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Make the hardclock test optional

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Known to fail on VMs (such as the buildbots), see eg
http://blog.badtrace.com/post/rdtsc-x86-instruction-to-detect-vms/
This commit is contained in:
Manuel Pégourié-Gonnard 2015-07-01 19:19:49 +02:00
parent 9bd0afdb22
commit 5791109707
2 changed files with 52 additions and 46 deletions
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4
include/mbedtls/timing.h
View file

@ -62,6 +62,10 @@ 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.
*/
unsigned long mbedtls_timing_hardclock( void );

94
library/timing.c
View file

@ -427,52 +427,7 @@ int mbedtls_timing_self_test( int verbose )
mbedtls_printf( "passed\n" );
if( verbose != 0 )
mbedtls_printf( " TIMING test #2 (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.
*/
hardfail = 0;
hard_test:
if( hardfail > 1 )
{
if( verbose != 0 )
mbedtls_printf( "failed\n" );
return( 1 );
}
/* 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" );
if( verbose != 0 )
mbedtls_printf( " TIMING test #3 (set/get_delay ): " );
mbedtls_printf( " TIMING test #2 (set/get_delay ): " );
for( a = 100; a <= 200; a += 100 )
{
@ -506,6 +461,53 @@ hard_test:
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.
*/
hardfail = 0;
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" );