feature request: option to exclude thread-local storage from coredumps

[JordanYates]

The thread stack coredump logic currently takes into account the case where less data exists than CONFIG_MEMFAULT_COREDUMP_STACK_SIZE_TO_COLLECT.

memfault-firmware-sdk/ports/zephyr/common/memfault_zephyr_ram_regions.c

Lines 235 to 240 in 03050f2

	// We know where the top of the stack is. Use that information to shrink
	// the area we need to collect if less than CONFIG_MEMFAULT_COREDUMP_STACK_SIZE_TO_COLLECT
	// is in use
	const uint32_t stack_top = thread->stack_info.start + thread->stack_info.size;
	size_t stack_size_to_collect =
	MEMFAULT_MIN(stack_top - (uint32_t)sp, CONFIG_MEMFAULT_COREDUMP_STACK_SIZE_TO_COLLECT);

However it does not take into account that a application specific amount at the top of the stack can be reserved for thread-local storage. This can be a non-trivial amount of ram (56 bytes on my nRF9151 application, ~20% of the default CONFIG_MEMFAULT_COREDUMP_STACK_SIZE_TO_COLLECT).
The size of this TLS data is accessible in the stack_info.delta variable.
https://github.com/zephyrproject-rtos/zephyr/blob/99a63a776980f855493ceb99036a5974a2b68fb5/include/zephyr/kernel/thread.h#L169-L173

In RAM limited applications, it would be good to have the option to exclude TLS data from the coredumps, so that the space can be allocated to more useful information.

[noahp]

Thanks for reporting, @JordanYates , apologies for my slow response here- I'll add an option to our next SDK release to support this!

[noahp]

This is fixed in 1.20.0. Let me know if there's any issues!