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/** Mutex usage verification framework. */
/*
* 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 <test/helpers.h>
#include <test/macros.h>
#if defined(MBEDTLS_TEST_MUTEX_USAGE)
#include "mbedtls/threading.h"
/** Mutex usage verification framework.
*
* The mutex usage verification code below aims to detect bad usage of
* Mbed TLS's mutex abstraction layer at runtime. Note that this is solely
* about the use of the mutex itself, not about checking whether the mutex
* correctly protects whatever it is supposed to protect.
*
* The normal usage of a mutex is:
* ```
* digraph mutex_states {
* "UNINITIALIZED"; // the initial state
* "IDLE";
* "FREED";
* "LOCKED";
* "UNINITIALIZED" -> "IDLE" [label="init"];
* "FREED" -> "IDLE" [label="init"];
* "IDLE" -> "LOCKED" [label="lock"];
* "LOCKED" -> "IDLE" [label="unlock"];
* "IDLE" -> "FREED" [label="free"];
* }
* ```
*
* All bad transitions that can be unambiguously detected are reported.
* An attempt to use an uninitialized mutex cannot be detected in general
* since the memory content may happen to denote a valid state. For the same
* reason, a double init cannot be detected.
* All-bits-zero is the state of a freed mutex, which is distinct from an
* initialized mutex, so attempting to use zero-initialized memory as a mutex
* without calling the init function is detected.
*
* The framework attempts to detect missing calls to init and free by counting
* calls to init and free. If there are more calls to init than free, this
* means that a mutex is not being freed somewhere, which is a memory leak
* on platforms where a mutex consumes resources other than the
* mbedtls_threading_mutex_t object itself. If there are more calls to free
* than init, this indicates a missing init, which is likely to be detected
* by an attempt to lock the mutex as well. A limitation of this framework is
* that it cannot detect scenarios where there is exactly the same number of
* calls to init and free but the calls don't match. A bug like this is
* unlikely to happen uniformly throughout the whole test suite though.
*
* If an error is detected, this framework will report what happened and the
* test case will be marked as failed. Unfortunately, the error report cannot
* indicate the exact location of the problematic call. To locate the error,
* use a debugger and set a breakpoint on mbedtls_test_mutex_usage_error().
*/
enum value_of_mutex_is_valid_field
{
/* Potential values for the is_valid field of mbedtls_threading_mutex_t.
* Note that MUTEX_FREED must be 0 and MUTEX_IDLE must be 1 for
* compatibility with threading_mutex_init_pthread() and
* threading_mutex_free_pthread(). MUTEX_LOCKED could be any nonzero
* value. */
MUTEX_FREED = 0, //!< Set by threading_mutex_free_pthread
MUTEX_IDLE = 1, //!< Set by threading_mutex_init_pthread and by our unlock
MUTEX_LOCKED = 2, //!< Set by our lock
};
typedef struct
{
void (*init)( mbedtls_threading_mutex_t * );
void (*free)( mbedtls_threading_mutex_t * );
int (*lock)( mbedtls_threading_mutex_t * );
int (*unlock)( mbedtls_threading_mutex_t * );
} mutex_functions_t;
static mutex_functions_t mutex_functions;
/** The total number of calls to mbedtls_mutex_init(), minus the total number
* of calls to mbedtls_mutex_free().
*
* Reset to 0 after each test case.
*/
static int live_mutexes;
static void mbedtls_test_mutex_usage_error( mbedtls_threading_mutex_t *mutex,
const char *msg )
{
(void) mutex;
if( mbedtls_test_info.mutex_usage_error == NULL )
mbedtls_test_info.mutex_usage_error = msg;
mbedtls_fprintf( stdout, "[mutex: %s] ", msg );
/* Don't mark the test as failed yet. This way, if the test fails later
* for a functional reason, the test framework will report the message
* and location for this functional reason. If the test passes,
* mbedtls_test_mutex_usage_check() will mark it as failed. */
}
static void mbedtls_test_wrap_mutex_init( mbedtls_threading_mutex_t *mutex )
{
mutex_functions.init( mutex );
if( mutex->is_valid )
++live_mutexes;
}
static void mbedtls_test_wrap_mutex_free( mbedtls_threading_mutex_t *mutex )
{
switch( mutex->is_valid )
{
case MUTEX_FREED:
mbedtls_test_mutex_usage_error( mutex, "free without init or double free" );
break;
case MUTEX_IDLE:
/* Do nothing. The underlying free function will reset is_valid
* to 0. */
break;
case MUTEX_LOCKED:
mbedtls_test_mutex_usage_error( mutex, "free without unlock" );
break;
default:
mbedtls_test_mutex_usage_error( mutex, "corrupted state" );
break;
}
if( mutex->is_valid )
--live_mutexes;
mutex_functions.free( mutex );
}
static int mbedtls_test_wrap_mutex_lock( mbedtls_threading_mutex_t *mutex )
{
int ret = mutex_functions.lock( mutex );
switch( mutex->is_valid )
{
case MUTEX_FREED:
mbedtls_test_mutex_usage_error( mutex, "lock without init" );
break;
case MUTEX_IDLE:
if( ret == 0 )
mutex->is_valid = 2;
break;
case MUTEX_LOCKED:
mbedtls_test_mutex_usage_error( mutex, "double lock" );
break;
default:
mbedtls_test_mutex_usage_error( mutex, "corrupted state" );
break;
}
return( ret );
}
static int mbedtls_test_wrap_mutex_unlock( mbedtls_threading_mutex_t *mutex )
{
int ret = mutex_functions.unlock( mutex );
switch( mutex->is_valid )
{
case MUTEX_FREED:
mbedtls_test_mutex_usage_error( mutex, "unlock without init" );
break;
case MUTEX_IDLE:
mbedtls_test_mutex_usage_error( mutex, "unlock without lock" );
break;
case MUTEX_LOCKED:
if( ret == 0 )
mutex->is_valid = MUTEX_IDLE;
break;
default:
mbedtls_test_mutex_usage_error( mutex, "corrupted state" );
break;
}
return( ret );
}
void mbedtls_test_mutex_usage_init( void )
{
mutex_functions.init = mbedtls_mutex_init;
mutex_functions.free = mbedtls_mutex_free;
mutex_functions.lock = mbedtls_mutex_lock;
mutex_functions.unlock = mbedtls_mutex_unlock;
mbedtls_mutex_init = &mbedtls_test_wrap_mutex_init;
mbedtls_mutex_free = &mbedtls_test_wrap_mutex_free;
mbedtls_mutex_lock = &mbedtls_test_wrap_mutex_lock;
mbedtls_mutex_unlock = &mbedtls_test_wrap_mutex_unlock;
}
void mbedtls_test_mutex_usage_check( void )
{
if( live_mutexes != 0 )
{
/* A positive number (more init than free) means that a mutex resource
* is leaking (on platforms where a mutex consumes more than the
* mbedtls_threading_mutex_t object itself). The rare case of a
* negative number means a missing init somewhere. */
mbedtls_fprintf( stdout, "[mutex: %d leaked] ", live_mutexes );
live_mutexes = 0;
if( mbedtls_test_info.mutex_usage_error == NULL )
mbedtls_test_info.mutex_usage_error = "missing free";
}
if( mbedtls_test_info.mutex_usage_error != NULL &&
mbedtls_test_info.result != MBEDTLS_TEST_RESULT_FAILED )
{
/* Functionally, the test passed. But there was a mutex usage error,
* so mark the test as failed after all. */
mbedtls_test_fail( "Mutex usage error", __LINE__, __FILE__ );
}
mbedtls_test_info.mutex_usage_error = NULL;
}
#endif /* MBEDTLS_TEST_MUTEX_USAGE */