lkml.org 
[lkml]   [2020]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [REGRESSION 5.8] x86/entry: DR0 break-on-write not working
On Wed, Aug 19, 2020 at 05:14:18PM -0700, Andy Lutomirski wrote:
> On Wed, Aug 19, 2020 at 3:47 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > What amazes me is that it successfully schedules back to the end of the
> > #DB handler finish and everything keeps working.
> >
> > Do we not have assertions in the scheduler to catch this?
>
> You almost nailed it.
>
> I'm pretty sure you have the buggy sequence of events right, but for
> the wrong reason. There's nothing wrong with scheduling when
> delivering SIGTRAP, but it's definitely wrong to blindly save and
> restore DR7 around scheduling and around ptrace invocations. Remember
> this is an entry from user mode, so it runs on the user stack.

Wow, I had no idea user #DB's run on the task stack. The scheduling
from #DB blew my mind :-) What's the purpose of that?

--
Josh

\
 
 \ /
  Last update: 2020-08-20 05:47    [W:1.340 / U:1.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site