At 14:22 +0100 on 12 Aug (1439389325), Ben Catterall wrote: > On 11/08/15 18:05, Tim Deegan wrote: > > BTW, I think there need to be three stacks anyway, since the depriv > > code shouldn't be allowed to write to the priv code's stack frames. > > Or maybe I've misunderstood how much access the depriv code will have. > So, just to clarify: > > We have a separate deprivileged stack allocated which the deprivileged > code uses. This is mapped in user mode. > > We have the privileged stack which Xen runs on. To prevent this being > clobbered when we are in our mode and take an interrupt, we copy this > out to a buffer. This buffer is the saved privileged stack state. > > So, we sort of have three stacks already, just the privileged stack is > copied out to a buffer, rather than switching pointers to another > interrupt stack. > > Hopefully that clarifies?
Yes, thanks -- the buffer is what I was thinking of as a third stack. Cheers, Tim. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
