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    SubjectRe: v4.10: kernel stack frame pointer .. has bad value (null)
    On Fri, Feb 24, 2017 at 11:04:39PM -0600, Josh Poimboeuf wrote:
    > 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()?

    Pavel, ping? I'd like to try to get to the bottom of this issue soon.

    I asked for the gcc version and the disassembly of start_secondary()
    because I suspect gcc may have done a funky stack alignment prologue
    which copies the return address on the stack a second time after
    aligning it.

    --
    Josh

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