diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
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+++ b/include/mbedtls/debug.h
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+/**
+ * \file debug.h
+ *
+ * \brief Functions for controlling and providing debug output from the library.
+ */
+/*
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+#ifndef MBEDTLS_DEBUG_H
+#define MBEDTLS_DEBUG_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include "ssl.h"
+
+#if defined(MBEDTLS_ECP_C)
+#include "ecp.h"
+#endif
+
+#if defined(MBEDTLS_DEBUG_C)
+
+#define MBEDTLS_DEBUG_STRIP_PARENS( ... )   __VA_ARGS__
+
+#define MBEDTLS_SSL_DEBUG_MSG( level, args )                    \
+    mbedtls_debug_print_msg( ssl, level, __FILE__, __LINE__,    \
+                             MBEDTLS_DEBUG_STRIP_PARENS args )
+
+#define MBEDTLS_SSL_DEBUG_RET( level, text, ret )                \
+    mbedtls_debug_print_ret( ssl, level, __FILE__, __LINE__, text, ret )
+
+#define MBEDTLS_SSL_DEBUG_BUF( level, text, buf, len )           \
+    mbedtls_debug_print_buf( ssl, level, __FILE__, __LINE__, text, buf, len )
+
+#if defined(MBEDTLS_BIGNUM_C)
+#define MBEDTLS_SSL_DEBUG_MPI( level, text, X )                  \
+    mbedtls_debug_print_mpi( ssl, level, __FILE__, __LINE__, text, X )
+#endif
+
+#if defined(MBEDTLS_ECP_C)
+#define MBEDTLS_SSL_DEBUG_ECP( level, text, X )                  \
+    mbedtls_debug_print_ecp( ssl, level, __FILE__, __LINE__, text, X )
+#endif
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+#define MBEDTLS_SSL_DEBUG_CRT( level, text, crt )                \
+    mbedtls_debug_print_crt( ssl, level, __FILE__, __LINE__, text, crt )
+#endif
+
+#if defined(MBEDTLS_ECDH_C)
+#define MBEDTLS_SSL_DEBUG_ECDH( level, ecdh, attr )               \
+    mbedtls_debug_printf_ecdh( ssl, level, __FILE__, __LINE__, ecdh, attr )
+#endif
+
+#else /* MBEDTLS_DEBUG_C */
+
+#define MBEDTLS_SSL_DEBUG_MSG( level, args )            do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_RET( level, text, ret )       do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_BUF( level, text, buf, len )  do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_MPI( level, text, X )         do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_ECP( level, text, X )         do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_CRT( level, text, crt )       do { } while( 0 )
+#define MBEDTLS_SSL_DEBUG_ECDH( level, ecdh, attr )     do { } while( 0 )
+
+#endif /* MBEDTLS_DEBUG_C */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \brief   Set the threshold error level to handle globally all debug output.
+ *          Debug messages that have a level over the threshold value are
+ *          discarded.
+ *          (Default value: 0 = No debug )
+ *
+ * \param threshold     theshold level of messages to filter on. Messages at a
+ *                      higher level will be discarded.
+ *                          - Debug levels
+ *                              - 0 No debug
+ *                              - 1 Error
+ *                              - 2 State change
+ *                              - 3 Informational
+ *                              - 4 Verbose
+ */
+void mbedtls_debug_set_threshold( int threshold );
+
+/**
+ * \brief    Print a message to the debug output. This function is always used
+ *          through the MBEDTLS_SSL_DEBUG_MSG() macro, which supplies the ssl
+ *          context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the message has occurred in
+ * \param line      line number the message has occurred at
+ * \param format    format specifier, in printf format
+ * \param ...       variables used by the format specifier
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_msg( const mbedtls_ssl_context *ssl, int level,
+                              const char *file, int line,
+                              const char *format, ... );
+
+/**
+ * \brief   Print the return value of a function to the debug output. This
+ *          function is always used through the MBEDTLS_SSL_DEBUG_RET() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      the name of the function that returned the error
+ * \param ret       the return code value
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_ret( const mbedtls_ssl_context *ssl, int level,
+                      const char *file, int line,
+                      const char *text, int ret );
+
+/**
+ * \brief   Output a buffer of size len bytes to the debug output. This function
+ *          is always used through the MBEDTLS_SSL_DEBUG_BUF() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the buffer being dumped. Normally the
+ *                  variable or buffer name
+ * \param buf       the buffer to be outputted
+ * \param len       length of the buffer
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_buf( const mbedtls_ssl_context *ssl, int level,
+                      const char *file, int line, const char *text,
+                      const unsigned char *buf, size_t len );
+
+#if defined(MBEDTLS_BIGNUM_C)
+/**
+ * \brief   Print a MPI variable to the debug output. This function is always
+ *          used through the MBEDTLS_SSL_DEBUG_MPI() macro, which supplies the
+ *          ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the MPI being output. Normally the
+ *                  variable name
+ * \param X         the MPI variable
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_mpi( const mbedtls_ssl_context *ssl, int level,
+                      const char *file, int line,
+                      const char *text, const mbedtls_mpi *X );
+#endif
+
+#if defined(MBEDTLS_ECP_C)
+/**
+ * \brief   Print an ECP point to the debug output. This function is always
+ *          used through the MBEDTLS_SSL_DEBUG_ECP() macro, which supplies the
+ *          ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the ECP point being output. Normally the
+ *                  variable name
+ * \param X         the ECP point
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_ecp( const mbedtls_ssl_context *ssl, int level,
+                      const char *file, int line,
+                      const char *text, const mbedtls_ecp_point *X );
+#endif
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+/**
+ * \brief   Print a X.509 certificate structure to the debug output. This
+ *          function is always used through the MBEDTLS_SSL_DEBUG_CRT() macro,
+ *          which supplies the ssl context, file and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param text      a name or label for the certificate being output
+ * \param crt       X.509 certificate structure
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_print_crt( const mbedtls_ssl_context *ssl, int level,
+                      const char *file, int line,
+                      const char *text, const mbedtls_x509_crt *crt );
+#endif
+
+#if defined(MBEDTLS_ECDH_C)
+typedef enum
+{
+    MBEDTLS_DEBUG_ECDH_Q,
+    MBEDTLS_DEBUG_ECDH_QP,
+    MBEDTLS_DEBUG_ECDH_Z,
+} mbedtls_debug_ecdh_attr;
+
+/**
+ * \brief   Print a field of the ECDH structure in the SSL context to the debug
+ *          output. This function is always used through the
+ *          MBEDTLS_SSL_DEBUG_ECDH() macro, which supplies the ssl context, file
+ *          and line number parameters.
+ *
+ * \param ssl       SSL context
+ * \param level     error level of the debug message
+ * \param file      file the error has occurred in
+ * \param line      line number the error has occurred in
+ * \param ecdh      the ECDH context
+ * \param attr      the identifier of the attribute being output
+ *
+ * \attention       This function is intended for INTERNAL usage within the
+ *                  library only.
+ */
+void mbedtls_debug_printf_ecdh( const mbedtls_ssl_context *ssl, int level,
+                                const char *file, int line,
+                                const mbedtls_ecdh_context *ecdh,
+                                mbedtls_debug_ecdh_attr attr );
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* debug.h */
+