arm: nxp: mpu: Fix region descriptor 0 attributes #484
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Clearing fields in the region descriptor attributes doesn't always have the expected effect of revoking permissions. In the case of bus master supervisor mode fields (MxSM), setting to zero actually enables read, write, and execute access. When we reworked handling of region descriptor 0, we inadvertently enabled execution from RAM by clearing the MxSM fields and enabling the descriptor. This caused samples/mpu_test run to throw a usage fault instead of an MPU-triggered bus fault. Fix this by setting all the MxSM fields to 2'b11, which gives supervisor mode the same access as user mode. Signed-off-by: Maureen Helm <[email protected]>
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+1 My tests pass with this change applied. |
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@mbolivar was in tree tests failing? Just curious if we need to expand or need a new test case. |
No, it happened while I was doing some mcuboot debugging while the MPU patches were going in. On frdm_k64f, the chain-loaded Zephyr image was usage faulting in the flash driver's system initialization routine at that time. IIRC, I was rebasing the out of tree flash write patches and hadn't gotten them right yet. Fixing those up let the system keep going. I'll retest with MPU on, flash writes off, and this patch when I get around to pulling in upstream again and see if flash init MPU faults instead of usage faults. |
Stop using the event.value because it's unreliable because of button bounce issues. Also, double edge interrupts are better used when the same action will be triggered either way. Here a better approach to make sure the lasers get turned off eventually is to check the button status repeatedly in a timer. This makes it more like Spaceship1.js but at least the lasers will turn on immediately, rather than syncing to 250ms timer, which is important when you're leading a TIE fighter. Signed-off-by: Geoff Gustafson <[email protected]>
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Clearing fields in the region descriptor attributes doesn't always have
the expected effect of revoking permissions. In the case of bus master
supervisor mode fields (MxSM), setting to zero actually enables read,
write, and execute access.
When we reworked handling of region descriptor 0, we inadvertently
enabled execution from RAM by clearing the MxSM fields and enabling the
descriptor. This caused samples/mpu_test run to throw a usage fault
instead of an MPU-triggered bus fault.
Fix this by setting all the MxSM fields to 2'b11, which gives supervisor
mode the same access as user mode.
Signed-off-by: Maureen Helm [email protected]