Trying to enable MBedTLS static buffer allocation

Question

Hello,

I'm currently trying to enable static buffer for MBedTLS as described here: https://tls.mbed.org/kb/how-to/using-static-memory-instead-of-the-heap.

I wrote a simple hello world example to test it out:

#include <zephyr.h>
#include <kernel.h>
#include <sys/printk.h>
#include <mbedtls/memory_buffer_alloc.h>


unsigned char mbedtls_static_buffer[4096];

void main(void)
{
    mbedtls_memory_buffer_alloc_init(mbedtls_static_buffer, sizeof(mbedtls_static_buffer));
	printk("Hello World!\n");
}

Clearly there is a problem with my prj.conf but I can't figure it out.

prj.conf

CONFIG_NRF_SECURITY=y
CONFIG_MBEDTLS=y

During build I got an linker error:

undefined reference to `mbedtls_memory_buffer_alloc_init'

although it seems to be enabled:

                                                                                            Symbol information
Name: MBEDTLS_MEMORY_BUFFER_ALLOC_C
Type: bool
Value: y

I'm working on Ubuntu 20.04 with nrfconnect version 1.9.0.

Can someone point out to me how to enable this?

Thanks

Amanda Hsieh · Accepted Answer

Hi, 
 Enabling the mbedtls heap in our sdk will use a static buffer anyway so there is no need to do this manually. 
 The heap initialization can be found here: 
 https://github.com/nrfconnect/sdk-nrfxlib/blob/main/nrf_security/src/legacy/mbedtls_heap.c 
 And the file is included here: 
 https://github.com/nrfconnect/sdk-nrfxlib/blob/79c55b287673dbae97e2cfded8acba570b19c8a2/nrf_security/src/zephyr/CMakeLists.txt#L15 
 Regards, Amanda

Trying to enable MBedTLS static buffer allocation

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