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INVPC Hard fault exception error

DrWhom DrWhom
Note: This was originally posted on 16th July 2009 at http://forums.arm.com

Using and Arm Cortex M3, the application that is running sometimes will generate a hard fault and deciphering the CFSR register tells me that the following user fault is triggerred.

From the Cortex manual:INVPC - Attempt to load EXC_RETURN into PC illegally. Invalid instruction, invalid context, invalid
value. The return PC points to the instruction that tried to set the PC.

Not sure where to proceed as the PC is pointing to the line in the exception handler. I am trying to figure out the instruction that triggerred the hard fault. Anybody have any suggestions?
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    Note: This was originally posted on 21st July 2009 at http://forums.arm.com

    Just seeing the register values at the starting of hardfault handler is not enough.
    You also need to find out the register values that are pushed to the stack as
    it enter hardfault handler.

    The value of R4 might not mean anything.  The program could have gone wrong
    for a number of cycle before entering hard fault, and load this value as a literal
    data accidentally. I don't know about the IAR function __iar_Tls_dtor__Isdst_rules.
    Have you contact IAR support about this? They might be able to help.

    Have you try to find out if IAR tool got exception event trace?
    If not, define a couple of global variables that work as a shift register to record the last couple of exceptions.
    This might help locate the problem.

    Are you using really Process Stack?
    Another possible issue is that the Main Stack Pointer and the Process Stack Pointer values are quite close.
    Are you sure they haven't got overlapped by mistake?



    We are using FreeRtos and I increased the priority on the main process Task in my program and I have not been able to reproduce the hardfault since. Could this issue have been cause by resource-sharing conflict?
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  • 0
    Note: This was originally posted on 21st July 2009 at http://forums.arm.com

    Just seeing the register values at the starting of hardfault handler is not enough.
    You also need to find out the register values that are pushed to the stack as
    it enter hardfault handler.

    The value of R4 might not mean anything.  The program could have gone wrong
    for a number of cycle before entering hard fault, and load this value as a literal
    data accidentally. I don't know about the IAR function __iar_Tls_dtor__Isdst_rules.
    Have you contact IAR support about this? They might be able to help.

    Have you try to find out if IAR tool got exception event trace?
    If not, define a couple of global variables that work as a shift register to record the last couple of exceptions.
    This might help locate the problem.

    Are you using really Process Stack?
    Another possible issue is that the Main Stack Pointer and the Process Stack Pointer values are quite close.
    Are you sure they haven't got overlapped by mistake?



    We are using FreeRtos and I increased the priority on the main process Task in my program and I have not been able to reproduce the hardfault since. Could this issue have been cause by resource-sharing conflict?
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