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/*
* 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
*/
#define _LGPL_SOURCE
#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"
/* Maximum number of nesting levels for the procname cache. */
#define PROCNAME_NESTING_MAX 2
/*
* 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[PROCNAME_NESTING_MAX][17];
static DEFINE_URCU_TLS(procname_array, cached_procname);
static DEFINE_URCU_TLS(int, procname_nesting);
static inline
char *wrapper_getprocname(void)
{
int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
return "<unknown>";
if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
/* Increment nesting before updating cache. */
cmm_barrier();
lttng_ust_getprocname(URCU_TLS(cached_procname)[nesting]);
URCU_TLS(cached_procname)[nesting][LTTNG_UST_PROCNAME_LEN - 1] = '\0';
/* Decrement nesting after updating cache. */
cmm_barrier();
CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
}
return URCU_TLS(cached_procname)[nesting];
}
/* Reset should not be called from a signal handler. */
void lttng_context_procname_reset(void)
{
CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
}
static
size_t procname_get_size(struct lttng_ctx_field *field, size_t offset)
{
return LTTNG_UST_PROCNAME_LEN;
}
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)
{
value->u.str = wrapper_getprocname();
}
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]));
}
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