Unsound {Fs,Gs}Base::write()

[mkroening]

Segment64::write_base() states:

Safety

The caller must ensure that this write operation has no unsafe side effects, as the segment base address might be in use.

On the other hand, FsBase::write() is not even unsafe.

This leads to this kind of code in our OS:

unsafe fn writefs(base: VirtAddr) {
    if CR4.FSGSBASE {
        unsafe {
            FS::write_base(base);
        }
    } else {
        FsBase::write(base);
    }
}

I think we should make FsBase::write() and GsBase::write() unsafe, right?

[Freax13]

I think we should make FsBase::write() and GsBase::write() unsafe, right?

Yes, I agree with your analysis. Feel free to open a PR.