I think there is no good way of doing that. Each time the user tries to run a x86_64 binary you’d have to actually checksum, or otherwise check the content of, the x86_64 binary to know if you have a translated version of it already.

inode meta data such as timestamps are insufficient I think. They can be tampered with.

> inode meta data such as timestamps are insufficient I think. They can be tampered with.

In macOS, there is a security-policy layer of some kind on top of xattrs, separate from the security-policy of the file itself. `com.apple.rootless` is an example of an xattr protected by this mechanism: users (even root) can't apply or remove `com.apple.rootless` from files on a filesystem mounted as the rootfs.

With this mechanism, it'd likely be possible to give executable binaries an xattr containing the checksum, generated by Gatekeeper+Rosetta, that the user couldn't modify, while still being able to otherwise modify/delete the file. (And, presumably, modifying the file would automatically invalidate/remove the checksum xattr.)

The kernel is aware when files are modified.

That's not generally applicable, e.g. not if files are on an external drive, or worse, a network filesystem (where they can change even during use).

In which case falling back on a hash is fine.