On Fri, Dec 6, 2019 at 2:27 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Thu, Dec 05, 2019 at 09:01:50AM -0800, Thomas Garnier wrote: > > On Thu, Dec 5, 2019 at 1:04 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Wed, Dec 04, 2019 at 04:09:41PM -0800, Thomas Garnier wrote: > > > > > > > @@ -1625,7 +1627,11 @@ first_nmi: > > > > addq $8, (%rsp) /* Fix up RSP */ > > > > pushfq /* RFLAGS */ > > > > pushq $__KERNEL_CS /* CS */ > > > > - pushq $1f /* RIP */ > > > > + pushq $0 /* Future return address */ > > > > > > We're building an IRET frame, the IRET frame does not have a 'future > > > return address' field. > > > > I assumed that's the target RIP after iretq. > > It is. But it's still the (R)IP field of the IRET frame. Calling it > anything else is just confusing. The frame is 5 words: SS, (R)SP, (R)FLAGS, > CS, (R)IP. > > > > > + pushq %rdx /* Save RAX */ > > > > + leaq 1f(%rip), %rdx /* RIP */ > > > > > > nonsensical comment > > > > That was the same comment from the push $1f that I changed. > > Yes, but there it made sense since the PUSH actually created that field > of the frame, here it is nonsensical. What this instruction does is put > the address of the '1f' label into RDX, which is then stuck into the > (R)IP field on the next instruction. Got it, make sense. Thanks. > > > > > + movq %rdx, 8(%rsp) /* Put 1f on return address */ > > > > + popq %rdx /* Restore RAX */
