GHSA-xw5j-gv2g-mjm2: Miscompilation in cortex-m-rt 0.7.1 and 0.7.2

Version 0.7.1 of the cortex-m-rt crate introduced a regression causing the stack to NOT be eight-byte aligned prior to calling main (or any other specified entrypoint), violating the [stack ABI of AAPCS32], the default ABI used by all Cortex-M targets. This regression is also present in version 0.7.2 of the cortex-m-rt crate.

This regression can cause certain compiler optimizations (which assume the eight-byte alignment) to produce incorrect behavior at runtime. This incorrect behavior has been [observed in real-world applications].

It is advised that ALL users of v0.7.1 and v0.7.2 of the cortex-m-rt crate update to the latest version (v0.7.3), AS SOON AS POSSIBLE. Users of v0.7.0 and prior versions of cortex-m-rt are not affected by this regression.

It will be necessary to rebuild all affected firmware binaries, and flash or deploy the new firmware binaries to affected devices.