Hard Fault exception is triggered when an user interrupt fired with uvisor enabled

Mbed OS
1

Hi All,
I am new to mbed and uVisor, when I enabled uvisor for a new platform having MPU in cortex-M4 cpu. I am now able to register one user interrupt successfully, but when ever the system fires a user interrupt, I am getting an Hard Fault exception(debug prints are showing). but in the HFSR(Hard fault status register) is having all zeros only.

I am working with “mbed OS 15.11 Technology Preview Release”.

Thanks for your quick answer.

2

cc @AlessandroA

3

If you have a license for uVision could you take a look at Blog | Mbed and share the stack trace?

4

Hi, you mentioned you are getting debug prints, so I guess you enabled semihosting. Could you please post here the full set of semihosting messages, from reset up to the fault?

Also, it would help to see a snippet that shows the code sequence you use to set, enable and handle an IRQ. Which platform are you running this code on?

5

Hi AlessandroA,
ARM’s Semihosting feature is not enabled in this case. and for debugging prints we are using UART. and coming to platform ours is a own in house platform.
Here are the debug UART prints for reference.

debug
uvisor_mode: 2
uvisor_ram : @0x00140200 (8192 bytes) [config]
(0x00140200 (8192 bytes) [linker]
MPU.REGIONS=8
MPU.ALIGNMENT=0x0000001F
MPU.ALIGNMENT_BITS=5

box stack segment start=0x00142200 end=0x00142200 (length=3584)

box[0] acl[00]={0x00100000,size=44864,acl=0x000000BF,rounded=65536}

box[0] acl[00]={0x00140000,size=262144,acl=0x000000BF,rounded=262144}

box[0] acl[00]={0xE0000000,size=1048575,acl=0x000000BF,rounded=1048576}

box[0] ACL list:
ctx=0 stack=0

box[0] acl[00]={0x40004000,size=04096,acl=0x00000AB6,rounded=04096}

box[0] acl[01]={0x40082000,size=04096,acl=0x00000AB6,rounded=04096}

box[1] ACL list:
box[1] stack=1024 context=17 rounded=2048

box[1] acl[02]={0x00142800,size=02048,acl=0x02000076,rounded=02048}

vmpu_load_boxes [DONE]
uvisor initialized

InitIRQ 3 registered to box 0

IRQ 3 enabled

***** uvisor-helloworld example *****

main unprivileged box configured

                HARD FAULT

  • HFSR : 0x00000000

  • EXCEPTION STACK FRAME
    Exception from privileged code
    Cannot print exception stack frame.

  • MPU CONFIGURATION

    Background region enabled

    MPU bypassed @NMI, @HardFault

    MPU enabled

    Region Start Size XN AP TEX S C B SRD Valid

    0 0x00100000 064KB 0 110 000 0 0 0 00000000 1

    1 0x00140000 256KB 0 110 000 0 0 0 00000000 1

    2 0xE0000000 001MB 0 110 000 0 0 0 00000000 1

    3 0x40004000 004KB 1 110 000 0 0 0 00000000 1

    4 0x40082000 004KB 1 110 000 0 0 0 00000000 1

    5 0x00000000 000B 0 000 000 0 0 0 00000000 0

    6 0x00000000 000B 0 000 000 0 0 0 00000000 0

    7 0x00000000 000B 0 000 000 0 0 0 00000000 0