lkml.org 
[lkml]   [2018]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch
Date
From
On Mon, 2018-01-08 at 15:56 -0800, Linus Torvalds wrote:
> On Mon, Jan 8, 2018 at 3:44 PM, David Woodhouse <dwmw2@infradead.org> wrote:
> >
> > To guard against this fill the return buffer with controlled
> > content during context switch. This prevents any underflows.
>
> Ugh. I really dislike this patch. Everything else in the retpoline
> patches makes me go "ok, that's reasonable". This one makes me go
> "Eww".
>
> It's hacky, it's ugly, and it looks pretty expensive too.
>
> Is there really nothing more clever we can do?

You get this part in the IBRS/microcode solution too. The IBRS MSR
doesn't catch everything; you still need to stuff the RSB in very
similar places (and/or use the IBPB MSR in some).[unhandled content-type:application/x-pkcs7-signature]
\
 
 \ /
  Last update: 2018-01-14 23:18    [W:0.116 / U:3.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site