search

zephyrproject-rtos / zephyr

Primary Git Repository for the Zephyr Project. Zephyr is a new generation, scalable, optimized, secure RTOS for multiple hardware architectures.
https://docs.zephyrproject.org
Apache License 2.0
10.91k stars 6.64k forks source link

ARM Cortex-M: Z_ARCH_EXCEPT not working for Baseline SOCs #18712

Open ioannisg opened 5 years ago

ioannisg commented 5 years ago

Describe the bug Z_ARCH_EXCEPT() is called, to signal errors directly from Software. In ARM Cortex-M, this is implemented with a synchronous SVC instruction, with code 2.

In Mainline SOCs this works well, because the kernel reserves the highest interrupt priority for the SVC Handler.

In Baseline cores, however, we do not reserve an interrupt priority for the SVC. So if Z_ARCH_EXCEPT() is invoked from an interrupt with the highest priority, the SVC Call won't be able to execute and will trigger a synchronous (Escalated) hard fault.

To Reproduce We have a bug report already for this: #18590

Impact We are not able to infer stack-fail checks in Baseline ARM CPUs with the STACK Sentinel feature.

We do get a system exception, however, so the user is still getting some information that something went wrong.

ioannisg commented 5 years ago

There is a work-around for this already merged, hence this should remain a low priority issue.

dleach02 commented 4 years ago

Removing 2.1 milestone. @ioannisg, can you add a reference to the PR of the workaround you referenced?

ioannisg commented 4 years ago

Removing 2.1 milestone. @ioannisg, can you add a reference to the PR of the workaround you referenced?

https://github.com/zephyrproject-rtos/zephyr/pull/18713

This PR fixed this by doing some inspection of the escalated hard fault.

ioannisg commented 4 years ago

Thinking about this, maybe we cab turn this to an enhancement, because the workaround has been stable for quite some time now. Z_ARCH_EXCEPT does work for Baseline cortex-m via the hard-fault inspection. Need to think if this should actually be made to work as it does for Mainline: it would probably eat an IRQ level for SVC and we don't have many levels available in Baseline.