include/mbedtls/timing.h

/**
 * \file timing.h
 *
 * \brief Portable interface to timeouts and to the CPU cycle counter
 */
/*
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
#ifndef MBEDTLS_TIMING_H
#define MBEDTLS_TIMING_H

#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

#if !defined(MBEDTLS_TIMING_ALT)
// Regular implementation
//

/**
 * \brief          timer structure
 */
struct mbedtls_timing_hr_time {
    unsigned char opaque[32];
};

/**
 * \brief          Context for mbedtls_timing_set/get_delay()
 */
typedef struct mbedtls_timing_delay_context {
    struct mbedtls_timing_hr_time   timer;
    uint32_t                        int_ms;
    uint32_t                        fin_ms;
} mbedtls_timing_delay_context;

#else  /* MBEDTLS_TIMING_ALT */
#include "timing_alt.h"
#endif /* MBEDTLS_TIMING_ALT */

extern volatile int mbedtls_timing_alarmed;

/**
 * \brief          Return the CPU cycle counter value
 *
 * \warning        This is only a best effort! Do not rely on this!
 *                 In particular, it is known to be unreliable on virtual
 *                 machines.
 *
 * \note           This value starts at an unspecified origin and
 *                 may wrap around.
 */
unsigned long mbedtls_timing_hardclock(void);

/**
 * \brief          Return the elapsed time in milliseconds
 *
 * \param val      points to a timer structure
 * \param reset    If 0, query the elapsed time. Otherwise (re)start the timer.
 *
 * \return         Elapsed time since the previous reset in ms. When
 *                 restarting, this is always 0.
 *
 * \note           To initialize a timer, call this function with reset=1.
 *
 *                 Determining the elapsed time and resetting the timer is not
 *                 atomic on all platforms, so after the sequence
 *                 `{ get_timer(1); ...; time1 = get_timer(1); ...; time2 =
 *                 get_timer(0) }` the value time1+time2 is only approximately
 *                 the delay since the first reset.
 */
unsigned long mbedtls_timing_get_timer(struct mbedtls_timing_hr_time *val, int reset);

/**
 * \brief          Setup an alarm clock
 *
 * \param seconds  delay before the "mbedtls_timing_alarmed" flag is set
 *                 (must be >=0)
 *
 * \warning        Only one alarm at a time  is supported. In a threaded
 *                 context, this means one for the whole process, not one per
 *                 thread.
 */
void mbedtls_set_alarm(int seconds);

/**
 * \brief          Set a pair of delays to watch
 *                 (See \c mbedtls_timing_get_delay().)
 *
 * \param data     Pointer to timing data.
 *                 Must point to a valid \c mbedtls_timing_delay_context struct.
 * \param int_ms   First (intermediate) delay in milliseconds.
 *                 The effect if int_ms > fin_ms is unspecified.
 * \param fin_ms   Second (final) delay in milliseconds.
 *                 Pass 0 to cancel the current delay.
 *
 * \note           To set a single delay, either use \c mbedtls_timing_set_timer
 *                 directly or use this function with int_ms == fin_ms.
 */
void mbedtls_timing_set_delay(void *data, uint32_t int_ms, uint32_t fin_ms);

/**
 * \brief          Get the status of delays
 *                 (Memory helper: number of delays passed.)
 *
 * \param data     Pointer to timing data
 *                 Must point to a valid \c mbedtls_timing_delay_context struct.
 *
 * \return         -1 if cancelled (fin_ms = 0),
 *                  0 if none of the delays are passed,
 *                  1 if only the intermediate delay is passed,
 *                  2 if the final delay is passed.
 */
int mbedtls_timing_get_delay(void *data);

#if defined(MBEDTLS_SELF_TEST)
/**
 * \brief          Checkup routine
 *
 * \return         0 if successful, or 1 if a test failed
 */
int mbedtls_timing_self_test(int verbose);
#endif

#ifdef __cplusplus
}
#endif

#endif /* timing.h */