Tagging pointers

[xxuejie]

For a design without MMU, ckb-vm can be more vulnerable to certain types of memory corruption problems. Since ckb-vm typically runs scripts that guards assets, this issue is much more critical.

One possible solution would be introducing tagging pointers, which might leverage, but would not eliminate the problem, this paper describes a similar attempt: https://arxiv.org/abs/2105.08712

[mohanson]

I realized that HeapSafe append the ROCC instructions, which would require us to modify the toolchains, versatility will be an issue.

[xxuejie]

Yes, tagging pointer will definitely require toolchain change. I've seen people limiting it to malloc library only. Considering we are patching malloc for non-MMU environment, I feel like the tradeoff here might be fine.