RTEMS Porting Guide
Whether or not the interrupt stack is hardware or software managed, RTEMS may allocate memory for the interrupt stack from the Executive Workspace. If RTEMS is going to allocate the memory for a dedicated interrupt stack in the Interrupt Manager, then the macro CPU_ALLOCATE_INTERRUPT_STACK should be set to TRUE.
NOTE: This should be TRUE is CPU_HAS_SOFTWARE_INTERRUPT_STACK is TRUE.
#define CPU_ALLOCATE_INTERRUPT_STACK TRUE
If the CPU_HAS_SOFTWARE_INTERRUPT_STACK macro is set to TRUE, then RTEMS automatically allocates the stack memory in the initialization of the Interrupt Manager and the switch to that stack is performed in _ISR_Handler on the outermost interrupt. The _CPU_Interrupt_stack_low and _CPU_Interrupt_stack_high variables contain the addresses of the the lowest and highest addresses of the memory allocated for the interrupt stack. Although technically only one of these addresses is required to switch to the interrupt stack, by always providing both addresses, the port has more options avaialble to it without requiring modifications to the portable parts of the executive. Whether the stack grows up or down, this give the CPU dependent code the option of picking the version it wants to use.
SCORE_EXTERN void *_CPU_Interrupt_stack_low; SCORE_EXTERN void *_CPU_Interrupt_stack_high;
NOTE: These two variables are required if the macro CPU_HAS_SOFTWARE_INTERRUPT_STACK is defined as TRUE.
RTEMS Porting Guide
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