I am working with A53 port of FreeRTOS and I do not understand something in portASM.S file.
My program is running in EL3.
Why when the context is saved we switch stack pointer to EL0 stack pointer?
Then at the end of “portSAVE_CONTEXT” macro, we switch back to EL3 stack pointer.
.macro portSAVE_CONTEXT /* Switch to use the EL0 stack pointer. */ MSR SPSEL, #0 ... /* Switch to use the ELx stack pointer. */ MSR SPSEL, #1 .endm
Same thing for .macro portRESTORE_CONTEXT.
If program is in EL3, why we do not use EL3 stack pointer?
Are there some security issues when we switch to EL0 stack pointer from EL3?