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I cannot write the sp register in the monitor mode

Takumi Shimada

I use a Cortex-A7 board and write start up code.

I try to use Security Extension.

I use `smc` instruction and make cpu mode monitor mode.

In the monitor handler, I tried to changed stack pointer value for calling other functions.

But after execute `ldr sp, =_stack_start`, sp value is 0x0 (Of course, _stack_start is not 0x0 and I check it in the assembler code).

Therefore, after `push` some registers and `pop` those registers, the data abort excetpions occurred!

How can I change the sp value?

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  • 0 in reply to Takumi Shimada

    You are not debugging on RPi2 by any chance?

    In that case you need to use the GPIO pins + a boot program to switch the

    multiplexed GPIO pins for that use. The two jtag-connectors are for LAN-chip and for GPU.

    Even if the cores are on the same chip as the GPU, (I'm told) the cores are not in the same

    scan chain with the GPU.

Reply
  • 0 in reply to Takumi Shimada

    You are not debugging on RPi2 by any chance?

    In that case you need to use the GPIO pins + a boot program to switch the

    multiplexed GPIO pins for that use. The two jtag-connectors are for LAN-chip and for GPU.

    Even if the cores are on the same chip as the GPU, (I'm told) the cores are not in the same

    scan chain with the GPU.

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