STM32 fault handling

http://blog.frankvh.com/2011/12/07/cortex-m3-m4-hard-fault-handler/

Here is the IAR version of the asm.

     NAME HardFault_Handler

     AAPCS BASE,INTERWORK
     PRESERVE8
     REQUIRE8

     EXTERN hard_fault_handler_c

     SECTION .text:CODE:REORDER(2)
     THUMB

     PUBLIC  HardFault_Handler
     PUBLIC  BusFault_Handler

HardFault_Handler
BusFault_Handler
     TST LR, #4
     ITE EQ
     MRSEQ R0, MSP
     MRSNE R0, PSP
     B hard_fault_handler_c

     END