Move constant_flow.h into the main library

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

library/constant_flow.h

@@ -0,0 +1,108 @@
+/**
+ * \file constant_flow.h
+ *
+ * \brief   This file contains tools to ensure tested code has constant flow.
+ */
+
+/*
+ *  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 TEST_CONSTANT_FLOW_H
+#define TEST_CONSTANT_FLOW_H
+
+#include "mbedtls/build_info.h"
+
+/*
+ * This file defines the two macros
+ *
+ *  #define TEST_CF_SECRET(ptr, size)
+ *  #define TEST_CF_PUBLIC(ptr, size)
+ *
+ * and
+ *
+ * #define TEST_CF_SAVE_SECRET(variable)
+ * #define TEST_CF_RESTORE_SECRET(variable)
+ *
+ * that can be used in tests to mark a memory area as secret (no branch or
+ * memory access should depend on it) or public (default, only needs to be
+ * marked explicitly when it was derived from secret data).
+ *
+ * The SAVE/RESTORE forms mark a variable as public, and subsequently restore its
+ * previous secret/not-secret state. This is used where library code is generating
+ * false positives and needs to temporarily disable Memsan checks for a particular
+ * variable, and then restore it's original state afterwards so it doesn't interfere
+ * with other checks.
+ *
+ * Arguments:
+ * - ptr: a pointer to the memory area to be marked
+ * - size: the size in bytes of the memory area
+ *
+ * - variable: a variable name
+ *
+ * Implementation:
+ * The basic idea is that of ctgrind <https://github.com/agl/ctgrind>: we can
+ * re-use tools that were designed for checking use of uninitialized memory.
+ * This file contains two implementations: one based on MemorySanitizer, the
+ * other on valgrind's memcheck. If none of them is enabled, dummy macros that
+ * do nothing are defined for convenience.
+ *
+ * \note #TEST_CF_SECRET must be called directly from within a .function file,
+ *       not indirectly via a macro defined under tests/include or a function
+ *       under tests/src. This is because we only run Valgrind for constant
+ *       flow on test suites that have greppable annotations inside them (see
+ *       `skip_suites_without_constant_flow` in `tests/scripts/all.sh`).
+ */
+
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
+#include <sanitizer/msan_interface.h>
+
+/* Use macros to avoid messing up with origin tracking */
+#define TEST_CF_SECRET  __msan_allocated_memory
+// void __msan_allocated_memory(const volatile void* data, size_t size);
+#define TEST_CF_PUBLIC  __msan_unpoison
+// void __msan_unpoison(const volatile void *a, size_t size);
+
+#define TEST_CF_SAVE_SECRET(_x) \
+    int _test_cf_is_public_ ## _x = __msan_test_shadow(&(_x), sizeof(_x)) == -1; \
+    TEST_CF_PUBLIC(&(_x), sizeof(_x));
+#define TEST_CF_RESTORE_SECRET(_x) \
+    if (!_test_cf_is_public_ ## _x) TEST_CF_SECRET(&(_x), sizeof(_x));
+
+#elif defined(MBEDTLS_TEST_CONSTANT_FLOW_VALGRIND)
+#include <valgrind/memcheck.h>
+
+#define TEST_CF_SECRET  VALGRIND_MAKE_MEM_UNDEFINED
+// VALGRIND_MAKE_MEM_UNDEFINED(_qzz_addr, _qzz_len)
+#define TEST_CF_PUBLIC  VALGRIND_MAKE_MEM_DEFINED
+// VALGRIND_MAKE_MEM_DEFINED(_qzz_addr, _qzz_len)
+
+#define TEST_CF_SAVE_SECRET(_x)
+#define TEST_CF_RESTORE_SECRET(_x)
+
+#else /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN ||
+         MBEDTLS_TEST_CONSTANT_FLOW_VALGRIND */
+
+#define TEST_CF_SECRET(ptr, size)
+#define TEST_CF_PUBLIC(ptr, size)
+
+#define TEST_CF_SAVE_SECRET(_x)
+#define TEST_CF_RESTORE_SECRET(_x)
+
+#endif /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN ||
+          MBEDTLS_TEST_CONSTANT_FLOW_VALGRIND */
+
+#endif /* TEST_CONSTANT_FLOW_H */

library/constant_time.c

@@ -30,7 +30,7 @@
 #include "mbedtls/error.h"
 #include "mbedtls/platform_util.h"
 
-#include "../tests/include/test/constant_flow.h"
+#include "constant_flow.h"
 
 #include <string.h>
 

library/constant_time_impl.h

@@ -37,7 +37,7 @@
 #include "mbedtls/bignum.h"
 #endif
 
-#include "../tests/include/test/constant_flow.h"
+#include "constant_flow.h"
 
 /* armcc5 --gnu defines __GNUC__ but doesn't support GNU's extended asm */
 #if defined(MBEDTLS_HAVE_ASM) && defined(__GNUC__) && (!defined(__ARMCC_VERSION) || \