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Self Modifying Code on the ARM1176JZF-S (raspberry pi)

Sally Chak
Note: This was originally posted on 6th April 2013 at http://forums.arm.com

Hello
I'm trying to write some Self modifying code (SMC) to run on my raspberry pi and I've been reading a few things and am slightly confused.
  • [size=2]From what I understand, ARMv6-M is thumb2 only (i.e. always in thumb mode)  So if I want to write SMC, it has to be in thumb 2? (despite the 1176JZF-S? being able to run both arm and thumb?)
    [/size]
  • [size=2]Should I use MCRR (and stay in the assembly) or linux's mmap/mprotect/__cache__clear (in the OS) for cache coherence?

    Currently, I just keep getting segmentation faults on my code


    Best
    Sally[/size]
Parents
  • Arm Employee Badge
    Note: This was originally posted on 7th April 2013 at http://forums.arm.com

    ARMv6-M is Thumb only.  However, the ARM1176JZF-S is an implementation of ARMv6 with the Security Extensions - not - ARMv6-M.  I know this can be somewhat confusing.  Basically ARMv6-M and ARMv7-M are the versions of the architecture of used by the Cortex-M microcontrollers.
    For the record, the ARM1176JZF-S does NOT support Thumb-2. It supports ARM and Thumb (or Thumb-1 if that's clearer).
    My Linux experience is admittedly limited, but I'd recommend use the kernel calls.  It will help make your code more portable, and is why they're provided in the first place.

Reply
  • Arm Employee Badge
    Note: This was originally posted on 7th April 2013 at http://forums.arm.com

    ARMv6-M is Thumb only.  However, the ARM1176JZF-S is an implementation of ARMv6 with the Security Extensions - not - ARMv6-M.  I know this can be somewhat confusing.  Basically ARMv6-M and ARMv7-M are the versions of the architecture of used by the Cortex-M microcontrollers.
    For the record, the ARM1176JZF-S does NOT support Thumb-2. It supports ARM and Thumb (or Thumb-1 if that's clearer).
    My Linux experience is admittedly limited, but I'd recommend use the kernel calls.  It will help make your code more portable, and is why they're provided in the first place.

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