Issue was due to messed up SRAM define in linker script. IDK what
datasheet I was reading.. But I had the location and size completely
wrong. That caused any access of SRAM to cause a hardfault of course.
First happening when popping anything to the stack. Which also explains
why I couldn't look at the stack to figure out the last called instruciton
to point to where the issue was...
copied stm32f0xx_*.h files over from STM32F0xx_StdPeriph_Driver/inc dir