Re: v4.10: kernel stack frame pointer .. has bad value (null)

[Josh Poimboeuf]

On Wed, Feb 22, 2017 at 10:05:48PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > Thinkpad X220, in 32 bit mode... and I'm getting rather scary messages
> > > from kernel during boot:
> > > 
> > > Git blame says that message comes from commit
> > > 
> > > commit 24d86f59093b0bcb3756cdf47f2db10ff4e90dbb
> > > Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > > Date:   Thu Oct 27 08:10:58 2016 -0500
> > > 
> > >     x86/unwind: Ensure stack grows down
> > > 
> > >     Add a sanity check to ensure the stack only grows down, and print
> > >     a
> > >         warning if the check fails.
> > > 
> > > Any ideas?
> > 
> > Hi Pavel,
> > 
> > I don't think I've seen this one.  Any chance this came after resuming
> > from a hibernation or suspend?
> 
> No, it was during the boot. Notice the timestamps...

Right, but doesn't waking from hibernation initially start with a
timestamp of zero?

The reason I asked is because of the following part of the stack dump:

> > > [    1.048429] f50cdf9c: 00000000c4000237 (startup_32_smp+0x16b/0x16d)
> > > [    1.048429] f50cdfa0: 0000000000200002 (0x200002)
> > > [    1.048430] f50cdfa4: 0000000000000000 ...
> > > [    1.048432] f50cdfa8: 00000000c4000237 (startup_32_smp+0x16b/0x16d)
> > > [    1.048432] f50cdfac: 0000000000000000 ...
> > > [    1.048433] f50cdff4: 0000000000000100 (0x100)
> > > [    1.048434] f50cdff8: 0000000000000200 (0x200)
> > > [    1.048435] f50cdffc: 0000000000000000 ...
> > > [    1.060368] [drm] Supports vblank timestamp caching Rev 2

Somehow, startup_32_smp() is on the stack twice.  The stack unwind led
to the startup_32_smp() frame at 0xf50cdf9c rather than the one at
0xf50cdfa8 (which is where it should normally be).  So the question is
how startup_32_smp() got executed the second time, with the wrong stack
offset.

-- 
Josh