7 May
2019
7 May
'19
11:30 a.m.
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_eaxAm 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...