Potential critical NuttX alignment issue

[LorenzMeier]

The full report is here and I'm including it to ensure that we're not forgetting about it:
https://bitbucket.org/nuttx/nuttx/issues/78/possible-bss-override-by-stack-coloration

@davids5 @dagar I would appreciate your review.

Thanks!

[BazookaJoe1900]

Note that for what I seen so far, for px4fmu there should be no issue, because the last var on the bss is io_timer_channel_stats, which is 4 byte aligned.
I have seen the issue because I didn't set BOARD_HAS_CAPTURE, 'once' var has become the last one, and its uint8_t

[dagar]

Add ALIGN to the linker scripts? https://github.com/PX4/Firmware/blob/master/nuttx-configs/px4fmu-v2/scripts/ld.script#L143

[BazookaJoe1900]

Yes, I think that adding
. = ALIGN(4);
Should to the work.
Can you confirm?

[davids5]

I will check and confirm it in the AM tomorrow.

[LorenzMeier]

@davids5 Did you have a chance to have a look?

[davids5]

@LorenzMeier yes. Current build is not affected, but I will do a PR to avoid any future issues.

[LorenzMeier]

Moving to v1.8.

[dagar]

Fixed in #8382.

[BazookaJoe1900]

@davids5 Thanks!