * Upon exec, procname changes, but exec takes care of throwing away

 * this cached version.

 * The procname can also change by calling prctl(). The procname should

 * be set for a thread before the first event is logged within this

 * thread.

 */

typedef char procname_array[17];

static DEFINE_URCU_TLS(procname_array, cached_procname);

static inline

char *wrapper_getprocname(void)

{

	if (caa_unlikely(!URCU_TLS(cached_procname)[0])) {

		lttng_ust_getprocname(URCU_TLS(cached_procname));

		URCU_TLS(cached_procname)[LTTNG_UST_PROCNAME_LEN - 1] = '\0';

	}

	return URCU_TLS(cached_procname);

}

void lttng_context_procname_reset(void)

{

	URCU_TLS(cached_procname)[0] = '\0';

}

static

size_t procname_get_size(struct lttng_ctx_field *field, size_t offset)

{

	size_t size = 0;

	size += LTTNG_UST_PROCNAME_LEN;

	return size;

}

static

void procname_record(struct lttng_ctx_field *field,

		 struct lttng_ust_lib_ring_buffer_ctx *ctx,

		 struct lttng_channel *chan)

{

	char *procname;

	procname = wrapper_getprocname();

	chan->ops->event_write(ctx, procname, LTTNG_UST_PROCNAME_LEN);

}

static

void procname_get_value(struct lttng_ctx_field *field,

		struct lttng_ctx_value *value)

{

	char *procname;

	procname = wrapper_getprocname();

	value->u.str = procname;

}

int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)

{

	struct lttng_ctx_field *field;

	field = lttng_append_context(ctx);

	if (!field)

		return -ENOMEM;

	if (lttng_find_context(*ctx, "procname")) {

		lttng_remove_context_field(ctx, field);

		return -EEXIST;

	}

	field->event_field.name = "procname";

	field->event_field.type.atype = atype_array;

	field->event_field.type.u.array.elem_type.atype = atype_integer;

	field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;

	field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;

	field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char);

	field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;

	field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;

	field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;

	field->event_field.type.u.array.length = LTTNG_UST_PROCNAME_LEN;

	field->get_size = procname_get_size;

	field->record = procname_record;

	field->get_value = procname_get_value;

	lttng_context_update(*ctx);

	return 0;

}

/*

 * Force a read (imply TLS fixup for dlopen) of TLS variables.

 */

void lttng_fixup_procname_tls(void)

{

	asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));

}