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Armv8-A A55 baremetal boot exception level from EL1 to EL0

zhuxiya

I was studying the A55 baremetal boot. I changed the execution level from EL3 to EL2 then to EL1 can work very well,but EL1 can not change to EL0.I use the spsr_eln and elr_eln register with the instrcuction eret from higher EL to lower EL. but the EL1 to EL0 always causes excepiton and the ESR_EL3  show the error infor is 92000050.I did not setup MMU.

Thanks by advance

Parents
  • 0 in reply to Martin Weidmann

    Thank you very much for your reply.I running the bare metal boot code on Cortex-A55.All the boot code is design by our teams.I just responsible for debug the assembly code which boot the running environment.I want switch EL1 to EL0 with the spsr_el1 and elr_el1 register,and use the eret instruction.Then it come across the exception.Now I found it was caused by without allocating stack space and El0 cannot access to the system register.Thank you 

Reply
  • 0 in reply to Martin Weidmann

    Thank you very much for your reply.I running the bare metal boot code on Cortex-A55.All the boot code is design by our teams.I just responsible for debug the assembly code which boot the running environment.I want switch EL1 to EL0 with the spsr_el1 and elr_el1 register,and use the eret instruction.Then it come across the exception.Now I found it was caused by without allocating stack space and El0 cannot access to the system register.Thank you 

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