ECDSA signing crashes when implemented with bluetooth

RE: ECDSA signing crashes when implemented with bluetooth

sethu — Mon, 11 Jan 2021 22:52:33 GMT

Hey Simon,

Thank you for taking the time to figure this out for me, really appreciate it. While you were working on it I did try the solution using the thread and semaphore which worked without any problem but wanted to know why it crashed when a thread wasn't used.

Regards,

Sethu

RE: ECDSA signing crashes when implemented with bluetooth

Simon — Mon, 11 Jan 2021 17:47:57 GMT

Forget my last comment, that assert triggered because I stopped the program using a breakpoint, before continuing.

However, I was able to get rid of the memfault by setting these in prj.conf:

CONFIG_BT_TINYCRYPT_ECC=n
CONFIG_BT_RX_STACK_SIZE=4096

The top config was enabled by default, and would cause zephyr\subsys\bluetooth\host\hci_ecc.c-->ecc_thread()--> emulate_le_p256_public_key_cmd() to run, and a stack overrflow-->memfault would happen.

When I disabled it, I still got a memfault, which I think is due to stack overflow because the rx stack was too small. As you can see in the call stack below, the functions notify_func()-->ecdsa_sign() are called within the rx thread(), and the call stack is quite large:

One quick fix is to simply increase the BT RX stack size. A better solution is probably to create an own thread that runs ecdsa_sign() and just use k_sem_take/k_sem_give to signal the thread.

Best regards,

Simon

RE: ECDSA signing crashes when implemented with bluetooth

Simon — Fri, 08 Jan 2021 08:58:34 GMT

It seems like an assert in mpsl_init.c-->m_assert_handler() makes the program crash. I'm not sure why this is, but will continue to investigate.

Best regards,

Simon