mbedtls: Use `tf_snprintf` instead of `snprintf`

The Trusted Firmware uses a subset of the APIs provided by mbed TLS.
This subset internally uses `snprintf`, but the only format specifier
used is '%d', which is supported by `tf_snprintf`.

This patch makes mbed TLS use `tf_snprintf` instead of `snprintf`,
saving 3 KB in both debug and release builds when TBBR is enabled.

Change-Id: I7f992a21015930d7c0f4660e7a28ceefd60b9597
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

diff --git a/drivers/auth/mbedtls/mbedtls_common.c b/drivers/auth/mbedtls/mbedtls_common.c
index aad49a7152ef58789eadb25371a9ee24240cf416..871831e2d8e646be1d8e8990b3c564829d0e973b 100644 (file)
--- a/drivers/auth/mbedtls/mbedtls_common.c
+++ b/drivers/auth/mbedtls/mbedtls_common.c
@@ -4,10 +4,11 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#include <assert.h>
+#include <debug.h>
 
 /* mbed TLS headers */
 #include <mbedtls/memory_buffer_alloc.h>
+#include <mbedtls/platform.h>
 
 /*
  * mbed TLS heap
@@ -29,6 +30,10 @@ void mbedtls_init(void)
        if (!ready) {
                /* Initialize the mbed TLS heap */
                mbedtls_memory_buffer_alloc_init(heap, MBEDTLS_HEAP_SIZE);
+
+               /* Use reduced version of snprintf to save space. */
+               mbedtls_platform_set_snprintf(tf_snprintf);
+
                ready = 1;
        }
 }

diff --git a/include/drivers/auth/mbedtls/mbedtls_config.h b/include/drivers/auth/mbedtls/mbedtls_config.h
index 7d8d17c357b1fd90faf76c10bc80e0e1abac0650..22e75742a34a11794f013dc9fa1a9fe722e1009f 100644 (file)
--- a/include/drivers/auth/mbedtls/mbedtls_config.h
+++ b/include/drivers/auth/mbedtls/mbedtls_config.h
@@ -19,6 +19,8 @@
 
 #define MBEDTLS_PLATFORM_MEMORY
 #define MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+/* Prevent mbed TLS from using snprintf so that it can use tf_snprintf. */
+#define MBEDTLS_PLATFORM_SNPRINTF_ALT
 
 #define MBEDTLS_PKCS1_V15
 #define MBEDTLS_PKCS1_V21