CHERIoT-Platform/llvm-project

Add parameter attributes for {deep,shallow} {immutable, no-capture} permissions.

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#4 opened on Nov 24, 2023

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 (0 comments) (0 reactions) (0 assignees)LLVM (15 forks)auto 404
good first issue

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Description

The CHERIoT ISA has permissions that are intended to be useful to remove on call boundaries:

  • Store (make something shallow read-only)
  • LoadMutable (make something deep read-only)
  • Global (shallow no capture)
  • LoadGlobal (deep no capture)

We should add parameter attributes that allow these to be removed declaratively, especially on cross-compartment calls that don't. They should also add the relevant LLVM IR attributes to allow optimisation in the caller based on the properties that we're enforcing in hardware.

Contributor guide

Research direction
Study the CHERI ISA documentation for permission attributes and the LLVM IR attribute system to understand how to add new parameter attributes.
Tech stack
None
Domain
securitycompilers
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
CHERI ISA knowledgeLLVM IR internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30