LWIP disables MPU during initialization and breaks uVisor

[sherrellbc]

MPU->CESR &= ~MPU_CESR_VLD_MASK;

https://github.com/ARMmbed/mbed-os/blob/master/features/net/FEATURE_IPV4/lwip-interface/lwip-eth/arch/TARGET_Freescale/hardware_init_MK64F12.c#L41

The MPU appears to be a protected memory region that cannot be accessed by unprivileged code. Access to this region results in a halt with uVisor.

My original post was over at uVisor as I originally thought it was a configuration related issue. See it here: ARMmbed/uvisor#315

@geky

[geky]

Thanks for reporting this issue. I went ahead and continued the discussion on ARMmbed/uvisor#315 to keep the progress on the issue consolidated.

[sg-]

This should be fixed with #2733

[sherrellbc]

@sg-

Although #2733 introduced support for LwIP using DMA, it alone was not a sufficient patch to allow LwIP to fully function. Take a look at my original issue; there were some run-time problems with memory management of mutexes, or similar.

The actual fix came with 2a42255, but so many changes were introduced that it is hard to say which patch corrected the offending code.

But, otherwise, yes, this specified issue has been fixed and, as such, can be closed.