library/timing.c

/*
 *  Portable interface 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.
 */

#include <string.h>

#include "common.h"

#include "mbedtls/platform.h"

#if defined(MBEDTLS_TIMING_C)

#include "mbedtls/timing.h"

#if !defined(MBEDTLS_TIMING_ALT)

#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
    !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
    !defined(__HAIKU__) && !defined(__midipix__)
#error "This module only works on Unix and Windows, see MBEDTLS_TIMING_C in config.h"
#endif

/* *INDENT-OFF* */
#ifndef asm
#define asm __asm
#endif
/* *INDENT-ON* */

#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)

#include <windows.h>
#include <process.h>

struct _hr_time {
    LARGE_INTEGER start;
};

#else

#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
/* time.h should be included independently of MBEDTLS_HAVE_TIME. If the
 * platform matches the ifdefs above, it will be used. */
#include <time.h>
#include <sys/time.h>
struct _hr_time {
    struct timeval start;
};
#endif /* _WIN32 && !EFIX64 && !EFI32 */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    (defined(_MSC_VER) && defined(_M_IX86)) || defined(__WATCOMC__)

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long tsc;
    __asm   rdtsc
    __asm   mov[tsc], eax
    return tsc;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          ( _MSC_VER && _M_IX86 ) || __WATCOMC__ */

/* some versions of mingw-64 have 32-bit longs even on x84_64 */
#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    defined(__GNUC__) && (defined(__i386__) || (                       \
    (defined(__amd64__) || defined(__x86_64__)) && __SIZEOF_LONG__ == 4))

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long lo, hi;
    asm volatile ("rdtsc" : "=a" (lo), "=d" (hi));
    return lo;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && __i386__ */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    defined(__GNUC__) && (defined(__amd64__) || defined(__x86_64__))

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long lo, hi;
    asm volatile ("rdtsc" : "=a" (lo), "=d" (hi));
    return lo | (hi << 32);
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && ( __amd64__ || __x86_64__ ) */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    defined(__GNUC__) && (defined(__powerpc__) || defined(__ppc__))

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long tbl, tbu0, tbu1;

    do {
        asm volatile ("mftbu %0" : "=r" (tbu0));
        asm volatile ("mftb  %0" : "=r" (tbl));
        asm volatile ("mftbu %0" : "=r" (tbu1));
    } while (tbu0 != tbu1);

    return tbl;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && ( __powerpc__ || __ppc__ ) */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    defined(__GNUC__) && defined(__sparc64__)

#if defined(__OpenBSD__)
#warning OpenBSD does not allow access to tick register using software version instead
#else
#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long tick;
    asm volatile ("rdpr %%tick, %0;" : "=&r" (tick));
    return tick;
}
#endif /* __OpenBSD__ */
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && __sparc64__ */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
    defined(__GNUC__) && defined(__sparc__) && !defined(__sparc64__)

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long tick;
    asm volatile (".byte 0x83, 0x41, 0x00, 0x00");
    asm volatile ("mov   %%g1, %0" : "=r" (tick));
    return tick;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && __sparc__ && !__sparc64__ */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&      \
    defined(__GNUC__) && defined(__alpha__)

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long cc;
    asm volatile ("rpcc %0" : "=r" (cc));
    return cc & 0xFFFFFFFF;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && __alpha__ */

#if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&      \
    defined(__GNUC__) && defined(__ia64__)

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    unsigned long itc;
    asm volatile ("mov %0 = ar.itc" : "=r" (itc));
    return itc;
}
#endif /* !HAVE_HARDCLOCK && MBEDTLS_HAVE_ASM &&
          __GNUC__ && __ia64__ */

#if !defined(HAVE_HARDCLOCK) && defined(_MSC_VER) && \
    !defined(EFIX64) && !defined(EFI32)

#define HAVE_HARDCLOCK

unsigned long mbedtls_timing_hardclock(void)
{
    LARGE_INTEGER offset;

    QueryPerformanceCounter(&offset);

    return (unsigned long) (offset.QuadPart);
}
#endif /* !HAVE_HARDCLOCK && _MSC_VER && !EFIX64 && !EFI32 */

#if !defined(HAVE_HARDCLOCK)

#define HAVE_HARDCLOCK

static int hardclock_init = 0;
static struct timeval tv_init;

unsigned long mbedtls_timing_hardclock(void)
{
    struct timeval tv_cur;

    if (hardclock_init == 0) {
        gettimeofday(&tv_init, NULL);
        hardclock_init = 1;
    }

    gettimeofday(&tv_cur, NULL);
    return (tv_cur.tv_sec  - tv_init.tv_sec) * 1000000U
           + (tv_cur.tv_usec - tv_init.tv_usec);
}
#endif /* !HAVE_HARDCLOCK */

volatile int mbedtls_timing_alarmed = 0;

#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)

unsigned long mbedtls_timing_get_timer(struct mbedtls_timing_hr_time *val, int reset)
{
    struct _hr_time t;

    if (reset) {
        QueryPerformanceCounter(&t.start);
        memcpy(val, &t, sizeof(struct _hr_time));
        return 0;
    } else {
        unsigned long delta;
        LARGE_INTEGER now, hfreq;
        /* We can't safely cast val because it may not be aligned, so use memcpy */
        memcpy(&t, val, sizeof(struct _hr_time));
        QueryPerformanceCounter(&now);
        QueryPerformanceFrequency(&hfreq);
        delta = (unsigned long) ((now.QuadPart - t.start.QuadPart) * 1000ul
                                 / hfreq.QuadPart);
        return delta;
    }
}

/* It's OK to use a global because alarm() is supposed to be global anyway */
static DWORD alarmMs;

static void TimerProc(void *TimerContext)
{
    (void) TimerContext;
    Sleep(alarmMs);
    mbedtls_timing_alarmed = 1;
    /* _endthread will be called implicitly on return
     * That ensures execution of thread function's epilogue */
}

void mbedtls_set_alarm(int seconds)
{
    if (seconds == 0) {
        /* No need to create a thread for this simple case.
         * Also, this shorcut is more reliable at least on MinGW32 */
        mbedtls_timing_alarmed = 1;
        return;
    }

    mbedtls_timing_alarmed = 0;
    alarmMs = seconds * 1000;
    (void) _beginthread(TimerProc, 0, NULL);
}

#else /* _WIN32 && !EFIX64 && !EFI32 */

unsigned long mbedtls_timing_get_timer(struct mbedtls_timing_hr_time *val, int reset)
{
    struct _hr_time t;

    if (reset) {
        gettimeofday(&t.start, NULL);
        memcpy(val, &t, sizeof(struct _hr_time));
        return 0;
    } else {
        unsigned long delta;
        struct timeval now;
        /* We can't safely cast val because it may not be aligned, so use memcpy */
        memcpy(&t, val, sizeof(struct _hr_time));
        gettimeofday(&now, NULL);
        delta = (now.tv_sec  - t.start.tv_sec) * 1000ul
                + (now.tv_usec - t.start.tv_usec) / 1000;
        return delta;
    }
}

static void sighandler(int signum)
{
    mbedtls_timing_alarmed = 1;
    signal(signum, sighandler);
}

void mbedtls_set_alarm(int seconds)
{
    mbedtls_timing_alarmed = 0;
    signal(SIGALRM, sighandler);
    alarm(seconds);
    if (seconds == 0) {
        /* alarm(0) cancelled any previous pending alarm, but the
           handler won't fire, so raise the flag straight away. */
        mbedtls_timing_alarmed = 1;
    }
}

#endif /* _WIN32 && !EFIX64 && !EFI32 */

/*
 * Set delays to watch
 */
void mbedtls_timing_set_delay(void *data, uint32_t int_ms, uint32_t fin_ms)
{
    mbedtls_timing_delay_context *ctx = (mbedtls_timing_delay_context *) data;

    ctx->int_ms = int_ms;
    ctx->fin_ms = fin_ms;

    if (fin_ms != 0) {
        (void) mbedtls_timing_get_timer(&ctx->timer, 1);
    }
}

/*
 * Get number of delays expired
 */
int mbedtls_timing_get_delay(void *data)
{
    mbedtls_timing_delay_context *ctx = (mbedtls_timing_delay_context *) data;
    unsigned long elapsed_ms;

    if (ctx->fin_ms == 0) {
        return -1;
    }

    elapsed_ms = mbedtls_timing_get_timer(&ctx->timer, 0);

    if (elapsed_ms >= ctx->fin_ms) {
        return 2;
    }

    if (elapsed_ms >= ctx->int_ms) {
        return 1;
    }

    return 0;
}

#endif /* !MBEDTLS_TIMING_ALT */

#if defined(MBEDTLS_SELF_TEST)
/*
 * Busy-waits for the given number of milliseconds.
 * Used for testing mbedtls_timing_hardclock.
 */
static void busy_msleep(unsigned long msec)
{
    struct mbedtls_timing_hr_time hires;
    unsigned long i = 0; /* for busy-waiting */
    volatile unsigned long j; /* to prevent optimisation */

    (void) mbedtls_timing_get_timer(&hires, 1);

    while (mbedtls_timing_get_timer(&hires, 0) < msec) {
        i++;
    }

    j = i;
    (void) j;
}

#define FAIL    do                                                      \
    {                                                                   \
        if (verbose != 0)                                              \
        {                                                               \
            mbedtls_printf("failed at line %d\n", __LINE__);          \
            mbedtls_printf(" cycles=%lu ratio=%lu millisecs=%lu secs=%lu hardfail=%d a=%lu b=%lu\n", \
                           cycles, ratio, millisecs, secs, hardfail,   \
                           (unsigned long) a, (unsigned long) b);     \
            mbedtls_printf(" elapsed(hires)=%lu status(ctx)=%d\n", \
                           mbedtls_timing_get_timer(&hires, 0),      \
                           mbedtls_timing_get_delay(&ctx));         \
        }                                                               \
        return 1;                                                    \
    } while (0)

/*
 * Checkup routine
 *
 * Warning: this is work in progress, some tests may not be reliable enough
 * yet! False positives may happen.
 */
int mbedtls_timing_self_test(int verbose)
{
    unsigned long cycles = 0, ratio = 0;
    unsigned long millisecs = 0, secs = 0;
    int hardfail = 0;
    struct mbedtls_timing_hr_time hires;
    uint32_t a = 0, b = 0;
    mbedtls_timing_delay_context ctx;

    if (verbose != 0) {
        mbedtls_printf("  TIMING tests note: will take some time!\n");
    }

    if (verbose != 0) {
        mbedtls_printf("  TIMING test #1 (set_alarm / get_timer): ");
    }

    {
        secs = 1;

        (void) mbedtls_timing_get_timer(&hires, 1);

        mbedtls_set_alarm((int) secs);
        while (!mbedtls_timing_alarmed) {
            ;
        }

        millisecs = mbedtls_timing_get_timer(&hires, 0);

        /* For some reason on Windows it looks like alarm has an extra delay
         * (maybe related to creating a new thread). Allow some room here. */
        if (millisecs < 800 * secs || millisecs > 1200 * secs + 300) {
            FAIL;
        }
    }

    if (verbose != 0) {
        mbedtls_printf("passed\n");
    }

    if (verbose != 0) {
        mbedtls_printf("  TIMING test #2 (set/get_delay        ): ");
    }

    {
        a = 800;
        b = 400;
        mbedtls_timing_set_delay(&ctx, a, a + b);            /* T = 0 */

        busy_msleep(a - a / 4);                        /* T = a - a/4 */
        if (mbedtls_timing_get_delay(&ctx) != 0) {
            FAIL;
        }

        busy_msleep(a / 4 + b / 4);                    /* T = a + b/4 */
        if (mbedtls_timing_get_delay(&ctx) != 1) {
            FAIL;
        }

        busy_msleep(b);                            /* T = a + b + b/4 */
        if (mbedtls_timing_get_delay(&ctx) != 2) {
            FAIL;
        }
    }

    mbedtls_timing_set_delay(&ctx, 0, 0);
    busy_msleep(200);
    if (mbedtls_timing_get_delay(&ctx) != -1) {
        FAIL;
    }

    if (verbose != 0) {
        mbedtls_printf("passed\n");
    }

    if (verbose != 0) {
        mbedtls_printf("  TIMING test #3 (hardclock / get_timer): ");
    }

    /*
     * Allow one failure for possible counter wrapping.
     * On a 4Ghz 32-bit machine the cycle counter wraps about once per second;
     * since the whole test is about 10ms, it shouldn't happen twice in a row.
     */

hard_test:
    if (hardfail > 1) {
        if (verbose != 0) {
            mbedtls_printf("failed (ignored)\n");
        }

        goto hard_test_done;
    }

    /* Get a reference ratio cycles/ms */
    millisecs = 1;
    cycles = mbedtls_timing_hardclock();
    busy_msleep(millisecs);
    cycles = mbedtls_timing_hardclock() - cycles;
    ratio = cycles / millisecs;

    /* Check that the ratio is mostly constant */
    for (millisecs = 2; millisecs <= 4; millisecs++) {
        cycles = mbedtls_timing_hardclock();
        busy_msleep(millisecs);
        cycles = mbedtls_timing_hardclock() - cycles;

        /* Allow variation up to 20% */
        if (cycles / millisecs < ratio - ratio / 5 ||
            cycles / millisecs > ratio + ratio / 5) {
            hardfail++;
            goto hard_test;
        }
    }

    if (verbose != 0) {
        mbedtls_printf("passed\n");
    }

hard_test_done:

    if (verbose != 0) {
        mbedtls_printf("\n");
    }

    return 0;
}

#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_TIMING_C */