On Tue, May 07, 2019 at 09:18:51AM +0000, David Laight wrote: > From: Peter Zijlstra > > Sent: 07 May 2019 09:58 > ... > > + /* > > + * When we're here from kernel mode; the (exception) stack looks like: > > + * > > + * 4*4(%esp) - <previous context> > > + * 3*4(%esp) - flags > > + * 2*4(%esp) - cs > > + * 1*4(%esp) - ip > > + * 0*4(%esp) - orig_eax > > Am I right in thinking that this is the only 'INT3' stack frame that > needs to be 'fiddled' with? > And that the 'emulate a call instruction' has verified that is the case?? > So the %cs is always the kernel %cs. Only the INT3 thing needs 'the gap', but the far bigger change here is that kernel frames now have a complete pt_regs set and all sorts of horrible crap can go away. For 32bit 'the gap' happens naturally when building a 5 entry frame. Yes it is possible to build a 5 entry frame on top of the old 3 entry one, but why bother...
