[nrf fromlist] modules: mbedtls: Expose MBEDTLS_PLATFORM_NO_STD_FUNCTIONS

The commit adds Kconfig options that allows users to select
 - MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
 - MBEDTLS_PLATFORM_SNPRINTF_ALT
allowing Mbed TLS to use alternative definitions of STD functions.

Upstream PR #: 87135

Signed-off-by: Dominik Ermel <[email protected]>

Author: de-nordic

modules/mbedtls/Kconfig.tls-generic

@@ -406,6 +406,23 @@ config MBEDTLS_GENPRIME_ENABLED
 config MBEDTLS_ASN1_PARSE_C
 	bool "Support for ASN1 parser functions"
 
+config MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+	bool "Mbed TLS will not use standard C functions"
+	help
+	  This replaces, within Mbed TLS, usage of functions like alloc, calloc,
+	  free, snprintf, or printf with Mbed TLS replaced aliases.
+	  This allows user to provide own implementations if platform lacks
+	  C standard functions.
+
+if MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+
+config MBEDTLS_PLATFORM_SNPRINTF_ALT
+	bool "Allow setting custom snprintf for Mbed TLS, at run-time"
+	help
+	  Allow setting custom snprinf function with mbedtls_platform_set_snprintf.
+
+endif # MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+
 config MBEDTLS_PEM_CERTIFICATE_FORMAT
 	bool "Support for PEM certificate format"
 	help

modules/mbedtls/configs/config-tls-generic.h

@@ -23,6 +23,14 @@
 #define MBEDTLS_PLATFORM_ZEROIZE_ALT
 #endif
 
+#if defined(CONFIG_MBEDTLS_PLATFORM_NO_STD_FUNCTIONS)
+#define MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+#endif /* defined(MBEDTLS_PLATFORM_NO_STD_FUNCTIONS) */
+
+#if defined(CONFIG_MBEDTLS_PLATFORM_SNPRINTF_ALT)
+#define MBEDTLS_PLATFORM_SNPRINTF_ALT
+#endif /* defined(MBEDTLS_PLATFORM_SNPRINTF_ALT) */
+
 #if defined(CONFIG_MBEDTLS_ENTROPY_POLL_ZEPHYR)
 #define MBEDTLS_ENTROPY_HARDWARE_ALT
 #else