strace/delay.c

/*
 * Copyright (c) 2018 The strace developers.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "defs.h"

struct inject_delay_data {
	struct timespec ts_enter;
	struct timespec ts_exit;
};

static struct inject_delay_data *delay_data_vec;
static size_t delay_data_vec_capacity; /* size of the arena */
static size_t delay_data_vec_size;     /* size of the used arena */

static timer_t delay_timer = (timer_t) -1;
static bool delay_timer_is_armed;

static void
expand_delay_data_vec(void)
{
	const size_t old_capacity = delay_data_vec_capacity;
	delay_data_vec = xgrowarray(delay_data_vec, &delay_data_vec_capacity,
				    sizeof(*delay_data_vec));
	memset(delay_data_vec + old_capacity, 0,
	       (delay_data_vec_capacity - old_capacity)
	       * sizeof(*delay_data_vec));
}

uint16_t
alloc_delay_data(void)
{
	const uint16_t rval = delay_data_vec_size;

	if (rval < delay_data_vec_size)
		error_func_msg_and_die("delay index overflow");

	if (delay_data_vec_size == delay_data_vec_capacity)
		expand_delay_data_vec();

	++delay_data_vec_size;
	return rval;
}

void
fill_delay_data(uint16_t delay_idx, struct timespec *val, bool isenter)
{
	if (delay_idx >= delay_data_vec_size)
		error_func_msg_and_die("delay_idx >= delay_data_vec_size");

	struct timespec *ts;
	if (isenter)
		ts = &(delay_data_vec[delay_idx].ts_enter);
	else
		ts = &(delay_data_vec[delay_idx].ts_exit);

	*ts = *val;
}

static bool
is_delay_timer_created(void)
{
	return delay_timer != (timer_t) -1;
}

bool
is_delay_timer_armed(void)
{
	return delay_timer_is_armed;
}

void
delay_timer_expired(void)
{
	delay_timer_is_armed = false;
}

void
arm_delay_timer(const struct tcb *const tcp)
{
	const struct itimerspec its = {
		.it_value = tcp->delay_expiration_time
	};

	if (timer_settime(delay_timer, TIMER_ABSTIME, &its, NULL))
		perror_msg_and_die("timer_settime");

	delay_timer_is_armed = true;

	debug_func_msg("timer set to %lld.%09ld for pid %d",
		       (long long) tcp->delay_expiration_time.tv_sec,
		       (long) tcp->delay_expiration_time.tv_nsec,
		       tcp->pid);
}

void
delay_tcb(struct tcb *tcp, uint16_t delay_idx, bool isenter)
{
	if (delay_idx >= delay_data_vec_size)
		error_func_msg_and_die("delay_idx >= delay_data_vec_size");

	debug_func_msg("delaying pid %d on %s",
		       tcp->pid, isenter ? "enter" : "exit");
	tcp->flags |= TCB_DELAYED;

	struct timespec *ts_diff;
	if (isenter)
		ts_diff = &(delay_data_vec[delay_idx].ts_enter);
	else
		ts_diff = &(delay_data_vec[delay_idx].ts_exit);

	struct timespec ts_now;
	clock_gettime(CLOCK_MONOTONIC, &ts_now);
	ts_add(&tcp->delay_expiration_time, &ts_now, ts_diff);

	if (is_delay_timer_created()) {
		struct itimerspec its;
		if (timer_gettime(delay_timer, &its))
			perror_msg_and_die("timer_gettime");

		const struct timespec *const ts_old = &its.it_value;
		if (ts_nz(ts_old) && ts_cmp(ts_diff, ts_old) > 0)
			return;
	} else {
		if (timer_create(CLOCK_MONOTONIC, NULL, &delay_timer))
			perror_msg_and_die("timer_create");
	}

	arm_delay_timer(tcp);
}