On Sunday 06 May 2007, Wink Saville wrote: > > > > > Thus code > > > +executing within the ACE area can also be executed from user space or > > > +kernel space. This is accomplished by using spin locks when executing > > > +within the ACE area and changes to arch/x86_64/kernel/entry.S such that > > > +when an interrupt occurs while executing code in the ACE area that code > > > +will be completed before the interrupt is dispatched. > > > > I don't understand how you can write to the spinlock when coming from > > user space. If the page is writable, how do you make sure the user can't > > write malicious code or data into it? > > Trusted code should only be allowed access to the feature, at the moment > it is enforced by requiring the applications to have root permissions to > open the character device driver.
This is a serious problem. There is a reason why we normally do things with system calls. Unless you can come up with a safe and reasonably clean way for unprivileged applications to use your code, I don't see how you expect it to get merged in the kernel. > > Can't you put this into the vdso? Calling into the right place sounds > > like a problem that is already solved. > > Possibly, but it isn't universally available, I hope to use this technique > on other architectures. It should be possible to implement vdso on any architecture that is still missing it. Not easy, but it's an established way of doing things and a lot cleaner than making up your own linkage model. Arnd <<< ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel