| commit | 1088e5c9ddc32aa70dc10e591a7323e4574995ef | [log] [tgz] |
|---|---|---|
| author | Andreas Kurth <adk@lowrisc.org> | Tue Aug 30 12:02:12 2022 +0000 |
| committer | Greg Chadwick <mail@gregchadwick.co.uk> | Wed Sep 07 15:54:03 2022 +0100 |
| tree | 7fc62a0e39c6073e24199d2eb488df5d853c2222 | |
| parent | 8d1849cbdc4b1302cda220c56011b73a6ad3f1b1 [diff] |
[otbn,rtl] Ignore bignum `rd` indirect error on call stack error Prior to this commit, a `BN.LID` where the index of `rd` comes from an empty call stack would raise an illegal instruction error (through the internal bignum `rd` indirect error) if the index of `rd` exceeded 31. Whether an illegal instruction error was raised or not would depend on the residual value in the empty call stack. Because call stack values are not reset, this could be physically random or residual charge from an earlier run (in silicon) or unknown (in RTL simulation). Therefore, the illegal instruction error would be uncorrelated with the current program, which should be avoided. This scenario already raises a call stack error, so the instruction is not committed. This problem can be reproduced by running the `bnlid-2.s` test program, which is run as part of the `otbn_multi_err` test. This commit fixes the described problem by ignoring bits [31:5] of the index of `rd` when a call stack error occurs. Signed-off-by: Andreas Kurth <adk@lowrisc.org>
OpenTitan is an open source silicon Root of Trust (RoT) project. OpenTitan will make the silicon RoT design and implementation more transparent, trustworthy, and secure for enterprises, platform providers, and chip manufacturers. OpenTitan is administered by lowRISC CIC as a collaborative project to produce high quality, open IP for instantiation as a full-featured product. See the OpenTitan site and OpenTitan docs for more information about the project.
This repository contains hardware, software and utilities written as part of the OpenTitan project. It is structured as monolithic repository, or “monorepo”, where all components live in one repository. It exists to enable collaboration across partners participating in the OpenTitan project.
The project contains comprehensive documentation of all IPs and tools. You can access it online at docs.opentitan.org.
Have a look at CONTRIBUTING and our documentation on project organization and processes for guidelines on how to contribute code to this repository.
Unless otherwise noted, everything in this repository is covered by the Apache License, Version 2.0 (see LICENSE for full text).