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

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: v4.10: kernel stack frame pointer .. has bad value (null)
Date	2017-02-25 06:30 +0100
Message-ID	<teD5D-33n-3@gated-at.bofh.it> (permalink)
References	(3 earlier) <tdME2-7PD-19@gated-at.bofh.it> <tdNTs-eQ-19@gated-at.bofh.it> <tdOcN-DJ-5@gated-at.bofh.it> <tdOmt-HE-9@gated-at.bofh.it> <te81P-6eq-11@gated-at.bofh.it>
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On Thu, Feb 23, 2017 at 09:10:39PM +0100, Pavel Machek wrote:
> Hi!
> 
> 
> > > > > 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.
> > > > 
> > > > Not much idea... but this is stack dump, right? Just because some
> > > > value is on the stack does not mean it is a return address, no?
> > > 
> > > Right, but the one at 0xf50cdfa8 is where the startup_32_smp() is
> > > *supposed* to be.  If the unwinder had unwinded to that one, it wouldn't
> > > have complained.  So it looks to me like the CPU somehow booted twice:
> > > the first time at the right stack address, and the second time it
> > > somehow ended up with a different stack address.
> > > 
> > > > And .... startup_32_smp is kind of "interesting" function. Take a
> > > > look...
> > > 
> > > Yes, it's used in bringing up the CPU.
> > 
> > Can you share your .config?  
> 
> Here you go...

What version of gcc are you using?

Can you post a disassembly of the first 10 instructions of
start_secondary()?

-- 
Josh

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Thread

v4.10: kernel stack frame pointer .. has bad value (null) Pavel Machek <pavel@ucw.cz> - 2017-02-21 23:20 +0100
  Re: v4.10: kernel stack frame pointer .. has bad value (null) "H. Peter Anvin" <hpa@zytor.com> - 2017-02-22 00:20 +0100
    Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-22 18:00 +0100
      Re: v4.10: kernel stack frame pointer .. has bad value (null) "H. Peter Anvin" <hpa@zytor.com> - 2017-02-22 22:00 +0100
        Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-22 22:20 +0100
  Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-22 00:20 +0100
    Re: v4.10: kernel stack frame pointer .. has bad value (null) Pavel Machek <pavel@ucw.cz> - 2017-02-22 22:10 +0100
      Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-22 22:30 +0100
        Re: v4.10: kernel stack frame pointer .. has bad value (null) Pavel Machek <pavel@ucw.cz> - 2017-02-22 23:50 +0100
          Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-23 00:10 +0100
            Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-23 00:20 +0100
              Re: v4.10: kernel stack frame pointer .. has bad value (null) Josh Poimboeuf <jpoimboe@redhat.com> - 2017-02-25 06:30 +0100

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