lkml.org 
[lkml]   [2016]   [Feb]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 06/12] powerpc/module: Rework is_early_mcount_callsite()
From
Date
On Thu, 2016-02-25 at 10:39 +1100, Balbir Singh wrote:
> On 25/02/16 01:28, Michael Ellerman wrote:
> > is_early_mcount_callsite() needs to detect either the two instruction or
> > the three instruction versions of the _mcount() sequence.
> >
> > But if we're running a kernel with the two instruction sequence, we need
> > to be careful not to read instruction - 2, otherwise we might fall off
> > the front of a page and cause an oops.
> >
> > While we're here convert to bool to make the return semantics clear.
> >
> > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> >
> Do we even need to do this anymore?

Yes. Otherwise the code in apply_relocate_add() will see a far call with no nop
slot after it to do the toc restore, and it considers that a bug (which it
usually is, except mcount is special).

As we discussed today I'm hoping we can clean this code up a bit more in the
medium term, but this works for now.

cheers

\
 
 \ /
  Last update: 2016-02-25 12:01    [W:0.064 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site