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FreeRTOS Support ArchiveThe FreeRTOS support forum is used to obtain active support directly from Real Time Engineers Ltd. In return for using our top quality software and services for free, we request you play fair and do your bit to help others too! Sign up to receive notifications of new support topics then help where you can.
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FreeRTOS A53 port : ELx stack pointers in save and restore contextPosted by mathieu-42 on November 29, 2016 Hello, 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 ~~~ 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? Best regards, Mathieu FreeRTOS A53 port : ELx stack pointers in save and restore contextPosted by rtel on November 29, 2016 I will have to consult the hardware reference manual to recall....get back to you. FreeRTOS A53 port : ELx stack pointers in save and restore contextPosted by mathieu-42 on November 30, 2016 Thanks. FreeRTOS A53 port : ELx stack pointers in save and restore contextPosted by rtel on December 11, 2016 Looking at the code it looks like the EL0 stack pointer is used so stack relative pushes/pops can be performed without corrupting the stack pointer used by the interrupt handler itself.
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NXP tweet showing LPC5500 (ARMv8-M Cortex-M33) running FreeRTOS.
Meet Richard Barry and learn about running FreeRTOS on RISC-V at FOSDEM 2019
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FreeRTOS and other embedded software careers at AWS.
