OpenTitan: Prepare to bump to the latest RTL SHA #3205
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We currently support detecting any number of ePMP regions by writing values and seeing if the new value sticks. This allows us to support multiple platforms, but it doesn't work if the bootloader has already enabled MML. This patch changes the behaviour if MML has been set, so that we ensure we won't accidently lock ourselves out. Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
A previous boot stage has enabled Machine Mode Whitelist Policy (mseccfg.MMWP), which we can't disable. That means that Tock will be denied a memory access if it doesn't match a PMP region This eventually won't matter, as Tock configures it's own regions, but it makes it difficult to setup. To allow us to setup the ePMP regions without locking ourselves out we create two special regions. We create an allow all region as the first and last region. This way no matter what the previous stage did, we should have a working fallback while we modify the rules. If the previous stage has an allow all in the first or last region, we won't get locked out. If the previous stage created a range of regions we also won't get locked out. Signed-off-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
2 tasks
twilfredo
approved these changes
Sep 9, 2022
bradjc
reviewed
Sep 9, 2022
bradjc
approved these changes
Sep 9, 2022
hudson-ayers
approved these changes
Sep 10, 2022
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Pull Request Overview
This is just the first few commits of #3056, focusing on the ePMP improvements to handle already configured ePMP regions.
See each commit for details
Testing Strategy
Tested as part of #3056
TODO or Help Wanted
Documentation Updated
/docs, or no updates are required.Formatting
make prepush.